title: A new facultatively autotrophic hydrogen- and sulfur-oxidizing bacterium from an alkaline environment.
abstract: An alkaliphilic bacterium, strain AHO 1, was isolated from an enrichment culture with hydrogen at pH 10 inoculated with a composite sample of sediments from five highly alkaline soda lakes (Kenya). This bacterium is a gram-negative, nonmotile, rod-shaped, obligately aerobic, and facultatively autotrophic hydrogen-oxidizing organism. It was able to oxidize reduced sulfur compounds to sulfate during heterotrophic growth. It utilized a wide range of organic compounds as carbon and energy sources and grew mixotrophically with hydrogen and acetate. With sulfur compounds, mixotrophic growth was observed only in acetate-limited continuous culture. The normal pH range for autotrophic growth with hydrogen was pH 8.0-10.25, with a pH optimum at 9-9.5. Growth at pH values lower than 8.0 was extremely slow. Heterotrophic growth with acetate was optimal at pH 10.0. The hydrogen-oxidizing activity of whole cells was maximal at pH 9.0 and still substantial up to pH 11. NAD-dependent hydrogenase activity was found in the soluble fraction of the cell-free extract, but no methylene blue-dependent activity in either the soluble or membrane fractions was observed. On the basis of its pH profile, the soluble hydrogenase of strain AHO 1 was a typical pH-neutral enzyme. Phylogenetic analysis revealed that strain AHO 1 belongs to the alpha-3 subgroup of the Proteobacteria with a closest relation to a recently described alkaliphilic aerobic bacteriochlorophyll a-containing bacterium "Roseinatronobacter thiooxidans."
authors.affiliation: Institute of Microbiology RAS, Moscow, Russia.
authors.forename: D Y
authors.initials: DY
authors.lastname: Sorokin
authors.forename: T P
authors.initials: TP
authors.lastname: Tourova
authors.forename: J G
authors.initials: JG
authors.lastname: Kuenen
mesh_terms: D000468:Alkalies; D001482:Base Composition; D002455:Cell Division; D003470:Culture Media; D003580:Cytochromes / Q000378:metabolism; D005618:Fresh Water / Q000382:microbiology; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006864:Hydrogenase / Q000378:metabolism*; D007630:Kenya; D008854:Microscopy, Electron; D009243:NAD / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D010084:Oxidation-Reduction; D010641:Phenotype; D010802:Phylogeny; D020560:Proteobacteria / Q000166:cytology / Q000201:enzymology / Q000302:isolation & purification* / Q000378:metabolism*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*
chemical_list: D000468:Alkalies; D003470:Culture Media; D003580:Cytochromes; D009243:NAD; D013455:Sulfur; D006859:Hydrogen; D006864:Hydrogenase; D012273:Ribulose-Bisphosphate Carboxylase; D009584:Nitrogen