Martínez de Tejada G, Miller J F, Cotter P A
Department of Microbiology and Immunology, UCLA School of Medicine 90095-1747, USA.
Mol Microbiol. 1996 Dec;22(5):895-908. doi: 10.1046/j.1365-2958.1996.01538.x.
Bordetella pertussis and Bordetella bronchiseptica contain nearly identical BvgAS signal-transduction systems that mediate a biphasic transition between virulent (Bvg+) and avirulent (Bvg-) phases. In the Bvg+ phase, the two species express a similar set of adhesins and toxins, and in both organisms the transition to the Bvg- phase occurs in response to the same environmental signals (low temperature or the presence of nicotinic acid or sulphate anion). These two species differ, however, with regard to Bvg(-)-phase phenotypes, host specificity, the severity and course of the diseases they cause, and also potentially in their routes of transmission. To investigate the contribution of the virulence-control system to these phenotypic differences, we constructed a chimeric B. bronchiseptica strain containing bvgAS from B. pertussis and compared it with wild-type B. bronchiseptica in vitro and in vivo. The chimeric strain was indistinguishable from the wild type in its ability to express Bvg(+)- and Bvg(-)- phase-specific factors. However, although the chimeric strain responded to the same signals as the wild type, it differed dramatically in sensitivity to these signals; significantly more nicotinic acid or MgSO4 was required to modulate the chimeric strain compared with the wild-type strain. Despite this difference in signal sensitivity, the chimeric strain was indistinguishable from the wild type in its ability to cause respiratory-tract infections in rats, indicating that the bvgAS loci of B. pertussis and B. bronchiseptica are functionally interchangeable in vivo. By exchanging discrete fragments of bvgAS, we found that the periplasmic region of BvgS determines signal sensitivity.
百日咳博德特氏菌和支气管败血博德特氏菌含有几乎相同的BvgAS信号转导系统，该系统介导在有毒力（Bvg +）和无毒力（Bvg -）阶段之间的双相转变。在Bvg +阶段，这两个菌种表达一组相似的粘附素和毒素，并且在这两种生物体中，向Bvg -阶段的转变都是对相同的环境信号（低温或存在烟酸或硫酸根阴离子）作出反应。然而，这两个菌种在Bvg（-）阶段的表型、宿主特异性、它们所引起疾病的严重程度和病程以及潜在的传播途径方面存在差异。为了研究毒力控制系统对这些表型差异的作用，我们构建了一个含有百日咳博德特氏菌bvgAS的支气管败血博德特氏菌嵌合菌株，并在体外和体内将其与野生型支气管败血博德特氏菌进行比较。该嵌合菌株在表达Bvg（+）和Bvg（-）阶段特异性因子的能力方面与野生型没有区别。然而，尽管嵌合菌株对与野生型相同的信号作出反应，但其对这些信号的敏感性却有显著差异；与野生型菌株相比，调节嵌合菌株需要更多的烟酸或硫酸镁。尽管在信号敏感性上存在这种差异，但嵌合菌株在引起大鼠呼吸道感染的能力方面与野生型没有区别，这表明百日咳博德特氏菌和支气管败血博德特氏菌的bvgAS基因座在体内功能上是可互换的。通过交换bvgAS的离散片段，我们发现BvgS的周质区域决定信号敏感性。
