费氏中华根瘤菌(Sinorhizobium fredii)质粒复制基因repC序列多样性的研究

采用质粒快速检测法从供试33株费氏中华根瘤菌中分别检测出2～4个内源大质粒。用根据豌豆根瘤菌的repC基因设计1对引物RCI和RC3，从供试菌株及3株华癸中生根瘤菌和1株大豆慢生根瘤菌中扩增得到repC基因片段，证明在费氏中华根瘤菌中广泛存在repC基因。通过对扩增产物的测序，并与已报道的repC基因序列进行聚类分析，发现供试菌株可分为2个群，群a和群b，群内十分保守，但群间差异明显；其中群b的序列与已知类型的差异明显。

Diversity of repC Plasmid-replication Sequences in Sinorhizobium fredii

Two to four plasmids were detected from thirty three strains of Sinorhizobiurn fredii by using modified Eckhardt method. A pair of primers RC1/RC3 were designed according to conservative sequences of repC gene and used for the amplification of repC genes from the above 33 strains, 3 strains of Mesorhizobium huakuii and I strain of Bradyrhizobium japonicum. The results suggested that the repC gene also existed in most strains of Sinorhizobium fredii. Amplified DNA fragments were cloned to pMD18-T and sequenced. The sequences were used to be compare with the reported repC genes. Results from clustering analysis indicated that the strains tested could be divided into group a and group b. The sequences in the same group were very conservative but shown great differences between group a and group b. The repC gene of group b was significantly different from repC genes reported.