Disruption of the Operon Encoding Ehb Hydrogenase Limits AnabolicCO2 Assimilation in the Archaeon Methanococcus maripaludis
Methanococcus maripaludis is a mesophilic archaeon thatreduces CO2 to methane with H2 or formate as an energy source. Itcontains two membrane-bound energy-conserving hydrogenases, Eha and Ehb.To determine therole of Ehb, a deletion in the ehb operon wasconstructed to yield the mutant, strain S40. Growth of S40 was severelyimpaired in minimal medium. Both acetate and yeast extract were necessaryto restore growth to nearly wild-type levels, suggesting that Ehb wasinvolved in multiple steps in carbon assimilation. However, nodifferences in the total hydrogenase specific activities were foundbetween the wild type and mutant in either cell extracts ormembrane-purified fractions. Methanogenesis by resting cells withpyruvate as the electron donor was also reduced by 30 percent in S40,suggesting a defect in pyruvate oxidation. CO dehydrogenase/acetylcoenzyme A (CoA) synthase and pyruvate oxidoreductase had higher specificactivities in the mutant, and genes encoding these enzymes, as well asAMP-forming acetyl-CoA synthetase, were expressed at increased levels.These observations support a role for Ehb in anabolic CO2 assimilation inmethanococci.
- Research Organization:
- COLLABORATION - U.Georgia
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 903126
- Report Number(s):
- LBNL-60432; JOBAAY; R&D Project: 626869; BnR: KP1103010; TRN: US200720%%92
- Journal Information:
- Journal of Bacteriology, Vol. 188, Issue 4; Related Information: Journal Publication Date: February2006; ISSN 0021-9193
- Country of Publication:
- United States
- Language:
- English
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