Bacterial resistances to toxic metal ions--a review

Gene. 1996 Nov 7;179(1):9-19. doi: 10.1016/s0378-1119(96)00323-x.


Bacterial plasmids encode resistance systems for toxic metal ions, including Ag+, AsO2-, AsO4(3-), Cd2+, Co2+, CrO4(2-), Cu2+, Hg2+, Ni2+, Pb2+, Sb3+, TeO3(2-), Tl+ and Zn2+. The function of most resistance systems is based on the energy-dependent efflux of toxic ions. Some of the efflux systems are ATPases and others are chemiosmotic cation/proton antiporters. The Cd(2+)-resistance ATPase of Gram-positive bacteria (CadA) is membrane cation pump homologous with other bacterial, animal and plant P-type ATPases. CadA has been labeled with 32P from [alpha-32P] ATP and drives ATP-dependent Cd2+ (and Zn2+) uptake by inside-out membrane vesicles (equivalent to efflux from whole cells). Recently, isolated genes defective in the human hereditary diseases of copper metabolism, namely Menkes syndrome and Wilson's disease, encode P-type ATPases that are more similar to bacterial CadA than to other ATPases from eukaryotes. The arsenic resistance efflux system transports arsenite [As(III)], alternatively using either a double-polypeptide (ArsA and ArsB) ATPase or a single-polypeptide (ArsB) functioning as a chemiosmotic transporter. The third gene in the arsenic resistance system, arsC, encodes an enzyme that converts intracellular arsenate [As(V)] to arsenite [As(III)], the substrate of the efflux system. The triple-polypeptide Czc (Cd2+, Zn2+ and Co2+) chemiosmotic efflux pump consists of inner membrane (CzcA), outer membrane (CzcC) and membrane-spanning (CzcB) proteins that together transport cations from the cytoplasm across the periplasmic space to the outside of the cell.

Publication types

  • Review

MeSH terms

  • Drug Resistance, Microbial
  • Genes, Bacterial
  • Gram-Negative Bacteria / genetics
  • Gram-Negative Bacteria / metabolism*
  • Gram-Positive Bacteria / genetics
  • Gram-Positive Bacteria / metabolism*
  • Hepatolenticular Degeneration / genetics
  • Humans
  • Ion Pumps / genetics
  • Ion Pumps / metabolism*
  • Menkes Kinky Hair Syndrome / genetics
  • Metals / metabolism
  • Metals / toxicity*
  • Metals, Heavy / metabolism
  • Metals, Heavy / toxicity
  • Plasmids


  • Ion Pumps
  • Metals
  • Metals, Heavy