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Anna-Louise Reysenbach
Anna-Louise Reysenbach

Hot Pursuit

Searching for new life forms at Earth's extremes

The water around thermal vents at the bottom of the ocean is too hot and acidic for most life, but certain microbes like it just fine. Anna-Louise Reysenbach, professor of biology, studies these organisms that live in Earth’s extreme environments. Using manned submarines like the deep-sea research submersible, Alvin, or one of a variety of remotely operated vehicles, like Jason, Reysenbach descends into this inhospitable realm. “You never really know what to expect,” she says. “It’s almost like going to Mars or the moon.”


A mile and a half down in the ocean, geysers spew super-heated water (as high as 400°C) laced with chemicals like hydrogen sulfide, iron, and carbon dioxide. When the scalding water hits the much colder water at the bottom of the sea, the minerals precipitate out in a cloud of black and then harden into porous rock formations.

The microbes Reysenbach studies live on these rocks, forming the base of a food chain built on geochemical energy, extracted through a process called chemosynthesis. Similar microbial ecosystems can be found in terrestrial vents like the ones in Yellowstone Park or in Iceland, Reysenbach says.

Reysenbach and her colleagues discovered many new heat-loving microbes from these environments, including the microbe Aciduliprofundum boonei that was first obtained from deep-sea vents in the Southwest Pacific, and named it after the late PSU professor David Boone. Under a microscope, the organism looks like a balloon with two little horns. “I call it the thermal devil blob,” she says. It is the first deep-sea microbe that can only grow in acidic conditions.  Many of these new organisms have possible industrial and medical applications.

“We have very little idea of who the microbes are and what they’re doing! They represent a huge amount of untapped and unknown genomic biodiversity,” says Reysenbach. So, she and her team bring samples back to their lab and recreate conditions around the vents. That allows them to study the organisms and their genes to determine what kind of organisms they are, how they might transform their environment, and whether they have unusual properties that could provide bionano-technological and medical benefits .

Ultimately, these microbes could help inform exploration for signs of past life elsewhere in the Solar System and could offer clues to life’s origins.

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