Draft genome sequence of a potential new species of Mesorhizobium isolated from Neltuma juliflora, a tropical legume in Costa Rica

We present the draft genome of the Mesorhizobium sp. LEGMi-168a strain isolated from Neltuma juliflora (Sw.) Raf. (Fabaceae, Caesalpinioideae) in Costa Rica. It exhibited an average nucleotide identity (ANI) of 91.88% and a digital DNA-DNA hybridization (dDDH) value of 49.90% compared to its closest relative, Mesorhizobium captivum van Lill et al. 2024 (VK22ET). Furthermore, the phylogenetic tree based on the 16S rRNA suggests that the strain belongs to a clade alongside Mesorhizobium shonense Degefu et al. 2013 (DSM 29846T) and Mesorhizobium sp. M1B.F.Ca.ET.045.04.1.1. However, the phylogenomic analyses suggest that this strain does not fall within any currently described species clade. Functional in silico annotation identified the presence of genes related to nodulation capacity (nodA, nodB, nodC, nodD, nodN, and nodO) and others associated with nitrogen fixation (fixU, nifA, nifB, nifE, nifH, nifN, nifQ, and nifW). The differences in ANI and dDDH values, combined with the phylogenomic position relative to known species observed in the in silico analysis, suggest that strain LEGMi-168a represents a potential new species. In this study, we presented the draft genome sequence of strain LEGMi-168a and provided genomic and phylogenetic evidence supporting its potential status as a novel Mesorhizobium species. The genome sequence provided a resource for future comparative, taxonomic, and symbiosis related studies of Mesorhizobium associated with leguminous plants.