title: Cell proliferation at 122 degrees C and isotopically heavy CH4 production by a hyperthermophilic methanogen under high-pressure cultivation.
abstract: 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 degrees C at 0.4 MPa to 122 degrees C at 20 MPa, providing the potential for growth even at 122 degrees C under an in situ high pressure. In addition, piezophilic growth significantly affected stable carbon isotope fractionation of methanogenesis from CO(2). 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 degrees 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.
authors.affiliation: Subground Animalcule Retrieval Program, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan. kent@jamstec.go.jp
authors.forename: Ken
authors.initials: K
authors.lastname: Takai
authors.forename: Kentaro
authors.initials: K
authors.lastname: Nakamura
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Toki
authors.forename: Urumu
authors.initials: U
authors.lastname: Tsunogai
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyazaki
authors.forename: Junichi
authors.initials: J
authors.lastname: Miyazaki
authors.forename: Hisako
authors.initials: H
authors.lastname: Hirayama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Takuro
authors.initials: T
authors.lastname: Nunoura
authors.forename: Koki
authors.initials: K
authors.lastname: Horikoshi
mesh_terms: D001483:Base Sequence; D002247:Carbon Isotopes / Q000032:analysis; D018929:Cell Culture Techniques / Q000295:instrumentation / Q000379:methods*; D005591:Chemical Fractionation; D019605:Euryarchaeota / Q000254:growth & development* / Q000378:metabolism; D007700:Kinetics; D008697:Methane / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D011312:Pressure; D016019:Survival Analysis; D013696:Temperature; D013816:Thermodynamics
chemical_list: D002247:Carbon Isotopes; D008697:Methane