Marine viruses (called cyanophages) that infect cyanobacteria enhance photosynthesis in their hosts by displacing host photosynthesis genes with viral-encoded homologues.

“Cyanophages are double-stranded DNA viruses belonging to three morphologically defined families: Podoviridae, Myoviridae, and Siphoviridae [3–5,9,10]. Among the cyanophages, podoviruses and siphoviruses tend to be very host-specific, whereas myoviruses generally have a broader host range, even across genera [5], and thus are potential vectors for horizontal gene transfer via transduction. The movement of genes between organisms is an important mechanism in evolution. As agents of gene transfer, phages play a role in host evolution by supplying the host with new genetic material [11–15] and by displacing ‘host’ genes with viral-encoded homologues [16–18]…Because maximal cyanophage production is dependent on [31,33], and the host PsbA turns over rapidly [34] and declines during infection [31], expression of these phage-encoded genes likely enhances photosynthesis during infection, thus increasing cyanophage fitness.” (Sullivan et al. 2006:1344-1345)

Last Updated March 23, 2018