Metal transport ATPase genes from Cupriavidus metallidurans CH34: a transcriptomic approach

Abstract

Cupriavidus metallidurans strain CH34 is a multiple metal resistant β-proteobacterium isolated from the sediments of a zinc metallurgical plant. This strain possesses a large diversity of heavy-metal-resistance genes that are located mostly on two large plasmids, pMOL28 and pMOL30. The metal efflux ATPases constitute the major mechanism by which metal ions are removed and pumped out from the cytoplasmic pool of thiol groups. The genome of C. metallidurans CH34 contains eight such P1-ATPases. This high number of ATPases, compared with the P1-ATPase content in other micro-organisms, is a typical feature of the adaptation of C. metallidurans CH34 to metal-rich biotopes. We performed a phylogenetic analysis, and used quantitative PCR to study the metal-specific induction of the ATPases genes and, for some of them, their neighbouring genes. One of the ATPases, a homologue of the E. coli zntA gene, was characterized in detail by analysing the phenotypes of zntA mutants in different genetic backgrounds. In addition to the already-reported sensitivity to Zn(II), Cd(II), and Pb(II), zntA mutants also displayed a higher sensitivity to Tl(I) and Bi(III), indicating that the ZntA protein might play a role in the tolerance of very large cations.

Keywords:

• Ralstonia
• Cupriavidus metallidurans
• P1-type ATPase
• Heavy-metal resistance
• ZntA
• Thallium
• Bismuth

Acknowledgements

Sequencing of the C. metallidurans genome has been carried out at the Joint Genome Institute (JGI) under the auspices of the US Department of Energy's Office of Science, the Biological and Environmental Research Program, and the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48, Lawrence Berkeley National Laboratory under contract No. DE-AC03-76SF0098 and Los Alamos National Laboratory under contract No. W-7405-ENG-36. The draft sequence of the genome is now available at the website http://genome.jgi-psf.org/draft_microbes/ralme/ralme.home.html. Plasmid pMOL28 was sequenced at BNL under the LDRD program. Thanks to Dr Paul Janssen, Dr Andrew Dobney, and Dr D. van der Lelie for careful reading and insightful criticisms on this manuscript.