紫云英根瘤菌天然抗药性和质粒研究

从同一稻田的紫云英根瘤上共分离到１５４株紫云英根瘤菌。将来自该田块１０株紫云英的１００株根瘤菌列为分析组Ａ；来自同一植株不同根瘤的４０株根瘤菌列为分析组Ｂ；来自植株两个根瘤的１４株根瘤菌列为分析组Ｃ。对所有菌株１０种抗生素的抗药性测定表明，分析组３９个不同抗药类群；分析组Ｂ分为２２个抗药类群。同一根瘤的分离株其抗药性也存在差异。质粒检测显示所有菌株都含有质粒，质粒数为１－５条；质粒分子量主要在８

STUDY ON IAR AND PLASMID PATTERNS OF RHIZOBIA ISOLATED FROM NODULES OF ASTRAGALUS SINICUS

In the present study we adopted a systematic isolation approach to obtain strains by isolating rhizobia from every nodule on the sample plants.Out of 154strains studied,100 were from 10 plants collected in the same field(designated as group A),40 were from the same single plant(group B),and 14 were from 2 nodules on one plant (group C).Intrinsic antibiotic resistance(IAR) of all strains were tested with 10antibiotcs and they could be classified into 51 IAR clusters.Group A strains had 39 IAR clusters,and group B had 22 IAR clusters;The strains from the same nodule also showed some difference in IAR.The plasmid profiles of 154 strains were examined by using a modified eckhard procedure of plasmid visualization. The plasmid number of strains varied from 1 to 5,and their molecular weights were estimated to be mainly 35to 600 MD or more in comparison with the plasmids of strain USDA205 as reference.There were 8 different plasmid patterns in the group A strains and 6 different plasmid patterns in group B.The Strains even from the same nodule showed some difference in plasmid content.