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

Abstract The genus Dysgonomonas, established in 2000 and currently comprising nine isolated species, belongs to the order Bacteroidales. 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 Dysgonomonas using core genome phylogeny, average amino acid identity and percentage of conserved proteins. These genome-based metrics and physiological data revealed that the genus Dysgonomonas comprises at least three distinct genus-level lineages, and (i) Dysgonomonas sensu stricto represented by Dysgonomonas gadei, (ii) Indolivaga gen. nov. represented by Dysgonomonas capnocytophagoides and (iii) Pseudodysgonomonas gen. nov. represented by Dysgonomonas massiliensis are proposed. In addition, two strains MK137_Hg11T and MK137_Hg34T, facultative anaerobic bacteria, were isolated from the gut of the subterranean termite Reticulitermes speratus. On the basis of the collected data, we propose that strain MK137_Hg11T represents a novel species within Dysgonomonas, while strain MK137_Hg34T represents a novel species belonging to a fourth, previously unrecognized genus within the family Dysgonomonadaceae. We therefore propose the names Dysgonomonas reticulitermitis sp. nov. (type strain MK137_Hg11T=JCM 35194T=DSM 118089T) and Viscerimonas tarda gen. nov., sp. nov. (type strain MK137_Hg34T=JCM 35195T=DSM 118090T).