Tölg M, Schmidt H, Schierl R, Datz M, Martin H H
Institut für Mikrobiologie, Technische Hochschule Darmstadt, FRG.
J Gen Microbiol. 1993 Nov;139(11):2715-22. doi: 10.1099/00221287-139-11-2715.
The mobilizable plasmid pMD101 (ampR, ampC) was constructed by inserting cloned ampC, the structural gene for the chromosomal AmpC beta-lactamase of Citrobacter freundii, and the closely linked ampR encoding the transcriptional regulator essential for enzyme induction, into the broad host-range plasmid pKT231. Plasmid pMD101 was transconjugated into Proteus mirabilis VI and its isogenic, cell-wall-less protoplast L-form LVI. AmpC beta-lactamase was expressed constitutively from cloned ampR and ampC in bacteria and in some L-form protoplasts. However, induction of the enzyme by beta-lactam antibiotics occurred only in bacterial cells and not in the cell-wall- and peptidoglycan-deficient L-form. In agreement with current models, induction of AmpC beta-lactamase is thought to be initiated by an induction signal arising from the metabolic disturbance of cell-wall peptidoglycan.
可移动质粒pMD101（ampR，ampC）的构建方法是，将克隆的ampC（弗氏柠檬酸杆菌染色体AmpCβ-内酰胺酶的结构基因）以及与之紧密相连的ampR（编码酶诱导所必需的转录调节因子）插入到广宿主范围质粒pKT231中。质粒pMD101通过转接合作用导入奇异变形杆菌VI及其同基因的无细胞壁原生质体L-型LVI。在细菌和一些L-型原生质体中，AmpCβ-内酰胺酶由克隆的ampR和ampC组成型表达。然而，β-内酰胺类抗生素对该酶的诱导仅发生在细菌细胞中，而在无细胞壁和肽聚糖的L-型中未发生。与当前模型一致，AmpCβ-内酰胺酶的诱导被认为是由细胞壁肽聚糖代谢紊乱产生的诱导信号引发的。
