Haugland R, Verma D P
J Mol Appl Genet. 1981;1(3):205-17.
Three strains of Rhizobium japonicum were examined for the presence of interspecific conserved plasmid-borne DNA sequences and the location of their nif DNA sequences. Strains 61A76 and 110, which both form effective (nitrogen fixing) nodules on soybeans show very low (24%) total DNA sequence homology with each other; strain 61A76 contains one plasmid, and strain 110 contains no identifiable plasmids. Strain 61A24 which forms ineffective nodules on soybeans shows relatively high (50%) sequence homology to strain 110 and contains two plasmids. While the total sequence homology between purified plasmid DNA isolated from strains 61A76 and 61A24 appears limited, heterologous hybridizations between plasmids and total DNAs from these strains and DNA from strain 110 suggest that several sequences which are plasmid-borne in one strain can occur in the chromosome or in very large plasmid(s) in the other strains. The plasmid isolated from strain 61A24 exhibits some homology with several SmaI fragments of an octopine Ti plasmid from Agrobacterium tumifaciens, whereas the 61A76 plasmid shows no homology to this Ti plasmid. DNA sequences from five strains of Rhizobium japonicum were found to hybridize with pSA30, a plasmid carrying the Klebsiella pneumoniae nif-KDH genes, but these sequences were not located on the isolated plasmids. The organization of these genes appears to be similar in strains 110 and 61A24, but is different in strain 61A76.
对三株日本根瘤菌进行了检测，以确定种间保守的质粒携带DNA序列的存在情况及其固氮DNA序列的位置。61A76和110菌株在大豆上均能形成有效的（固氮）根瘤，它们的总DNA序列同源性非常低（24%）；61A76菌株含有一个质粒，110菌株未发现可识别的质粒。61A24菌株在大豆上形成无效根瘤，与110菌株的序列同源性相对较高（50%），且含有两个质粒。虽然从61A76和61A24菌株中分离出的纯化质粒DNA之间的总序列同源性似乎有限，但这些菌株的质粒与总DNA以及110菌株的DNA之间的异源杂交表明，在一个菌株中由质粒携带的几个序列可能出现在其他菌株的染色体或非常大的质粒中。从61A24菌株中分离出的质粒与根癌土壤杆菌章鱼碱Ti质粒的几个SmaI片段表现出一些同源性，而61A76质粒与该Ti质粒无同源性。发现五株日本根瘤菌的DNA序列与携带肺炎克雷伯氏菌固氮-KDH基因的质粒pSA30杂交，但这些序列不在分离出的质粒上。这些基因在110和61A24菌株中的组织方式似乎相似，但在61A76菌株中有所不同。
