三个根瘤菌新群的DNA-DNA杂交分析

DNA DNA Hybridization Analysis of Three New Rhizobia Groups

从数值分类获得苜蓿、草木樨和锦鸡儿根瘤菌的 3个新群。本实验对这 3个新群内菌株及部分已知种参比菌株进行了 DNA- DNA杂交分析和 G+Cmol%测定。结果表明 :三群中心菌株 XJ96 0 6 0 ,XJ96 4 0 8,NM0 19与其相应群内菌株的 DNA同源性分别为 71.7%～ 97.6 % ,80 .8%～ 98.7% ,82 .7%～ 86 .9% ,均大于 70 % ;各群的 ΔTm 值分别为 3.2℃ ,2 .8℃ ,2 .6℃ ,均小于 5℃ ;与各已知种的 DNA同源性分别为 0～4 1.7% ,0～ 39.3% ,4 .0 %～ 4 4 .7% ,均低于 70 % ;确证这 3个新群为 3个不同于已知种的、独立 DNA同源群 .此 3群的 G+Cmol%分别为 6 0 .3%～ 6 2 .9% ,59.7%～ 6 2 .4 % ,6 0 .2 %～ 6 2 .6 % 。

Three groups isolated from Medicago sativa, Melilotus spp., Caragana spp. were ascertained by the numerical taxonomy. The contents of G+C mol% of all examined strains were measured, and DNA DNA homologies among the strains within three groups as well as DNA DNA homologies between centrostrain of three groups and reference strains of some known species were analyzed. The results showed that DNA DNA homologies among strains within three groups were above 70% (71.7%～97.6%, 80.8%～98.7% and 82.7%～ 86.9% respectively); Δ T m of three groups were below 5 ℃ ( 3.2 ℃, 2.8 ℃ and 2.6 ℃ respectively ). The DNA DNA isogenesis idex among centrostrains of three groups and type strains of known rhizobium species were much below 70%(0～41.7%, 0～39.3%and 4.0%～44.7% respectively). All these results indicate that three groups are the new DNA homologous groups and different from known rhizobium species. The contents of G+C mol% of three groups are 60.3% ～ 62.9% , 59.7% ～ 62.4% and 60.2% ～ 62.6% respectively, which shows that they are characteristic of the fast growing root nodule bacteria.