Patent Publication Number: US-10774379-B2

Title: Random access of data encoded by polynucleotides

Description:
BACKGROUND 
     Much of the data being produced by computing devices is stored on conventional data storage systems that include various kinds of magnetic storage media, optical storage media, and/or solid state storage media. The capacity of conventional data storage systems is not keeping pace with the rates of data being produced by computing devices. Polynucleotides, such as deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), can be used to store very large amounts of data on a scale that exceeds the capacity of conventional storage systems. An arrangement of nucleotides included in a polynucleotide (e.g., CTGAAGT . . . ) can correspond to an arrangement of bits that encodes digital data (e.g., 11010001 . . . ). The digital data can include audio data, video data, image data, text data, software, combinations thereof, and the like. 
     The retrieval of digital data stored by polynucleotide sequences can be achieved using processes that amplify polynucleotides that encode the digital data that is being requested. For example, polymerase chain reaction (PCR) can be used to amplify polynucleotides that encode the digital data being requested. Amplification of polynucleotides can produce an amplification product that includes an amount of the target polynucleotides being amplified that is several orders of magnitude greater than the original quantity of the target polynucleotides. 
     The amplification of polynucleotides that encode digital data may be performed selectively such that the polynucleotides encoding the desired digital data are amplified much more than other polynucleotides. To illustrate, polynucleotides of two different data files can be stored in a container of a polynucleotide data storage system and one of the data files can be the subject of a request for digital data. After selective amplification, the number of polynucleotides associated with the requested data file will be orders of magnitude greater than the number of polynucleotides of the other data file. A sample of the amplification product can be sequenced by a sequencing machine and the sequencing data that includes reads from the sequencing machine can be analyzed to reproduce the original bits of the requested digital data. Although the polynucleotides associated with the data file that was not requested are still present, the probability of sequencing these polynucleotides is very small because there are so many more copies of the polynucleotides from the requested data file. Thus, the polynucleotide sequences included in the sequencing data that correspond to the requested digital data can be identified because they are found in greater quantities than the polynucleotide sequences that are not associated with the digital data request. 
     In some cases, the amplification processes can take place in an uneven manner with some polynucleotides being amplified at a faster rate than others. For example, digital data of some data files can be encoded by a greater quantity of polynucleotides than digital data of other data files due to the number of bits included in the data files. When polynucleotides of different data files are amplified together, the data files encoded by the greater numbers of polynucleotides may be amplified at a faster rate than the polynucleotides of the other data files. Although both data files are targets of a request, the difference in amplification rates may result in the sequencing machine failing to sequence both sets of polynucleotides equally. Therefore, differences in the amplification rates of the polynucleotides that encode digital data of the data files of varying sizes can lead to inefficiencies in the random access and sequencing processes. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter nor is it intended to be used to limit the scope of the claimed subject matter. 
     Synthesized polynucleotides can include regions that encode digital data. The digital data can be included in a data file that corresponds to content that can be processed by a computing device, such as audio content, video content, text content, image content, or combinations thereof. The region of a polynucleotide that encodes digital data can be referred to herein as a “payload.” The length of polynucleotides that encode digital data can be limited because as the length of the polynucleotides increases beyond a threshold length, the possibility that the polynucleotides will lose their linear structure and/or form secondary structures increases. As used herein, the “length” of a polynucleotide can refer to the number of nucleotides included in a linear chain of nucleotides that comprises the polynucleotide. Based on the limitations to the lengths of polynucleotides that encode digital data, the digital data may be segmented before the polynucleotides are synthesized. In this way, the lengths of the payloads of the polynucleotides are limited, which can lead to minimizing the possibility of disrupting the linear configuration of the polynucleotides. 
     In situations where polynucleotides encode segments of digital data of a data file, the individual segments that encode the digital data can each be associated with the data file according to a particular framework. In some implementations, each data file may be associated with a file identifier and the polynucleotides encoding the digital data of the data files include regions that encode the respective file identifiers. However, a lack of parameters regarding the number of segments used to encode the digital data of the data files may result in differing rates of amplification of polynucleotides during sequencing and inefficient use of the sequencing resources due to over amplification of the polynucleotides that amplify readily in order to detect the polynucleotides with lower rates of amplification. 
     Implementations described herein provide frameworks for storing polynucleotides utilized to encode digital data that minimize inefficiencies that can take place during the retrieval of the polynucleotides in response to a request for digital data. For example, each data file can be associated with a number of polynucleotide groups and each group can include a specified quantity of polynucleotides. In various implementations, each group of polynucleotides can be associated with an individual, unique group identifier and the individual group identifiers can be associated with the particular data file having digital data that is encoded by the polynucleotides included in the respective groups. In some cases, the quantity of polynucleotides included in each group can be the same. In these situations, the rate of amplification of the polynucleotides included in the various groups can be relatively the same. In other cases, the quantity of polynucleotides included in each group can be different. In the scenarios where the quantity of polynucleotides included in each polynucleotide group is different, the quantity of polynucleotides can be within an upper threshold and a lower threshold. The upper threshold and the lower threshold can be set such that differences between the quantity of polynucleotides in each group has a minimal effect on the rates of amplification of the polynucleotides included in the individual groups. 
     In response to a request to retrieve digital data of one or more data files, the group identifiers corresponding to the one or more data files can be determined. The group identifiers can correspond to primer target regions of the polynucleotides that encode the digital data being requested. Thus, primers that are complementary to the group identifiers can be identified and used in the amplification processes that are part of the retrieval of digital data encoded by polynucleotides. In this way, the polynucleotides that encode the digital data being requested can be selectively amplified and subsequently sequenced and decoded to provide the requested digital data. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The Detailed Description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items. 
         FIG. 1  is a schematic diagram of a process to produce a framework for designing and storing polynucleotides that encode digital data as part of a polynucleotide data storage system. 
         FIG. 2  shows a schematic diagram of a framework to store polynucleotides that encode digital data of different files. 
         FIG. 3  shows a schematic representation of an example process to design polynucleotides that can be used to store digital data and retrieve the digital data from a polynucleotide storage system. (SEQ ID NOs: 1-5) 
         FIG. 4  shows a block diagram of an example computing device to produce a framework for designing polynucleotides that encode digital data and retrieving the digital data from the polynucleotides. 
         FIG. 5  is a flow diagram of an example process to produce a framework that encodes digital data using polynucleotides and arranges the polynucleotides of an individual data file into a number of groups. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure describes frameworks and techniques to improve random access to digital data encoded by polynucleotides. In particular, the rates of amplification of the polynucleotides that encode requested digital data are within a specified range regardless of the size of the data file or the number of polynucleotides utilized to encode the requested digital data. As a result, the inefficiencies in the retrieval of digital data encoded by polynucleotides can be minimized. 
     In situations where digital storage media utilize random access of digital data, digital data stored anywhere on the digital storage media can be accessed without first accessing another portion of the digital data. In contrast, sequential access of digital data comprises the access of digital data in an ordered sequence. Thus, for sequential access of digital data, one or more additional portions of the digital data may be accessed before accessing the requested digital data, while random access of digital data enables the access of the requested digital data without first accessing other portions of the digital data. Random access of digital data can be accomplished by providing address information, such as metadata, for each element of digital data that indicates a storage location for the respective elements of digital data. Upon receiving a request to obtain a portion of the digital data, the addressing information can be accessed and the storage location utilized to obtain the requested digital data from one or more digital storage media. 
     Random access in the context of polynucleotide data storage systems can take place through encoding addressing information in sequences of polynucleotides. The addressing information can uniquely identify the data encoded by the sequences of polynucleotides. At least a portion of the addressing information can comprise a primer target sequence. In response to a request for particular digital data encoded by polynucleotides, primers that correspond to the primer target sequences of the target polynucleotides can be obtained. The primers can then be utilized to selectively amplify the target polynucleotides in a sample that includes both the target polynucleotides and other polynucleotides that encode digital data other than the requested digital data. Thus, the quantity of the target polynucleotides will be much greater than the other polynucleotides stored with the target polynucleotides. In this way, the probability of sequencing the target polynucleotides will be greater than the probability of sequencing the non-target polynucleotides and the sequences of the target polynucleotides can be decoded to reproduce the requested digital data. 
     In various implementations, digital data of a data file can be encoded as a series of nucleotides and one or more polynucleotide sequences can be generated that encode the digital data for the data file. Multiple polynucleotide sequences can be utilized to encode digital data of a single data file due to the segmentation of the digital data. In particular implementations, each polynucleotide sequence can encode an individual segment of the digital data. The portion of the polynucleotide sequence that encodes an individual segment of the digital data can be referred to herein as a payload region. The digital data can be segmented to ensure that the length of the polynucleotide sequences is less than a threshold length that is based on a probability of secondary structure formation by the polynucleotide sequences. 
     The polynucleotide sequences described in implementations herein can include regions to encode the digital data and regions encoding identifiers for the data file that includes the digital data being encoded. For example, the identifiers encoded by regions of the polynucleotide sequences can correspond to various groups of polynucleotide sequences that encode digital data for a particular data file. That is, for each data file, the digital data of the data file is encoded by one or more groups of polynucleotide sequences. Additionally, each polynucleotide sequence included in a particular group includes at least one region that encodes the same identifier. Further, the frameworks and techniques described herein can provide some structure around the quantity of polynucleotide sequences included in each group. To illustrate, the quantity of polynucleotide sequences included in each group can be substantially similar or the number of polynucleotide sequences included in each group can be within a specified range. In addition, the frameworks can include metadata indicating the particular group identifiers that encode the digital data of the data file. 
