Modular architecture of the T4 phage superfamily: a conserved core genome and a plastic periphery.
Among the most numerous objects in the biosphere, phages show enormous diversity in morphology and genetic content. We have sequenced 7 T4-like phages and compared their genome architecture. All seven phages share a core genome with T4 that is interrupted by several hyperplastic regions (HPRs) where most of their divergence occurs. The core primarily includes homologues of essential T4 genes, such as the virion structure and DNA replication genes. In contrast, the HPRs contain mostly novel genes of unknown function and origin. A few of the HPR genes that can be assigned putative functions, such as a series of novel Internal Proteins, are implicated in phage adaptation to the host. Thus, the T4-like genome appears to be partitioned into discrete segments that fulfil different functions and behave differently in evolution. Such partitioning may be critical for these large and complex phages to maintain their flexibility, while simultaneously allowing them to conserve their highly successful virion design and mode of replication.
Comeau
André M
AM
Laboratoire de Microbiologie et Génétique Moléculaire, CNRS-UMR5100, 31062 Toulouse Cedex 9, France.
Bertrand
Claire
C
Letarov
Andrei
A
Tétart
Françoise
F
Krisch
H M
HM
D000595:Amino Acid Sequence; D017122:Bacteriophage T4 / Q000235:genetics*; D001483:Base Sequence; D004279:DNA, Viral / Q000235:genetics; D019143:Evolution, Molecular; D023061:Gene Order; D005814:Genes, Viral; D014644:Genetic Variation; D016679:Genome, Viral / Q000235:genetics*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D026801:Synteny; D013604:T-Phages / Q000235:genetics*
D004279:DNA, Viral