Harkness R E, Braun V
Mikrobiologie II, Universität Tübingen, Federal Republic of Germany.
Mol Gen Genet. 1990 Jun;222(1):37-40. doi: 10.1007/BF00283020.
The colicin M structural gene, cma, was subcloned in a vector which allowed temperature-inducible control of its expression. Induction of expression of cma in colicin M uptake proficient strains was lethal for the host cell when the colicin M immunity protein was not present. In liquid culture cells lysed, and no colonies were formed on solid media. These effects were not observed in mutants defective in the colicin receptor (FhuA) or uptake functions (TonB, TolM), nor in wild-type cells treated with trypsin prior to induction of cma expression. It was concluded that cytoplasmic colicin M is not toxic for the producing cell. To exert a lethal effect the colicin has to enter the cell from outside. Cells expressing cma released small amounts of colicin M.
大肠杆菌素M结构基因cma被亚克隆到一个载体中，该载体可实现对其表达的温度诱导控制。当不存在大肠杆菌素M免疫蛋白时，在能够摄取大肠杆菌素M的菌株中诱导cma表达对宿主细胞是致命的。在液体培养中细胞裂解，在固体培养基上未形成菌落。在大肠杆菌素受体（FhuA）或摄取功能（TonB、TolM）有缺陷的突变体中，以及在诱导cma表达之前用胰蛋白酶处理的野生型细胞中，均未观察到这些效应。得出的结论是，细胞质中的大肠杆菌素M对产生该毒素的细胞无毒。为了发挥致死作用，大肠杆菌素必须从外部进入细胞。表达cma的细胞释放少量大肠杆菌素M。
