Foster T J
J Gen Microbiol. 1975 Oct;90(2):303-10. doi: 10.1099/00221287-90-2-303.
The isolation of Escherichia coli chromosomal mutants that increased the level of resistance of a partially tetracycline-sensitive mutant of RI00-I is described. Plasmid-less derivatives of these moderately resistant mutants were phenotypically similar to the cmlB mutants described by Reeve (1966, 1968), and also mapped in the same region. The level of intrinsic resistance to both chloramphenicol and tetracycline was increased about twofold. Also, the levels of R factor-determined resistance to these drugs were increased by this host mutation and tetracycline resistance was expressed constitutively. A cmlB accumulated tetracycline at a threefold lower rate than the wild-type strain, and it is proposed that the mutants have an altered permeability to the drugs and that this acts synergistically with the products of the R factor chloramphenicol and tetracycline resistance genes.
本文描述了大肠杆菌染色体突变体的分离，这些突变体提高了RI00-I部分对四环素敏感突变体的抗性水平。这些中度抗性突变体的无质粒衍生物在表型上与Reeve（1966年、1968年）描述的cmlB突变体相似，并且也定位在同一区域。对氯霉素和四环素的固有抗性水平提高了约两倍。此外，这种宿主突变增加了R因子决定的对这些药物的抗性水平，并且四环素抗性组成性表达。一个cmlB突变体积累四环素的速率比野生型菌株低三倍，并且有人提出这些突变体对药物的通透性发生了改变，并且这与R因子氯霉素和四环素抗性基因的产物协同作用。
