Burdett V, Inamine J, Rajagopalan S
J Bacteriol. 1982 Mar;149(3):995-1004. doi: 10.1128/jb.149.3.995-1004.1982.
We found that naturally occurring tetracycline resistance in streptococci is encoded by more than one genetic determinant. Two of these distinct determinants were cloned, and the regions that are necessary and sufficient for expression of tetracycline resistance were defined by deletion analysis. These cloned determinants were further characterized by DNA-DNA hybridization experiments which also identified a third genetically unrelated tetracycline resistance determinant. Some of these genetic differences appear to represent mechanistic differences. The tetL determinant was associated with small nonconjugative plasmids and mediated resistance to tetracycline. The tetM determinant was most often "nonplasmid" associated and mediated resistance to minocycline as well as tetracycline. The tetN determinant was represented on a large conjugative plasmid and was genetically distinct from tetL and tetM, although phenotypically it resembled tetM.
我们发现，链球菌中天然存在的四环素抗性由多个遗传决定因素编码。其中两个不同的决定因素被克隆出来，通过缺失分析确定了四环素抗性表达所必需且足够的区域。这些克隆的决定因素通过DNA-DNA杂交实验进一步表征，该实验还鉴定出第三个与基因无关的四环素抗性决定因素。这些遗传差异中的一些似乎代表了机制上的差异。tetL决定因素与小型非接合性质粒相关，并介导对四环素的抗性。tetM决定因素最常与“非质粒”相关，并介导对米诺环素以及四环素的抗性。tetN决定因素存在于一个大型接合质粒上，在基因上与tetL和tetM不同，尽管在表型上它与tetM相似。
