Proposal for reclassification of the species Hungatella xylanolytica as Lacrimispora xylanisolvens nom. nov. and transfer of the genus Hungatella to the family Lachnospiraceae

Hungatella xylanolytica X5-1 T is an anaerobic, xylan-fermenting bacterium first isolated from methane-producing cattle manure. Initially identified as Bacteroides xylanolyticus , this species was later reclassified as H. xylanolytica in 2019. Although this reclassification found support through Genome blast Distance Phylogeny analysis which placed H. xylanolytica X5-1 T into the same clade as Hungatella effluvii DSM 24995 T , it was contradicted by 16S rRNA gene phylogenetic analysis, which associated it with a set of misnamed Clostridium species later reassigned into the genus Lacrimispora . To ascertain its taxonomic position, comparative analyses were performed to re-examine the relationship between H. xylanolytica X5-1 T and all species of the genera Hungatella and Lacrimispora . The ranges of 16S rRNA gene sequence similarity, average amino acid identity, and percentage of conserved protein prediction values were higher between H. xylanolytica X5-1 T and species of the genus Lacrimispora than Hungatella . In addition, H. xylanolytica X5-1 T was found to harbour genes and pathways conserved and exclusive to species within the genus Lacrimispora but not Hungatella . Essentially, in both the 16S rRNA gene phylogenetic tree and the core-genome phylogenomic tree, H. xylanolytica X5-1 T clustered into the same clade as species of the genus Lacrimispora , distinct from species of the genus Hungatella . It is thus clear that H. xylanolytica X5-1 T represents a species within the genus Lacrimispora , which we propose to reclassify as Lacrimispora xylanisolvens nom. nov. Finally, based on the results from the phylogenetic and comparative analyses, the genus Hungatella was transferred to the family Lachnospiraceae .