From photons to phage particles: How viruses of cyanobacteria manipulate host photosynthesis

Photosynthesis is the primary route that energy and carbon enters the biosphere. The most abundant organisms capable of photosynthesis are the single celled, marine cyanobacteria Synechococcus and Prochlorococcus. These genera dominate in large swaths of the Earth’s Oceans, where they also co-occur with viruses (cyanophages). Cyanophages infecting Prochlorococcus and Synechococcus were amongst the first bacteriophages to have their genomes sequenced. Remarkably, these genomes coded for genes directly involved in photosynthesis, including core, photosystem II reaction centre proteins, D1 and D2.

I will present data on how cyanophages use these genes (amongst others) to exploit the host’s photosynthetic metabolism during infection. Specifically, I will describe how viruses promote cyclic and pseudo-cyclic electron transport at the expense of linear electron transport, how they completely inhibit the Calvin Benson cycle and what this means for carbon cycling in our Oceans?

In the second half of my talk, I will introduce more recent data on the mechanisms by which cyanophage can possibly co-exist with their host. This includes how cyanophage avoid host resistance mechanisms as well as the effects of host physiology (nutrient status and growth rate) on cyanophage productivity. Together these studies contribute to understanding of the function of bacteriophages in microbial communities.

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