     The polynucleotide sequences can be generated by a computing system and represented by polynucleotide data. The polynucleotide data can be used by a polynucleotide synthesizing machine to synthesize physical polynucleotides according to the polynucleotide sequence data. A polynucleotide data storage system can store the polynucleotides in one or more containers that may also contain a medium, such as a liquid. In particular implementations, polynucleotides can be stored in a liquid, such as water. Each container can store polynucleotides that encode digital data. In some cases, a container of the polynucleotide data storage system can store polynucleotides encoding digital data of a number of data files. For example, a container of a polynucleotide data storage system can store polynucleotides encoding digital data of a first data file and polynucleotides encoding digital data of a second data file. Additionally, the data files that have polynucleotides stored in a container of the polynucleotide data storage system can have different amounts of data. Thus, the number of polynucleotides that encode digital data for the various data files can be different and, correspondingly, the number of groups of polynucleotides associated with each data file can also be different. Further, the quantity of polynucleotides included in each group, may be intentionally designed according to the frameworks and techniques described herein, to include relatively the same number of polynucleotides or similar numbers that are within a specified range. 
     In response to receiving a request to retrieve particular digital data, one or more polynucleotides can be identified that encode the requested digital data. For example, a memory structure that stores the metadata indicating the groups corresponding to the requested digital data can be accessed and the group identifiers associated with the requested digital data can be obtained. Primers can then be selected that are complementary to the group identifiers and the polynucleotides that encode the digital data can be selectively amplified using the primers. In situations where digital data from a plurality of data files are being requested, the primers complementary to the group identifiers corresponding to each of the plurality of data files can be identified. After amplification of the polynucleotides and sequencing of the amplification product, the polynucleotide sequencing data produced by the sequencing operations can be decoded to reproduce the requested digital data. Because the quantity of polynucleotides included in each group being amplified is relatively the same or within a particular range regardless of the number of data files for which digital data is being requested or the size of the data files, the rates of amplification of the polynucleotides corresponding to the data files are also relatively the same or within a specified range. In this way, selective access of polynucleotides using group identifiers rather than a particular file identifier, can minimize the resources utilized in the data retrieval process in situations where different data files may include different amounts of digital data. In a particular example, when sequencing is conducting using a flow cell, the area of the flow cell is efficiently utilized to sequence the polynucleotides related to the requested digital due to the uniformity in the quantity of polynucleotides included in each group. 
       FIG. 1  is a schematic diagram of a process  100  to produce a framework for designing and storing polynucleotides that encode digital data as part of a polynucleotide data storage system. The process  100  can take place before the synthesis of polynucleotides that encode digital data. 
     At operation  102 , the process  100  can include obtaining digital data  104 . The digital data  104  can include a sequence of 1s and 0s that can be processed by a computing device. The digital data  104  can include input and/or output related to one or more applications. In illustrative implementations, the digital data  104  can be related to at least one of audio content, video content, image content, or text content. The digital data  104  can be associated with one or more data files. 
     At operation  106 , the process  100  can include performing a segmentation process with regard to the digital data  104 . The segmentation process can include dividing the digital data  104  into segments  108 . The number of the segments  108  can be based at least partly on a number of bits included in the digital data  104 . The number of the segments  108  can also be based at least partly on an encoding scheme used to encode the bits of the digital data  104  as nucleotides. Additionally, the number of the segments  108  can be based at least partly on a length of polynucleotides (e.g., 60 to 300 nucleotides) stored by the polynucleotide data storage system that minimizes the potential for the polynucleotides to form secondary structures. Further, the number of the segments  108  can be based at least partly on the different types of information encoded by the polynucleotides stored by the polynucleotide data storage system. In some implementations, the number of the segments  108  can be based at least partly on a combination of one or more of the number of bits included in the digital data  104 , the encoding scheme used to encode the digital data  104  as nucleotides, the length of the polynucleotides stored by the polynucleotide data storage system, and the different types of information encoded by the polynucleotides of the polynucleotide data storage system. 
     In particular implementations, the encoding scheme utilized to encode the bits of the digital data  104  can affect the length of the segments  108  because, in some cases, more than one bit of the digital data  104  can be encoded by a single nucleotide. In these situations, the number of the segments  108  produced can be less than a number of the segments  108  produced when a single nucleotide encodes a single bit of the digital data  104 . Additionally, the different types of information encoded by the polynucleotides can affect the length of the segments  108  because the digital data  104  that is encoded by the polynucleotides is encoded by the payload region of the polynucleotides, but other information such as error correction information and addressing information can also be encoded by the nucleotides of the polynucleotides. Thus, the more information encoded by various regions of the polynucleotides, the fewer nucleotides that can be dedicated to encoding the digital data  104  and a greater number of polynucleotides may be utilized to encode the digital data  104 . 
     At operation  110 , the process  100  can include encoding the digital data  104  as one or more sequences of nucleotides, such as the group of payload sequences  112 . The encoding of the digital data  104  as the group of payload sequences  112  can be performed according to one or more techniques that associate one or more bits of the digital data  104  with one or more nucleotides. In some implementations, a first group of bits can be associated with a first nucleotide, a second group of bits can be associated with a second nucleotide, a third group of bits can be associated with a third nucleotide, and a fourth group of bits can be associated with a fourth nucleotide. In an illustrative example, a bit pair 00 can correspond to a first nucleotide, such as A; a second bit pair 01 can correspond to a second nucleotide, such as C; a third bit pair 10 can correspond to a third nucleotide, such as G; and a fourth bit pair 11 can correspond to a fourth nucleotide, such as T. In another illustrative example, the digital data  104  can be mapped to a base-4 string with each number in base-4 mapping to a corresponding letter representing a nucleotide. To illustrate, 0, 1, 2, and 3 can each map to one of A, C, G, or T. In an additional illustrative example, the digital data  104  can be mapped to a base-3 string with a nucleotide mapping to each number of the base 3 string (e.g., 0, 1, 2) based on a rotating code. 
     The encoding of the digital data at operation  110  can be performed, in some implementations, before performing the segmentation process at operation  106 . For example, the encoding operations can be performed on the entire string of bits included in the digital data  104 . In these implementations, the segmentation process at operation  106  can produce the group of payload sequences  112  instead of producing the bit segments  108 . In other implementations, the encoding of the bits as nucleotides performed at operation  110  can take place at other points in the process  100 . 
     At operation  114 , the process  100  includes producing identifiers  116 . Individual identifiers  116  can be used to identify individual groups of polynucleotide sequences that encode the digital data  104 . The identifiers  116  can correspond to primers that are used to amplify and replicate polynucleotides that encode the digital data  104 . In particular, one or more regions of polynucleotides produced according to implementations described herein can encode the identifiers  116  and comprise a primer target region of the polynucleotides. In these situations, the primers utilized in the polynucleotide data storage system can be complementary to at least a portion of the regions of the polynucleotides that encode the identifiers  116 . In some implementations, the identifiers  116  can include a series of unique alphanumeric symbols that are encoded by nucleotides. In illustrative examples, the techniques utilized to encode the digital data  104  as nucleotides can be the same as those utilized to encode the identifiers as nucleotides. In various implementations, the identifiers  116  can be generated by a pseudo-random number generation algorithm. 
     At operation  118 , the process  100  includes assigning the identifiers  116  to the bit segments  108  or to the payload sequences  112 . In particular, the bit segments  108  or the payload sequences  112  can be divided into groups and each group can be assigned an individual identifier  116 . In situations where the digital data  104  has been encoded as nucleotides before assigning the identifiers  116 , the individual payload sequences  112  can be grouped and assigned to respective identifiers  116 . In instances where the digital data  104  has not been encoded as nucleotides before operation  118 , the individual bit segments  108  can be grouped and assigned to respective identifiers  116 . In an illustrative example, when the bit segments  108  have been encoded to produce the payload sequences  112  before assigning the identifiers  116 , operation  118  can produce group assignments  120  that associate individual identifiers  116  with various groups of payload sequences  112 . In another illustrative example, when the bit segments  108  have not been encoded as nucleotides before operation  118 , operation  118  can produce group assignments  122  that associate individual identifiers  116  with various groups of the bit segments  108 . 
     In some implementations, the number of groups included in the group assignments  120 ,  122  can be based on a number of factors. For example, the number of group assignments produced can be based on a number of primers utilized in a polynucleotide data storage system and a number of polynucleotides stored together. In various implementations, the number of polynucleotides stored together can correspond to the number of polynucleotides stored in a container of the polynucleotide data storage system. In some implementations, the number of bit segments  108  or the number of payload sequences assigned to each group identifier  116  can be approximately the same. In an illustrative example, a polynucleotide data storage system can utilize a pool of 10,000 primers for the retrieval of data encoded by the polynucleotides of the polynucleotide data storage system and each container of the polynucleotide data storage system can store 1 million polynucleotides. In this illustrative example, the bit segments  108  or the payload sequences  112  can be divided into groups of about 10,000 in each group. Thus, in this example, the identifiers  116  can be associated with about 10,000 different polynucleotides stored in the polynucleotide data storage system. In other cases, the number of segments included in each group can be within a certain percentage of an average number. To illustrate, in a polynucleotide data storage system that utilizes a pool of 10,000 primers and includes a container that can store 1 million polynucleotides, an average number of segments that can be included in each group can be 10,000, but the number of segments included in each group can vary. In a particular illustrative example, the number of the bit segments  108  or the payload sequences  112  included in each group can be within a threshold amount of an average number. In some cases, the threshold amount can be a particular number, such as 100 bit segments  108  or payload sequences  112  greater than or less than the average number. In other cases, the number of the bit segments  108  or payload sequences  112  included in each group can be a percentage of the average number, such as within 10% of the average number. In particular implementations, the variation in the number of the bit segments  108  or the payload sequences  112  included in each group can correspond to minimizing differences between the rates of amplification when the groups are amplified together. 
