霍乱弧菌O1和O139分离物使用霍乱毒素(CT)和毒素共同调节的菌毛(TCP)来引起腹泻病霍乱。编码CT和TCP的ctxtAB和tcpA基因是两个获得性遗传元件的一部分,CTX噬菌体和弧菌致病性岛-1(VPI-1),分别。ToxR和ToxT蛋白是霍乱弧菌O1和O139毒力基因的关键调节因子。属于O1/O139以外的血清群的霍乱弧菌分离株,称为非O1/非O139,通常没有毒力相关元件,并且是非致病性的。这里,我们已经分析了环境产毒霍乱弧菌非O1/非O139菌株的可用全基因组序列,VCE232,携带CTX噬菌体和VPI-1。广泛的生物信息学和系统发育分析表明,VCE232基因组序列与霍乱弧菌O1菌株的基因组高度相似,包括VPI-1基因座的组织,ctxAB,tcpA和toxT基因,和发起人。我们确定VCE232菌株在30°C下在AKI条件下产生最佳量的CT。探讨ToxT和ToxR在毒力因子调控中的作用,我们构建了ΔtoxT,VCE232的ΔtoxR和ΔtoxTΔtoxR缺失突变体。对这些突变体的广泛遗传分析表明,VCE232的toxT和toxR基因对于CT和TCP生产至关重要。然而,与O1分离株不同,在VCE232中,toxT或toxR基因的存在足以实现最佳CT产生。此外,VCE232ΔtoxR突变体显示出主要外膜蛋白的差异调节,OmpT和OmpU。这是探索环境产毒霍乱弧菌非O1/非O139菌株中主要毒力基因和调节剂表达调控的首次尝试。
Vibrio cholerae O1 and O139 isolates deploy cholera toxin (CT) and toxin-coregulated pilus (TCP) to cause the diarrhoeal disease cholera. The ctxAB and tcpA genes encoding CT and TCP are part of two acquired genetic elements, the CTX phage and Vibrio pathogenicity island-1 (VPI-1), respectively. ToxR and ToxT proteins are the key regulators of virulence genes of V. cholerae O1 and O139. V. cholerae isolates belonging to serogroups other than O1/O139, called non-O1/non-O139, are usually devoid of virulence-related elements and are non-pathogenic. Here, we have analysed the available whole genome sequence of an environmental toxigenic V. cholerae non-O1/non-O139 strain, VCE232, carrying the CTX phage and VPI-1. Extensive bioinformatics and phylogenetic analyses indicated high similarity of the VCE232 genome sequence with the genome of V. cholerae O1 strains, including organization of the VPI-1 locus, ctxAB, tcpA and toxT genes, and promoters. We established that the VCE232 strain produces an optimal amount of CT at 30 °C under AKI conditions. To investigate the role of ToxT and ToxR in the regulation of virulence factors, we constructed ΔtoxT, ΔtoxR and ΔtoxTΔtoxR deletion mutants of VCE232. Extensive genetic analyses of these mutants indicated that the toxT and toxR genes of VCE232 are crucial for CT and TCP production. However, unlike O1 isolates, the presence of either toxT or toxR gene is sufficient for optimal CT production in VCE232. In addition, the VCE232 ΔtoxR mutant showed differential regulation of the major outer membrane proteins, OmpT and OmpU. This is the first attempt to explore the regulation of expression of major virulence genes and regulators in an environmental toxigenic V. cholerae non-O1/non-O139 strain.