Rosner J L, Slonczewski J L
Laboratory of Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, Maryland 20892.
J Bacteriol. 1994 Oct;176(20):6262-9. doi: 10.1128/jb.176.20.6262-6269.1994.
The roles of the marRAB (multiple antibiotic resistance) operon and soxRS (superoxide response) genes in the regulation of inaA, an unlinked weak-acid-inducible gene, were studied. inaA expression was estimated from the beta-galactosidase activity of a chromosomal inaA1::lacZ transcriptional fusion. marR mutations that elevate marRAB transcription and engender multiple antibiotic resistance elevated inaA expression by 10- to 20-fold over that of the wild-type. Similarly, one class of inaA constitutive mutants that mapped to the mar region were multiply antibiotic resistant. Overexpression of marA alone on a multicopy plasmid caused high constitutive expression of inaA in a strain with an extensive (39-kbp) marRAB deletion. Salicylate, an inducer of marRAB and of an unidentified mar-independent antibiotic resistance system, induced inaA by 6-fold. A portion of this induction was also mar independent. Two soxRS constitutive mutants that were tested showed elevated levels of inaA. Paraquat, an inducer of the soxRS system, elevated inaA expression by 6- to 9-fold. This induction was soxRS dependent and not mar dependent, whereas induction of inaA by salicylate was not dependent on soxRS. Paraquat induced resistance to norfloxacin in the mar-deleted strain but not in a soxRS-deleted strain. Thus, induction of multiple antibiotic resistance and inaA by salicylate occurs via mar and an unidentified pathway, while induction by paraquat occurs via soxRS.
研究了marRAB（多重抗生素抗性）操纵子和soxRS（超氧化物应答）基因在调控inaA（一个不连锁的弱酸诱导基因）中的作用。通过染色体inaA1::lacZ转录融合体的β-半乳糖苷酶活性来评估inaA的表达。提高marRAB转录并产生多重抗生素抗性的marR突变使inaA的表达比野生型提高了10至20倍。同样，一类定位于mar区域的inaA组成型突变体具有多重抗生素抗性。在多拷贝质粒上单独过表达marA会导致在一个具有广泛（39-kbp）marRAB缺失的菌株中inaA出现高组成型表达。水杨酸酯是marRAB和一个未知的不依赖mar的抗生素抗性系统的诱导剂，它能使inaA诱导6倍。这种诱导的一部分也是不依赖mar的。测试的两个soxRS组成型突变体显示inaA水平升高。百草枯是soxRS系统的诱导剂，它能使inaA表达提高6至9倍。这种诱导是依赖soxRS而不依赖mar的，而水杨酸酯对inaA的诱导不依赖soxRS。百草枯在mar缺失菌株中诱导对诺氟沙星的抗性，但在soxRS缺失菌株中不诱导。因此，水杨酸酯诱导多重抗生素抗性和inaA是通过mar和一条未知途径发生的，而百草枯诱导是通过soxRS发生的。
