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Marine Viruses Inhibit Metabolism in Important Photosynthesizing Microbes

Stephanie Wolek
13th June, 2016

Cyanobacteria, a phylum of bacteria that gain energy through photosynthesis, are responsible for trapping huge amounts of carbon dioxide from the atmosphere. Recent research published in Current Biology, however, shows that we may be overestimating just how much they’re able to capture. Like most other organisms, cyanobacteria are vulnerable to viral infections. David Scanlan, along with his colleagues from the University of Warwick, published a paper on June 9th showing what happens when two of the most abundant cyanobacteria are infected by common marine viruses. The two cyanobacteria species tested, Synechococcus and Prochlorococcus, were infected with two viruses in separate trials, cyanophage S-PM2d and cyanophage S-RSM4. The researchers found that both viruses seriously affected the microbes’ cell metabolism. The cyanobacteria could continue to photosynthesize but the energy captured from the sun went directly to helping the viruses reproduce. In other words, the cyanobacteria lost the ability to trap and utilize CO2 while infected. This is significant because up to 60% of cyanobacteria may be infected on a given day. The exact rates of infection aren’t currently known but even if a small percentage harbors the virus, it could seriously impact how much CO2 is absorbed out of the atmosphere. In past research, it was assumed that the quantity of cyanobacteria was directly linked to how much CO2 was absorbed by the ocean. Now, the researchers estimate that up to 5.39 billion metric tons of CO2 may not be trapped by the ocean’s microbes at all. Since carbon dioxide is a major greenhouse gas contributing significantly to climate change, these previous overestimations mean that the situation could be even worse than we originally thought. Clearly, more research is needed so we can get proper data on rates of infection. The authors also added that both Synechococcus and Prochlorococcus are likely to do well as temperatures increase. As these cyanobacteria increase in population size, the viruses may also become more abundant. Further research should give us better models for how much CO2 is absorbed by these microbes, now taking into account cyanobacteria that have been infected by marine viruses. REFERENCE R.J. Puxty et al. Viruses Inhibit CO2 Fixation in the Most Abundant Phototrophs on Earth. Current Biology. Published online June 9, 2016.