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Microbiologist Seeks Microbes in their Inhospitable Habitats

Karen Lloyd and Kate Fullerton
Karen Lloyd and colleague Kate
Fullerton. Credit: Catherine Pratt.

Microbiologist Karen Lloyd regularly journeys out of her lab to study single-celled organisms that live in some of the earth's most inhospitable places. The AAAS Member has clung to the sides of volcanoes, worked under the midnight sun on the edge of the Arctic Sea, and sampled hot springs in Argentina’s Andes mountains.

"I absolutely do feel like Indiana Jones," she says. "One minute, I'm lecturing in front of students, and then I hop on a plane, and the next thing you know, I am literally getting out my machete in the jungle. This is stuff I do for my job. It's pretty cool."

Lloyd, Associate Professor at the University of Tennessee at Knoxville, grew up on the North Carolina Coast, fascinated with marine life. But she found what she calls her true love, organic chemistry, as an undergraduate at Swarthmore College in Pennsylvania. Lloyd uses single-cell genomics, a technology that allows researchers to explore the genetics and functional properties of an individual cell, to investigate what microorganisms use for food and energy in places like hydrothermal vents, oceanic cold seeps or even under the ocean floor.

The creatures that live beneath the ocean floor, unknown until the 1980s, never see the sun under normal circumstances, use infinitesimal amounts of energy, and live long, slow, sedentary lives. As Lloyd says in one of two TED talks about her work, it's thought that the Pharaohs were ruling Egypt the last time some of them experienced cell division.

Kate Fullerton and Karen Lloyd
Kate Fullerton and Karen Lloyd.
Credit: Tom Owens.

There are two ways to access the microbes that live up to three miles below the earth's surface, Lloyd says: "You can go to them, or you can wait for them to come to you." In either case, scientists like Lloyd have to travel to some of the most remote, dangerous places on earth.

To find these microbes in their actual habitat, it's necessary to drill into the ocean floor, pulling up core samples that measure up to 10 yards long. That can mean a rugged expedition of two months or so on a specially fitted research drillship. "On the plus side, we know exactly where those samples come from, and they come up fairly uncontaminated," Lloyd says.

When these microbes are already on surfaces, it's as a result of disturbances in the earth's tectonic plates — via a hot spring bubbling up in the scrubby landscape of the Andes, for example, or a massive spew from an active volcano. Lloyd says she often thinks of the fact that the Poás volcano in Costa Rica erupted only six weeks after she was gathering microbes there in 2017.

How far can we go into the earth and still find life? "We just don't know," she says. One of her career goals is to answer that question. "I hope to really find out what the full range of life is like on earth," she says.

Lloyd also works with microbes that live in the sediment trapped in glaciers in the arctic fjords of the Norwegian Svalbard archipelago. Polar bears, which Lloyd has seen in the distance, present such a danger to scientists working there that someone in the party must be armed at all times. On those trips, she notes, climate change is "absolutely apparent. It is the driving signal that's dominating the whole system right now."

Karen Lloyd
Karen Lloyd in the Arctic.
Credit: Joy Buongiorno.

Her team's project in the arctic is to investigate the "vibrant" community of microbes, including chemolithoautotrophs (which make their own "food" from inorganic compounds), in that cold, often dark environment. When they eventually take the plunge into the sea, those microbes carry important minerals to the marine ecosystem. What will happen to the "ecosystem services" these microbes perform if the glaciers melt entirely? Lloyd says that tracking those microorganisms will help scientists understand what's going on behind the visible effects of climate change.

Lloyd has also been part of the Deep Carbon Observatory (DCO), an international consortium of more than 1,000 scientists, funded by the Alfred P. Sloan Foundation, that for 10 years investigated the 90% of the world's carbon that's buried inside the Earth. Her work in Costa Rica was part of the DCO's 12-day 2017 "Biology Meets Subduction" sampling investigation in that country. She also took part in a number of oceanographic cruises and led early-career scientists on several coastal field expeditions with the organization.

While the DCO is now wrapping up, Lloyd says, "It definitely changed the way I do science. If the goal was to create connections between the kind of siloes where scientists normally don't talk to one another, it absolutely did that."

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