Polyphasic and comparative genomic characterization of a novel Mariniflexile species in the rhizosphere microbiome of tomato resistant to bacterial wilt.

A plethora of microbes resides in the plant rhizosphere, and some play roles in host health and disease. We previously isolated a Gram-negative, aerobic, rod-shaped rhizobacterium, TRM1-10, that contributes to bacterial wilt resistance of tomato caused by Ralstonia solanacearum. In this study, we characterized TRM1-10 through physiological and biochemical analyses, complemented by whole genome sequencing and comparative genomic analyses. Phylogenetic analysis using the 16S rRNA gene and genome sequences revealed that TRM1-10 belongs to the genus Mariniflexile and represents a new lineage. TRM1-10 also exhibits noticeable differences in physiological and biochemical characteristics compared to other Mariniflexile species. Thus, based on phylogenetic affiliation and chemotaxonomic characteristics, we propose this bacterium as a novel species in the genus, Mariniflexile rhizosphaerae sp. nov. (type strain TRM1-10^T = KCTC 18646P^T = DSM 33122^T). Comparative genome analyses revealed that TRM1-10 harbors more genes linked to soil adaptation compared to other phylogenetically related Mariniflexile species, most of which are associated with marine habitats. The genomic features of TRM1-10 and other strains in the species may allow the taxon to adapt to the soil and rhizosphere, compete effectively with the resident soil microbiota, and contribute to plant health.