     In various implementations, the identifiers  116  can be assigned to groups of bit segments  108  or groups of payload sequences  112  that correspond to different data files. In some situations, the polynucleotides associated with the different data files can be designated as being stored in a same container of a polynucleotide data storage system. For example, the digital data  104  being stored in a polynucleotide storage system can include bits from a number of different data files. The number of data files associated with a particular group of identifiers  116  can be based at least partly on the number of polynucleotides designated to be stored in a container of a polynucleotide data storage system and a number of polynucleotides utilized to encode the digital data of each file. Thus, if a container of a polynucleotide data storage system stores 1 million polynucleotides, the total number of polynucleotides encoding one or more data files will be less than or equal to 1 million. To illustrate, a first data file can be encoded by 600,000 polynucleotides stored in a container of the polynucleotide data storage system and a second data file can be encoded by 400,000 polynucleotides stored in the container of the polynucleotide data storage system. 
     In particular situations, a set of the identifiers  116  associated with a particular group of the bit segments  108  or a particular group of the payload sequences  112  can be different from additional sets of the identifiers  116  associated with other groups of the bit segments  108  or the payload sequences  112 . For example, a first set of the identifiers  116  can be associated with a first group of the bit segments  108  or a first group of the payload sequences  112  and a second, different set of the identifiers  116  can be associated with a second group of the bit segments  108  or a second group of the payload sequences  112 . In this way, a first set of primers corresponding to the first set of the identifiers  116  can be utilized to amplify a first group of polynucleotides associated with the first group of the bit segments  108  or the first group of the payload sequences  112  and a second set of the identifiers  116  can be utilized to amplify a second group of polynucleotides associated with the second group of the bit segments  108  or the second group of the payload sequences  112 . In various implementations, the first group of polynucleotides and the second group of polynucleotides can be stored in a same container of a polynucleotide data storage system. In these situations, the portions of the digital data  104  associated with the first group of polynucleotides can be selectively accessed using the first group of primers and not the second group of primers, while the portions of the digital data  104  associated with the second group of polynucleotides can be selectively accessed using the second group of primers and not the first group of primers. 
     In situations where the bit segments  108  have not been encoded as nucleotides before operation  118  takes place, the bit segments  108  can be encoded as nucleotides after the assigning of identifiers to the groups of bit segments that occurs at operation  118 . 
     At  124 , the process  100  includes generating polynucleotide data for a number of polynucleotide sequences. The polynucleotide data can be used as a template or design for synthesizing polynucleotide molecules that correspond to the polynucleotide data. The polynucleotide data can indicate a sequence of nucleotides that includes at least one region that encodes digital data. In an illustrative example, a representative polynucleotide sequence  126  can include a payload sequence  128  that encodes digital data  104 . The payload sequence  128  can be included in the payload sequences  112  generated as part of operation  110 . The polynucleotide sequence  126  can also include a group identifier region  130  that encodes one of the identifiers  116  that has been assigned to the payload sequence  126  at operation  118 . In some instances, the identifier  116  corresponding to the group identifier region  130  can be encoded as nucleotides according to the same scheme utilized to encode the bit segments  108  as the payload sequences  112 . In other situations, the identifier  116  corresponding to the group identifier region  130  can be encoded as nucleotides according to a different scheme than the scheme utilized to encode the bit segments  108  as the payload sequences  112 . Other information can also be encoded by the nucleotides of the polynucleotide sequence  126 . For example, error correction information can be encoded by one or more regions of the polynucleotide  126 . In another example, addressing information can be encoded by one or more regions of the polynucleotide  126 . The addressing information can indicate a location within the digital data  104  for the particular bits encoded by the payload region  128 . In additional examples, a file identifier corresponding to a data file that includes at least a portion of the digital data  104  can be encoded by nucleotides of one or more regions of the polynucleotide sequence  126 . In some implementations, the file identifier along with the identifiers of the respective groups can be utilized in the retrieval of the digital data  104 . After the polynucleotide data has been generated for each polynucleotide, the polynucleotide data can be provided to an oligonucleotide synthesizer to synthesize the physical polynucleotides corresponding to the polynucleotide data produced at  124 . 
       FIG. 2  shows a schematic diagram of a framework  200  to store polynucleotides that encode digital data of different data files. In particular, the framework  200  includes a first data file  202  and a second data file  204 . Although the illustrative example of  FIG. 2  includes two data files, more data files can be included in the framework  200 . Each data file  202 ,  204  can include digital data. The digital data of data files  202 ,  204  can be encoded using a number of polynucleotide sequences. For example, the first data file  202  can include first digital data that is encoded by a first group of polynucleotide sequences and the second data file  204  can include second digital data that is encoded by a second group of polynucleotide sequences. The number of polynucleotides sequences used to encode the digital data of the first data file  202  and the digital data of the second data file  204  can be different. In some cases, the number of polynucleotide sequences used to encode the digital data of the first data file  202  and the digital data of the second data file  204  can be based at least partly on the respective number of bits included in the first data file  202  and the second data file  204 . 
     The polynucleotide sequences that encode the digital data of the first data file  202  and the digital data of the second data file  204  can be arranged in a number of groups. The illustrative example of  FIG. 2  shows that the polynucleotide sequences encoding the digital data of the first data file  202  can be arranged into at least a first group  206  and a second group  208 . In addition, the illustrative example of  FIG. 2  shows that the polynucleotide sequences encoding the digital data of the second data file  204  can be arranged into at least a third group  210  and a fourth group  212 . Individual groups of polynucleotide sequences can include a particular number of polynucleotide sequences, such as representative polynucleotide sequence  214 . The representative polynucleotide sequence  214  can include at least a payload region. The representative polynucleotide sequence  214  can also include additional regions that encode other information, such as a region to encode the group identifier  216 , a region to encode addressing information, a region to encode an identifier of the first data file  202 , a region to encode error correction information, combinations thereof, and the like. In some implementations, the individual groups of polynucleotide sequences can include a same number of polynucleotide sequences. In other implementations, the individual groups of polynucleotide sequences can include a number of polynucleotide sequences in a specified range. In particular implementations, the specified range can indicate an average number of polynucleotide sequences to include in each group, a maximum threshold number above the average number, and a minimum threshold number below the average number. 
     Additionally, individual groups of polynucleotides can have a corresponding identifier. For example, the first group  206  can have a first identifier  216 , the second group  208  can have a second identifier  218 , the third group  210  can have a third identifier  220 , and the fourth group  212  can have a fourth identifier  222 . The identifiers  216 ,  218 ,  220 ,  222  can be represented by nucleotides included in one or more regions of the polynucleotide sequences associated with the respective groups  206 ,  208 ,  210 ,  212 . 
     In various implementations, the information associated with the first data file  202  and the second data file  204  can be stored in a data storage structure. For example, the information associated with the first data file  202  and the second data file  204  can be stored on one or more computer-readable media as a table, array, record, tree, linked list, or combinations thereof. To illustrate, the polynucleotide sequences of the first group  206  can be stored in association with the first identifier  216 , the polynucleotide sequences of the second group  208  can be stored in association with the second identifier  218 , the polynucleotide sequences of the third group  210  can be stored in association with the third identifier  220 , and the polynucleotide sequences of the fourth group  212  can be stored in association with the fourth identifier  222 . In some implementations, the first file  202  can be represented by a first file identifier and the information of the first data file  202  can be stored in association with the first file identifier and the second file  204  can be represented by a second file identifier and the information of the second data file  204  can be stored in association with the second file identifier. In particular implementations, the first file identifier and the second file identifier can be represented as respective polynucleotide sequences, as a series of bits, or both. In various implementations, the first data file  202  and the second data file  204  can be associated with multiple file identifiers. 
     In particular implementations, at least a portion of the information associated with the first data file  202  and the second data file  204  can be stored as metadata of the first data file  202  and metadata of the second data file  204 . The metadata can be utilized to selectively access the digital data encoded by the payload sequences of the groups corresponding to a particular data file. For example, a file identifier corresponding to the first data file  202  and the group identifiers corresponding to the first data file  202  (e.g., the first identifier  218  and the second identifier  220 ) can be utilized to access the digital data of the first data file  202 . In this way, file identifiers and group identifiers can be used in conjunction with one another to access digital data encoded by polynucleotides. 
     Additionally, at  224 , the framework  200  can include synthesizing polynucleotides. In particular, the polynucleotide sequences included in the groups  206 ,  208 ,  210 ,  212  can be a design template used to synthesize polynucleotide molecules. The polynucleotides represented by the polynucleotide sequences included in the groups  206 ,  208 ,  210 ,  212  can be stored together in a container  226 . In this way, the polynucleotides encoding digital data of different data files, such as polynucleotides encoding data of the first data file  202  and polynucleotides encoding data of the second data file  204 , can be stored in the same container  226 . 
