Characteristics of Rhizobium tianshanense sp. nov., a Moderately and Slowly Growing Root Nodule Bacterium Isolated from an Arid Saline Environment in Xinjiang, People's Republic of China

Abstract

We performed a numerical analysis of 148 phenotypic characteristics of 20 strains of root nodule bacteria isolated from an arid saline desert soil in the Xinjiang region of northwestern People's Republic of China and compared these organisms with 28 Rhizobium and Bradyrhizobium strains obtained from different regions of the People's Republic of China and from other countries, including nine type strains of different species. All of the strains examined clustered into two groups at a similarity level of more than 63%. Group I included all of the previously described Rhizobium species and was divided into eight subgroups, which corresponded to previously described Rhizobium species, at a similarity level of more than 82%. Group I1 was divided into the following three subgroups at a similarity level of more than 80% Bradyrhizubium japonicum, a cluster containing 17 moderately and slowly growing strains isolated in the Xinjiang region, and a small subgroup containing three fast-growing strains. The generation times of the moderately and slowly growing strains were 5 to 15 h, and these organisms produced acid in medium containing mannitol. The DNA G+C contents of the members of this group ranged from 59 to 63 mol%. DNA-DNA hybridization experiments revealed that the levels of DNA homology among all of the moderately and slowly growing strains obtained from Xinjiang were more than 70% and that the levels of DNA homology between representative strains of this group and the type strains of all previously described species of root-and stem-nodulating bacteria were low. All of our experimental data indicated that the moderately and slowly growing rhizobia isolated from Xinjiang are members of a new species. Partial 16s rRNA gene sequencing of the type strain. A-1BS (= CCBAU3306), and a comparison of the resulting sequence with the sequences of previously described species revealed that strain A-1BS is closely related to Rhizobium loti, Rhizobium huakuii, and Rhizobium galegae, but not to B. japonicum and Azorhizobium caulinodans. On the basis of our results, we propose that the strains which we studied are members of a new species, Rhizobium tianshanense. The type strain, A-1BS (= CCBAU3306), has been deposited in the Culture Collection of Beijing Agricultural University, Beijing, People's Republic of China.At the present time, all bacteria that induce nodules on the roots of leguminous plants are assigned to three genera (8,14). The genus Rhizobium comprises a group of fast growers and includes eight species, Rhizobium leguminosarum, Rhizobium meliloti, Rhizobium loti (14), Rhizobium fredii (20), Rhizobium huakuii (2), Rhizobium galegae (15), Rhizobium tropici (16), and Rhizobium etli (21). Each of these species is associated with a group of host plants and is distinguished from the other species mainly on the basis of DNA relatedness values, 16s rRNA homology values, and some phenotypic characteristics. The genus Bradyrhizobium comprises a group of slow growers and contains one species, Bradyrhizobium japonicum, which i...

Tolerância de bactérias diazotróficas simbióticas à salinidade in vitro

“…A literatura é bem diversificada quanto a informações sobre as diferentes capacidades de bactérias diazotróficas, tanto associativas quanto simbióticas, em tolerar salinidade (CHEN et al, 1995;SHEREEN et al, 1998;RASA et al, 2001;TAMIMI, 2001;HUNGRIA et al, 2001;NÓBREGA et al, 2004), e as faixas de tolerância das espécies diazotróficas simbióticas observadas variaram de 0 a 60 g L -1 de NaCl. Estudos com essa finalidade objetivam não só identificar estirpes potenciais para usos diversos, mas também auxiliar na caracterização das espécies bacterianas (CHEN et al, 2000;FRIONI et al, 2001;NÓBREGA, et al, 2004).…”

Mesorhizobium septentrionale sp. nov. and Mesorhizobium temperatum sp. nov., isolated from Astragalus adsurgens growing in the northern regions of China

“…It has been shown that different plants in the same geographical region can share the same rhizobial group for nodulation; examples are Mesorhizobium tianshanense (Chen et al, 1995), Mesorhizobium plurifarium (de Lajudie et al, 1998) and Rhizobium hainanense . Conversely, the same plant species may associate with different rhizobial species; for example, soybean is nodulated by Bradyrhizobium japonicum, Bradyrhizobium liaoningense (Xu et al, 1995), Mesorhizobium tianshanense (Chen et al, 1995), Sinorhizobium fredii and Sinorhizobium xinjiangense (Chen et al, 1988;Peng et al, 2002) in different regions of China. However, the geographical ranges of host plants and microsymbionts are often restricted and rhizobial inocula are necessary in many cases when legumes are introduced into new areas (e.g.…”

Mesorhizobium shangrilense sp. nov., isolated from root nodules of Caragana species

“…They are ecologically important because they serve as forage resources for wild animals and are preferred plants for use in reforestation against desertification and erosion (Fan et al, 2007;Su et al, 2005). Most of the rhizobia associated with Caragana belong to the genus Mesorhizobium (Chen et al, 1995;Guan et al, 2008;Lu et al, 2009;Yan et al, 2007) and two species, Mesorhizobium tianshanense and Mesorhizobium caraganae, have been described so far (Chen et al, 1995;Guan et al, 2008).…”

“…They are ecologically important because they serve as forage resources for wild animals and are preferred plants for use in reforestation against desertification and erosion (Fan et al, 2007;Su et al, 2005). Most of the rhizobia associated with Caragana belong to the genus Mesorhizobium (Chen et al, 1995; Guan et al, 2008;Lu et al, 2009;Yan et al, 2007) and two species, Mesorhizobium tianshanense and Mesorhizobium caraganae, have been described so far (Chen et al, 1995; Guan et al, 2008).During the study of rhizobia nodulating Caragana species from three different regions of China, 144 strains (of a total of 174) were characterized and classified in the genus Mesorhizobium based on 16S rRNA gene sequence analysis, BOX-PCR fingerprinting and SDS-PAGE profiles of wholecell soluble proteins (Lu et al, 2009). Five of the isolates from nodules of Caragana bicolor and Caragana erinacea grown in Yunnan Province of China exhibited distinct characteristics and differed from the known species of Mesorhizobium.…”