Marine ecosystems: Bacterial photosynthesis genes in a virus

Cyanobacteria contribute to the overall photosynthetic production of oxygen in the oceans, but they are susceptible to infection by viruses and also to photo-inhibition when sunlight is too intense. Here we show that the genomic sequence of one such virus, a bacteriophage known as S-PM2, encodes the D1 and D2 proteins that are key components of one of the photosynthetic reaction centres (photosystem II, PSII), which are crucial sites of damage in photo-inhibition. The presence of this virus, and others like it, in the ocean may ensure that photo-inhibition is prevented in infected cells, allowing photosynthesis to continue and therefore provide the energy needed by the virus for its replication.