Research Highlights: Microbes with high metabolic activity found in deep, hot subseafloor environment


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Microbes with high metabolic activity found in deep, hot subseafloor environment

  • About 25 percent of the world’s seabed sediment can be found at a depth where temperature is more than 80 °C.
  • Scientists previously proposed that 80 °C is the thermal barrier for life in the strata below the Earth’s surface.
  • Researchers discovered a population of methanogenic and sulfate-reducing organisms in deep buried marine sediment.
  • Methanogenic organisms produce methane as a metabolic byproduct in low oxygen conditions.[1]
  • Sulfate-reducing organisms can perform anaerobic respiration by using sulfate as terminal electron acceptor and reducing it to hydrogen sulfide.[2]
  • The IODP (International Ocean Discovery Program) Expedition 370 drilled and collected sediment cores in the Nankai Trough subduction zone just south of Japan.
  • The Nankai Trough subduction zone can reach temperatures of about 120 °C.
  • Subduction zone is the place where two plates of the Earth come together, one is found over the other.[3]
  • Researchers utilized a considerable suite of radiotracer experiments.
  • Radiotracers is a compound that contains a radioactive element and can be used to study the mechanism of chemical reactions.[4]
  • The small microbes discovered from the Nankai Trough subduction zone survived with high potential cell-specific rates of energy metabolism, similar to the rates in active surface microbes and laboratory cultures.
  • Researchers initially expected that the metabolic rates in the deep subseafloor will be extremely low.
  • The cells appear to expend almost all of their energy to repair damages from the high temperature.
  • At the same time, the cells are forced to balance between supporting themselves at a minimum level near the thermal barrier for life and a rich source of substrates and energy from the reactions of the sedimentary organic matter caused by the high temperature environment.

Sources:

Beulig, F., Schubert, F., Adhikari, R.R. et al. Rapid metabolism fosters microbial survival in the deep, hot subseafloor biosphere. Nat Commun 13, 312 (2022). https://doi.org/10.1038/s41467-021-27802-7

[1] https://en.wikipedia.org/wiki/Methanogen

[2] https://en.wikipedia.org/wiki/Sulfate-reducing_microorganism

[3] https://earthquake.usgs.gov/learn/glossary/?term=subduction%20zone

[4] https://www.iaea.org/topics/radiotracers


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