The tiniest life forms on Earth have a big impact on the way carbon dioxide is cycled between the atmosphere and the ocean, new research from the University of Warwick has found.

These life forms are viruses of some of the most abundant organisms on our planet: marine cyanobacteria.

The new research, Viruses Inhibit CO₂ Fixation in the Most Abundant Phototrophs on Earth and published by Current Biology, demonstrates that the viruses of these cyanobacteria, cyanophages, use these genes to maintain the so-called “light-reactions” of photosynthesis, while shutting down the “dark-reactions”.

Cyanobacteria have had an incredible impact on the Earth by seeding the atmosphere with oxygen about 3 billion years ago, allowing for the existence of life as we know it. Today, this same process that acts to produce oxygen sucks up CO₂ from the atmosphere.

Professor David Scanlan of the University of Warwick’s School of Life Sciences, the lead author of the research, said: “CO₂ is a key greenhouse gas directly implicated in global warming. Given CO₂ is converted into organic compounds during photosynthesis, factors that directly affect this process play a key role in modulating atmospheric CO₂ levels.”

“We have known about these viruses for several decades” said Scanlan. “Things changed in 2003 when we discovered that these viruses have stolen genes from cyanobacteria that participate in photosynthesis. Now we have shown that these viruses modify photosynthesis during the demise of their host”.

On a global scale this results in losses of 0.02-5.39 Pg C yr-1 to viral induced inhibition of CO₂ fixation. Per annum this upper figure is approximately 10% of the total CO2 fixed in the marine environment.

This data has important implications for measuring greenhouse gasses. Professor Scanlan explains:

“Quantification of net primary productivity is usually determined by directly measuring cyanobacterial photosynthesis and these methods rely on the coupling of light reactions to CO₂ fixation”.

“In virus infected cells, this assumption of light reactions linked to CO₂ fixation is incorrect and can therefore lead to a significant over estimation of CO₂ fixation. This has very important implications for our understanding, and the estimates of, global warming.”

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Contacts:

Professor Dave Scanlan
Email: D.J.Scanlan@warwick.ac.uk
Tel: + 44 24 76 528363

Dr Andrew Millard
Email: Andrew.Millard@warwick.ac.uk 
Tel: + 44 24 76 523589