Characterization of two Martinezella spp. species: M. legmii sp. nov. and M. ivanii sp. nov., from tropical legume trees in Costa Rica

Four rhizobial strains were discovered in root nodules of tropical leguminous plants in Costa Rica. LEGMi-135b came from Lonchocarpus felipei nodules, LEGMi-12c from Cojoba arborea, LEGMi-198b from Calliandra haematocephala, and Rhizobium altiplani LEGMi-166a from Mimosa pigra. Phylogenetic studies based on the 16S rRNA gene and four housekeeping genes placed these strains within Martinezella and Rhizobium, with LEGMi-135b, LEGMi-12c, and LEGMi-198b falling under Martinezella, and LEGMi-166a under Rhizobium.

Genome comparison indicated that LEGMi-135b had 94% ANI and 53.2% dDDH with Martinezella hainanensis CCBAU 57015T, supporting its status as a distinct species. LEGMi-12c showed 98% ANI and 87% dDDH with Martinezella hainanensis CCBAU 57015T, while LEGMi-198b was most similar to Rhizobium cerradonense CNPSo 3464, with 98% ANI and 81.4% dDDH.

LEGMi-166a was confirmed with 100% ANI and 99.3% dDDH with Rhizobium altiplani BR 10423, solidifying its classification in Rhizobium. The unique characteristics of LEGMi-135b and LEGMi-198b were further confirmed by their distinct phenotypic, physiological, and biochemical properties. Based on the comprehensive evidence, the study proposes the naming of two new rhizobial species: Martinezella legmii sp. nov., with LEGMi-135b as the type strain, and Martinezella ivanii sp. nov., with LEGMi-198b as the type strain.

This research contributes to our knowledge of rhizobia associated with nitrogen-fixing symbiosis, particularly among Costa Rican tropical leguminous plants.