Billions of years ago, long before oxygen was readily available, the infamous toxic arsenic could have been the compound that breathed new life into our planet.
In the Atacama Desert in Chile, in a place called Laguna La Brava, scientists have been studying a purple strip of photosynthetic microbes that live in a hyper-salty lake permanently devoid of oxygen.
“I’ve been working with microbial mats for about 35 years or so,” Says Geoscientist Peter Fisher of the University of Connecticut.
“This is the only system on Earth where I can find a microbial mat that works perfectly in the absence of oxygen.”
Microbial mats, which turned into fossils into stratolites, were abundant on Earth at least 3.5 billion years ago, however, for the first billions of their existence, there was no oxygen for photosynthesis.
How these forms of life survived in such extreme conditions is still unknown, but when examining stromatolites and people who live today, researchers discovered a range of possibilities.
While iron, sulfur and hydrogen have been for a long time Proposed As potential alternatives to oxygen, this was not until the discovery.ArsenicotrophyIn Lake Searles and Lake Mono in California, arsenic has also become a competitor.
Since then, stromatolites from the Tombiana Formation in Western Australia revealed that trapping light and arsenic was once a valid method for photosynthesis in the Precambrian era. The same cannot be said of iron or sulfur.
Just last yearResearchers have discovered an abundant form of life in the Pacific that also breathes arsenic.
Even Labrava’s life forms are very similar to the purple sulfur bacteria that are called Ectothiorhodospira sp.Which was late have found In an arsenic-rich lake in Nevada that appears to photosynthesize by oxidizing the arsenic compound into a different form – senes.
While more research needs to be verified if La Brava’s microbes are also metabolizing arsenic, preliminary research has found that the effluent water surrounding these mats is filled with hydrogen sulfide and arsenic.
If the authors are right, and the Labrava microbes are indeed arsenic “breathing”, these life forms will be the first to do so in a microbial mat permanently and completely free of oxygen, similar to what we would expect in pre-Cambrian environments.
As such, its mats are a great model for understanding some of the possible early life forms on our planet.
While genetic research indicates that La Brava mats have the tools to metabolize arsenic and sulfur, the authors say reducing arsenic appears to be more effective than reducing sulfate.
Regardless, they say there is strong evidence of both pathways, and this would have been sufficient to support the broad microbial mats in the early days of life on Earth.
If the team is right, we may need to expand our search for life forms elsewhere.
“In search of evidence of life on Mars, [scientists] They’ll look for iron and maybe they should look for arsenic as well. ” Says Fisher.
It really is much more than just a poison.
The study was published in Earth and Environment Communications.