Ueda S, Kuramitsu H K
Department of Microbiology-Immunology, Northwestern University Medical and Dental Schools, Chicago, Illinois 60611.
Mol Microbiol. 1988 Jan;2(1):135-40. doi: 10.1111/j.1365-2958.1988.tb00014.x.
Spontaneous mutants of Streptococcus mutans GS-5 defective in sucrose-dependent colonization of smooth surfaces are generated at frequencies above the spontaneous mutation rate. Southern blot analysis of such mutants suggested rearrangement of the genes coding for glucosyltransferase (GTF) activity. Two strain GS-5 homologous tandem genes, gtfB and gtfC, coding for GTF-I and GTF-S activities respectively, were demonstrated to undergo recombination when introduced into recombination-proficient Escherichia coli transformants. However, the two genes were quite stable when transformed on a single DNA fragment into a recA mutant of E. coli. The DNA fragment coding for GTF activity from one S. mutans colonization-defective mutant, SP2, was isolated and shown also to have undergone recombination between the gtfB and gtfC genes, resulting in reduced GTF activity. These results are discussed relative to the in vivo generation of colonization-defective mutants in cultures of S. mutans.
变形链球菌GS-5在蔗糖依赖的光滑表面定植方面存在缺陷的自发突变体，其产生频率高于自发突变率。对此类突变体的Southern印迹分析表明，编码葡糖基转移酶（GTF）活性的基因发生了重排。两个菌株GS-5同源串联基因gtfB和gtfC，分别编码GTF-I和GTF-S活性，当导入重组能力强的大肠杆菌转化子时，被证明会发生重组。然而，当这两个基因通过单个DNA片段转化到大肠杆菌的recA突变体中时，它们相当稳定。从一个变形链球菌定植缺陷突变体SP2中分离出编码GTF活性的DNA片段，结果表明该片段在gtfB和gtfC基因之间也发生了重组，导致GTF活性降低。针对变形链球菌培养物中定植缺陷突变体的体内产生情况，对这些结果进行了讨论。
