title: Growth kinetics and energetics of a deep-sea hyperthermophilic methanogen under varying environmental conditions.
abstract: A hyperthermophilic deep-sea methanogen, Methanocaldococcus strain JH146, was isolated from 26°C hydrothermal fluid at Axial Volcano to model high temperature methanogenesis in the subseafloor. Emphasis was placed on defining growth kinetics, cell yields and growth energy demand (GE) across a range of conditions. The organism uses H2 and CO2 as its sole carbon and energy sources. At various temperatures, pHs, and chlorinities, its growth rates and cell yields co-varied while GE remained uniform at 1.69 × 10(-11) J cell(-1)s(-1) ± 0.68 × 10(-11) J cell(-1)s(-1) (s.d., n = 23). An exception was at superoptimal growth temperatures where GE increased to 7.25 × 10(-11) J cell(-1)s(-1) presumably due to heat shock. GE also increased from 5.1 × 10(-12) J cell(-1)s(-1) to 7.61 × 10(-11) J cell(-1)s(-1) as NH4 (+) concentrations decreased from 9.4 mM to 0.14 mM. JH146 did not fix N2 or assimilate NO3 (-), lacked the N2-fixing (cluster II) nifH gene, and became nitrogen limited below 0.14 mM NH4Cl. Nitrogen availability may impact growth in situ since ammonia concentrations at Axial Volcano are < 18 μM. Our approach contributes to refining bioenergetic and carbon flux models for methanogens and other organisms in hydrothermal vents and other environments.
authors.affiliation: Department of Microbiology, University of Massachusetts, Amherst, MA, 01003, USA.
authors.forename: Helene C
authors.initials: HC
authors.lastname: Ver Eecke
authors.forename: Nancy H
authors.initials: NH
authors.lastname: Akerman
authors.forename: Julie A
authors.initials: JA
authors.lastname: Huber
authors.forename: David A
authors.initials: DA
authors.lastname: Butterfield
authors.forename: James F
authors.initials: JF
authors.lastname: Holden
mesh_terms: D017753:Ecosystem; D004734:Energy Metabolism; D006358:Hot Temperature; D007700:Kinetics; D008697:Methane / Q000032:analysis / Q000378:metabolism*; D063747:Methanocaldococcus / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012623:Seawater / Q000382:microbiology*
chemical_list: D008697:Methane