In Vivo Titration of Mitomycin C Action by Four Escherichia coli Genomic Regions on Multicopy Plasmids

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Abstract
Mitomycin C (MMC), a DNA-damaging agent, is a potent inducer of the bacterial SOS response; surprisingly, it has not been used to select resistant mutants from wild-type Escherichia coli . MMC resistance is caused by the presence of any of four distinct E. coli genes ( mdfA, gyrl, rob , and sdiA ) on high-copy-number vectors. mdfA encodes a membrane efflux pump whose overexpression results in broad-spectrum chemical resistance. The gyrI (also called sbmC ) gene product inhibits DNA gyrase activity in vitro, while the rob protein appears to function in transcriptional activation of efflux pumps. SdiA is a transcriptional activator of ftsQAZ genes involved in cell division.