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Journal of Bacteriology, April 2008, p. 2680-2689, Vol. 190, No. 8
0021-9193/08/$08.00+0     doi:10.1128/JB.01494-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Interplay of Different Transporters in the Mediation of Divalent Heavy Metal Resistance in Pseudomonas putida KT2440{triangledown}

Anu Leedjärv,1,2* Angela Ivask,2,{dagger} and Marko Virta1

Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland,1 Laboratory of Molecular Genetics, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia2

Received 17 September 2007/ Accepted 27 November 2007

According to in silico analysis, the genome of Pseudomonas putida KT2440 encodes at least four Zn/Cd/Pb efflux transporters—two P-type ATPases (CadA1 and CadA2) and two czc chemiosmotic transporters (CzcCBA1 and CzcCBA2). In this study we showed that all these transporters are functional, but under laboratory conditions only two of them were involved in the mediation of heavy metal resistance in P. putida KT2440. CadA2 conferred Cd2+ and Pb2+ resistance, whereas CzcCBA1 was involved in export of Zn2+, Cd2+, and possibly Pb2+. CadA1, although nonfunctional in P. putida, improved Zn2+ resistance and slightly improved Cd2+ resistance when it was expressed in Escherichia coli. CzcCBA2 contributed to Zn resistance of a czcA1-defective P. putida strain or when the CzcA2 subunit was overexpressed in a transporter-deficient strain. It seemed that CzcA2 could complex with CzcC1 and CzcB1 subunits and therefore complement the loss of CzcA1. The CzcCBA2 transporter itself, however, did not function. Expression of cadA1, cadA2, and czcCBA1 was induced by heavy metals, and the expression levels were dependent on the growth medium and growth phase. Expression of cadA2 and czcCBA1 was nonspecific; both genes were induced by Zn2+, Cd2+, Pb2+, Ni2+, Co2+, and Hg2+. On the other hand, remarkably, expression of cadA1 was induced only by Zn2+. Possible roles of distinct but simultaneously functioning transporters are discussed.

* Corresponding author. Mailing address: Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 56, FIN-00014 Helsinki, Finland. Phone: 358 9 191 57585. Fax: 358 9 191 59322. E-mail: anu.leedjarv{at}helsinki.fi

{triangledown} Published ahead of print on 7 December 2007.

{dagger} Requests for strains should be addressed to A. Ivask (E-mail: angela{at}kbfi.ee).

Journal of Bacteriology, April 2008, p. 2680-2689, Vol. 190, No. 8
0021-9193/08/$08.00+0     doi:10.1128/JB.01494-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Haritha, A., Sagar, K. P., Tiwari, A., Kiranmayi, P., Rodrigue, A., Mohan, P. M., Singh, S. S. (2009). MrdH, a Novel Metal Resistance Determinant of Pseudomonas putida KT2440, Is Flanked by Metal-Inducible Mobile Genetic Elements. J. Bacteriol. 191: 5976-5987 [Abstract] [Full Text]  


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