Overexpression of the robA gene increases organic solvent tolerance and multiple antibiotic and heavy metal ion resistance in Escherichia coli

Abstract

Escherichia coli K-12 OST3410 was isolated previously as a stable cyclohexane-tolerant mutant derived from cyclohexane-sensitive strain JA300. A plasmid which provides cyclohexane tolerance to strain JA300 was isolated from the OST3410 genomic library. Subcloning and sequence analysis showed that the plasmid contained the robA gene, whose gene product was reported to bind specifically to the right border of oriC. We observed that the robA gene on the multicopy plasmid generally increased the organic solvent tolerance of several E. coli strains. We also observed an increase in the organic solvent tolerance of JA300 carrying the lac-robA fusion gene on a low-copy plasmid by isopropyl-␤-D-thiogalactopyranoside induction. Strain JA300 carrying the multicopy robA plasmid also showed an increase in resistance to a number of unrelated antibiotics and heavy metal ions, and the spectrum of resistance was significantly similar to that of the soxS-overexpressing strain.

Transcriptional response of mar, sox and rob regulon against concentration gradient carbapenem stress within Escherichia coli isolated from hospital acquired infection

“…In an earlier study salicylate was reported to be capable of activating marRAB via rob [28]. It has also been reported that the overexpression of rob exhibits resistance against antibiotics, organic solvents and superoxide-generating agents through plasmid [16,29]. In this study strong correlations between overexpression of rob and carbapenem resistance was observed when exposed to concentration gradient meropenem stress which is not being reported earlier.…”

Bile salts and fatty acids induce the expression of Escherichia coli AcrAB multidrug efflux pump through their interaction with Rob regulatory protein

“…The mechanism of induction of acrAB by bile acids and fatty acids is not known. Interestingly, the overproduction of yet another member of the AraC/XylS family, Rob, is known to increase resistance (Ariza et al ., 1995;Nakajima et al ., 1995;Lee et al ., 1996), presumably through increased production of the AcrAB pump (Jair et al ., 1996;White et al ., 1997). Rob is constitutively present at very high concentrations (Skarstad et al ., 1993;Kakeda et al ., 1995), and these overproduction experiments are unlikely to reflect physiological regulatory mechanisms.…”

Systematic mutagenesis of the DNA binding sites for SoxS in the Escherichia coli zwf and fpr promoters: identifying nucleotides required for DNA binding and transcription activation

“…In Escherichia coli, the induction of a common set of < 16 genes (acnA,acrAB,fldA,fpr,fumC,inaA,mar,micF,nfo,nfsA,poxB,ribA,sodA,tolC and zwf) confers tolerance to organic solvents, resistance to a variety of antibiotics and heavy metals and combats the oxidative stress imposed by redox-cycling compounds such as paraquat (Nakajima et al, 1995;Demple, 1996;Alekshun and Levy, 1997). Three distinct regulatory systems can stimulate the expression of these genes, with the direct transcriptional activators of each system being the highly related proteins SoxS, MarA and Rob, which comprise a subgroup of the AraC/XylS family of bacterial regulatory proteins (Gallegos et al, 1997).…”