Kowarz L, Coynault C, Robbe-Saule V, Norel F
Unité des Entérobactéries, Institut Pasteur, Institut National de la Santé et de la Recherche Médicale, Paris, France.
J Bacteriol. 1994 Nov;176(22):6852-60. doi: 10.1128/jb.176.22.6852-6860.1994.
The spv region of Salmonella virulence plasmids is essential for the development of a systemic infection in mice. Transcriptional activation of the spvABCD operon occurs during stationary growth phase and is mediated by the regulatory gene product SpvR. We have previously shown that expression of a spvRAB'-cat fusion in Escherichia coli was dependent on the katF (rpoS) locus which encodes an alternative sigma factor (sigma S). The katF gene from Salmonella typhimurium has been cloned, sequenced, and used to construct Salmonella katF mutants by allelic replacement. Using these mutants, we demonstrated by mRNA and gene fusion analyses that sigma S, in conjunction with SpvR, controls the transcription of the regulatory gene spvR. In a second series of experiments, we sought to clarify the relationship between sigma S and SpvR in the control of spvABCD transcription. It was shown that expression of a transcriptional spvAB'-lacZ fusion could be restored in E. coli and Salmonella katF mutants when spvR was expressed in trans from an exogenous promoter. Moreover, identical spvA mRNA startpoints were detected in katF+ and katF strains. These results indicate that the reduction of spvABCD transcription in katF mutants is mainly due to decreased expression of spvR. Finally, mouse inoculation studies with S. typhimurium katF mutants of both wild-type and virulence plasmid-cured strains suggest that katF contributes to Salmonella virulence via the regulation of chromosomal genes in addition to that of spv genes.
沙门氏菌毒力质粒的spv区域对于小鼠全身性感染的发展至关重要。spvABCD操纵子的转录激活发生在稳定生长期，由调节基因产物SpvR介导。我们先前已表明，在大肠杆菌中spvRAB'-cat融合基因的表达依赖于编码替代西格玛因子（西格玛S）的katF（rpoS）位点。鼠伤寒沙门氏菌的katF基因已被克隆、测序，并用于通过等位基因替换构建沙门氏菌katF突变体。利用这些突变体，我们通过mRNA和基因融合分析证明，西格玛S与SpvR共同控制调节基因spvR的转录。在第二系列实验中，我们试图阐明在控制spvABCD转录过程中西格玛S与SpvR之间的关系。结果表明，当spvR从外源启动子反式表达时，转录性spvAB'-lacZ融合基因的表达在大肠杆菌和沙门氏菌katF突变体中可以恢复。此外，在katF+和katF菌株中检测到相同的spvA mRNA起始点。这些结果表明，katF突变体中spvABCD转录的减少主要是由于spvR表达的降低。最后，对野生型和毒力质粒消除菌株的鼠伤寒沙门氏菌katF突变体进行小鼠接种研究表明，katF除了通过调节spv基因外，还通过调节染色体基因对沙门氏菌毒力有贡献。
