Genome sequencing of lytic and temperate phages infecting members of the Roseobacter clade

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Marine bacteria are probably the most abundant group of organisms on the planet and are of pivotal importance in the major elemental cycles. Their abundance as biological entities is only exceeded by the viruses (phages) that infect them. Bacterially mediated transformations of organic and inorganic matter have important implications for atmospheric composition and climate regulation. The Roseobacter group is a clade of marine bacteria that is commonly found at high abundance throughout the oceans, and studies of a large number of cultivated representatives have shown this to be a physiologically diverse group. A methyl halide (methyl bromide and methyl chloride) and DMSP degrading strain, Roseovarius sp. 217, has recently been isolated at Warwick and the genome of this strain has been sequenced. Further genome sequences of strains from this clade are available now and allow to study these organisms in more detail at the proteomic and transcriptomics level. Marine viruses influence biogeochemical cycles through lysis of host cells, diverting carbon flow from heterotrophic protists into the pool of dissolved organic matter. Recently, phages infecting marine cyanobacteria have been shown to carry genes that encode proteins of the photosynthetic reaction centre of cyanobacteria. These genes were expressed during the phase of virus replication constituting virus-encoded photosynthesis in the marine environment. Phages infecting members of the ubiquitous Roseobacter clade (roseophages) may affect the extent of biogeochemical cycling carried out by Roseobacters, but these phage have received little attention until now. We have isolated three roseophages, including one that infects Roseovarius sp. 217, and propose to sequence the genomes of these three phages. This will inform us of particular features of these phage and will give us clues about their life strategy and evolution. It is not clear what these genome sequences will tell us, but given the exciting insights from cyanophage genomes, and considering the abundance, genetic and physiologic diversity of their hosts, the outcomes of this research will be very informative in the context of the evolution and ecology of Roseobacters and their phages and are very likely to give us exciting new insights into the properties of roseophages.