Rhizobium halophytocola sp. nov., isolated from the root of a coastal dune plant

Abstract

During a study of endophytic bacteria from coastal dune plants, a bacterial strain, designated YC6881T, was isolated from the root ofRosa rugosacollected from the coastal dune areas of Namhae Island, Korea. The bacterium was found to be Gram-staining-negative, motile, halophilic and heterotrophic with a single polar flagellum. Strain YC6881Tgrew at temperatures of 4–37 °C (optimum, 28–32 °C), at pH 6.0–9.0 (optimum, pH 7.0–8.0), and at NaCl concentrations in the range of 0–7.5 % (w/v) (optimum, 4–5 % NaCl). Strain YC6881Twas catalase- and oxidase-positive and negative for nitrate reduction. According to phylogenetic analysis using 16S rRNA gene sequences, strain YC6881Tbelonged to the genusRhizobiumand showed the highest 16S rRNA gene sequence similarity of 96.9 % toRhizobium rosettiformans, followed byRhizobium borbori(96.3 %),Rhizobium radiobacter(96.1 %),Rhizobium daejeonense(95.9 %),Rhizobium larrymoorei(95.6 %) andRhizobium giardinii(95.4 %). Phylogenetic analysis of strain YC6881TbyrecA,atpD,glnIIand 16S–23S intergenic spacer (IGS) sequences all confirmed the phylogenetic arrangements obtained by using 16S rRNA gene sequences. Cross-nodulation tests showed that strain YC6881Twas a symbiotic bacterium that nodulatedVigna unguiculataandPisum sativum. The major components of the cellular fatty acids were C18 : 1ω7c(53.7 %), C19 : 0cyclo ω8c(12.6 %) and C12 : 0(8.1 %). The DNA G+C content was 52.8 mol%. Phenotypic and physiological tests with respect to carbon source utilization, antibiotic resistance, growth conditions, phylogenetic analyses of housekeeping genesrecA,atpDandglnII, and fatty acid composition could be used to discriminate strain YC6881Tfrom other species of the genusRhizobiumin the same sublineage. Based on the results obtained in this study, strain YC6881Tis considered to represent a novel species of the genusRhizobium, for which the nameRhizobium halophytocolasp. nov. is proposed. The type strain is YC6881T( = KACC 13775T = DSM 21600T).