Reclassification of the genus Dysgonomonas and description of Dysgonomonas reticulitermitis sp. nov. and Viscerimonas tarda gen. nov., sp. nov. from the gut of the subterranean termite Reticulitermes speratus

The genus <i>Dysgonomonas</i>, established in 2000 and currently comprising nine isolated species, belongs to the order <i>Bacteroidales</i>. Despite its increasing ecological and clinical relevance, the genus remains taxonomically ambiguous, and criteria for genus-level classification have not been systematically assessed. In this study, we re-evaluated the taxonomy of <i>Dysgonomonas</i> using core genome phylogeny, average amino acid identity and percentage of conserved proteins. These genome-based metrics and physiological data revealed that the genus <i>Dysgonomonas</i> comprises at least three distinct genus-level lineages, and (i) <i>Dysgonomonas sensu stricto</i> represented by <i>Dysgonomonas gadei</i>, (ii) <i>Indolivaga</i> gen. nov. represented by <i>Dysgonomonas capnocytophagoides</i> and (iii) <i>Pseudodysgonomonas</i> gen. nov. represented by <i>Dysgonomonas massiliensis</i> are proposed. In addition, two strains MK137_Hg11^T and MK137_Hg34^T, facultative anaerobic bacteria, were isolated from the gut of the subterranean termite <i>Reticulitermes speratus</i>. On the basis of the collected data, we propose that strain MK137_Hg11^T represents a novel species within <i>Dysgonomonas</i>, while strain MK137_Hg34^T represents a novel species belonging to a fourth, previously unrecognized genus within the family <i>Dysgonomonadaceae</i>. We therefore propose the names <i>Dysgonomonas reticulitermitis</i> sp. nov. (type strain MK137_Hg11^T=JCM 35194^T=DSM 118089^T) and <i>Viscerimonas tarda</i> gen. nov., sp. nov. (type strain MK137_Hg34^T=JCM 35195^T=DSM 118090^T).