From Deep Blue Mud, Unexpected Life Emerges

Explore

TThe deep sea is a disturbing, almost impenetrable place for us surface dwellers; darkness prevents photosynthesis, and animals living at great depths must withstand extremely low temperatures, high pressures, and scarce nutrients. Yet ecosystems just beneath the seafloor contain about 15 percent of Earth’s living biomass, in the form of extremely resourceful microbes that get by in the deep.

Robust communities of microbes inhabit the ocean crust, clustered around hydrothermal vents, which spew vital minerals into superheated waterways. Now, a study in Earth and Environment Communications heralds marine microbial life that pushes the boundaries of environmental tolerance even further.

Researchers and colleagues from the University of Bremen looked for evidence of microbes in two sediment cores extracted from mud volcanoes near the Mariana Trench. The cores, which were drilled from the seafloor more than 9,800 feet deep, contained mud up to 5.4 feet below the seafloor, down to what is called serpentinite, a layer of sediment tinted a bright blue.

In this blue slime, the pH is a surprisingly alkaline 12, the same as some household bleaches, oven cleaners, and relaxers. But scientists, thanks to the analysis of lipids, detected, in this punishing mud, fat molecules which could only result from biological activity.

Read more: »The bacteria that revolutionized the world»

Conditions are more alkaline than those known for any other ecosystem on Earth. “What is fascinating about these findings is that life in these extreme conditions, such as high pH and low concentrations of organic carbon, is even possible,” said Florence Shubotz, an organic geochemist from the Center for Marine Environmental Sciences at the University of Bremen and co-author Florence Shubotz.

Add to these challenges the virtual lack of oxygen at such depths, and life must find unique ways to achieve this. Known deep-sea microbes obtain their energy through chemosynthesis, exploiting minerals in rocks and gaseous hydrocarbons from vents. The same appears to be true for these newly discovered organisms.

The lipid molecules detected in the study come from the cell membranes of bacteria or archaea, an ancient domain of organisms that resemble bacteria. In the cell membranes of these microbes, fats provide a barrier against alkaline conditions. Their status indicates whether the microbes are alive or long dead. Intact lipid molecules indicate a living community, whereas degraded lipid molecules could originate from fossil organisms. The results showed both types of lipids in the sediment cores: a community of contemporary microbes and evidence of ancient microbial populations.

These extremophile organisms could also open a window on the origin of life on Earth. “We suspect that primordial life could have arisen precisely at such sites,” Shubotz added. What’s more, the cores have only scratched the surface of a habitat that could extend much further beneath the seafloor, offering even deeper insights into the earliest forms of life here on Earth – and potentially beyond.

Enjoy Nautilus? Subscribe to our free newsletter.

Main image: Ethan Daniels / Shutterstock

• Devin Reese

  Published on November 11, 2025

  Devin Reese is the editor-in-chief of Natural history and a science writer based in Alexandria, Virginia.