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Update(MM/DD/YYYY):01/31/2023

Characterization of Methanogenic Microorganisms Living in Deep Subseafloor Sediments of the Nankai Trough

– A clue to elucidating methane hydrate formation –

 
Researchers) KATAYAMA Taiki, Senior Researcher, YOSHIOKA Hideyoshi, Group Leader, KANEKO Masanori, Senior Researcher, SAKATA Susumu, Invited Senior Researcher, TAKAHASHI Hiroshi, Senior Researcher, Geological Survey of Japan

Points

  • Isolation of phylogenetically and metabolically diverse methanogenic microorganisms from hydrate-bearing subseafloor sediments
  • Cultivation experiments demonstrate the importance of temperature in sediments for methane production
  • Contributing to the elucidation of methane hydrate formation and assessment of resource quantity

Figure of new research results

Fluorescence micrographs of 6 different strains of methanogenic microorganisms isolated from subseafloor sediments from the Nankai Trough
It took up to five years for cultivation. Methanogenic microorganisms show auto-fluorescence under ultraviolet irradiation. Scale bars, 10 µm.


Background

Natural gas is a clean energy resource that emits less air pollutants and carbon dioxide than other fossil fuels such as oil and coal. Despite of its increasing demand, 95% or more of natural gas consumed in Japan is currently supplied from overseas. Methane hydrate (Hereafter MH) is expected to become a domestic natural gas resource in the future as it is widely distributed under the seafloor off the coast of Japan. Methane in marine MH in many areas is considered to be biogenic, i.e., a product from methanogenic microorganisms (methanogens). However, population, diversity, physiology and ecology of methanogens are largely unknown in MH-bearing subseafloor sediments. Such knowledge is fundamental to understanding the formation process of biogenic MH and to improving techniques for its exploration and resource assessment.

 

Summary

In collaboration with the Japan Oil, Gas and Metals National Corporation (JOGMEC) and the National Institutes for Quantum Science and Technology (QST), researchers in AIST succeeded in cultivation and characterization of living methanogens from the deep subseafloor sediments of the eastern Nankai Trough where biogenic MH is widely deposited. The depth profile of the methane production potential from the seafloor to the MH concentrated zone and the temperature profile of activity of methanogen isolates were compared to suggest that the growth temperature of methanogens is a key factor for methane production potential. These findings provide better understanding of the MH formation process.





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