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Abstract：
A large motility operon, referred to as the flgB operon, was identified, characterized, and mapped at 310 to 320 kb on the linear chromosome of the spirochete Borrelia burgdorferi. This is the first report that a sigma70-like promoter rather than a sigma28-like promoter is involved in the transcription of a major motility operon in bacteria. From these results in conjunction with results from a previous study (Y. Ge and N. W. Charon, Gene, in press), we have identified 26 genes in this operon that are relevant to motility and flagellar synthesis. With few exceptions, the gene order and deduced gene products were most similar to those of other spirochetes and Bacillus subtilis. Primer extension analysis indicated that transcription initiated from a conserved sigma70-like promoter immediately upstream of flgB; this promoter mapped within the heat-shock-induced protease gene hslU. Reverse transcriptase PCR analysis indicated that a single transcript of 21 kb initiated at this promoter and extended through flgE and (with our previous results) onto the putative motility gene flbE. The flgB promoter element had strong activity in both Escherichia coli and Salmonella typhimurium. As expected, a mutant of S. typhimurium with an inactivated flagellum-specific sigma28 factor did not affect the function of this promoter. Western blot analysis indicated that B. burgdorferi recombinant FliG and FliI were antigenically similar to those of E. coli and other spirochetes. Although complementation of E. coli or S. typhimurium fliG or fliI mutants with the B. burgdorferi genes was unsuccessful, B. burgdorferi recombinant FliI completely inhibited flagellar synthesis and motility of wild-type E. coli and S. typhimurium. These results show that spirochete motility genes can influence flagellar synthesis in other species of bacteria. Finally, Western blot analysis with sera from infected humans and animals indicated a weak or nondetectable response to recombinant FliG and FliI. These results indicate that these antigens are not favorable candidate reagents to be used in the diagnosis of Lyme disease.
摘要：
一个大的运动性操纵子，称为flgB操纵子，被确认,characterized,并在螺旋体伯氏螺旋体的线性染色体上定位在310至320kb。这是首次报道sigma70样启动子而不是sigma28样启动子参与细菌中主要运动性操纵子的转录。从这些结果与先前研究的结果（Y.Ge和N.W.Charon,Gene,inpress),我们在这个操纵子中鉴定了26个与运动性和鞭毛合成相关的基因。除了少数例外,基因顺序和推导的基因产物与其他螺旋体和枯草芽孢杆菌最相似。引物延伸分析表明，转录是从紧靠flgB上游的保守的sigma70样启动子启动的；该启动子位于热休克诱导的蛋白酶基因hslU内。逆转录酶PCR分析表明，在该启动子处启动了21kb的单个转录物，并通过flgE和（根据我们先前的结果）延伸到假定的运动性基因flbE上。flgB启动子元件在大肠杆菌和鼠伤寒沙门氏菌中均具有很强的活性。不出所料,具有失活鞭毛特异性sigma28因子的鼠伤寒沙门氏菌突变体不影响该启动子的功能。Western印迹分析表明,B.burgdorferi重组FliG和FliI在抗原上与大肠杆菌和其他螺旋体相似。尽管用B.burgdorferi基因互补大肠杆菌或鼠伤寒沙门氏菌flG或fli突变体是不成功的，B.burgdorferi重组FliI完全抑制了野生型大肠杆菌和鼠伤寒沙门氏菌的鞭毛合成和运动。这些结果表明，螺旋体运动基因可以影响其他细菌种类的鞭毛合成。最后,用感染的人和动物的血清进行的Western印迹分析表明对重组FliG和FliI的反应较弱或不可检测。这些结果表明,这些抗原不是用于诊断莱姆病的有利候选试剂。
