Growth kinetics and energetics of a deep-sea hyperthermophilic methanogen under varying environmental conditions

Environ Microbiol Rep. 2013 Oct;5(5):665-71. doi: 10.1111/1758-2229.12065. Epub 2013 May 6.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Ecosystem
  • Energy Metabolism*
  • Hot Temperature
  • Kinetics
  • Methane / analysis
  • Methane / metabolism*
  • Methanocaldococcus / genetics
  • Methanocaldococcus / growth & development*
  • Methanocaldococcus / isolation & purification
  • Methanocaldococcus / metabolism*
  • Molecular Sequence Data
  • Phylogeny
  • Seawater / microbiology*

Substances

  • Methane