Methane-Producing Microbes Found in Rocks at Freshwater Springs in California

Deep in vents on the ocean floor, methane-producing microbes feed off chemical reactions between water and rock. Scientists working on freshwater springs in California have found new evidence suggesting this process also takes place on land.

They report evidence of hardy, methane-producing microbes in water that surfaces from deep underground at The Cedars, a set of freshwater springs in Sonoma County [1].

It is the first time scientists have found these methane-producing microbes, which thrive in harsh environments, living anywhere outside of the deep sea. The new finding could offer clues into how early microbes lived on Earth billions of years ago and if they might be present on other planets like Mars.

The study, which is published in the Journal of Geophysical Research, also shows the newly-discovered microbes are likely capable of using carbon dioxide to produce methane – a finding that could have implications for future carbon sequestration projects being proposed in areas similar to The Cedars, said Lukas Kohl, a biogeochemist at Memorial University of Newfoundland in St. John’s, Newfoundland and lead author of the study.

“As our technology’s expanding, we’re able to look outside of the box a little to capture some of these groups [of microbes],” said Matt Schrenk (Michigan State University, USA; DCO Deep Life Scientific Steering Committee member). “As we’re beginning to look into some of these natural environments [deep underground], our view of the microbial world, and of life in general, is really expanding.”

Serpentinization, a process where water reacts with rock to create a green stone called serpentine, is common on the ocean floor. In the process, byproducts of the reaction, including methane, hydrogen, and heat, are released. The Cedars—a small, isolated set of springs flowing out of a large patch of red rock from Earth’s mantle – is one of the few easily-accessible sites of serpentinization on land.

Scieintists have detected communities of microbes at many serpentinization sites across the globe, including in oceanic vents and sites deep underground. Such harsh, high-pH environments have few organic molecules for organisms to feed on. These hardy microbes likely use the byproducts of serpentinization as an energy source.

Previous analysis of water from The Cedars suggested some of the methane found in the springs could have come from microbes. To confirm microbes are producing methane at The Cedars, the study’s authors took water samples from the springs and exposed the samples to different conditions in the laboratory. In one group of samples they killed any living microbes. In these samples, they did not detect any additional methane being produced.

The samples with live microbes, however, produced significant amounts of methane. In some cases, the live-microbe vials contained 650 percent more methane than vials with dead microbes. The team was also able to trace the methane, and determine that it had been produced by microbes, rather than as a product of serpentinization. The new study, combined with previous data, suggests a significant portion of methane in water at The Cedars likely comes from the microbes living there.

The new study also sheds light on how microbes could have used the energy and chemicals from serpentinization to survive on early Earth when the atmosphere contained less oxygen and fewer organic molecules, said William Brazelton, an astrobiologist at the University of Utah in Salt Lake City who was not involved with the study. Further, the methane they released could have had an impact on the environment and Earth’s evolution, he added.

The discovery of the methane-producing microbes at The Cedars also gives hope to those searching for life on Mars, Brazelton said. Some surveys of the Martian atmosphere have found methane, which was thought to be a product of serpentinization. This study shows the methane could be a product of both serpentinization and microbes.

Article adapted from source.

Images: Above left: The Cedars is a small, isolated set of springs flowing out of a large patch of red rock from Earth’s mantle in Sonoma County, California. The Cedars is one of the few easily-accessible sites of serpentinization on land. Middle right: Carbon dioxide reacts with the products of serpentinization to form white deposits of carbonate on the rocks at The Cedars. Credit: Lukas Kohl

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