DNA同源性分析最终确定新疆中华根瘤菌（Sinorhizobium xinjiangensis）为一独立种

针对S.xinjiangensis分类地位的争议，从新疆再次分离获得34株快生大豆根瘤菌，在16SrDNAPCR-RFLP分析和SDS全细胞蛋白电泳分群的基础上，进行了16SrDNA全序列相似性和DNA同源性分析.所测4个菌株和S.fredii模式菌株USDA205的16SrDNA全序列有很高的相似性.而DNA同源性分析说明新分离的菌株代表与原定的S.xinjiangensis为一个DNA同源群.其模式菌株CCBAU110与S.fredii的2株参比菌株USDA194、2048之间的DNA同源性分别为31.5%和28.7%.S.fredii的模式菌株USDA205与新分离的菌株代表及原定的S.xinjiangensis的模式菌株和2个参比菌株之间的DNA同源性为20.8%～39%，远低于70%.属于种水平上的差异.按照国际细菌分类委员会以DNA同源性≥70%且△Tm≤5℃作为定种的标准，S.xinjiangensis是Sinorhizobium属中不同于S.fredii的一个独立的种.表3参20

SINORHIZOBIUM XINJIANGENSIS AS AN INDEPENDENT SPECIES CONFIRMED BY DNA HOMOLOGY ANALYSIS

In this study, based on the results from 16S rDNA PCR-RFLP of 34 fast-growing soybean rhizobia strains isolated from Xinjiang in comparison with several type and reference strains of related species, and SDS-PAGE whole-cell protein patterns of new representative isolates and other strains in Sinorhizobium, new representative isolates were further analyzed by 16S rDNA full sequencing, G+C mol% tests and DNA-DNA hybridization. 4 strains were analyzed by 16S rDNA full sequencing, indicating that type strain CCBAU 110 of S. xinjiangensis and type strain USDA 205 of S. fredii shared high similarity. The DNA homologies indicated that new representative isolates and S. xinjiangensis were of the same DNA homology groups. The DNA homologies between CCBAU 110 and the reference strains of S. fredii: USDA 194, 2048 were 31.5% and 28.7%, respectively. The DNA-DNA hybridization values between USDA 205 and CCBAU 110, 2 reference strains of S. xinjiangensis, representative of new isolates were 20.8%～39%, which confirmed that S. xinjiangensis and S. fredii belonged to the different DNA homology groups, and S. xinjiangensis was an unique, independent species in Sinorhizobium. Tab 3, Ref 20