Rhizobium vallis sp. nov., isolated from nodules of three leguminous species

Abstract

Four bacterial strains isolated from root nodules of Phaseolus vulgaris, Mimosa pudica and Indigofera spicata plants grown in the Yunnan province of China were identified as a lineage within the genus Rhizobium according to the analysis of 16S rRNA gene sequences, sharing most similarity with Rhizobium lusitanum P1-7 T (99.1 % sequence similarity) and Rhizobium rhizogenes IAM 13570 T (99.0 %). These strains also formed a distinctive group from the reference strains for defined species of the genus Rhizobium in a polyphasic approach, including the phylogenetic analyses of the 16S rRNA gene and housekeeping genes (recA, atpD, glnII), DNA-DNA hybridization, BOX-PCR fingerprinting, phenotypic characterization, SDS-PAGE of whole-cell proteins, and cellular fatty acid profiles. All the data obtained in this study suggested that these strains represent a novel species of the genus Rhizobium, for which the name Rhizobium vallis sp. nov. is proposed. The DNA G+C content (mol%) of this species varied between 60.9 and 61.2 (T m ). The type strain of R. vallis sp. nov. is CCBAU 65647 T (5LMG 25295 T 5HAMBI 3073 T ), which has a DNA G+C content of 60.9 mol% and forms effective nodules on Phaseolus vulgaris.Rhizobia are symbiotic nitrogen-fixing bacteria that reduce N 2 to ammonia after forming root and/or stem nodules with leguminous plants. To date, about 80 rhizobial species have been reported within the four main genera Rhizobium, Ensifer (Sinorhizobium), Mesorhizobium and Bradyrhizobium, as well as in several other genera in the classes Alphaproteobacteria and Betaproteobacteria (Wang et al., 2006). The genus Rhizobium (Frank, 1889) was the first and only rhizobial genus described for a century, before the genus Bradyrhizobium was reported (Jordan, 1982). Since then, a series of taxonomic changes have been made in the genus Rhizobium and at the time of writing it contains 47 species, including the recently described species Rhizobium soli (Yoon et al., 2010), Rhizobium borbori (Zhang et al., 2011b), Rhizobium vignae (Ren et al., 2011) and Rhizobium tubonense (Zhang et al., 2011a).In a survey of rhizobial resources in Yunnan, a tropical province of China, four strains isolated from root nodules of Phaseolus vulgaris, Mimosa pudica and Indigofera spicata were identified as a distinct lineage in the genus Rhizobium by sequence analysis of the 16S rRNA gene, which was used to screen all the isolates. In order to clarify the taxonomic position of the four strains, a polyphasic study including phylogenetic analyses of the 16S rRNA gene and housekeeping genes (recA, atpD, glnII), BOX-PCR fingerprinting, DNA-DNA hybridization, phenotypic characterization, SDS-PAGE of whole-cell proteins, and cellular fatty acid composition was performed in comparison with reference strains of defined species of the genus Rhizobium. Based on the results, these four isolates represent a different group from all defined species and, therefore, a novel species is proposed.The four novel bacterial strains and the reference strains used in this study ...

An invasive Mimosa in India does not adopt the symbionts of its native relatives

“…The present study has confirmed that Cupriavidus strains similar to C. taiwanensis are common symbionts of M. pudica in several other locations in India, but has gone further and shown for the first time that strains in the species B. mimosarum and B. phymatum are also common M. pudica symbionts, and even that some Rhizobium strains (e.g. MP10, which is similar to R. vallis; Wang et al, 2011) can be symbiotic with this species in India. Our study of M. pudica symbionts in India has some parallels with that of Liu et al (2012) from southern China, in which the same three species, C. taiwanensis, B. mimosarum and B. phymatum, were always found to nodulate M. pudica in varying proportions depending upon location, but the present study differs from Liu et al (2012) in that some sites in India were dominated by one symbiont type, e.g.…”

Diversity of native rhizobia isolated in south Brazil and their growth promotion effect on white clover (Trifolium repens) and rice (Oryza sativa) plants

“…Strains belonging to several species of the rhizobia genera have previously been isolated from the root nodules of leguminous plants (Zhang et al 1991;Wang et al 2010). However, a large number of native microbial population studies also include rhizobia species in the bulk soil and rhizosphere of non-leguminous plants Arruda et al 2012;Farina et al 2012;Souza et al 2012).…”

Site-specific distribution and competitive ability of indigenous bean-nodulating rhizobia isolated from organic fields in Minnesota

“…This suggests that these fields may be good candidates to establish novel populations of effective rhizobia with less competitive interference from indigenous strains. While many species of rhizobia can nodulate dry beans (Martinez-Romero et al, 1991;Segovia et al, 1993;Wang et al, 2011), this study found only two main species of dry bean-rhizobia in organic fields; R. leguminosarum bv. phaseoli (67.1%) and R. etli (30.2%).…”