Caudovirales - wikipedia Caudovirales hide This article has multiple issues. Please help improve it or discuss these issues on the talk page. ( Learn how and when to remove these template messages ) This article may be too technical for most readers to understand. Please help improve it to make it understandable to non-experts, without removing the technical details. ( April 2013 ) This article relies largely or entirely on a single source. Relevant discussion may be found on the talk page. Please help improve this article by introducing citations to additional sources. ( April 2013 ) Caudovirales From left to right : Myoviridae, Podoviridae, and Siphoviridae Scientific classification Group : Group I ( dsDNA ) Order : Caudovirales Families Myoviridae Podoviridae Siphoviridae The Caudovirales are an order of viruses also known as the tailed bacteriophages ( cauda is Latin for `` tail '' ). Under the Baltimore classification scheme, the Caudovirales are group I viruses as they have double stranded DNA ( dsDNA ) genomes, which can be anywhere from 18,000 base pairs to 500,000 base pairs in length. The virus particles have a distinct shape ; each virion has an icosahedral head that contains the viral genome, and is attached to a flexible tail by a connector protein. The order encompasses a wide range of viruses, many of which containing genes of similar nucleotide sequence and function. Some tailed bacteriophage genomes can vary quite significantly in nucleotide sequence, however, even among the same genus. Due to their characteristic structure and possession of potentially homologous genes, it is believed these bacteriophages possess a common origin. There are at least 350 recognised species in this order. Contents 1 Infection 2 Assembly and maturation 3 Taxonomy 4 Bacteriophage evolution 5 References 6 Further reading Infection Upon encountering a host bacterium, the tail section of the virion binds to receptors on the cell surface and delivers the DNA into the cell by use of an injectisome - like mechanism ( an injectisome is a nanomachine that evolved for the delivery of proteins by type III secretion ). The tail section of the virus punches a hole through the bacterial cell wall and plasma membrane and the genome passes down the tail into the cell. Once inside the genes are expressed from transcripts made by the host machinery, using host ribosomes. Typically, the genome is replicated by use of concatemers, in which overlapping segments of DNA are made, and then put together to form the whole genome. Assembly and maturation Viral capsid proteins come together to form a precursor prohead, into which the genome enters. Once this has occurred, the prohead undergoes maturation by cleavage of capsid subunits to form an icosahedral phage head with 5-fold symmetry. After the head maturation, the tail is joined in one of two ways : Either the tail is constructed separately, and joined with the connector, or the tail is constructed directly onto the phage head. The tails consist of helix based proteins with 6-fold symmetry. After maturation of virus particles, the cell is lysed by lysins, holins, or a combination of the two. Taxonomy Because of the lack of homology between the amino acid and DNA sequences of these viruses these factors are precluded from being used as taxonomic markers as is common for other organisms, the three families here are defined on the basis of morphology. This classification scheme was originated by Bradley in 1969 and has been extended since. All viruses in this order have icosahedral or oblate heads but differ in the length and contractile abilities of their tails. The Myoviridae have long tails that are contractile ; the Podoviridae have short noncontractile tails ; and the Siphoviridae have long noncontractile tails. Siphoviridae constitute the majority of the known tailed viruses. Bradley referred to what is now known as the Myoviridae as type A, Siphonviridae as type B, and the Podoviridae as type C. He also divided his groups on the basis of head morphology : Within group A, A1 have small isometric heads ; A2 have prolate heads ; and A3 have elongated heads. Within groups B and C, numbers were similarly assigned : B1 and C1 have small isometric heads ; B2 and C2 have prolate heads ; and B3 and C3 have elongated heads. Bacteriophage evolution Bacteriophages occur in over 195 bacterial or archaeal genera. They arose repeatedly in different hosts and there are at least 11 separate lines of descent. Over 6300 bacteriophages have been examined in the electron microscope since 1959. Of these, more than 96 percent have tails. Of the tailed phages, about 57 percent have long, noncontractile tails ( Siphoviridae ). Tailed phages appear to be monophyletic and are the oldest known virus group. References Jump up ^ Ackermann HW ( 1998 ). `` Tailed bacteriophages : the order caudovirales ''. Advances in Virus Research. 51 : 135 -- 201. doi : 10.1016 / S0065 - 3527 ( 08 ) 60785 - X. PMID 9891587. ^ Jump up to : `` Double - Stranded DNA Bacteriophages ''. Boundless. Jump up ^ Maniloff, J. ; Ackermann, H.W. ( 1998 ). `` Taxonomy of bacterial viruses : establishment of tailed virus genera and the other Caudovirales ''. Archives of Virology. Springer - Verlag. 143 ( 10 ) : 2051 -- 2063. doi : 10.1007 / s007050050442. PMID 9856093. ^ Jump up to : Ackermann, H.W. ( 2003 ). `` Bacteriophage observations and evolution ''. Research in microbiology. Elsevier. 154 ( 4 ) : 245 -- 251. doi : 10.1016 / S0923 - 2508 ( 03 ) 00067 - 6. PMID 12798228. Jump up ^ Ackermann, HW ; Prangishvili, D ( October 2012 ). `` Prokaryote viruses studied by electron microscopy ''. Archives of Virology. 157 ( 10 ) : 1843 -- 9. doi : 10.1007 / s00705 - 012 - 1383 - y. PMID 22752841. Further reading Xu J, Hendrix RW, Duda RL ( 2004 ). `` Conserved translational frameshift in dsDNA bacteriophage tail assembly genes ''. Mol. Cell. 16 ( 1 ) : 11 -- 21. doi : 10.1016 / j. molcel. 2004.09. 006. PMID 15469818. Casjens SR ( 2005 ). `` Comparative genomics and evolution of the tailed - bacteriophages ''. Curr. Opin. Microbiol. 8 ( 4 ) : 451 -- 8. doi : 10.1016 / j. mib. 2005.06. 014. PMID 16019256. Taxon identifiers Wikidata : Q6521 Wikispecies : Caudovirales EoL : 8031 EPPO : 1CAUDO GBIF : 843 iNaturalist : 152501 IRMNG : 10955 NCBI : 28883 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Caudovirales&oldid=843736204 '' Categories : Caudovirales Bacteriophages Virus orders Hidden categories : Wikipedia articles that are too technical from April 2013 All articles that are too technical Articles needing expert attention from April 2013 All articles needing expert attention Articles needing additional references from April 2013 All articles needing additional references Articles with multiple maintenance issues Articles with ' species ' microformats Talk Contents About Wikipedia Wikispecies Deutsch Español Interlingua Italiano Português Русский 中文 Edit links This page was last edited on 31 May 2018, at 03 : 23 ( UTC ). About Wikipedia

Question: tailed bacteriophages fall within which of baltimore groups
Answer: group I