Rhizobium altiplani sp. nov. isolated from effective nodules on Mimosa pudica growing in untypically alkaline soil in Central Brazil

Root nodule bacteria were isolated from nodules on Mimosa pudica L. growing in neutral-alkaline soils from the Distrito Federal in Central Brazil. The 16S rRNA gene sequence analysis of ten strains placed them into the genus Rhizobium with the closest neighbouring species (each with 99% similarity) being R. grahamii, R. cauense, R. mesoamericanum and R. tibeticum. This high similarity, however, was not confirmed by multi locus sequence analysis (MLSA) using three housekeeping genes (recA, glnII and rpoB), which revealed R. mesoamericanum strain CCGE 501T to be the closest type strain (92% sequence similarity or less). Chemotaxonomic data, including fatty acid profiles (with majority being C 19:0 cyclo w8c and Summed Feature 8 (C18:1 w6c), DNA G+C content (57.6% mol), and carbon compound utilization patterns supported the placement of the novel strains in the genus Rhizobium. Results of Average Nucleotide Identity (ANI) differentiated the novel strains from the closest Rhizobium species, R. mesoamericanum, R. grahamii and R. tibeticum with 89.0, 88.1 and 87.8% similarity, respectively. The symbiotic genes essential for nodulation (nodC) and nitrogen fixation (nifH) were most similar (99-100%) to those of R. mesoamericanum, another Mimosa-nodulating species.Based on the current data, these ten strains represent a novel species for which the name Rhizobium altiplani sp. nov. (BR 10423T = HAMBI 3664T) is proposed.