As indicated above, the improvement in sequencing speed and efficiency led to a rapid accumulation of genome sequences and necessitated more efficient methods for large-scale access to genomes, annotations, subsystems, and genome-scale models within the SEED database. A SOAP server was first developed to allow programmatic access to the SEED data [21] , but several performance issues prevented the service from scaling with the volume of data contained within the SEED database. The server abstraction layer required the loading of numerous large modules on each invocation of server functionality, resulting in a noticeable delay in response to each server request. The encapsulation of the results in SOAP XML conferred significant overhead on the data being transferred. Finally, each operation of the SOAP server was atomic, accepting a single argument and returning a single datum. Trivial requests such as retrieving all the functions for all of the proteins in a genome took unacceptably long to complete, requiring a separate call for each protein and instantiating many threads on the server. The four SEED servers described here provide programmatic access to the SEED data and methods. They expose the current data in a form that is conveniently accessed computationally. The installation and maintenance of the client-side software require minimal effort. We have constructed the underlying methods to support relatively large-grained data transfers, allowing the construction of relatively efficient programs. In comparison to the SOAP server [21] , the new web services provide access to larger amounts of data in less time, and they have been engineered to respond to server requests with little or no server-side delay. Furthermore, the new web services provide a more efficient and flexible computing approach because they are designed to process batches of requests at a time, streaming the responses as they complete. These services provide access to the integrated genomic data, subsystems, FIGfams, co-occurrence data, annotation services, RAST annotation submission and job retrieval (thereby offering access to our continuing improvements in microbial annotation), and metabolic modeling. All client modules, code examples and documentation are available online at http:// servers.theseed.org, and we are continually expanding these services and improving the underlying documentation.