     The framework  200  can also include a set of primers  228 . The set of primers  228  can include individual primers that have nucleotide sequences that are complementary to the group identifiers  216 ,  218  associated with the first data file  202  and the group identifiers  220 ,  222  associated with the second data file  204 . In particular illustrative examples, nucleotide sequences representing the group identifiers  216 ,  218 ,  220 ,  222  can serve as primer target regions of the polynucleotides stored in the container  226  and the set of primers  228  can include primers that are complementary to the polynucleotide sequences of the group identifiers  216 ,  218 ,  220 ,  222 . By storing the information of the first data file  202  and the second data file  204  according to the implementations described herein, the information associated with each data file  202 ,  204  can be accessed in the retrieval of digital data encoded by polynucleotides. For example, when information of the first data file  202  is requested, primers from the set of primers  228  that correspond to the group identifiers associated with the first data file  202  (e.g., the first group identifier  216  and the second group identifier  218 ) can be identified. To illustrate, primers included in the set of primers  228  that are complementary to the first group identifier  216  and the second group identifier  218  can be selected. The selected primers can then be added to a sample of the polynucleotides included in the container  226  or to the container  226  itself along with additional materials utilized to amplify the polynucleotides associated with the first data file  202 , such as PCR reagents that can include at least one polymerase, nucleotides, buffering agents, and the like. A sample of the amplification product can be sequenced and analyzed to reproduce the requested digital data of the first data file  202  in a manner that will be described in more detail with respect to  FIG. 3 . At least a portion of the set of primers  228  can be synthesized before receiving a request to obtain digital data from a data file  202 ,  204 , in some cases, while in other situations, at least a portion of the set of primers  228  can be synthesized after receiving a request to obtain digital data from a data file  202 ,  204 . 
     In some implementations, primers included in the set of primers  228  can also be complementary to file identifiers related to the first data file  202  and the second data file  204 . In various implementations, the polynucleotides that encode digital data of the first data file  202  and the second data file  204  can include sequences that correspond to file identifiers of the first data file  202  and the second data file  204 . In this way, the digital data of the first data file  202  and the second data file  204  that is encoded by polynucleotides can be selectively accessed by primers of the set of primers  228  that are complementary to both the file identifier sequences of the respective data files  202 ,  204  and the group identifiers  216 ,  218 ,  220 ,  220  of the data files  202 ,  204 . In a particular illustrative example, a polynucleotide encoding digital data of the first data file  202  can include a file identifier sequence adjacent to a group identifier sequence. Additionally, a primer of the set of primers  228  can have a sequence that is complementary to the file identifier sequence and the group identifier sequence or a sequence that is complementary to at least a portion of the file identifier sequence and at least a portion of the group identifier sequence. Continuing with this example, in response to a request for digital data included in the first data file  202 , this primer can be selected from the set of primers  228  to amplify the polynucleotide that encodes a portion of the digital data of the first data file  202 . 
       FIG. 3  shows a schematic representation of an example process  300  to design polynucleotides that can be used to store digital data and retrieve the digital data from a polynucleotide storage system. In particular implementations, the sequences of the polynucleotides can be designed by executing computer-readable instructions of one or more computer software applications. The polynucleotides can be designed using a number of payloads  302  and a number of group identifiers  304 . The number of payloads  302  can each encode data from one or more data files that include digital data. The group identifiers  304  can each correspond to a respective group of the payloads  302 . In addition, metadata  306  can be used to indicate relationships between the payloads  302 , the group identifiers  304 , and data files for which the payloads  302  encode digital data. In the illustrative example of  FIG. 3 , the metadata  306  indicates that a first payload (Payload  1 ) and a second payload (Payload  2 ) are both associated with a first group identifier (Group ID 1). Additionally, in the illustrative example of  FIG. 3 , the metadata  306  indicates that a third payload (Payload  3 ) is associated with a second group identifier (Group ID 2). Further, in the illustrative example of  FIG. 3 , the metadata  306  indicates that the first payload, the second payload, the third payload, the first group identifier, and the second group identifier are associated with the same data file (Data File 1). Thus, in this illustrative example, the first payload, the second payload, and the third payload include sequences of nucleotides that encode digital data from the first data file. Additionally, the payloads that encode the digital data of the first data file are divided into at least two groups: a first group corresponding to the first group identifier (Group ID 1) and a second group corresponding to the second group identifier (Group ID 2). 
     At  308 , the process  300  includes designing polynucleotide sequences. In particular, the polynucleotide sequences can be designed using individual payloads  302  and their corresponding group identifiers  304 . In a particular example, a representative polynucleotide sequence  310  can be designed with a payload  312  included in the payloads  302  and a group identifier  314  included in the group identifiers  304 . Thus, the polynucleotide sequence can include a payload region  316  that includes the payload  312 , a first group identifier region  318  that includes the group identifier  314 , and a second group identifier region  320  that includes the group identifier  314 . The first group identifier region  318  can be placed at a 5′ end of the polynucleotide sequence  310  and the second group identifier region  320  can be placed at a 3′ end of the polynucleotide sequence  310 . 
     In some implementations, additional nucleotides  322  can be included in an additional region  324  of the polynucleotide sequence  310 . In some examples, at least a portion of the additional region  324  can include nucleotides that encode a file identifier corresponding to the payload  312 , such as nucleotides that encode an identifier for Data File 1. In other examples, at least a portion of the additional region  324  can include nucleotides that encode addressing information that indicates a location of the bits encoded by the payload  312  within the digital data file. In another example, at least a portion of the additional region  324  can include nucleotides that encode error correction information. Although the position of the additional region  324  is shown between the first group identifier region  318  and the payload region  316 , the additional region  324  can be located at one or more different positions of the polynucleotide sequence  310 . 
     At  326 , the process  300  includes synthesizing polynucleotides and adding the polynucleotides to a polynucleotide storage system  328 . The polynucleotides can be synthesized using the polynucleotide sequences designed at  308 . Synthesizing the polynucleotides can include chemically bonding the nucleotides represented by the polynucleotide sequences, such as polynucleotide sequence  310 , together in a linear chain. In some implementations, the polynucleotides can be synthesized by producing reactive forms of the individual nucleotides to be included in the polynucleotides and blocking certain functional groups by adding blocking molecules to the functional groups that are to be blocked from participating in reactions between the nucleotides. The non-blocked functional groups can be used to chemically join the nucleotides and then the blocking molecules can be removed from the remaining functional groups. In some situations, reactivity of certain remaining functional groups can be reduced, such as through a capping process, and other processes, such as an oxidation process, can be performed to prepare the polynucleotides for storage. 
     The polynucleotide storage system  328  can include a number of containers, such as container  330 . Container  330  can include a medium  332  that stores a number of different polynucleotides. The medium  332  can include any medium that can maintain the chemical bonding and structure of polynucleotides over an extended period of time, such as several years, several decades, or longer. In some implementations, the medium  332  can include water. Additionally, in other implementations, the polynucleotide storage system  328  can store polynucleotides using a media free arrangement, such as storing dried polynucleotide pellets. 
     In some implementations, the container  330  can store multiple copies of a polynucleotide. Additionally, in various implementations, more than one of the containers of the polynucleotide storage system  328  can store a particular polynucleotide. To illustrate, the container  330  and an additional container  334  of the polynucleotide storage system  328  can each store separate copies of a particular polynucleotide. In particular implementations, the polynucleotides stored in the polynucleotide storage system  328  can be stored according to the group identifiers of the polynucleotides. For example, a first number of polynucleotides that correspond to a first set of the group identifiers  304  can be stored in a first container of the polynucleotide storage system  328  and a second number of polynucleotides that correspond to a second set of the group identifiers  304  can be stored in a second container of the polynucleotide storage system  328 . Also, the polynucleotides that encode data of a particular data file can be stored together. For example, the polynucleotides that encode the digital data for the Data File 1 can be stored in a particular container of the polynucleotide storage system  328 , such as the container  330 . Further, polynucleotides that encode digital data for multiple data files can be stored in a particular container. To illustrate, the container  330  can store polynucleotides of multiple data files, including the polynucleotides of the Data File 1. 
     The polynucleotides stored in individual containers of the polynucleotide storage system  328 , the group identifiers of polynucleotides stored in individual containers of the polynucleotide storage system  328 , and/or the file identifiers related to polynucleotides stored in individual containers of the polynucleotide storage system  328  can be tracked and recorded. In this way, additional metadata can be generated that indicates the polynucleotides stored in the individual containers of the polynucleotide storage system  328 . For example, additional metadata of the polynucleotide storage system  328  can indicate that polynucleotides associated with the first group identifier (Group ID 1), the second group identifier (Group ID 2), or both, are stored in the container  330 . In other examples, additional metadata of the polynucleotide storage system  328  can indicate that polynucleotides associated with the first data file (Data File 1) are stored in the container  330 . 
     At  336 , the process  300  includes receiving a request for digital data. The request for digital data can be received from a computing device, such as computing device  338 . After receiving the request for the digital data, the one or more polynucleotides that correspond to the digital data can be determined using a lookup table or other data structure that indicates the polynucleotides that encode the requested digital data. For example, the metadata  306  can be accessed and parsed to identify information for a data file being requested and the metadata  306  can be utilized to determine group identifiers and/or at least one file identifier for the data file. The group identifiers can correspond with primers that can be used to amplify and replicate the polynucleotides stored by the polynucleotide storage system  328 . The primers that correspond to the group identifiers for one or more data files that include digital data being requested can be included in a set of primers  340 . In some implementations, the primers used to replicate and amplify the polynucleotides stored by the polynucleotide storage system  328  can be at least partially complementary to the group identifiers of the polynucleotides stored by the polynucleotides storage system  328 . In some cases, the nucleotides included in at least a threshold number of positions of the primers included in the set of primers  340  can be complementary to at least a threshold number of positions of the group identifier regions associated with polynucleotides stored by the polynucleotide storage system  328 . In this way, the primers of the set of primers  340  that correspond to the group identifiers of the requested digital data can be used to selectively amplify the polynucleotides that correspond to the digital data being requested. In various implementations, primers that correspond to a file identifier, as well as the group identifiers, can also be utilized to amplify the polynucleotides that encode requested digital data. 
