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首页> 外文期刊>Infection and immunity >Bacteriophage Mu d1(Apr lac) generates vir-lac operon fusions in Shigella flexneri 2a.
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Bacteriophage Mu d1(Apr lac) generates vir-lac operon fusions in Shigella flexneri 2a.

机译：噬菌体Mu d1（Apr lac）在弗氏志贺氏菌2a中产生vir-lac操纵子融合体。

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Previous studies have demonstrated that expression of virulence in Shigella spp. is controlled by growth temperature. To study the regulation of virulence (vir) genes, we set out to develop a rapid, easily-assayed phenotype with which to measure expression of virulence. This report described a procedure for isolating vir-lac operon fusions in S. flexneri 2a by using the specialized transducing bacteriophage Mu d1(Apr lac) of Casadaban and Cohen (M. Casadaban and S. N. Cohen, Proc. Natl. Acad. Sci. U.S.A. 76:4530-4533, 1976). Mu d1(Apr lac) lysogens were isolated and screened for loss of virulence and for temperature-dependent expression of the lactose genes on Mu d1(Apr lac). A recombinant plasmid carrying the Mu immunity gene was also introduced into lysogens of interest to stabilize the Mu d1(Apr lac) insertion and prevent possible thermal induction at 37 degrees C. The mutant which we isolated failed to penetrate tissue culture cells in the assay for virulence and produced almost 15-fold more beta-galactosidase when grown at 37 degrees C than when grown at 30 degrees C. The site of insertion of Mu d1(Apr lac) in this strain was shown to be in the 140-megadalton plasmid pSf2a140, which is known to be associated with virulence. P1L4-mediated transduction of the insertion into a virulent recipient demonstrated genetic linkage of Mu d1(Apr lac) with loss of virulence and temperature-dependent expression of beta-galactosidase. All of these features fulfill the phenotype expected for a Mu d1(Apr lac)-induced vir-lac operon fusion. This mutant provides us with a means of measuring expression of a gene function required for virulence by assaying for beta-galactosidase. The insertion will also serve as a starting point for mapping of genes on pSf2a140 which are necessary for expression of virulence.
机译：先前的研究表明，志贺氏菌属中有毒力表达。由生长温度控制。为了研究毒力（vir）基因的调控，我们着手开发一种快速，易于测定的表型，用以测量毒力的表达。该报告描述了通过使用Casadaban和Cohen（M. Casadaban和SN Cohen，Proc。Natl。Acad。Sci。USA）的专门转导噬菌体Mu d1（Apr lac）在弗氏链球菌2a中分离vir-lac操纵子融合体的方法76：4530-4533，1976）。分离了Mu d1（Apr lac）溶原菌，筛选了毒力损失和Mu d1（Apr lac）上乳糖基因的温度依赖性表达。还将携带Mu免疫基因的重组质粒引入目标溶原体中，以稳定Mu d1（Apr lac）插入并防止在37摄氏度下可能的热诱导。我们分离出的突变体在在37°C时生长的毒力比在30°C时生长的β-半乳糖苷酶高出将近15倍。Mud1（Apr lac）在该菌株中的插入位点显示在140 megadalton质粒pSf2a140中，已知与毒力有关。 P1L4介导的向强毒受体插入的转导证明了Mu d1（Apr lac）的遗传连锁与毒性的丧失和β-半乳糖苷酶的温度依赖性表达有关。所有这些功能均满足Mu d1（Apr lac）诱导的vir-lac操纵子融合的预期表型。该突变体为我们提供了一种通过测定β-半乳糖苷酶来测量毒力所需的基因功能表达的手段。插入也将作为在pSf2a140上绘制表达毒力所必需的基因的起点。

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