RESUMO
Root nodule bacteria were isolated from Centrolobium paraense Tul. grown in soils from the Amazon region, State of Roraima (Brazil). 16S rRNA gene sequence analysis of seven strains (BR 10247(T), BR 10296, BR 10297, BR 10298, BR 10299, BR 10300 and BR 10301) placed them in the genus Bradyrhizobium with the closest neighbours being the type strains of Bradyrhizobium paxllaeri (98.8â% similarity), Bradyrhizobium icense (98.8â%), Bradyrhizobium lablabi (98.7â%), Bradyrhizobium jicamae (98.6â%), Bradyrhizobium elkanii (98.6â%), Bradyrhizobium pachyrhizi (98.6â%) and Bradyrhizobium retamae (98.3â%). This high similarity, however, was not confirmed by the intergenic transcribed spacer (ITS) 16S-23S rRNA region sequence analysis nor by multi-locus sequence analysis. Phylogenetic analyses of five housekeeping genes (dnaK, glnII, gyrB, recA and rpoB) revealed Bradyrhizobium iriomotense EK05(T) (â=âLMG 24129(T)) to be the most closely related type strain (95.7â% sequence similarity or less). Chemotaxonomic data, including fatty acid profiles [major components being C16â:â0 and summed feature 8 (18â:â1ω6c/18â:â1ω7c)], DNA G+C content, slow growth rate and carbon compound utilization patterns, supported the placement of the novel strains in the genus Bradyrhizobium. Results of DNA-DNA relatedness studies and physiological data (especially carbon source utilization) differentiated the strains from the closest recognized species of the genus Bradyrhizobium. Symbiosis-related genes for nodulation (nodC) and nitrogen fixation (nifH) placed the novel species in a new branch within the genus Bradyrhizobium. Based on the current data, these seven strains represent a novel species for which the name Bradyrhizobium neotropicale sp. nov. is proposed. The type strain is BR 10247(T) (â=âHAMBI 3599(T)).
Assuntos
Bradyrhizobium/classificação , Fabaceae/microbiologia , Filogenia , Nódulos Radiculares de Plantas/microbiologia , Técnicas de Tipagem Bacteriana , Composição de Bases , Bradyrhizobium/genética , Bradyrhizobium/isolamento & purificação , Brasil , DNA Bacteriano/genética , DNA Espaçador Ribossômico/genética , Ácidos Graxos/química , Genes Bacterianos , Dados de Sequência Molecular , Tipagem de Sequências Multilocus , Fixação de Nitrogênio , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , RNA Ribossômico 23S/genética , Análise de Sequência de DNA , SimbioseRESUMO
Root-nodule bacteria were isolated from Inga laurina (Sw.) Willd. growing in the Cerrado Amazon region, State of Roraima, Brazil. The 16S rRNA gene sequences of six strains (BR 10250(T), BR 10248, BR 10249, BR 10251, BR 10252 and BR 10253) showed low similarities with currently described species of the genus Bradyrhizobium. Phylogenetic analyses of sequences of five housekeeping genes (dnaK, glnII, gyrB, recA and rpoB) revealed Bradyrhizobium iriomotense EK05(T) to be the closest type strain (97.4% sequence similarity or less). Chemotaxonomic data, including fatty acid profiles [with the major components C16:0 and summed feature 8 (C18:1ω6c/C18:1ω7c)], the slow growth rate and carbon compound utilization patterns supported the assignment of our strains to the genus Bradyrhizobium. Results from DNA-DNA hybridizations and physiological traits differentiated our strains from the closest related species of the genus Bradyrhizobium with validly published names. Sequences of symbiosis-related genes for nodulation (nodC) and nitrogen fixation (nifH) grouped together with those of B. iriomotense EK05(T) and Bradyrhizobium sp. strains BR 6610 (used as a commercial inoculant for Inga marginata in Brazil) and TUXTLAS-10 (previously observed in Central America). Based on these data, the six strains represent a novel species, for which the name Bradyrhizobium ingae sp. nov. is proposed. The type strain is BR 10250(T) ( = HAMBI 3600(T)).