Growth Kinetics, Carbon Isotope Fractionation, and Gene Expression in the Hyperthermophile Methanocaldococcus jannaschii during Hydrogen-Limited Growth and Interspecies Hydrogen Transfer

• Begüm D. Topçuoğlu ^[2] ; Cem Meydan ^[3] ; Tran B. Nguyen ^[1] ; Susan Q. Lang ^[1] ; James F. Holden ^[2]
  1. [1] University of South Carolina

     University of South Carolina

     Estados Unidos

     
  2. [2] a Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, USA
  3. [3] b Institute for Computational Biomedicine, Weill Cornell Medical College, New York, New York, USA

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• Localización: Applied and Environmental Microbiology, ISSN 0099-2240, Vol. 85, Nº 9, 2019
• Idioma: inglés
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  • Hyperthermophilic methanogens and H2-producing heterotrophs are collocated in high-temperature subseafloor environments, such as petroleum reservoirs, mid-ocean ridge flanks, and hydrothermal vents. Abiotic flux of H2 can be very low in these environments, and there is a gap in our knowledge about the origin of CH4 in these habitats. In the hyperthermophile Methanocaldococcus jannaschii, growth yields increased as H2 flux, growth rates, and CH4 production rates decreased. The same trend was observed increasingly with interspecies H2 transfer between M. jannaschii and the hyperthermophilic H2 producer Thermococcus paralvinellae. With decreasing H2 availability, isotopic fractionation of carbon during methanogenesis increased, resulting in isotopically more negative CH4 with a concomitant decrease in H2-dependent methylene-tetrahydromethanopterin dehydrogenase gene expression and increase in F420-dependent methylene-tetrahydromethanopterin dehydrogenase gene expression. The significance of our research is in understanding the nature of hyperthermophilic interspecies H2 transfer and identifying biogeochemical and molecular markers for assessing the physiological state of methanogens and possible source of CH4 in natural environments.