Agrobacterium sp. II CCBAU 21244 isolated from root nodules of Wisteria sinensis was verified as an endophytic bacterium by inoculation and reisolation tests. However, inoculation with a mixture of this strain and a Sinorhizobium meliloti strain could induce root nodules on W. sinensis and two other woody legumes, which do not form a symbiosis with S. meliloti alone. Rod-shaped and irregular nodules were found on the inoculated plants, in which the S. meliloti strain was detected in all of the nodules; while the Agrobacterium strain was inside of the rod-shaped nodules, or occupied only the nodule surface of the irregular globe-shaped nodules. These findings revealed novel interactions among the symbiotic bacteria, endophytic bacteria and the legume plants, although the mechanisms are still unknown.
A group of rhizobial strains isolated from nodules of multiple legume species grown in different geographical regions of China had identical 16S rRNA genes. Phylogenetic analysis based on the 16S rRNA gene sequences showed that the novel strains formed a subclade in the genus Rhizobium together with Rhizobium galegae, Rhizobium huautlense and Rhizobium alkalisoli, with 99.8 % gene sequence similarity between the strains. The DNA-DNA relatedness values between the representative strain CCBAU 05176 T and R. galegae ATCC 43677 T , R. huautlense S02 T and R. alkalisoli CCBAU 01393 T were 22.6 %, 8.9 % and 15.9 %, respectively. The novel strains were distinguished from recognized species of the genus Rhizobium by using a polyphasic approach, including PCR-based restriction fragment length polymorphism analysis (RFLP) of the 16S-23S intergenic spacer (IGS), phenotypic and physiological tests, sequence comparisons of housekeeping genes and cellular fatty acid profiles. Therefore, it is suggested that this group of strains represents a novel species for which the name Rhizobium vignae sp. nov. is proposed. The type strain is CCBAU 05176 T (5HAMBI 3039 T 5LMG 25447 T ).Rhizobia are Gram-negative rod-shaped bacteria that induce the formation of nodules on the roots or stems of leguminous plants. Within the nodules, they convert atmospheric nitrogen to ammonia and then provide organic nitrogenous compounds such as glutamine or ureides to the plant. In the past two decades, the description of novel taxa of root-and stem-nodule bacteria has been accelerated by the adoption of a polyphasic taxonomic approach (Vandamme et al., 1996) to characterize new isolates from various leguminous plants. The genus Rhizobium, proposed for a group of fast-growing, nodule-forming rhizobia, was firstly described by Frank (1889) and at the time of writing contained 34 species, including the recently described species In previous studies, seven strains of root-nodule bacteria isolated from Vigna radiata (Zhang et al., 2006), Astragalus dahuricus, Astragalus oxyglottis (Zhao et al., 2008) and Desmodium microphyllum (Gu et al., 2007) grown in different regions of China were classified into the genus Rhizobium and were demonstrated to be closely related to Rhizobium galegae by using amplified rDNA restriction analysis (ARDRA). The nodulation ability of the strains on their hosts of origin was confirmed in each of the previous studies. In the present study, the taxonomic status of these strains was clarified by analysis of the 16S-23S rRNA intergenic spacer (IGS-RFLP) and housekeeping gene (atpD, recA and glnII) sequences, cellular fatty acid profiles, DNA-DNA relatedness and the determination of phenotypic characteristics.Seven novel strains (Table 1) and the reference strains were purified and cultured using a standard procedure on yeast mannitol agar (YMA) medium (Vincent, 1970). They were maintained on YMA at 4 u C for temporary storage and in 20 % (w/v) glycerol at 280 u C for long-term storage.Total DNA from each strain was prepared as descri...
Seven Rhizobium strains associated with various legume species grown in different geographical regions of China were defined into four genomic groups related to Rhizobium giardinii, based upon ribosomal intergenic spacer RFLP, phylogenies of 16S rRNA and housekeeping (atpD, recA and glnII) genes, and DNA relatedness. Three strains in group I were classified as R. giardinii, as they showed high gene sequence similarities (.97 %) and DNA relatedness (64.3-67.5 %) to R. giardinii H152 T . Groups II, III and IV differed from all defined Rhizobium species based upon the consensus of all analyses. As group II contained two strains that originated from two distinct populations, we propose this group as a novel species, Rhizobium herbae sp. nov., with strain CCBAU 83011 T (5LMG 25718 T 5HAMBI 3117 T ) as the type strain.
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