Identification and characterization of four novel gut bacterial taxa: Alvibacillus kangbaii gen. nov., sp. nov., Jutongia huiwenae sp. nov., Flintibacter aciditolerans sp. nov., and Dizhoua hominis gen. nov., sp. nov. isolated from human feces.

The families Clostridiaceae, Lachnospiraceae, and Oscillospiraceae are key but poorly cultured constituents of the human gut microbiota. From healthy Chinese adults, four anaerobic strains (SJQ-1T, SJQ-5T, SJQ-6T, and SJQ-8T) were isolated. 16S rRNA gene phylogeny placed SJQ-1T and SJQ-5T in Clostridiaceae, SJQ-6T in Lachnospiraceae, and SJQ-8T in Oscillospiraceae. Genomic comparisons (16S rRNA gene similarity, ANI, AAI, and dDDH) indicated they represent novel species or genera. Their closest relatives are the "Anaeromassilibacillus senegalensis" mt9ᵀ (a non-validly published genus name), the Jutongia huaianensis NSJ-37ᵀ, and the Flintibacter porci P01025ᵀ, respectively. Strain SJQ-5ᵀ exhibited ANI/AAI/dDDH values far below genus boundaries, supporting a novel genus. All strains produced short-chain fatty acids and displayed distinct carbon utilization and enzymatic profiles. Based on those results, we propose new taxa Alvibacillus kangbaii gen. Nov., sp. nov. for type strain SJQ-1T and Dizhoua hominis gen. Nov., sp. nov. for type strain SJQ-5ᵀ, and 2 other new species Jutongia huiwenae sp. nov. (type strain SJQ-6ᵀ) and Flintibacter aciditolerans sp. nov. (type strain SJQ-8ᵀ). This study expands the cultured diversity of the order Eubacteriales and provides new bioresources and taxonomic foundation for future mechanistic and functional investigations.