Microbiology: Metabolism key to microbial survival under the seafloor

High rates of energy metabolism may enable a microbial community to survive in sediments over a kilometre below the seafloor at temperatures of up to 120°C, suggests a study published in Nature Communications. The findings shed light on the survival strategies of organisms living at what is thought to be the upper temperature limit for life.

Marine sediments below the Earth’s surface are thought to contain a large proportion of the microbial life on the planet. A previous expedition recovered sediment cores from the Nankai Trough subduction zone to explore the extent of life in these habitats. At this site, despite temperatures in the deepest sediments reaching 120°C, a small microbial community was found to be thriving, but how these organisms had adapted to survive was unclear.

Building on their earlier work, Tina Treude and colleagues used sensitive radiotracer experiments under highly sterile working conditions to explore how the organisms survived in the sediments. They found that the microbes in the deep, hot sediments had exceptionally high rates of energy metabolism, which is in stark contrast with the slow microbial life previously observed in the deep subseafloor. The authors propose that, in the extreme environment, the microbial community has to maintain a high metabolic rate to provide the energy required to repair cell damage caused by heat, but are supported by an abundance of nutrients supplied by the heating of organic matter in these sediments.

The authors suggest their findings have implications for our understanding of the sedimentary environment below the Earth’s surface and the proposed upper temperature limit for life.