Stress Response of Multiple-Antibiotic-Resistance (Mar) Mutants of Escherichia coli K-12

ABSTRACT

The survival or growth rate of multiple-antibiotic-resistance (Mar) mutants of Escherichia coli K-12 MC4100 or W3110, influenced by many stresses (4% ethanol, 3mM HzO, 0.5M NaC1, pH 2, pH 5, and heat-shock (42C)), and the effects of salicylate (SAL) induction were evaluated by growth rate. Under the stress conditions of pH 5 and heat-shock, growth rates of Mar mutants derived from MC4100 or W3110 induced by salicylate (SAL) were higher than those of wild type Escherichia coli K-12 and E. coli clinical isolates. Under the SAL induction, growth rates of wild type MC4100 or W3110 were higher than those of Mar mutants in case of 0.5M NaC1 or pH 2 stress, respectively. Without SAL induction, growth rates of wild type E. coli were higher than those of Mar mutants, in case of MC4100 grown with 4% ethanol, HO, or heat-shock stresses, in case of W3110 grown with pH 2, or heat-shock stress. There were sorne instances of cytotoxic effect of SAL to the Mar mutants, wild type E. coli, or E. coli clinical isolates under some stress conditions.