Identification and molecular characterization of an efflux system involvedin Pseudomonas putida S12 multidrug resistance

The authors previously described srpABC, an operon involved in proton-depen dent solvent efflux in the solvent-tolerant Pseudomonas putida 512. Recentl y, it was shown that organic solvents and not antibiotics induce this opero n. In the present study, the authors characterize a new efflux pump, design ated ArpABC, on the basis of two isolated chloramphenicol-sensitive transpo son mutants. The ArpABC operon is involved in the active efflux of multiple antibiotics, such as tetracycline, chloramphenicol. carbenicillin, strepto mycin. erythromycin and novobiocin. The deduced amino acid sequences encode d by the three genes involved show a striking resemblance to proteins of th e resistance/nodulation/cell division family, which are involved in both or ganic solvent and multiple drug efflux. These findings demonstrate that Arp ABC is highly homologous to the MepABC and TtgABC efflux systems for organi c solvents and multiple antibiotics. However, ArpABC does not contribute to organic solvent tolerance in P. putida 512 but is solely involved in multi drug resistance.