     At  342 , the process  300  can include amplification of polynucleotides corresponding to the requested digital data using primers of the set of primers  340  that correspond to the group identifiers and/or at least one file identifier associated with a data file that includes the digital data being requested. Amplification of the polynucleotides can produce an amplification product. At  342 , the process  300  can also include, sequencing of the polynucleotides included in the amplification product and decoding the polynucleotides of the amplification product. In some implementations, the primers and enzymes used to selectively amplify the polynucleotides corresponding to the requested digital data can be added to one or more containers of the data storage system  328  or to one or more other containers outside of the polynucleotide storage system  328  that include the polynucleotides that correspond to the requested digital data. 
     In an illustrative example, PCR can be used to amplify the polynucleotides that correspond to the requested digital data. PCR can also be utilized during the sequencing of the polynucleotides. A PCR reaction has three main components: the template, the primers, and enzymes. The template is a single- or double-stranded molecule containing the (sub)sequence of nucleotides to be amplified. The primers are short synthetic strands that define the beginning and end of the region to be amplified. The enzymes include polymerases and thermostable polymerases such as DNA polymerase, RNA polymerase and reverse transcriptase. The enzymes create double-stranded polynucleotides from a single-stranded template by “filling in” complementary nucleotides one by one through addition of nucleoside triphosphates, starting from a primer bound to that template. PCR happens in “cycles,” each of which doubles the number of templates in a solution. The process can be repeated until the desired number of copies is created. 
     A variety of PCR techniques are known and can be used in the implementations described herein. PCR techniques are typically used for the amplification of at least a portion of a polynucleotide. The sample to be amplified is contacted with the first and second primers; a nucleic acid polymerase; and nucleotide triphosphates corresponding to the nucleotides to be added during PCR. Natural nucleotide triphosphates can include dATP, dCTP, dGTP, dTTP, and dUTP. Nucleoside triphosphates of non-standard nucleotides can also be added, if desired or needed. Suitable polymerases for PCR are known and include, for example, thermostable polymerases such as native and altered polymerases of  Thermus  species, including, but not limited to  Thermus aquaticus  (Taq),  Thermus flavus  (Tfl), and  Thermus thermophilus  (Tth), as well as the Klenow fragment of DNA polymerase I and the HIV-1 polymerase. 
     An additional type of PCR is Droplet Digital™ PCR (ddPCR™) (Bio-Rad Laboratories, Hercules, Calif.). ddPCR technology uses a combination of microfluidics and surfactant chemistry to divide PCR samples into water-in-oil droplets. The droplets support PCR amplification of the target template nucleotides they contain and use reagents and workflows similar to those used for most standard Taqman probe-based assays. Following PCR, each droplet is analyzed or read in a flow cytometer to determine the fraction of PCR-positive droplets in the original sample. These data are then analyzed using Poisson statistics to determine the target concentration in the original sample. See Bio-Rad Droplet Digital™ (ddPCR™) PCR Technology. 
     While ddPCR™ is one PCR approach, other sample partition PCR methods based on the same underlying principles may also be used. The partitioned nucleotides of a sample can be amplified by any suitable PCR methodology that can be practiced within spdPCR. Illustrative PCR types include allele-specific PCR, assembly PCR, asymmetric PCR, endpoint PCR, hot-start PCR, in situ PCR, intersequence-specific PCR, inverse PCR, linear after exponential PCR, ligation-mediated PCR, methylation-specific PCR, miniprimer PCR, multiplex ligation-dependent probe amplification, multiplex PCR, nested PCR, overlap-extension PCR, polymerase cycling assembly, qualitative PCR, quantitative PCR, real-time PCR, single-cell PCR, solid-phase PCR, thermal asymmetric interlaced PCR, touchdown PCR, universal fast walking PCR, etc. Ligase chain reaction (LCR) can also be used. 
     Emulsion PCR can also be utilized in the implementations described herein. Emulsion PCR includes providing a water-in-oil emulsion that includes reagents used during the PCR process, such as a polymerase, primers, buffers, and the like. As the PCR process takes place, strands of the polynucleotides are replicated within the oil droplets using a polymerase and then denatured. The process continues for multiple cycles with replication of the new single stranded polynucleotides taking place within the droplets. The polynucleotides that have been produced during emulsion PCR can be recovered after breaking the emulsion and performing one or more separation processes. In some cases, beads can be used in emulsion PCR where polynucleotides bind to the surface of the beads within the emulsion and the replication of the polynucleotides takes place on the surface of the beads. 
     The amplification of polynucleotides can be performed using a thermocycler. A thermocycler (also known as a thermal cycler, PCR machine, or DNA amplifier) can be implemented with a thermal block that has holes where tubes holding an amplification reaction mixture can be inserted. The term “amplification reaction mixture” can refer to an aqueous solution comprising the various reagents used to amplify a target nucleic acid. The thermocycler can then raise and lower the temperature of the block in discrete, pre-programmed steps. Other implementations can utilize a miniaturized thermocycler in which the amplification reaction mixture moves via a channel through hot and cold zones on a microfluidic chip. 
     After the amplification process, one or more samples of the amplification product can be extracted and sequenced by a sequencing machine. The sequencing machine can provide raw sequence data output referred to herein as reads. Each position in a read is an individual nucleotide determined by the sequencing machine based on properties of the nucleotides sensed by components of the sequencing machine. A read can represent a determination of which of the four nucleotides—A, G, C, and T (or U)—in a strand of DNA (or RNA) is present at a given position in the sequence. The sequencing machine can produce polynucleotide data  344  that corresponds to the sequences of the polynucleotides read by the sequencing machine. The polynucleotide data  344  can be decoded using a reverse process that was used to encode the original digital data to produce a bit string  346  that corresponds to the original digital data being requested. The bit string  346  can be provided to the computing device  338  in response to the request for the digital data. 
       FIG. 4  shows a block diagram of an example system  400  including at least one computing device  402  to produce a framework for designing polynucleotides that encode digital data and retrieving the digital data from the polynucleotides. The computing device  402  can be implemented with one or more processing unit(s)  404  and memory  406 , both of which can be distributed across one or more physical or logical locations. For example, in some implementations, the operations described as being performed by the computing device  402  can be performed by multiple computing devices. In some cases, the operations described as being performed by the computing device  402  can be performed in a cloud computing architecture. 
     The processing unit(s)  404  can include any combination of central processing units (CPUs), graphical processing units (GPUs), single core processors, multi-core processors, application-specific integrated circuits (ASICs), programmable circuits such as Field Programmable Gate Arrays (FPGA), and the like. In one implementation, one or more of the processing units(s)  404  can use Single Instruction Multiple Data (SIMD) parallel architecture. For example, the processing unit(s)  404  can include one or more GPUs that implement SIMD. One or more of the processing unit(s)  404  can be implemented as hardware devices. In some implementations, one or more of the processing unit(s)  404  can be implemented in software and/or firmware in addition to hardware implementations. Software or firmware implementations of the processing unit(s)  404  can include computer- or machine-executable instructions written in any suitable programming language to perform the various functions described. Software implementations of the processing unit(s)  404  may be stored in whole or part in the memory  406 . 
     Alternatively, or additionally, the functionality of computing device  402  can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), Application-specific Integrated Circuits (ASICs), Application-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), etc. 
     Memory  406  of the computing device  402  can include removable storage, non-removable storage, local storage, and/or remote storage to provide storage of computer-readable instructions, data structures, program modules, and other data. The memory  406  can be implemented as computer-readable media. Computer-readable media includes at least two types of media: computer-readable storage media and communications media. Computer-readable storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data. Computer-readable storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computing device. 
     In contrast, communications media can embody computer-readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transmission mechanism. As defined herein, computer-readable storage media and communications media are mutually exclusive. 
     The computing device  402  can include and/or be coupled with one or more input/output devices  408  such as a keyboard, a pointing device, a touchscreen, a microphone, a camera, a display, a speaker, a printer, and the like. Input/output devices  408  that are physically remote from the processing unit(s)  404  and the memory  406  can also be included within the scope of the input/output devices  408 . 
     Also, the computing device  402  can include a network interface  410 . The network interface  410  can be a point of interconnection between the computing device  402  and one or more networks  412 . The network interface  410  can be implemented in hardware, for example, as a network interface card (NIC), a network adapter, a LAN adapter or physical network interface. The network interface  410  can be implemented in software. The network interface  410  can be implemented as an expansion card or as part of a motherboard. The network interface  410  can implement electronic circuitry to communicate using a specific physical layer and data link layer standard, such as Ethernet or Wi-Fi. The network interface  410  can support wired and/or wireless communication. The network interface  410  can provide a base for a full network protocol stack, allowing communication among groups of computers on the same local area network (LAN) and large-scale network communications through routable protocols, such as Internet Protocol (IP). 
     The one or more networks  412  can include any type of communications network, such as a local area network, a wide area network, a mesh network, an ad hoc network, a peer-to-peer network, the Internet, a cable network, a telephone network, a wired network, a wireless network, combinations thereof, and the like. 
