Plasmid required for virulence of Agrobacterium tumefaciens
Plasmid required for virulence of Agrobacterium tumefaciens
复制标题
根癌农杆菌毒力所需的质粒
作者：
B. Watson;T. C. Currier;M. Gordon;M. Chilton;E. Nester
农杆菌C-58菌株在37℃的生长过程中，由于失去了一个大的质粒（1.2 X 10-8道尔顿），导致了诱导冠瘿的能力的不可逆丧失。在高温下导致质粒高损失率的基因似乎位于质粒上。此外，另一种自发的无毒性变异，即瘤胃分枝杆菌菌株IIBNV6，被证明缺乏其有毒性的兄弟菌株IIBV7所具有的毒力质粒。脱氧核糖核酸重关联测量证明，在这两种无毒衍生物中，质粒被消除，而不是整合到染色体中。毒力从供体菌株C-58转移到无毒的受体菌株A136是通过质粒的转移产生的，通过脱氧核糖核酸重关联测量，该质粒与供体质粒相同。另一个杂交品种K27 X A136的毒力转移也被证明是由一个大质粒的转移引起的。这些发现明确地表明，大质粒决定毒力。在菌株C-58的毒力质粒上发现了另外两个遗传决定因素：利用诺帕林的能力和对菌株84产生的细菌素的敏感性。后一特性可用于菌株C-58的无毒无质粒衍生物的选择。菌株IIBV7和K27的毒力质粒上似乎也存在野碱利用的特征。
The irreversible loss of crown gall-inducing ability of Agrobacterium tumefaciens strain C-58 during growth at 37 C is shown to be due to loss of a large plasmid (1.2 X 10-8 daltons). The gene responsible for this high rate of plasmid loss at elevated temperatures seems to be located on the plasmid. In addition, another spontaneous avirulent variant, A. tumefaciens strain IIBNV6 is shown to lack the virulence plasmid which its virulent sibling strain, IIBV7, possesses. Deoxyribonucleic acid reassociation measurements prove that the plasmid is eliminated, not integrated into the chromosome, in both of the avirulent derivatives. Transfer of virulence from donor strain C-58 to avirulent recipient strain A136 results from the transfer of a plasmid, which appears identical to the donor plasmid by deoxyribonucleic acid reassociation measurements. The transfer of virulence in another cross, K27 X A136, was also shown to result from the transfer of a large plasmid. These findings establish unequivocally that the large plasmid determines virulence. Two additional genetic determinants have been located on the virulence plasmid of A. tumefaciens strain C-58: the ability to utilize nopaline and sensitivity to a bacteriocin produced by strain 84. The latter trait can be exploited for selection of avirulent plasmid-free derivatives of strain C-58. The trait of nopaline utilization appears to be on the virulence plasmid also in strains IIBV7 and K27.