Rhizobium tibeticum sp. nov., a symbiotic bacterium isolated from Trigonella archiducis-nicolai (Sirj.) Vassilcz.

Abstract

Rhizobium tibeticum sp. nov., a symbiotic bacterium isolated from Trigonella archiducisnicolai (Š irj.) Vassilcz. Isolated from root nodules of Trigonella archiducis-nicolai (Š irj.) Vassilcz. grown in Tibet, China, cells of the bacterial strains CCBAU 85039 T and CCBAU 85027 were Gram-negative, aerobic, motile, non-spore-forming rods that formed colonies that were semi-translucent and opalescent on yeast extract-mannitol agar. In numerical taxonomy, SDS-PAGE analysis of whole-cell proteins and DNA-DNA hybridization, the two strains were very similar and were different from reference strains of defined Rhizobium species. In the phylogeny based on 16S rRNA gene sequences, they were most similar to Rhizobium etli CFN 42 T (98.2 % similarity) and R. leguminosarum USDA 2370 T (97.6 %). Sequence analyses of the housekeeping genes recA, atpD and glnII and the 16S-23S rRNA intergenic spacer, phenotypic characteristics and cellular fatty acid profiles strongly suggested that these two strains represented a novel species within Rhizobium. Crossnodulation tests and sequencing of nifH and nodA genes showed that these two strains were symbiotic bacteria that nodulated Trigonella archiducis-nicolai, Medicago lupulina, Medicago sativa, Melilotus officinalis, Phaseolus vulgaris and Trigonella foenum-graecum. Based on the results, the novel species Rhizobium tibeticum sp. nov. is described to accommodate the two strains. The type strain is CCBAU 85039 T (5LMG 24453 T 5CGMCC 1.7071 T ). The DNA G+C content of this strain is 59.7 mol% (T m ).The genus Rhizobium was first described by Frank (1889) to accommodate all symbiotic nitrogen-fixing bacteria associated with legumes. After a series of revisions, some earlier described species have been moved into Bradyrhizobium (Jordan, 1982), Sinorhizobium (de Lajudie et al., 1994) and Mesorhizobium (Jarvis et al., 1997), while many novel species and genera of rhizobia within the Alphaproteobacteria and Betaproteobacteria have been reported (NZ Rhizobia, 2008). The current genus Rhizobium includes about 30 species of fast-growing, acid-producing rhizobia, which can be differentiated from Sinorhizobium species on the basis of 16S rRNA gene sequence-based phylogeny. With the exception of Rhizobium cellulosilyticus (Garcia-Fraile et al., 2007), most of them can induce root nodules on a certain range of legume species.In a survey of rhizobial resources in Tibet, 12 strains of root-nodule bacteria were isolated with yeast mannitol agar (YMA) medium according to the method of Vincent (1970) from root nodules of Trigonella archiducis-nicolai (Širj.) Vassilcz., an ephemeral legume growing in grasslands at altitudes of 3700-4000 m. Six of them were identified as Sinorhizobium meliloti, and six as Rhizobium strains (Hou et al., 2009). Among the Rhizobium strains, CCBAU 85039 T and CCBAU 85027 were classified as a small group by numerical taxonomy, amplified 16S rRNA gene restriction analysis, amplified 16S-23S intergenic spacer restriction analysis and 16S rRNA gene phylogeny (Hou et al., 2009). To...

Rhizobium populi sp. nov., an endophytic bacterium isolated from Populus euphratica

“…R. rosettiformans W3 T and R. borbori DN316 T were incubated for 36 h in TSB medium at 28 u C since they have faster growth rates than strain K-38 T . Fatty acids were extracted (Hou et al, 2009) and identified using the standard method of the Microbial Identification System (MIDI) by GC (6850; Agilent) using the database TSBA6 for identification of the peaks. The cellular fatty acid profile of strain K-38 T contained summed feature 8 (comprising C 18 : 1 v7c and/or C 18 : 1 v6c; 57.2 %), C 16 : 0 (13.6 %) and summed feature 2 [comprising C 12 : 0 aldehyde, C 14 : 0 3-OH/iso-C 16 : 1 I and/or unknown equivalent chain length (ECL) 10.928; 11.0 %] as major components.…”

Legume-nodulating bacteria (LNB) from three pasture legumes (Vicia sativa, Trigonella maritima and Hedysarum spinosissimum) in Tunisia

“…viciae (Jordan 1984;Laguerre et al 2003;Mutch et al 2003;Slattery et al 2004;Mutch and M. Mahdhi (*) : A. Fterich : M. Rejili : M. Mars Laboratoire de Biotechnologies Végétales Appliquées à l'Amélioration des Cultures, Université de Gabès, Faculté des Sciences de Gabès, Cité Erriadh Zrig, 6072 Gabès, Tunisia e-mail: mosbahtn@yahoo.fr Young 2004;Moschetti et al 2005). Although, Trigonella plants mainly nodulate with Sinorhizobium meliloti (Roumiantseva et al 2002;You et al 2008), strains belonging to the genera Bradyrhizobium (Pandey et al 2004) and Rhizobium (Wang et al 2006;Hou et al 2009) have also been isolated from two Trigonella species in China. The genus Hedysarum L. comprises about 100 species, of herbaceous legumes, widely distributed in the Mediterranean, temperate Europe, North and South Africa, Asia Minor, Siberia, North America from Arizona into Alaska and the Arctic regions of Canada.…”

Genetic diversity of rhizobia associated with alfalfa in Serbian soils

“…The results permitted identification of the strains 246-1 and SLD2 as R. tibeticum. R. tibeticum was isolated from Trigonella archiducis-nicolai root nodules in Tibet and found to nodulate M. sativa under laboratory conditions (Hou et al 2009). Our results are the first to confirm the presence of R. tibeticum in root nodules of M. sativa and provide evidence that it can be its natural host plant.…”