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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.