Rashtchian A, Dubes G R, Booth S J
J Bacteriol. 1982 Apr;150(1):141-7. doi: 10.1128/jb.150.1.141-147.1982.
Tetracycline resistance of three Bacteroides fragilis strains was shown to be inducible by subinhibitory concentrations of tetracycline. Tetracycline resistance markers could be transferred to another B. fragilis strain by filter mating. The transferability was inducible by subinhibitory concentrations of tetracycline and did not take place in the absence of tetracycline. The optimum concentration of tetracycline for induction of transfer was about 2 microgram/ml. The transfer was shown to be a conjugation-like process requiring cell-to-cell contact between donor and recipient. Screening of parental donor strains for the presence of plasmid DNA did not demonstrate any detectable plasmids in two of the strains. A 3.0-megadalton plasmid, designated pBY5, was present in the third donor strain. Mobilization of pBY5 by another plasmid (pBF4) showed that pBY5 did not carry the genes responsible for tetracycline resistance. It appears that the genes responsible for resistance to tetracycline as well as those responsible for conjugal transfer may be carried on the chromosome in all three donor strains.
三种脆弱拟杆菌菌株的四环素抗性被证明可由亚抑制浓度的四环素诱导产生。四环素抗性标记可通过滤膜交配转移至另一株脆弱拟杆菌。这种转移性可由亚抑制浓度的四环素诱导，且在无四环素的情况下不会发生。诱导转移的四环素最佳浓度约为2微克/毫升。该转移过程显示为一种类似接合的过程，需要供体和受体之间的细胞与细胞接触。对亲本供体菌株进行质粒DNA检测，结果表明其中两株未检测到任何可检测的质粒。第三株供体菌株中存在一个3.0兆道尔顿的质粒，命名为pBY5。另一质粒（pBF4）对pBY5的动员表明，pBY5不携带负责四环素抗性的基因。看来，在所有三株供体菌株中，负责四环素抗性的基因以及负责接合转移的基因可能都位于染色体上。
