A novel endophytic bacterium, designated strain BGMRC 0089T, was isolated from a surface-sterilized root of Sonneratia apetala. Cells were observed to be Gram-negative, rod-shaped and motile with polar flagella. Strain BGMRC 0089T was found to grow optimally at 28-30 °C, pH 7.0-8.0 and in the presence of 1 % (w/v) NaCl. Strain BGMRC 0089T contained ubiquinone Q-10 and the predominant fatty acid was summed feature 8. The polar lipid profile of strain BGMRC 0089T was found to contain diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmonomethylethanolamine and phosphatidylethanolamine. Based on the results of 16S rRNA gene analysis, this isolate has the closest phylogenetic relationships with Rhizobium lemnae L6-16T (96.5 %) and Allorhizobium oryziradicis N19T (96.4 %). Average nucleotide identity, amino acid identity and digital DNA-DNA hybridization values of the isolate with the type strains of the genera Rhizobium and Allorhizobium were below 84.6, 73.9 and 22.1 %, respectively. Analysis the 4.55 Mb draft genome of strain BGMRC 0089T revealed several plant-associated genes, which may play important roles for the plant in the adaptation to the mangrove habitat. Based on its distinct phylogenetic, phenotypic and chemotaxonomic characteristics, strain BGMRC 0089T is proposed to represent a novel Allorhizobium species, for which the name Allorhizobium sonneratiae sp. nov. is proposed (type strain BGMRC 0089T=DSM 100171T=MCCC 1K04805T).
Keywords: Allorhizobium; endophytic bacterium; taxonomy.