Denitratisoma oestradiolicum gen. nov., sp nov., a 17β-oestradiol-degrading, denitrifying betaproteobacterium

A Gram-negative, motile, denitrifying bacterium (strain AcBE2-1(T)) was isolated from activated sludge of a municipal wastewater treatment plant using 17 beta-oestradiol (E2) as sole source of carbon and energy. Cells were curved rods, 0(.)4-0(.)8 x 0(.)8-2(.)0 mu m in size, non-fermentative, non-spore-forming, oxidase-positive and catalase-negative. E2 was oxidized completely to carbon dioxide and water by reduction of nitrate to a mixture of dinitrogen monoxide and dinitrogen, with the intermediate accumulation of nitrite. Electron recoveries were between 90 and 100%, taking assimilated E2 into account. With nitrate as the electron acceptor, the bacterium also grew on fatty acids (C-2 to C-6), isobutyrate, crotonate, DL-lactate, pyruvate, fumarate and succinate. Phylogenetic analysis of its 16S rRNA gene sequence revealed that strain AcBE2-1(T) represents a separate line of descent within the family Rhodocyclaceae (Betaproteobacteria). The closest relatives are the cholesterol-degrading, denitrifying bacteria Sterolibacterium denitriticans IDSM 13999(T) and strain 72Chol (=DSM 12783), with < 93.9% sequence similarity. The G+C content of the DNA was 61(.)4 mol%. Detection of a quinone system with ubiquinone 0-8 as the predominant compound and a fatty acid profile that included high concentrations of C-16:1 omega 7c/iso-C-15:0 2-OH and C-16:0, in addition to C-18:1 omega 7c and small amounts of C-8:0 3-OH, supported the results of the phylogenetic analysis. On the basis of 16S rRNA gene sequence data in combination with chemotaxonomic and physiological data, strain AcBE2-1(T) (=DSM 16959(T) = JCM 12830(T)) is placed in a new genus Denitratisoma gen. nov. as the type strain of the type species Denitratisoma oestradiolicum gen. nov., sp. nov.