Assessment of the Carbon Monoxide Metabolism of the Hyperthermophilic Sulfate-Reducing ArchaeonArchaeoglobus fulgidusVC-16 by Comparative Transcriptome Analyses

Abstract

The hyperthermophilic, sulfate-reducing archaeon,Archaeoglobus fulgidus, utilizes CO as an energy source and it is resistant to the toxic effects of high CO concentrations. Herein, transcription profiles were obtained fromA. fulgidusduring growth with CO and sulfate or thiosulfate, or without an electron acceptor. This provided a basis for a model of the CO metabolism ofA. fulgidus. The model suggests proton translocation by “Mitchell-type” loops facilitated by Fqo catalyzing aFdred:menaquinone oxidoreductase reaction, as the major mode of energy conservation, rather than formate or H2cycling during respiratory growth. The bifunctional CODH (cdhAB-2) is predicted to play an ubiquitous role in the metabolism of CO, and a novel nitrate reductase-associated respiratory complex was induced specifically in the presence of sulfate. A potential role of this complex in relation toFdredand APS reduction is discussed. Multiple membrane-bound heterodisulfide reductase (DsrMK) could promote both energy-conserving and non-energy-conserving menaquinol oxidation. Finally, the FqoF subunit may catalyze aFdred:F420oxidoreductase reaction. In the absence of electron acceptor, downregulation of F420H2dependent steps of the acetyl-CoA pathway is linked to transient formate generation. Overall, carboxidotrophic growth seems as an intrinsic capacity ofA. fulgiduswith little need for novel resistance or respiratory complexes.