OVEREXPRESSION OF THE ROBA GENE INCREASES ORGANIC-SOLVENT TOLERANCE AND MULTIPLE ANTIBIOTIC AND HEAVY-METAL ION RESISTANCE IN ESCHERICHIA-COLI

Escherichia coli K-12 OST3410 was isolated previously as a stable cycl ohexane-tolerant mutant derived from cyclohexane-sensitive strain JA30 0. A plasmid which provides cyclohexane tolerance to strain JA300 was isolated from the OST3410 genomic library. Subcloning and sequence ana lysis showed that the plasmid contained the robA gene, whose gene prod uct was reported to bind specifically to the right border of oriC. We observed that the robA gene on the multicopy plasmid generally increas ed the organic solvent tolerance of several E. coli strains. We also o bserved an increase in the organic solvent tolerance of JA300 carrying the lac-robA fusion gene on a low-copy plasmid by isopropyl-beta-D-th iogalactopyranoside induction. Strain JA300 carrying the multicopy rob A plasmid also showed an increase in resistance to a number of unrelat ed antibiotics and heavy metal ions, and the spectrum of resistance wa s significantly similar to that of the soxS-overexpressing strain.