RESUMO
Twenty-two genospecies belonging mainly to Mesorhizobium, and occasionally to Rhizobium and Bradyrhizobium, were defined among the 174 rhizobia strains isolated from Caragana species. Highly similar nodC genes were found in the sole Bradyrhizobium strain and among all the detected Mesorhizobium strains. A clear correlation between rhizobial genospecies and the eco-regions where they were isolated was found using homogeneity analysis. All these results demonstrated that Caragana species had stringently selected the rhizobia symbiotic genotype, but not the genomic background; lateral transfer of symbiotic genes from Mesorhizobium to Bradyrhizobium and among the Mesorhizobium species has happened in the Caragana rhizobia; and biogeography of Caragana rhizobia exists. Furthermore, a combined cluster analysis, based upon the patterns obtained from amplified 16S rRNA gene and 16S-23S intergenic spacer restriction analyses, BOX PCR and SDS-PAGE of proteins, was reported to be an efficient method to define the genospecies.
Assuntos
Caragana/microbiologia , Variação Genética , Rhizobiaceae/classificação , Rhizobiaceae/isolamento & purificação , Proteínas de Bactérias/análise , Proteínas de Bactérias/genética , China , Análise por Conglomerados , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , DNA Espaçador Ribossômico/química , DNA Espaçador Ribossômico/genética , Eletroforese em Gel de Poliacrilamida , Transferência Genética Horizontal , Geografia , Dados de Sequência Molecular , N-Acetilglucosaminiltransferases/genética , Filogenia , Proteoma/análise , RNA Ribossômico 16S/genética , Rhizobiaceae/química , Rhizobiaceae/genética , Análise de Sequência de DNARESUMO
Five rhizobial strains representing the largest group in the genus Mesorhizobium associated with Caragana spp. in China were characterized taxonomically. Phylogenetic analysis based on 16S rRNA gene sequences indicated that these microsymbionts belonged to the genus Mesorhizobium, with Mesorhizobium tianshanense USDA 3592(T), Mesorhizobium temperatum SDW018(T) and Mesorhizobium mediterraneum UPM-Ca36(T) as the closest neighbours (>/=99.5 % 16S rRNA gene sequence similarity). Genotypic fingerprinting by whole-cell protein electrophoresis, DNA-DNA hybridization, comparative housekeeping sequence analysis of the atpD, glnII and recA genes, fatty acid profiles and a series of phenotypic and physiological tests allowed the novel group to be differentiated from all previously recognized species of the genus Mesorhizobium. This group therefore represents a novel species, for which the name Mesorhizobium caraganae sp. nov. is proposed with the type strain CCBAU 11299(T) (=LMG 24397(T)=HAMBI 2990(T)). Cross-inoculation tests showed that strain CCBAU 11299(T) could form effective nodules on Caragana microphylla, Caragana intermedia, Glycyrrhiza uralensis, Astragalus adsurgens and Phaseolus vulgaris.
Assuntos
Alphaproteobacteria/classificação , Caragana/microbiologia , Alphaproteobacteria/química , Alphaproteobacteria/genética , Alphaproteobacteria/fisiologia , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Técnicas de Tipagem Bacteriana , China , DNA Bacteriano/análise , DNA Ribossômico/análise , Ácidos Graxos/análise , Genes de RNAr , Dados de Sequência Molecular , Fixação de Nitrogênio , Hibridização de Ácido Nucleico , Fenótipo , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
Fourteen strains representing 11 Caragana-nodulating Mesorhizobium genomic species were identified as representing Mesorhizobium amorphae, Mesorhizobium huakuii, Mesorhizobium septentrionale and groups related to Mesorhizobium plurifarium, Mesorhizobium temperatum, Mesorhizobium tianshanense and Mesorhizobium mediterraneum by sequencing of the 16S rRNA gene, 16S-23S internal transcribed spacer, partial housekeeping recA gene, and previously performed sodium dodecyl sulfate polyacrylamide gel electrophoresis of proteins and BOX-PCR fingerprinting. Despite their different taxonomic affiliation, highly similar symbiotic genes (>93% similarity for nodC and >91.8% similarity for nifH) were found among the Caragana strains and the three type strains for M. tianshanense, M. temperatum and M. septentrionale. Cross nodulation tests revealed that each of these 14 Caragana mesorhizobia and the three type strains mentioned above could effectively infect each of their original host plants, Caragana microphylla, Glycyrrhiza (host for M. tianshanense type strain) and Astragalus adsurgens (host for M. temperatum and M. septentrionale type strains). These results provide evidence that different Mesorhizobium species can nodulate with Caragana, and they have similar symbiotic genes (probably acquired by a phenomenon of lateral gene transfer) and common host ranges.
Assuntos
Alphaproteobacteria/classificação , Alphaproteobacteria/genética , Caragana/microbiologia , Genes Bacterianos , Simbiose , Alphaproteobacteria/isolamento & purificação , Alphaproteobacteria/fisiologia , Proteínas de Bactérias/genética , Impressões Digitais de DNA , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , DNA Espaçador Ribossômico/genética , Eletroforese em Gel de Poliacrilamida , Dados de Sequência Molecular , N-Acetilglucosaminiltransferases/genética , Oxirredutases/genética , Proteoma/análise , RNA Ribossômico 16S/genética , Recombinases Rec A/genética , Análise de Sequência de DNA , Homologia de Sequência de AminoácidosRESUMO
Caragana species are woody legumes widely distributed in the arid regions of China. These plants form root nodules but their nodule bacteria have not been clearly classified. A total of 112 symbiotic bacterial isolates were obtained from four Caragana species grown in Liaoning Province and were characterized with ARDRA, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins, BOX-PCR and sequencing of the 16S rRNA gene. Most of them were classified as Mesorhizobium belonging to 11 putative species. Three isolates were identified as Rhizobium etli and Burkholderia spp. This study offers new information about the Caragana-rhizobia association and resource for selection of inoculants used in sustainable agriculture and for further studies on the Caragana rhizobia.
