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The discovery of bacteria that can live on trace gases in the atmosphere changes the possibilities for extraterrestrial life.
Scientists have found bacteria in the frozen wastes of Antarctica that can survive on air alone without the sunlight or geothermal energy that powers all other known ecosystems. The discovery may change our ideas when pondering the forms extra-terrestrial life might take.
A team of scientists led by Belinda Ferrari of UNSW in Sydney, Australia, report the stunning finding in a paper in Nature.
The cold and remote Antarctic has desert regions that are hostile to the few living things that survive on the rest of the continent. Plummeting temperatures, limited water, carbon and nitrogen, months of darkness, searing UV radiation, and persistent cycles of freezing and thawing that can rot the very stones, all make it an unlikely home for diverse ecosystems.
Yet that’s exactly what the researchers found in the thin desert soils, at least at the microbial level. This posed something of a puzzle: how do these diverse communities of single-celled organisms survive in such extreme conditions?
When conditions are at their worst, many organisms retreat into a dormant state, but they too need energy to maintain themselves. It has been unclear, until now, just how they have done this.
Ferrari and her team used the techniques of metagenomics, the study of genetic material taken directly from the environment, to investigate microbial communities at two eastern Antarctic sites: one near Casey Station in Wilkes Land and the other a few hundred kilometres from Davis Station in Princess Elizabeth Land.
Soil samples were taken, and any genetic material broken into smaller pieces and then sequenced, a technique known as ‘shotgun DNA sequencing’. The fragments are reassembled into the genomes of individual species, giving a picture of the types and abundance of microbes present in the soil. Interestingly, in the course of their research, Ferrari and her team identified two new phyla of bacteria that were previously unknown to science.
Every ecosystem is based on what are known as ‘primary producers’: living things that turn inorganic chemicals and energy into living matter, or biomass. Most of the time this involves photosynthesis, using sunlight to convert atmospheric carbon into sugar.
What Ferrari and her team discovered is that this was not the case at their Antarctic sites. Instead, they found through genetic clues about the metabolisms of the microbes, including the two newly discovered phyla, that they produce energy directly from atmospheric hydrogen, carbon dioxide and carbon monoxide.
“Whereas most ecosystems are driven by solar or geologically driven energy,” write the authors, “primary production in these Antarctic desert surface soils appear to be supported by atmospheric trace gases.”
This is the first time air-eating life on Earth has ever been reported. In addition to enhancing our understanding of how life survives the extreme conditions of Antarctica, Ferrari says, it also “opens up the possibility of atmospheric gases supporting life on other planets”.