RESUMO
A novel rhizobial group, cluster 9, defined in previous research [Tan, Z. Y., Wang, E. T., Peng, G. X., Zhu, M. E., Martinez-Romero, E. & Chen, W. X. (1999). Int J Syst Bacteriol 49, 1457-1469], was further characterized by determination of DNA base composition, whole-cell protein SDS-PAGE analysis, DNA-DNA hybridization, 16S rRNA gene sequencing and host specificity. These isolates were collected from the wild legumes Amphicarpaea trisperma, Coronilla varia and Gueldenstaedtia multiflora growing in arid and semi-arid regions in northwestern China. Isolates within cluster 9 grouped into a single cluster above a similarity level of 90.6% in a cluster analysis based on protein SDS-PAGE, and they were differentiated from defined rhizobial species. Comparative analysis of 16S rRNA gene sequences showed that isolate CCBAU 71623T, representing cluster 9, was most related to Rhizobium gallicum and Rhizobium mongolense. The DNA-DNA homologies were lower than 42.4% among cluster 9 and defined species, including R. gallicum and R. mongolense. These data indicated that cluster 9 was a unique genomic species. Isolates within this cluster could share their host plants. They could not nodulate Galega orientalis and Leucaena leucocephala and formed ineffective nodules on Phaseolus vulgaris. This group could also be differentiated from defined species by phenotypic characteristics. It is therefore proposed as a new species, Rhizobium yanglingense, with isolate CCBAU 71623 as the type strain.
Assuntos
DNA Ribossômico/genética , Filogenia , RNA Ribossômico 16S/genética , Rhizobium/classificação , Rhizobium/genética , China , Clima Desértico , Fabaceae/microbiologia , Dados de Sequência Molecular , Plantas Medicinais , Rhizobium/fisiologiaRESUMO
Of 42 rhizobial isolates from Medicago sativa and Melilotus spp. growing in arid saline fields in Xinjiang, China, 40 were identified as Sinorhizobium meliloti by a polyphasic approach. However, diverse groups were obtained from these isolates in numerical taxonomy and SDS-PAGE of proteins. They could grow at pH 10.5 and were tolerant to 2.5-4.0% (w/v) NaCl.