     A device interface  414  can be part of the computing device  402  that provides hardware to establish communicative connections to other devices, such as a sequencer  416 , a polynucleotide synthesizer  418 , etc. The device interface  414  can also include software that supports the hardware. The device interface  414  can be implemented as a wired or wireless connection that does not cross a network. A wired connection may include one or more wires or cables physically connecting the computing device  402  to another device. The wired connection can be created by a headphone cable, a telephone cable, a SCSI cable, a USB cable, an Ethernet cable, FireWire, or the like. The wireless connection may be created by radio waves (e.g., any version of Bluetooth, ANT, Wi-Fi IEEE 802.11, etc.), infrared light, or the like. 
     The computing device  402  can include multiple modules that may be implemented as instructions stored in the memory  406  for execution by processing unit(s)  404  and/or implemented, in whole or in part, by one or more hardware logic components or firmware. The memory  406  can be used to store any number of functional components that are executable by the one or more processing units  404 . In many implementations, these functional components can comprise instructions or programs that are executable by the one or more processing units  404  and that, when executed, implement operational logic for performing the operations attributed to the computing device  402 . Functional components of the computing device  402  that can be executed on the one or more processing units  404  for implementing the various functions and features related to generating polynucleotide sequences for the storage and retrieval of digital data, as described herein, include a digital data encoding module  420 , a polynucleotide group formation module  422 , a polynucleotide design module  424 , and a digital data retrieval module  426 . One or more of the modules,  420 ,  422 ,  424 ,  426  can be used to implement process  100  or framework  200 , and at least a portion of the process  300  of  FIG. 1 ,  FIG. 2 , and  FIG. 3 . 
     The digital data encoding module  420  can include computer-readable instructions that are executable by the processing unit(s)  404  to encode digital data as a sequence of nucleotides. The digital data encoding module  420  can obtain digital data from one or more sources. In some cases, the digital data can also be stored by the memory  406 . Also, the digital data can be stored by a data storage device coupled to, or otherwise accessible to, the computing device  402 . The digital data can be related to image content, video content, text content, audio content, combinations thereof, and so forth. The digital data can include a bit string comprised of 1s and 0s. In some cases, the digital data can be included in a data file. 
     The digital data encoding module  420  can encode the 1s and 0s of the digital data as a sequence of nucleotides, such as A, T, G, C, or U. In particular implementations, each 1 or 0 of the digital data can be encoded as a particular nucleotide. In some cases, groups of 1s and groups of 0s of the digital data can be encoded as a particular nucleotide. In various implementations, the 1s and 0s of the digital data can be converted to a number in a number system other than base-2 before encoding. For example, the 1s and 0s of the digital data can be converted to a base-3 format or a base-4 format before encoding. 
     In illustrative implementations, the digital data encoding module  420  can encode the 1s and 0s of the digital data according to a binary encoding scheme. For example, the digital data encoding module  420  can encode the series of bits 00 as a first nucleotide (e.g., A), the series of bits 01 as a second nucleotide (e.g., T), the series of bits 10 as a third nucleotide (e.g., G), and the series of bits 11 as a fourth nucleotide (e.g., C). 
     In other illustrative implementations, the digital data encoding module  420  can encode the 1s and 0s of the digital data according to a ternary encoding scheme. For example, the digital data encoding module  420  can convert the 1s and 0s of the digital data to modified digital data comprising 0s, 1s, and 2s. Subsequently, the digital data encoding module  420  can encode the 0s, 1s, and 2s of the modified digital data as nucleotides. In some implementations, the data encoding module  420  can encode the 0s, 1s, and 2s of the modified digital data as nucleotides according to a preceding nucleotide in the sequence of nucleotides. To illustrate, a 0 preceded by G could be encoded as T, while a 0 preceded by A could be encoded as C. 
     In additional illustrative implementations, the digital data encoding module  420  can encode the 1s and 0s of the digital data according to a base-4 encoding scheme. In an example, the digital data encoding module  420  can convert the 1s and 0s of the digital data to modified digital data comprising 0s, 1s, 2s, and 3s. In these situations, when 4 nucleotides are used to encode the digital data, each type of nucleotide being used to do the encoding can correspond with a respective base-4 number. Thus, in a particular illustrative example, 0 can correspond with A, 1 can correspond with T, 2 can correspond with G, and 3 can correspond with C. 
     In some cases, the length of the sequences of nucleotides encoding the digital data can be limited. For example, if the length of the sequence of nucleotides encoding the digital data is greater than a particular number of nucleotides, the sequence can become unstable and/or otherwise lose its linear arrangement, such as by forming secondary structures. In illustrative implementations, the sequences of nucleotides used to encode digital data can have from 60 to 300 nucleotides, from 80 to 150 nucleotides, from 90 to 120 nucleotides, or from 100 to 140 nucleotides. In situations where multiple sequences are used to encode the digital data, the digital data encoding module  420  can divide the bits of the digital data into segments. The digital data encoding module  420  can encode each of the segments of the digital data as a separate sequence of nucleotides. In some cases, the segments can be the same length, while in other situations, the segments can have varying lengths. In implementations where the segments have different lengths, the length of the segments can be within a range of lengths. The range of lengths can be based at least partly on a probability that polynucleotides may lose a linear structure when the length is greater than an upper threshold length or when the length is less than a lower threshold length. 
     The polynucleotide group formation module  422  can include computer-readable instructions that, when executed by the processing unit(s)  404 , can arrange polynucleotides that encode digital data into a number of groups. The polynucleotide group formation module  422  can also determine identifiers for each of the groups. In some instances, the group identifiers can be utilized to determine a data file that includes digital data being encoded by polynucleotides of one or more groups. For example, the polynucleotide group formation module  422  can assign one or more group identifiers to respective groups that include the polynucleotides that encode digital data of a data file. The polynucleotide group formation module  422  can also generate metadata that indicates the group identifiers that correspond to the data file. 
     In addition, the polynucleotide group formation module  422  can determine a quantity of polynucleotides to include in individual groups. For example, the polynucleotide group formation module  422  can determine a number of individual polynucleotides to include in individual groups. In some cases, the quantity of polynucleotides included in individual groups can be a range having an upper threshold and a lower threshold. In particular implementations, the quantity of polynucleotides included in individual groups can be within a range of a specified average number of polynucleotides to include in individual groups. 
     In some implementations, the polynucleotide group formation module  422  can determine that a number of polynucleotides included in a group is less than a threshold number of polynucleotides. In situations where the number of polynucleotides included in individual groups is the same number, the polynucleotide group formation module  422  can determine that the quantity of polynucleotides included in a group is less than the number specified for each individual group. Additionally, in implementations where individual groups include a quantity of polynucleotides within a specified range, the polynucleotide group formation module  422  can determine that the quantity of polynucleotides included in a group is less than a lower threshold of the range. 
     Based at least partly on determining that the quantity of polynucleotides included in a group is less than a threshold number, the polynucleotide group formation module  422  can generate sequences of filler polynucleotides for the group. The quantity of filler polynucleotides for the group can bring the total number of polynucleotides for the group to at least the threshold number. For example, the quantity of polynucleotides of individual groups can be specified as 9,000 to 11,000 and a particular group may have 8,500 polynucleotides. In this situation, the polynucleotide group formation module  422  can generate at least 500 filler polynucleotides to include in the group such that the total number of polynucleotides for the group is at least 9,000. In another example, the quantity of polynucleotides of individual groups can be specified as 10,000 and a particular group may have 9,750 polynucleotides. Continuing with this example, the polynucleotide group formation module  422  can generate 250 filler polynucleotides to bring the total number of polynucleotides included in the group up to 10,000. 
     The polynucleotide group formation module  422  can generate additional metadata that tracks the filler polynucleotides added to one or more groups. To illustrate, the polynucleotide group formation module  422  can generate additional metadata indicating the sequences of the filler polynucleotides that are included in particular groups. In this way, the additional metadata can be used to identify filler polynucleotides that can be removed during the decoding of polynucleotides when digital data is requested that is encoded by the other, non-filler, polynucleotides included in the group. In other implementations, the polynucleotide group formation module  422  can generate one or more sequences of nucleotides that indicates polynucleotides that are filler polynucleotides. Thus, polynucleotides that are decoded that include a sequence of nucleotides specifying a filler polynucleotide may be removed from consideration when reconstructing digital data from other polynucleotides included in the group. 
     The polynucleotide design module  424  can include computer-readable instructions that, when executed by the processing unit(s)  404 , generate polynucleotide data that correspond to polynucleotides that encode digital data. The polynucleotide design module  424  can utilize data corresponding to payloads produced by the digital data encoding module  420  to generate the polynucleotide data. The polynucleotide design module  424  can also utilize data corresponding to group identifiers associated with the payloads to generate polynucleotide data. Additionally, the polynucleotide design module  424  can utilize data corresponding to file identifiers associated with the payloads to generate polynucleotide data. 
     The polynucleotide design module  424  can also produce data corresponding to polynucleotide sequences that include nucleotides in addition to the nucleotides comprising the group identifiers and payloads. For example, the polynucleotide design module  424  can include nucleotides in a polynucleotide sequence that correspond with addressing information for the payload. In situations where a string of bits is divided into a number of segments before being encoded as a sequence of nucleotides, addressing information can indicate the segment of the bit string that is being encoded by a particular payload sequence and the location of the segment within the bit string. The polynucleotide design module  424  can generate one or more nucleotides that encode the addressing information and add the nucleotides encoding the addressing information into a polynucleotide sequence. The group identifiers can also include nucleotides that correspond to a key that can be used to retrieve the digital data encoded by a payload of a polynucleotide. The polynucleotide design module  424  can also add nucleotides to a polynucleotide sequence that correspond to error correction information. Further, the polynucleotide design module  424  can add nucleotides to a polynucleotide sequence that correspond to a file identifier. 
