棒杆菌宿主中质粒不稳定性的研究

重组质粒pNAR4是由钝齿棒杆菌质粒pNAT65和大肠杆菌质粒pACYCl84构建的穿梭质粒。质粒pNAR4转化不同棒杆菌，在钝齿棒杆菌T6—13和答氨酸棒杆菌l0l47中为结构型不稳定，在钝齿棒杆菌B9中为分离型不稳定。而pNAT65转化谷氨酸棒杆菌10147后，转化于中的质粒分子大小及主要酶切位点与pxz10145相同。DNA杂交实验结果表明．在10147菌中有一种与z10145高度同源的超螺旋DNA组分，而这一组分与pxz10145的来源宿主中的另一小质粒具有相同的分子量。提出了质粒结构不稳定与宿主中存在的pxz10145高度同源的小质粒(超螺旋组分)有关，并提出产生质粒分子结构反复变化原因的假设。

Study of the Plasmid Instability in Corynebacterium

Recombinant plasmid pNAR4, which can be used as shuttle vector between E. coli and coryneform bacteria, was constructed by ligation the DNA fragments of pNAT65 and pACYC177. Plasmid instability was found when pNAR4 was transformed into various coryneform bacteria strains, segregational instability in C. crenatum B9 and structural instability in C. glutamicum 10147 and C. crenatum T6-13. When pNAT65 was transformed into C. glutamicum 10147,the plasmid in transformants were found different to pNAT65. The size and main restriction sites in these plasmids were identical with that, of pXZl0145. DNA hybridization experiments indicated that in C. glutamicum 10147, there was a supercoiled DNA content which was highly homologous with pXZ10145, An assumption is given here in which the existence of this supercioled DNA content is related to the phenomena of various plasmid instabilityMand inter-or/and intra-molecular recombination may be the reason to explain the related phenomena found in our work.