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Antimicrobial Agents and Chemotherapy, October 2003, p. 3067-3072, Vol. 47, No. 10
0066-4804/03/$08.00+0     DOI: 10.1128/AAC.47.10.3067-3072.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Antibiotic-Dependent Induction of Pseudomonas putida DOT-T1E TtgABC Efflux Pump Is Mediated by the Drug Binding Repressor TtgR

Wilson Terán, Antonia Felipe, Ana Segura, Antonia Rojas, Juan-Luis Ramos,* and María-Trinidad Gallegos

Consejo Superior de Investigaciones Científicas, Estación Experimental del Zaidín, Department of Plant Biochemistry, Molecular and Cellular Biology, Granada, Spain

Received 19 May 2003/ Returned for modification 13 June 2003/ Accepted 8 July 2003

Pseudomonas putida is well known for its metabolic capabilities, but recently, it has been shown to exhibit resistance to a wide range of antibiotics. In P. putida DOT-T1E, the TtgABC efflux pump, which has a broad substrate specificity, extrudes antibiotics such as ampicillin, carbenicillin, tetracycline, nalidixic acid, and chloramphenicol. We have analyzed the expression of the ttgABC efflux pump operon and its regulatory gene, ttgR, in response to several structurally unrelated antibiotics at the transcriptional level and investigated the role of the TtgR protein in this process. ttgABC and ttgR are expressed in vivo at a moderate basal level, which increases in the presence of hydrophobic antibiotics like chloramphenicol and tetracycline. In vitro experiments show that, in the absence of inducers, TtgR binds to a palindromic operator site which overlaps both ttgABC and ttgR promoters and dissociates from it in the presence of chloramphenicol and tetracycline. These results suggest that the TtgR repressor is able to bind to structurally different antibiotics, which allows induction of TtgABC multidrug efflux pump expression in response to these antimicrobial agents. This is the first case in which the expression of a drug transporter of the resistance-nodulation-division family has been shown to be regulated directly by antibiotics.

* Corresponding author. Mailing address: CSIC-Estación Experimental del Zaidín, Apdo. de Correos 419, E-18008 Granada, Spain. Phone: 34-958181608. Fax: 34-958135740, E-mail: jlramos{at}eez.csic.es.

Antimicrobial Agents and Chemotherapy, October 2003, p. 3067-3072, Vol. 47, No. 10
0066-4804/03/$08.00+0     DOI: 10.1128/AAC.47.10.3067-3072.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



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