     The polynucleotide data generated by the polynucleotide design module  424  can be used to synthesize molecules that include the polynucleotide sequences designed by the polynucleotide design module  424 . In some implementations, the polynucleotide design module  424  can communicate polynucleotide data corresponding to the polynucleotide sequences to one or more devices, such as a polynucleotide synthesizer  418 , used to synthesize the polynucleotides. For example, the polynucleotide design module  424  can communicate polynucleotide data to a service provider that synthesizes polynucleotides via the one or more networks  412 . In another example, the polynucleotide design module  424  can communicate polynucleotides to a device that synthesizes polynucleotides via the one or more networks  412  and/or to one or more devices (e.g., synthesizer  418 ) via the device interface  414 . 
     The digital data retrieval module  426  can receive the sequences of the polynucleotides from one or more devices, such as sequencer  416 , and decode the polynucleotides using a reverse process from the encoding performed by the digital data encoding module  420 . For example, in implementations where 00 in a string of bits is encoded as A, the digital data retrieval module  426  can decode each A in the polynucleotide sequences as 00. The digital data retrieval module  426  can reproduce the bit string of the digital data being requested and provide the bit string to one or more devices that requested the digital data. 
     The digital data retrieval module  426  can communicate with one or more devices, such as via the device interface  414 , to request the polynucleotides that correspond to the group identifiers. In some implementations, the one or more devices in communication with the digital data retrieval module  426  can be coupled to, or otherwise associated with, a polynucleotide data storage system. In various implementations, the digital data retrieval module  426  can provide to another computing device the group identifiers and/or at least one file identifier associated with the requested digital data to a computing device that can determine primers to be used to amplify the polynucleotides of the groups. In addition, the digital data retrieval module  426  can access metadata indicating a storage location (e.g., one or more container identifiers) within a polynucleotide storage system that store polynucleotides that correspond to the requested digital data. In particular implementations, the storage location can be identified based at least partly on matching the group identifiers associated with the requested digital data with the group identifiers associated with the containers of the polynucleotide data storage system. In some implementations, the digital data retrieval module  426  can provide the information regarding the primers used to amplify the polynucleotides corresponding to the requested digital data and/or the information regarding the storage location of the polynucleotides corresponding to the requested digital data to one or more additional computing devices, such as a computing device coupled with a polynucleotide data storage system. 
     The digital data retrieval module  426  can receive the sequences of the polynucleotides from one or more devices, such as device  416 , and decode the polynucleotides using a reverse process from the encoding performed by the digital data encoding module  420 . For example, in implementations where 00 in a string of bits is encoded as A, the digital data retrieval module  426  can decode each A in the polynucleotide sequences as 00. The digital data retrieval module  426  can reproduce the bit string of the digital data being requested and provide the bit string to one or more devices that requested the digital data. 
     In some implementations, the digital data retrieval module  426  can identify filler polynucleotides that are to be removed during the decoding process. In some cases, the filler polynucleotides can be identified by the digital data retrieval module  426  comparing sequence data received from the sequencer to additional sequences included in metadata that indicate the filler polynucleotides. Based on the comparison, the digital data retrieval module  426  can determine polynucleotide sequences included in the sequencing data that correspond to filler polynucleotides and refrain from decoding the sequences of the filler polynucleotides. In other cases, the filler polynucleotides can be identified based at least partly on analyzing particular regions of polynucleotide sequences included in the sequencing data that indicate filler polynucleotides. 
       FIG. 5  is a flow diagram of an example process  500  to produce a framework that encodes digital data using polynucleotides and arranges the polynucleotides of an individual data file into a number of groups. The operations illustrated in the example flow diagram of  FIG. 5  can be implemented in hardware, software, or a combination thereof. In the context of software, the blocks can represent computer-executable instructions stored on one or more computer-readable media that, when executed by one or more processors, perform the operations recited in the blocks of the example flow diagram. The order in which the operations are described should not be construed as a limitation. Any number of the described blocks can be combined in any order and/or in parallel to implement the process  500 , or alternative processes, and not all of the blocks need be executed. 
     At  502 , the process  500  includes encoding digital data as nucleotides. The digital data can be associated with a plurality of data files. The digital data can be encoded according to an encoding scheme such that one or more bits of the digital data are encoded by at least one nucleotide. In some cases, the encoding of the digital data can produce payload sequences with individual payload sequences encoding a group of bits included in a digital data file. In particular implementations, a plurality of groups of bits can be produced from a string of bits of a data file using a segmentation process. The segmentation process can produce payload sequences that each have a length that is included in a particular range, such as 60 to 300 nucleotides, 50 to 150 nucleotides, or 75 to 125 nucleotides. 
     At  504 , the process  500  includes determining a number of groups of payload sequences that encode digital data for the data files. In particular, the payload sequences associated with each data file can be divided into a number of groups. Accordingly, a subset of the payload sequences of a data file can be included in an individual group. In an illustrative example, a first portion of the payload sequences of a data file can comprise a first group of payload sequences and a second portion of the payload sequences of the data file can comprise a second group of the payload sequences. The number of groups for each data file can differ based on the amount of digital data included in the data file. The quantity of payload sequences included in each group can be somewhat uniform. That is, in some cases, the quantity of payload sequences included in each group can be a same number of payload sequences (e.g., 10,000 payload sequences per group). In other situations, the quantity of payload sequences in each group can fall within a specified range. To illustrate, each group of payload sequences for each of the data files that have been encoded using nucleotides can include from 9,000 to 11,000 payload sequences. 
     At  506 , the process  500  includes determining identifiers for the groups of payload sequences. The identifiers can include a sequence of nucleotides. In some cases, the sequences of the identifiers can represent alphanumeric symbols associated with the individual identifiers. An individual identifier can be assigned to an individual group of payload sequences. In this way, each payload sequence included in a particular group of payload sequences is associated with the same group identifier. Additionally, each data file can be associated with a number of identifiers that correspond to the groups of payload sequences that encode the digital data of the individual data files. In some cases, each data file can also be associated with at least one file identifier that can also be used to identify the polynucleotide sequences used to encode digital data of the data file. 
     At  508 , the process  500  includes generating polynucleotide data based at least partly on the payload sequences and the group identifiers. In particular implementations, the polynucleotide data can include polynucleotide sequences that include a payload sequence and at least one group identifier sequence. For polynucleotide sequences that include payload sequences that have been grouped together, these polynucleotide sequences can each include the same group identifier sequence with differing payload sequences. In some examples, the polynucleotide data sequences represented by the polynucleotide data can also include a file identifier. In this way, each polynucleotide sequence encoding digital data from a same data file can include a file identifier sequence in addition to a group identifier sequence and a payload sequence. 
     At  510 , the process  500  can include generating metadata for polynucleotide sequences that encode digital data. The metadata can be included in one or more additional data files and indicate the correlations between the group identifiers and the data files associated with the various group identifiers. For example, the metadata can indicate the plurality of group identifiers that are associated with polynucleotide sequences that encode digital data for individual data files. To illustrate, the metadata can indicate a first group of identifiers associated with a first group of polynucleotide sequences that encode digital data of a first data file and a second group of identifiers associated with a second group of polynucleotide sequences that encode digital data of a second data file. In some implementations, the metadata can also indicate a location within a polynucleotide data storage system where polynucleotides that encode digital data for individual data files are stored. In an illustrative example, the metadata can indicate one or more container identifiers corresponding to one or more containers of a polynucleotide data storage system that store polynucleotides encoding the digital data of a particular data file. 
     In some implementations, the metadata can be accessed in conjunction with a request to retrieve digital data encoded by polynucleotides. For example, a request for digital data included in a data file can cause the metadata to be accessed by a processor and the metadata can be parsed to identify information about the data file included in the metadata. In particular implementations, the metadata can be accessed to determine the group identifiers that are associated with the polynucleotide sequences that encode the digital data of the data file. In some cases, the metadata can also be accessed to determine at least one file identifier associated with the polynucleotide sequences that encode the digital data of the data file. The group identifiers can be used to identify primers that can selectively amplify the polynucleotides that encode the digital data of the data file. Additionally, the metadata can be accessed to determine a storage location within a polynucleotide data storage system of the polynucleotide molecules that encode the digital data of the data file. In various implementations, portions of the metadata, such as the group identifiers, at least one file identifier, and one or more storage locations within the polynucleotide data storage system, can be sent to other devices. In this way, the metadata can be used in other processes used in the retrieval of digital data stored by polynucleotides, such as the amplification of the polynucleotides that encode the digital data of the requested data file. 
     Illustrative Embodiments 
     The following clauses described multiple possible embodiments for implementing the features described in this disclosure. The various embodiments described herein are not limiting nor is every feature from any given embodiment required to be present in another embodiment. Any two or more of the embodiments may be combined together unless context clearly indicates otherwise. As used herein in this document “or” means and/or. For example, “A or B” means A without B, B without A, or A and B. As used herein, “comprising” means including all listed features and potentially including addition of other features that are not listed. “Consisting essentially of” means including the listed features and those additional features that do not materially affect the basic and novel characteristics of the listed features. “Consisting of” means only the listed features to the exclusion of any feature not listed. 
     The following clauses described multiple possible embodiments for implementing the features described in this disclosure. The various embodiments described herein are not limiting nor is every feature from any given embodiment required to be present in another embodiment. Any two or more of the embodiments may be combined together unless context clearly indicates otherwise. As used herein in this document “or” means and/or. For example, “A or B” means A without B, B without A, or A and B. As used herein, “comprising” means including all listed features and potentially including addition of other features that are not listed. “Consisting essentially of” means including the listed features and those additional features that do not materially affect the basic and novel characteristics of the listed features. “Consisting of” means only the listed features to the exclusion of any feature not listed. 
