title: Analysis of the fnrL gene and its function in Rhodobacter capsulatus.
abstract: The fnr gene encodes a regulatory protein involved in the response to oxygen in a variety of bacterial genera. For example, it was previously shown that the anoxygenic, photosynthetic bacterium Rhodobacter sphaeroides requires the fnrL gene for growth under anaerobic, photosynthetic conditions. Additionally, the FnrL protein in R. sphaeroides is required for anaerobic growth in the dark with an alternative electron acceptor, but it is not essential for aerobic growth. In this study, the fnrL locus from Rhodobacter capsulatus was cloned and sequenced. Surprisingly, an R. capsulatus strain with the fnrL gene deleted grows like the wild type under either photosynthetic or aerobic conditions but does not grow anaerobically with alternative electron acceptors such as dimethyl sulfoxide (DMSO) or trimethylamine oxide. It is demonstrated that the c-type cytochrome induced upon anaerobic growth on DMSO is not synthesized in the R. capsulatus fnrL mutant. In contrast to wild-type strains, R. sphaeroides and R. capsulatus fnrL mutants do not synthesize the anaerobically, DMSO-induced reductase. Mechanisms that explain the basis for FnrL function in both organisms are discussed.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, 77225, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Zeilstra-Ryalls
authors.forename: K
authors.initials: K
authors.lastname: Gabbert
authors.forename: N J
authors.initials: NJ
authors.lastname: Mouncey
authors.forename: S
authors.initials: S
authors.lastname: Kaplan
authors.forename: R G
authors.initials: RG
authors.lastname: Kranz
mesh_terms: D000595:Amino Acid Sequence; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D003574:Cytochrome c Group / Q000096:biosynthesis; D003624:Darkness; D004121:Dimethyl Sulfoxide / Q000378:metabolism; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D010084:Oxidation-Reduction; D010100:Oxygen / Q000494:pharmacology; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000096:biosynthesis; D016354:Rhodobacter capsulatus / Q000235:genetics* / Q000528:radiation effects; D012242:Rhodobacter sphaeroides / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; C096744:FnrL protein, Rhodobacter sphaeroides; D045322:Photosynthetic Reaction Center Complex Proteins; D015534:Trans-Activators; D010100:Oxygen; D004121:Dimethyl Sulfoxide