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Synopses of Research Articles The Cyanophage Molecular Mixing Bowl of Photosynthesis Genes Emma Hill | DOI: 10.1371/journal.pbio.0040264 Among the wealth of microbial organisms inhabiting marine environments, cyanobacteria (blue-green algae) are the most abundant photosynthetic cells. Prochlorococcus and Synechococcus, the two most common cyanobacteria, account for 30% of global carbon fi xation (through the photosynthetic process in which sugars are manufactured from carbon dioxide and water). By drawing on natural resources, these microbes use photosystems (PS) I and II (the two reaction centers in photosynthesis) to harness energy. Intriguingly, some viruses that infect cyanobacteria (called cyanophage), carry genes that encode two PSII core reaction- center proteins: PsbA (the most rapidly turned over core protein in all oxygen-yielding photosynthetic organisms) and PsbD (which forms a complex with PsbA). By expressing their own copies of psbA and psbD during infection, these cyanophages have managed to co-opt host genes to suit their own purposes: enhancing photosynthesis. It seems likely that they do this in the interests of their own fi tness, since cyanophage production is optimal when photosynthesis is maintained during infection. Until recently, only a small sample of cyanophages had been examined, leaving open the questions of how widespread PSII genes are in these organisms and where the genes came from. To answer these questions, Matthew Sullivan, Debbie Lindell, Sallie Chisholm, and colleagues DOI: 10.1371/journal.pbio.0040264.g001 examined a pool of 33 cyanophage isolates (cultured from samples collected from the Sargasso Sea and the Red Sea), Cyanophages—viruses that infect photosynthetic marine bacteria— not only possess genes for photosynthesis but also exchange along with data already availa