Description of Hoskinsella mucinilytica gen. nov., sp. nov., a mucin-degrading isolate from human faeces, and reclassification of Amedibacillus hominis Abdugheni et al. 2023 as a later heterotypic synonym of Eubacterium hominis Liu et al. 2022 within the genus Hoskinsella gen. nov.

Mucin-degrading bacteria are recognized as potential players in weakening of the colonic mucus barrier and increased susceptibility to pathogens in the human gut due to their use of mucus as a nutrient source, sometimes in the context of a fibre-deficient diet. Using intact porcine gastric mucin glycoprotein as the main nutrient source, we isolated a Gram-positive, non-motile, rod-shaped, obligately anaerobic bacterium (UGRO018_0423T) from faecal samples of a healthy adult. The strain grows with cells arranged in chains. Based on 16S rRNA gene sequence, the strain UGRO018_0423T shared the highest similarity (96.94% and 96.75%) with Eubacterium hominis New-5T and Amedibacillus hominis NSJ-176T, respectively. Phylogenomic analyses based on 120 concatenated phylogenetically informative protein markers (full-length protein and protein domain sequences) and examination of the placement within the Genome Taxonomy Database (GTDB) reference tree revealed that the strain UGRO018_0423T is not affiliated with the genera Eubacterium or Amedibacillus sensu stricto, and placed UGRO018_0423T within the family Erysipelotrichaceae. This also indicated the problematic taxonomic status of both E. hominis and A. hominis that were placed within the same genus as UGRO018_0423T based on phylogenomic analyses. Genomic comparisons based on average nucleotide identity and digital DNA-DNA hybridization between UGRO018_0423T and E. hominis New-5T and A. hominis NSJ-176T indicated that the strain UGRO018_0423T represents a novel species. These results combined with further chemotaxonomic and phenotypic characterization indicated that strain UGRO018_0423T (=DSM 116809T=ATCC TSD-466T) represents a novel species within a novel genus in the family Erysipelotrichaceae, for which the name Hoskinsella mucinilytica gen. nov., sp. nov. is proposed. In addition, based on genomic comparisons and phylogenomic analysis, A. hominis is reclassified as a later heterotypic synonym of E. hominis, and both species are transferred into the genus Hoskinsella gen. nov. with reclassification of E. hominis as Hoskinsella hominis comb. nov. and A. hominis as Hoskinsella hominifaecis nom. nov.