Characteristic Strain 1 Strain 2 Strain 3 Strain 4 Cell morphology Rod Curved rod Curved rod Slightly curved rod Cell size (μm) 0.5-0.75 x 1.0-2.2 0.5-0.6 x 1.0-1.3 0.4-0.8 x 0.8-2.0 0.3-0.5 x 0.6-1.6 Motility + + + + DNA G+C (mol%) ND 65.3 61.4 61.9 Phylogenetic group β-Proteobacteria β-Proteobacteria β-Proteobacteria γ-Proteobacteria Oxidase ND + + + Catalase + + - + Optimal pH for growth 7.2 7.0 7.0-7.2 7.0 Optimal temperature (°C) for growth 32 30-32 28-30 28 Available carbon and energy source (with nitrate as the electron acceptors): Cholesterol + + - - 4-Androstene-3,17-dione - + - + Testosterone ND (+) - + 17β-Estradiol - - + + Acetate - (+) + + Propionate (+) (+) + + Valerate (+) (+) + + Caproate (+) - + + Heptanoate (+) (+) - + Palmiate - + - ND Stearate + + - ND Pyruvate - - + ND Fumarate - - + ND Succinate - - + ND Glutamate - - - + Available electron acceptors (with steroids as the carbon source): Nitrate + + + + Chlorate - - - - Perchlorate - - - - Oxygen + + - + Sulfate - - - - Strain 1, 72Chol (=DSM 12783); Strain 2, Sterolibacterium denitrificans Chol-1ST(=DSM 13999); 3, Denitratisoma oestradiolicum (= DSM 16959); 4, Steroidobacter denitrificans (=DSM 18526). +, positive or growth; (+), weak growth; (-), negative or no growth. ND, no data available.

Table 1: Morphological, physiological and phylogenetic characteristics of the denitrifying bacterial strains which are able to grow on steroid compounds.