Life found in a place scientists thought impossible

Because so few living cells exist there, detecting DNA is often impossible. Instead, the researchers used trace analysis techniques sensitive enough to identify even faint biochemical signals. "But we were able to detect fats," says Kumawat, currently a PhD candidate in the Geosciences Department. "With the help of these biomarkers we were able to obtain insights into the survival strategies of methane- and sulfate-metabolizing microbes in this extreme environment."

Microbial Clues Hidden in Deep-Sea Chemistry

Microbial life in the deep ocean plays an important role in the global carbon cycle, processing carbon and other elements far below the surface. The communities identified by Kumawat's team draw their energy not from sunlight but from minerals in rocks and gases like carbon dioxide and hydrogen, producing methane in the process -- an important greenhouse gas. These biochemical reactions occur independently of the ocean above, showing that these microbes operate in a self-contained ecosystem.

The lipid molecules also help determine whether the microbes are alive or remnants from ancient communities. Intact biomolecules suggest active or recently living cells, while degraded ones indicate fossilized "geomolecules" from long ago. Kumawat explains that combining isotope data with lipid biomarkers shows evidence of both modern and ancient microbial populations inhabiting this hostile environment. "This distinction helps us when working in areas with extremely low biomass and nutrient deficiency," he notes.

Discovering Life at the Limits

Co-author Dr. Florence Schubotz, an organic geochemist at MARUM -- Center for Marine Environmental Sciences at the University of Bremen, emphasizes how remarkable the discovery is. "What is fascinating about these findings is that life under these extreme conditions, such as high pH and low organic carbon concentrations, is even possible," she says. "Until now, the presence of methane-producing microorganisms in this system has been presumed, but could not be directly confirmed. Furthermore, it is simply exciting to obtain insights into such a microbial habitat because we suspect that primordial life could have originated at precisely such sites."

Uncovering Hidden Volcanoes Beneath the Pacific

The team's samples came from sediment cores collected in 2022 during Expedition SO 292/2 aboard the Research Vessel Sonne. During this mission, scientists discovered previously unknown mud volcanoes in the Mariana forearc region and were able to collect samples directly from them.

The work forms part of the Cluster of Excellence "The Ocean Floor -- Earth's Uncharted Interface." Building on their findings, Kumawat and his colleagues now plan to cultivate these microorganisms in controlled incubators to learn more about how they obtain nutrients and persist in such inhospitable environments.