This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Porat, I. Articles by Whitman, W. B. Search for Related Content PubMed PubMed Citation Articles by Porat, I. Articles by Whitman, W. B.

Disruption of the Operon Encoding Ehb Hydrogenase Limits Anabolic CO₂ Assimilation in the Archaeon Methanococcus maripaludis

Iris Porat,¹ Wonduck Kim,^1, Erik L. Hendrickson,³ Qiangwei Xia,^2,3 Yi Zhang,^2,3, Tiansong Wang,^2,3 Fred Taub,³ Brian C. Moore,³ Iain J. Anderson,^1,¶ Murray Hackett,² John A. Leigh,³ and William B. Whitman^1*

Department of Microbiology, University of Georgia, Athens, Georgia 30602,¹ Department of Chemical Engineering, University of Washington, Seattle, Washington 98195,² Department of Microbiology, University of Washington, Seattle, Washington 98195³

Received 4 August 2005/ Accepted 21 November 2005

Methanococcus maripaludis is a mesophilic archaeon that reduces CO₂ to methane with H₂ or formate as an energy source. It contains two membrane-bound energy-conserving hydrogenases, Eha and Ehb. To determine the role of Ehb, a deletion in the ehb operon was constructed to yield the mutant, strain S40. Growth of S40 was severely impaired in minimal medium. Both acetate and yeast extract were necessary to restore growth to nearly wild-type levels, suggesting that Ehb was involved in multiple steps in carbon assimilation. However, no differences in the total hydrogenase specific activities were found between the wild type and mutant in either cell extracts or membrane-purified fractions. Methanogenesis by resting cells with pyruvate as the electron donor was also reduced by 30% in S40, suggesting a defect in pyruvate oxidation. CO dehydrogenase/acetyl coenzyme A (CoA) synthase and pyruvate oxidoreductase had higher specific activities in the mutant, and genes encoding these enzymes, as well as AMP-forming acetyl-CoA synthetase, were expressed at increased levels. These observations support a role for Ehb in anabolic CO₂ assimilation in methanococci.

Present address: Department of Microbiology, The Ohio State University, 484 12th Ave., Columbus, OH 43210-1292.

Present address: Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139-4307.

^¶ Present address: Microbial Genome Analysis Program, DOE Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598.

This article has been cited by other articles:

• Hendrickson, E. L., Liu, Y., Rosas-Sandoval, G., Porat, I., Soll, D., Whitman, W. B., Leigh, J. A. (2008). Global Responses of Methanococcus maripaludis to Specific Nutrient Limitations and Growth Rate. J. Bacteriol. 190: 2198-2205 [Abstract] [Full Text]  
• Hendrickson, E. L., Haydock, A. K., Moore, B. C., Whitman, W. B., Leigh, J. A. (2007). Functionally distinct genes regulated by hydrogen limitation and growth rate in methanogenic Archaea. Proc. Natl. Acad. Sci. USA 104: 8930-8934 [Abstract] [Full Text]  
• Matsumi, R., Manabe, K., Fukui, T., Atomi, H., Imanaka, T. (2007). Disruption of a Sugar Transporter Gene Cluster in a Hyperthermophilic Archaeon Using a Host-Marker System Based on Antibiotic Resistance. J. Bacteriol. 189: 2683-2691 [Abstract] [Full Text]