     Clause A. A method comprising: encoding a series of bits as a plurality of polynucleotide sequences; producing a plurality of group identifiers that includes a particular group identifier; dividing the plurality of polynucleotides sequences into a plurality of groups of polynucleotide sequences such that a quantity of individual polynucleotide sequences included in individual groups of polynucleotide sequences of the plurality of groups of polynucleotide sequences is within a range having an upper threshold and a lower threshold; assigning the particular group identifier to a particular group of polynucleotide sequences included in the plurality of groups of polynucleotide sequences; and generating polynucleotide sequence data that includes a polynucleotide sequence of the particular group of polynucleotide sequences as a payload region and the particular group identifier as a group identifier region. 
     Clause B. The method of clause A, further comprising assigning an additional group identifier of the plurality of group identifiers to an additional group of polynucleotide sequences included in the plurality of groups of polynucleotide sequences, the additional group of polynucleotide sequences including a quantity of additional polynucleotide sequences that is within the upper threshold and the lower threshold. 
     Clause C. The method of clause B, wherein the series of bits comprises digital data of a data file; the plurality of polynucleotide sequences encode the digital data of the data file, and the polynucleotide sequence data includes a file identifier sequence that encodes a file identifier of the data file. 
     Clause D. The method of clause A, further comprising: synthesizing a polynucleotide based at least partly on the polynucleotide sequence data; and storing the polynucleotide in a container of a polynucleotide data storage system. 
     Clause E. The method of clause D, wherein the series of bits comprises digital data of a data file; and the method further comprises: receiving a request for the digital data of the data file; selecting a primer that corresponds to nucleotides of the group identifier region; amplifying, using the primer, the polynucleotide to produce an amplification product; sequencing the amplification product to produce sequencing data that includes at least one polynucleotide sequence; and decoding the at least one polynucleotide sequence. 
     Clause F: The method of clause E, wherein: the polynucleotide sequence data includes a file identifier region that encodes a file identifier of the data file; and the primer also corresponds to at least a portion of the nucleotides of the file identifier region. 
     Clause G: The method of clause F, wherein the file identifier region is adjacent to the group identifier region. 
     Clause H. A method comprising: dividing a string of bits into bit segments, the string of bits being associated with a data file; determining a plurality of groups of the bit segments with each group of the plurality of groups including a same quantity of individual bit segments; assigning a group identifier to a group of bit segments of the plurality of groups of the bit segments; generating payload data indicating a payload sequence that encodes a bit segment of the group of bit segments as a sequence of nucleotides; and generating polynucleotide sequence data indicating a polynucleotide sequence that includes the payload sequence and a group identifier sequence that corresponds to the group identifier. 
     Clause I. The method of clause H, wherein the group identifier is one of a plurality of group identifiers that are assigned to individual bit segment groups of the plurality of groups of the bit segments. 
     Clause J. The method of clause I, further comprising: synthesizing a set of primers with individual primers of the set of primers being at least partially complementary to individual group identifier sequences that correspond to individual group identifiers of the plurality of group identifiers; receiving a request to obtain digital data of the data file; and amplifying polynucleotides that encode the string of bits utilizing at least a portion of the primers included in the set of primers. 
     Clause K. The method of clause J, wherein the same quantity of individual bit segments is based at least partly on a number of the primers included in the set of primers and a quantity of polynucleotides stored in a container of a polynucleotide data storage system, the container storing at least the polynucleotides that encode the string of bits. 
     Clause L. The method of clause H, further comprising: storing polynucleotides that encode the string of bits in a container of a polynucleotide data storage system; producing additional polynucleotides that encode an additional string of bits of an additional data file; storing the additional polynucleotides in the container; receiving a request to obtain digital data of the data file; identifying a number of primers that correspond to a set of group identifiers encoded by the polynucleotides; and amplifying the polynucleotides using the number of primers. 
     Clause M. The method of clause L, wherein identifying the number of primers that correspond to the set of group identifiers includes: accessing metadata indicating individual sets of group identifiers that correspond to individual data files; and determining, based at least partly on the metadata, that the set of group identifiers corresponds to the data file. 
     Clause N. The method of clause H, wherein the same quantity of individual bit segments includes a range having an upper threshold number and a lower threshold number. 
     Clause O. The method of clause N, further comprising: identifying an additional group of the bit segments that includes less than the lower threshold number; generating data indicating a plurality of polynucleotide sequences that encode the additional group of bit segments; and generating additional data indicating a number of filler polynucleotide sequences that do not encode the additional group of bit segments, wherein the number of filler polynucleotide sequences and a number of the additional group of bit segments sum to at least the lower threshold number. 
     Clause P. The method of clause O, further comprising generating metadata indicating the filler polynucleotide sequences. 
     Clause Q. The method of clause P, further comprising: receiving a request to obtain digital data; amplifying polynucleotides to produce an amplification product; obtaining sequencing data indicating polynucleotide sequences of the amplification product; determining, based at least partly on the metadata, that the filler polynucleotide sequences are included in the sequencing data; and decoding a portion of the polynucleotide sequences of the sequencing data that excludes the filler polynucleotide sequences. 
     Clause R. A system comprising: one or more processing units; memory in communication with the one or more processing units, the memory storing computer-readable instructions that, when executed by at least one processing unit of the one or more processing units, perform operations comprising: generating data indicating a plurality of payload sequences, individual payload sequences of the plurality of payload sequences encoding a number of bits of a series of bits, the series of bits being associated with a data file; generating metadata indicating that a subset of payload sequences of the plurality of payload sequences is associated with a group identifier, wherein: the metadata further indicates a plurality of additional group identifiers related to the data file with individual group identifiers of the plurality of additional group identifiers corresponding to additional individual subsets of the plurality of payload sequences; and individual subsets of the plurality of payload sequences include a quantity that is within an upper threshold and a lower threshold; and generating polynucleotide data indicating a polynucleotide sequence including a payload sequence of the subset of payload sequences and a group identifier sequence corresponding to the group identifier. 
     Clause S. The system of clause R, wherein: the operations further comprise segmenting a series of bits of the data file into a plurality of bit segments; and individual payload sequences of the plurality of payload sequences correspond to individual bit segments of the plurality of bit segments. 
     Clause T. The system of clause R, wherein: the metadata indicates a plurality of sets of identifiers with individual sets of identifiers corresponding to individual data files; and the individual sets of identifiers correspond to polynucleotide sequences that encode digital data of the individual data files. 
     Clause U. The system of clause T, wherein the metadata indicates a container of a polynucleotide data storage system that stores polynucleotides that encode the series of bits. 
     Clause V. The system of clause R, wherein the metadata indicates at least one file identifier of the data file. 
     Clause W. The system of clause U, wherein the operations further comprise: receiving a request for digital data of the data file; identifying, in response to the request and based at least partly on the metadata, the group identifier, the additional group identifiers, and an identifier of the container; and sending, to a computing device, data indicating the group identifier, the additional group identifiers, and the identifier of the container. 
     Clause X. A system comprising: means for generating data indicating a plurality of payload sequences, individual payload sequences of the plurality of payload sequences encoding a number of bits of a series of bits, the series of bits being associated with a data file; means for generating metadata indicating that a subset of payload sequences of the plurality of payload sequences is associated with a group identifier, wherein: the metadata further indicates a plurality of additional group identifiers related to the data file with individual group identifiers of the plurality of additional group identifiers corresponding to additional individual subsets of the plurality of payload sequences; and individual subsets of the plurality of payload sequences include a quantity that is within an upper threshold and a lower threshold; and means for generating polynucleotide data indicating a polynucleotide sequence including a payload sequence of the subset of payload sequences and a group identifier sequence corresponding to the group identifier. 
     Clause Y. The system of clause X, further comprising means for segmenting a series of bits of the data file into a plurality of bit segments, and wherein individual payload sequences of the plurality of payload sequences correspond to individual bit segments of the plurality of bit segments. 
     Clause Z. The system of clause X, wherein: the metadata indicates a plurality of sets of identifiers with individual sets of identifiers corresponding to individual data files; and the individual sets of identifiers correspond to polynucleotide sequences that encode digital data of the individual data files. 
     Clause AA. The system of clause Z, wherein the metadata indicates a container of a polynucleotide data storage system that stores polynucleotides that encode the series of bits. 
     Clause BB. The system of clause X, wherein the metadata indicates at least one file identifier of the data file. 
     Clause CC. The system of claim AA, further comprising: means for receiving a request for digital data of the data file; means for identifying, in response to the request and based at least partly on the metadata, the group identifier, the additional group identifiers, and an identifier of the container; and means for sending, to a computing device, data indicating the group identifier, the additional group identifiers, and the identifier of the container. 
     CONCLUSION 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts are disclosed as example forms of implementing the claims. 
     The terms “a,” “an,” “the” and similar referents used in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. 
     Certain embodiments are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. Skilled artisans will know how to employ such variations as appropriate, and the embodiments disclosed herein may be practiced otherwise than specifically described. Accordingly, all modifications and equivalents of the subject matter recited in the claims appended hereto are included within the scope of this disclosure. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. 
     Furthermore, references have been made to publications, patents and/or patent applications (collectively “references”) throughout this specification. Each of the cited references is individually incorporated herein by reference for their particular cited teachings as well as for all that they disclose.