Clostridium glycyrrhizinilyticum sp nov., a glycyrrhizin-hydrolysing bacterium isolated from human faeces

Screening of faecal bacteria for glycyrrhetic acid (GA) production by hydrolysing of glycyrrhizin (GL) resulted in the isolation of two strains, designated ZM35(T) and ZM38. Strains ZM35(T) and ZM38 were Gram-positive, obligate anaerobic, non-spore-forming and rod-shaped bacteria. Analysis of the 16S rRNA gene sequences indicated that strains ZM35(T) and ZM38 belonged to cluster XIVa of the genus Clostridium. The 16S rRNA gene sequences of strains ZM35(T) and ZM38 were identical. Strain ZM35(T) exhibited approximately 94% to 95% identity with the validly described species, Clostridium oroticum (94.5%), Eubacterium contortum (93.8%), Ruminococcus gnavus (94.5%) and R. torques (95.1%). In an experiment of DNA-DNA hybridization, it was confirmed that strains ZM35(T) and ZM38 were the same species. The guanine-plus-cytosine (G+C) content of strain ZM35(T) is 45.7 mol%. Based on the phylogenetic and phenotypic findings, we propose that strains ZM35(T) and ZM38 be assigned to a novel species named Clostridium glycyrrhizinilyticum. The type strain is ZM35(T) (=JCM 13368(T) =DSM 17593(T)).