New markers for Eubacterium lentum.

Of 37 strains of Eubacterium lentum and phenotypically similar organisms, 26 (70%) synthesized a corticoid 21-dehydroxylase and/or a 3 alpha-hydroxysteroid dehydrogenase. It appeared that the corticoid 3 alpha-hydroxysteroid dehydrogenase was identical to the bile acid 3 alpha-hydroxysteroid dehydrogenase. Steroid-metabolizing enzymes were found both in E. lentum and in phenotypically similar organisms. E. lentum is characterized by nitrate reduction and enhanced growth in the presence of arginine. Many phenotypically similar organisms possess either one or the other of the two markers. In contrast, using the steroid-metabolizing enzymes as markers, a "steroid-active" and a "steroid-inactive" group were established with minimal overlapping of metabolic characteristics. Synthesis of the steroid enzymes was positively correlated with production of gas from H2O2 and formation of H2S. A simple method for the detection of corticoid 21-dehydroxylase and 3 alpha-hydroxysteroid dehydrogenase, one or both of which were present in 92% of the steroid-active group, is described.