Microbes use sunscreens too

Microbes can withstand extreme levels of atmospheric ultraviolet light (UV) by producing their own sunscreens. Unlike humans, some bugs may even be able to survive without any help from the ozone layer scientists heard today (Thursday 19 September) at the Society for General Microbiology autumn meeting at Loughborough University.

“A group of microbes called cyanobacteria produce substances called mycosporines in response to UV light. We’ve shown that this is an ancient mechanism dating back over 1500 million years ago – before the ozone layer was formed,” says Dr Ferran Garcia-Pichel of Arizona State University.

“We have studied the family tree of cyanobacteria using DNA typing methods, particularly concentrating on the occurrence of bacterial suncreens, which has revealed patterns that are consistent with the proposed long-term history of UV exposure on Earth. Several lines of evidence, including stellar evolution and atmospheric modelling, suggest that severe changes in the amount and wavelengths of solar UV radiation reaching the ground have occurred during Earth’s history,” explains Dr Garcia-Pichel.

Cyanobacteria can be viewed as the predecessors of plants as they were the first organisms to produce oxygen by photosynthesis. But in doing so they left themselves open injury because, together, UV light and oxygen can cause enormous damage to cells. “It is this point in time (500-1500 million years ago) that we can date the diversification of these chemical UV-defence mechanisms among cyanobacteria,” says Dr Garcia-Pichel.

Dr Garcia-Pichel concludes, “ Efforts are also underway by a number of researchers to identify whether these microbial products can be used in human medicine.