Anaerotruncus colihominis gen. nov., sp. nov., from human faeces

This study describes the identification and formal taxonomic classification of a previously unknown bacterium isolated from human fecal samples. Two isolates were recovered from stool specimens of children at Rush Children's Hospital in Chicago. Using phenotypic characterization and 16S rRNA gene sequencing, researchers determined that these gram-positive, anaerobic, rod-shaped bacteria formed a distinct lineage within the Clostridium leptum cluster. The organisms were non-spore-forming, catalase-negative, produced acetic and butyric acids as metabolic end products, and had a DNA G+C content of approximately 54 mol%. Based on phylogenetic analysis showing at least 10% sequence divergence from known C. leptum group members and distinct phenotypic differences from related taxa, the authors propose a novel genus and species: Anaerotruncus colihominis. The type strain is WAL 14565T. This work demonstrates the value of combining culture-dependent techniques with molecular sequencing to discover and characterize previously unidentified members of the human gut microbiota.

Key findings

• A novel genus and species, Anaerotruncus colihominis, was identified from human fecal samples and formally described with type strain WAL 14565T.
• The bacterium is gram-positive, strictly anaerobic, non-spore-forming, catalase-negative, and produces acetic and butyric acids as sole fermentation end products.
• Phylogenetic analysis of 16S rRNA genes demonstrated the organism forms a distinct sublineage within the Clostridium leptum rRNA cluster with ≥10% sequence divergence from described relatives.
• The organism has a DNA G+C content of 54 mol% and grows within a pH range of 5.5–11 and temperature range of 36–40°C.
• Integration of traditional anaerobic culturing with molecular sequencing enabled discovery and characterization of this previously unknown member of the human gut microbiota.