“It’s rare to find a place where there are no microbes,” says Jeffrey J. Marlow, a Boston University College of Arts & Sciences assistant professor of biology.

But there are exceptions: extreme environments like hot molten lava where the absence of microbes gives scientists an opportunity to study how these organisms survive and change over time. How long, for example, does it take for microbes to inhabit a cooling piece of molten rock, and where do they even come from?

In 2021, a new volcanic eruption began in Iceland’s Fagradalsfjall volcano after 781 years of dormancy. And then, it erupted again in August 2022. Locals and tourists all rushed to the scene to take epic photos, of course. But for researchers, this presented a rare opportunity to collect fresh rock samples, and get a close look at the molten insides of our planet. Marlow and his team of students went to the volcano site when the land was still hot and lava was still trickling underground from the first one.

In the week they were there, the team collected samples, incubated and preserved them, and brought them back to Boston – all while ensuring they didn’t become contaminated.

Once lava cools and hardens into a rock, microbes can move in—but how long does that take? And who are they? Where do they come from?

In the past, researchers have found that it takes less than four months for microbes to move into a newly formed rock, Marlow says, but the specifics beyond that have not been well documented.

Marlow and his team are using DNA samples to see what type of microbial communities appear on rocks just a few days old, ten months old and over a year old, and ultimately, what particular environmental and biological factors set a chunk of volcanic rock on the path toward becoming a developed ecosystem.

Microbes use a wide array of chemical reactions to break down rocks. Acids can dissolve mineral grains, releasing elements like sodium, phosphor, sulfur, magnesium and iron. Microorganisms can thrive on those nutrients. More important, by combining elements like iron with oxygen or sulfur, energy is released, used by lifeforms to fuel their metabolism.

“Our work provides an opportunity to discern how microbes wrest control of an abiotic environment, using a continuing volcanic eruption as an ideal natural laboratory,” explains Peter Schroedl, a Ph.D. student in BU’s Program in Ecology, Behavior & Evolution who works in Marlow’s lab. He stayed in the weeks after Marlow’s group left to continue doing research with NASA’s RAVEN project, which tests drones in Iceland’s lava fields for future Mars exploration. He was there to witness Fagradalsfjall roar to life in 2022 and took the opportunity to collect additional samples.

Beyond our own planet, scientists are using microbes found in extreme environments as templates for finding single-celled life on other planets and moons – as barren landscapes are the most analogous places we have to Mars and other rocky planets. By continuing the hunt for early microbes in the most harsh places, Marlow and his team hope to contribute more to understanding life here and beyond.

Material provided by Jessica Colarossi, Boston University.

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