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Journal of Bacteriology, August 2009, p. 5159-5168, Vol. 191, No. 16
0021-9193/09/$08.00+0     doi:10.1128/JB.00384-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Functional and Expression Analyses of the cop Operon, Required for Copper Resistance in Agrobacterium tumefaciens{triangledown} ,{dagger}

Sirikan Nawapan,1,3 Nisanart Charoenlap,2 Anchalee Charoenwuttitam,3 Panatda Saenkham,4 Skorn Mongkolsuk,2,4,5 and Paiboon Vattanaviboon1,2,6*

Chulabhorn Graduate Institute, Bangkok 10210, Thailand,1 Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok 10210, Thailand,2 Post-Graduate Education, Training and Research Program in Environmental Science, Technology, and Management, Asian Institute of Technology, Pathumthani 12120, Thailand,3 Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand,4 Center for Emerging Bacterial Infections, Faculty of Science, Mahidol University, Bangkok 10400, Thailand,5 Center for Environmental Health, Toxicology and Management of Chemicals, Bangkok, Thailand6

Received 20 March 2009/ Accepted 29 May 2009

The copper resistance determinant copARZ, which encodes a CPx-type copper ATPase efflux protein, a transcriptional regulator, and a putative intracellular copper chaperone, was functionally characterized for the phytopathogenic bacterium Agrobacterium tumefaciens. These genes are transcribed as an operon, and their expression is induced in response to increasing copper and silver ion concentrations in a copR-dependent fashion. Analysis of the copARZ promoter revealed a putative CopR binding box located within the spacer of the –35 and –10 promoter motifs. In vitro, purified CopR could specifically bind to the box. The inactivation of the copARZ operon or copZ reduces the level of resistance to copper but not to other metal ions. Also, the copARZ operon mutant shows increased sensitivity to the superoxide generators menadione and plumbagin. In addition, the loss of functional copZ does not affect the ability of copper ions to induce the copARZ promoter, indicating that CopZ is not involved in the copper-sensing mechanism of CopR. Altogether, the results demonstrate a crucial role for the copARZ operon as a component of the copper resistance machinery in A. tumefaciens.

* Corresponding author. Mailing address: Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand. Phone: 662 574 0622, ext. 3815. Fax: 662 574 2027. E-mail: paiboon{at}cri.or.th

{triangledown} Published ahead of print on 5 June 2009.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, August 2009, p. 5159-5168, Vol. 191, No. 16
0021-9193/09/$08.00+0     doi:10.1128/JB.00384-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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