title: Role of the Mycobacterium tuberculosis P55 efflux pump in intrinsic drug resistance, oxidative stress responses, and growth.
abstract: Bacterial efflux pumps have traditionally been studied as low-level drug resistance determinants. Recent insights have suggested that efflux systems are often involved with fundamental cellular physiological processes, suggesting that drug extrusion may be a secondary function. In Mycobacterium tuberculosis, little is known about the physiological or drug resistance roles of efflux pumps. Using Mycobacterium bovis BCG as a model system, we showed that deletion of the Rv1410c gene encoding the P55 efflux pump made the strain more susceptible to a range of toxic compounds, including rifampin (rifampicin) and clofazimine, which are first- and second-line antituberculosis drugs. The efflux pump inhibitors carbonyl cyanide m-chlorophenylhydrazone (CCCP) and valinomycin inhibited the P55-determined drug resistance, suggesting the active export of the compounds by use of the transmembrane proton and electrochemical gradients as sources of energy. In addition, the P55 efflux pump mutant was more susceptible to redox compounds and displayed increased intracellular redox potential, suggesting an essential role of the efflux pump in detoxification processes coupled to oxidative balance within the cell. Finally, cells that lacked the p55 gene displayed smaller colony sizes and had a growth defect in liquid culture. This, together with an increased susceptibility to the cell wall-targeting compounds bacitracin and vancomycin, suggested that P55 is needed for proper cell wall assembly and normal growth in vitro. Thus, P55 plays a fundamental role in oxidative stress responses and in vitro cell growth, in addition to contributing to intrinsic antibiotic resistance. Inhibitors of the P55 efflux pump could help to improve current treatments for tuberculosis.
authors: Departamento de Microbiología, Medicina Preventiva y Salud Pública, Universidad de Zaragoza, Zaragoza 50009, Spain. ramon@interchange.ubc.ca
authors: Santiago
authors: S
authors: Ramón-García
authors: Carlos
authors: C
authors: Martín
authors: Charles J
authors: CJ
authors: Thompson
authors: José A
authors: JA
authors: Aínsa
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002991:Clofazimine / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects* / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000235:genetics; D005978:Glutathione / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress; D012293:Rifampin / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; C425143:P55 protein, Mycobacterium; D014634:Valinomycin; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D006861:Hydrogen Peroxide; D002991:Clofazimine; D005978:Glutathione; D004229:Dithiothreitol; D012293:Rifampin