Formate-dependent H2 Production by the Mesophilic Methanogen Methanococcus Maripaludis

Appl Environ Microbiol. 2008 Nov;74(21):6584-90. doi: 10.1128/AEM.01455-08. Epub 2008 Sep 12.

Abstract

Methanococcus maripaludis, an H(2)- and formate-utilizing methanogen, produced H(2) at high rates from formate. The rates and kinetics of H(2) production depended upon the growth conditions, and H(2) availability during growth was a major factor. Specific activities of resting cells grown with formate or H(2) were 0.4 to 1.4 U mg(-1) (dry weight). H(2) production in formate-grown cells followed Michaelis-Menten kinetics, and the concentration of formate required for half-maximal activity (K(f)) was 3.6 mM. In contrast, in H(2)-grown cells this process followed sigmoidal kinetics, and the K(f) was 9 mM. A key enzyme for formate-dependent H(2) production was formate dehydrogenase, Fdh. H(2) production and growth were severely reduced in a mutant containing a deletion of the gene encoding the Fdh1 isozyme, indicating that it was the primary Fdh. In contrast, a mutant containing a deletion of the gene encoding the Fdh2 isozyme possessed near-wild-type activities, indicating that this isozyme did not play a major role. H(2) production by a mutant containing a deletion of the coenzyme F(420)-reducing hydrogenase Fru was also severely reduced, suggesting that the major pathway of H(2) production comprised Fdh1 and Fru. Because a Deltafru-Deltafrc mutant retained 10% of the wild-type activity, an additional pathway is present. Mutants possessing deletions of the gene encoding the F(420)-dependent methylene-H(4)MTP dehydrogenase (Mtd) or the H(2)-forming methylene-H(4)MTP dehydrogenase (Hmd) also possessed reduced activity, which suggested that this second pathway was comprised of Fdh1-Mtd-Hmd. In contrast to H(2) production, the cellular rates of methanogenesis were unaffected in these mutants, which suggested that the observed H(2) production was not a direct intermediate of methanogenesis. In conclusion, high rates of formate-dependent H(2) production demonstrated the potential of M. maripaludis for the microbial production of H(2) from formate.

Publication types

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

MeSH terms

  • Formate Dehydrogenases / genetics
  • Formate Dehydrogenases / metabolism
  • Formates / metabolism*
  • Gene Deletion
  • Hydrogen / metabolism*
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Kinetics
  • Metabolic Networks and Pathways / genetics
  • Methane / metabolism
  • Methanococcus / enzymology
  • Methanococcus / growth & development
  • Methanococcus / metabolism*
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism

Substances

  • Formates
  • Isoenzymes
  • formic acid
  • Hydrogen
  • Oxidoreductases
  • coenzyme F420 hydrogenase
  • Formate Dehydrogenases
  • Methane