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Cell proliferation at 122°C and isotopically heavy CH₄ production by a hyperthermophilic methanogen under high-pressure cultivation
- Takai, Ken, Nakamura, Kentaro, Toki, Tomohiro, Tsunogai, Urumu, Miyazaki, Masayuki, Miyazaki, Junichi, Hirayama, Hisako, Nakagawa, Satoshi, Nunoura, Takuro, Horikoshi, Koki
- Proceedings of the National Academy of Sciences of the United States of America 2008 v.105 no.31 pp. 10949-10954
- carbon dioxide, cell proliferation, high pressure treatment, isotope fractionation, methane, methane production, methanogens, rubber, stable isotopes, temperature
- We have developed a technique for cultivation of chemolithoautotrophs under high hydrostatic pressures that is successfully applicable to various types of deep-sea chemolithoautotrophs, including methanogens. It is based on a glass-syringe-sealing liquid medium and gas mixture used in conjunction with a butyl rubber piston and a metallic needle stuck into butyl rubber. By using this technique, growth, survival, and methane production of a newly isolated, hyperthermophilic methanogen Methanopyrus kandleri strain 116 are characterized under high temperatures and hydrostatic pressures. Elevated hydrostatic pressures extend the temperature maximum for possible cell proliferation from 116°C at 0.4 MPa to 122°C at 20 MPa, providing the potential for growth even at 122°C under an in situ high pressure. In addition, piezophilic growth significantly affected stable carbon isotope fractionation of methanogenesis from CO₂. Under conventional growth conditions, the isotope fractionation of methanogenesis by M. kandleri strain 116 was similar to values (-34[per thousand] to-27[per thousand]) previously reported for other hydrogenotrophic methanogens. However, under high hydrostatic pressures, the isotope fractionation effect became much smaller (<-12[per thousand]), and the kinetic isotope effect at 122°C and 40 MPa was -9.4[per thousand], which is one of the smallest effects ever reported. This observation will shed light on the sources and production mechanisms of deep-sea methane.