Akerley B J, Monack D M, Falkow S, Miller J F
Department of Microbiology and Immunology, School of Medicine, University of California, Los Angeles 90024.
J Bacteriol. 1992 Feb;174(3):980-90. doi: 10.1128/jb.174.3.980-990.1992.
The products of the bvgAS locus coordinately regulate the expression of Bordetella virulence factors in response to environmental conditions. We have identified a phenotype in Bordetella bronchiseptica that is negatively controlled by bvg. Environmental signals which decrease (modulate) the expression of bvg-activated genes lead to flagellum production and motility in B. bronchiseptica. Wild-type (Bvg+) strains are motile and produce peritrichous flagella only in the presence of modulating signals, whereas Bvg- (delta bvgAS or delta bvgS) strains are motile in the absence of modulators. The bvgS-C3 mutation, which confers signal insensitivity and constitutive activation of positively controlled loci, eliminates the induction of motility and production of flagellar organelles. The response to environmental signals is conserved in a diverse set of clinical isolates of both B. bronchiseptica and B. avium, another motile Bordetella species; however, nicotinic acid induced motility only in B. bronchiseptica. Purification of flagellar filaments from B. bronchiseptica strains by differential centrifugation followed by CsCl equilibrium density gradient centrifugation revealed two classes of flagellins of Mr 35,000 and 40,000. A survey of clinical isolates identified only these two flagellin isotypes, and coexpression of the two forms was not detected in any strain. All B. avium strains tested expressed a 42,000-Mr flagellin. Amino acid sequence analysis of the two B. bronchiseptica flagellins revealed 100% identity in the N-terminal region and 80% identity with Salmonella typhimurium flagellin. Monoclonal antibody 15D8, which recognizes a conserved epitope in flagellins in members of the family Enterobacteriaceae, cross-reacted with flagellins from B. bronchiseptica and B. avium. Our results highlight the biphasic nature of the B. bronchiseptica bvg regulon and provide a preliminary characterization of the Bvg-regulated motility phenotype.
bvgAS基因座的产物可根据环境条件协同调节博德特氏菌毒力因子的表达。我们在支气管败血博德特氏菌中鉴定出一种受bvg负调控的表型。降低（调节）bvg激活基因表达的环境信号会导致支气管败血博德特氏菌产生鞭毛并具有运动性。野生型（Bvg +）菌株仅在存在调节信号时才具有运动性并产生周生鞭毛，而Bvg-（缺失bvgAS或缺失bvgS）菌株在没有调节剂的情况下也具有运动性。bvgS - C3突变赋予信号不敏感性并组成性激活正调控基因座，消除了运动性的诱导和鞭毛细胞器的产生。支气管败血博德特氏菌和鸟博德特氏菌（另一种运动性博德特氏菌）的多种临床分离株对环境信号的反应是保守的；然而，烟酸仅在支气管败血博德特氏菌中诱导运动性。通过差速离心继以CsCl平衡密度梯度离心从支气管败血博德特氏菌菌株中纯化鞭毛丝，发现了分子量为35,000和40,000 的两类鞭毛蛋白。对临床分离株的调查仅发现了这两种鞭毛蛋白同种型，并且在任何菌株中均未检测到这两种形式的共表达。所有测试的鸟博德特氏菌菌株均表达一种分子量为42,000的鞭毛蛋白。对两种支气管败血博德特氏菌鞭毛蛋白的氨基酸序列分析显示，其N端区域具有100％的同一性，与鼠伤寒沙门氏菌鞭毛蛋白具有80％的同一性。识别肠杆菌科成员鞭毛蛋白中保守表位的单克隆抗体15D8与支气管败血博德特氏菌和鸟博德特氏菌的鞭毛蛋白发生交叉反应。我们的结果突出了支气管败血博德特氏菌bvg调节子的双相性质，并提供了Bvg调节的运动性表型的初步特征。
