Desulfovibrio aerotolerans sp. nov., an oxygen tolerant sulphate-reducing bacterium isolated from activated sludge

A new mesophilic sulphate-reducing bacterium, designated strain DvO5T (T=type strain), was isolated from the outermost sulphate reduction-positive most-probable-number tube (10−6 dilution) of an activated sludge sample, which had been oxygenated at 100% air saturation for 120 h. The motile, Gram-negative, curved 1 by 2-5 μm and non-spore-forming cells of strain DvO5T existed singly or in chains. Strain DvO5T grew optimally at 29 °C, pH 6.9 and 0.05% (w/v) NaCl in a medium containing lactate, sulphate and yeast extract. Sulphite, thiosulphate and elemental sulphur also served as electron acceptors whereas nitrate, nitrite or ferric iron were not reduced. Lactate, pyruvate, H2 (with acetate as carbon source), ethanol and glycerol efficiently supported growth as electron donors. Pyruvate and malate were fermented. Strain DvO5T reduced oxygen by oxidising endogenous polyglucose at rates ranging from 0.4 to 6.0 nmol O2/mg protein min depending on the oxygen concentration, the highest rates being observed at atmospheric oxygen saturation. The G+C content of the DNA was 57.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain DvO5T was a member of the genus Desulfovibrio with D. magneticus (98.2% 16S rRNA gene sequence similarity) and D. burkinensis (97.5% 16S rRNA gene sequence similarity) being its closest relatives among validly described species. A similar phylogenetic affiliation was obtained by sequence analyses of the genes encoding the alpha and the beta subunit of dissimilatory sulphite reductase (dsrAB) as well as the alpha subunit of adenosine-5′-phosphosulphate reductase (apsA) of strain DvO5T. On the basis of genotypic and phenotypic characteristics, strain DvO5T (DSM 16695T, JCM 12613T) is proposed as the type strain of a new species, Desulfovibrio aerotolerans sp. nov.