Lightning may have produced an important source of food for the planet’s first microbes: a rare form of phosphorus, according to a study published in Nature Geoscience.Researchers examined 10 chunks of sand melted together by lightning, formations called fulgurites, and found a high concentration of the minerals phosphite and hypophosphite in five of them. The soil surrounding the fulgurites contained only phosphate, not phosphites, suggesting that the lightning itself gave rise to phosphites.
“When lightning strikes, it acts like a mini smelter, and the organic molecules strip off oxygen from the phosphorus” [Scientific American], says study coauthor Matthew Pasek.The fact that microbes still have the machinery to digest these phosphites has long puzzled scientists, since phosphites are much rarer than other forms of phosphorus. Lightning forges about two to three tons of the [phosphite] compounds each year, barely enough for life to take notice. But modern bacteria still retain the ability to eat phosphite, which may be a holdover from antiquity [Discovery News].
The researchers believe that the relative abundance of various forms of phosphorus has shifted with time. That’s because most phosphorus is now released as granite and other rocks weather over time, releasing the molecule orthophosphate: a phosphorus atom linked to a hydrogen and four oxygens [Scientific American]. Today, human activities such as burning fossil fuels produces plenty of phosphites, a form of phosphorus that has just three oxygen atoms.
But the researchers theorize that before humans, lightning served as an important phosphite producer, feeding early microbes.“Early life may have used phosphite to form its key biomolecules, like RNA and DNA” [New Scientist], says Pasek. Life continues to rely on phosphorus–it serves as a crucial ingredient for teeth and bones, for example, and remains a key part of DNA and RNA.
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Image: flickr / KM Photography