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the research; ML SU5402 nmr and YB analyzed data; ML and HWS wrote the paper. All authors have read and approved the final manuscript.”
“Background Efflux pumps of the resistance-nodulation-division (RND) superfamily contribute to antibiotic Astemizole resistance, virulence and solvent tolerance in Gram-negative bacteria [1–3]. The clinical significance of RND efflux pumps and their relevance to bioremediation necessitate understanding the factors influencing their expression and activity. Previous studies seeking the inducers of genes encoding RND efflux pumps focussed on known substrates of the pumps [4, 5]. However, such studies showed that substrates are often not inducers, and the pumps are present in bacterial cells that have not been exposed to antibiotics or solvents [5–7]. Furthermore, genes encoding RND efflux pumps can be induced by stress responses such as ribosome disruption or membrane-damaging agents [4, 7–9]. These observations suggest a physiological function for RND efflux systems beyond the transport of antibiotics or solvents. Knowledge of the primary physiological role for such pumps in Gram-negative bacteria may aid development of new methods to combat antibiotic resistance [7] and improvement of biocatalytic processes such as production of enantio-pure compounds from hydrocarbons or bioremediation of polycyclic aromatic hydrocarbon (PAH) pollutants.