Relationship between regulation of cholera toxin production by lysophosholipase and ToxR.

通过脉冲场电泳和Southern杂交，发现lypA带toxR基因位于同一条霍乱弧菌染色体NotI DNA片段上。这表明lypA和toxR接近。利用含有lypA基因内片段的自杀载体构建了lypA基因的插入突变体。这些插入突变体产生霍乱毒素的能力降低，特别是在产生大量毒素的菌株中，如菌株569B。在减少霍乱毒素产生的插入突变株中，toxR的转录也下调。我们通过双交叉重组完全删除了lypA基因。在这个缺失突变体中，霍乱毒素的产生和toxR的转录没有明显减少。这表明，将质粒插入到插入突变体的lypA中可能会影响邻近基因，从而影响霍乱毒素的产生。

By pulse-field electrophoresis and Southern hybridization, we found the lypA band toxR geneswere in the same NotI DNA fragment of Vibrio cholerae chromosome. This suggest close proximity between lypA and toxR.Insertional mutants in the lypA gene was constructed using suicide vector containing inner fragment of the lypA gene. Cholera toxin-producing ability was reduced in these insertional mutants, especially in the strain which highly produces the toxin, such as strain 569B.In the insertional mutant strain which reduced production of cholera toxin, transcription of toxR was also down-regulated.We deleted the lypA gene completely by double-crossover recombination. In this deletion mutant, production of cholera toxin and transcription of toxR were not reduced clearly. This suggest that insertion of plasmid into the lypA in the insertional mutant may affect the neighboring genes, which affect production of cholera toxin.