Genes for all metals--a bacterial view of the periodic table. The 1996 Thom Award Lecture

J Ind Microbiol Biotechnol. 1998 Jan;20(1):1-12. doi: 10.1038/sj.jim.2900483.


Bacterial chromosomes have genes for transport proteins for inorganic nutrient cations and oxyanions, such as NH4+, K+, Mg2+, Co2+, Fe3+, Mn2+, Zn2+ and other trace cations, and PO4(3-), SO4(2-) and less abundant oxyanions. Together these account for perhaps a few hundred genes in many bacteria. Bacterial plasmids encode resistance systems for toxic metal and metalloid ions including Ag+, AsO2-, AsO4(3-), Cd2+, Co2+, CrO4(2-), Cu2+, Hg2+, Ni2+, Pb2+, TeO3(2-), Tl+ and Zn2+. Most resistance systems function by energy-dependent efflux of toxic ions. A few involve enzymatic (mostly redox) transformations. Some of the efflux resistance systems are ATPases and others are chemiosmotic ion/proton exchangers. The Cd(2+)-resistance cation pump of Gram-positive bacteria is membrane P-type ATPase, which has been labeled with 32P from [gamma-32P]ATP and drives ATP-dependent Cd2+ (and Zn2+) transport by membrane vesicles. The genes defective in the human hereditary diseases of copper metabolism, Menkes syndrome and Wilson's disease, encode P-type ATPases that are similar to bacterial cadmium ATPases. The arsenic resistance system transports arsenite [As(III)], alternatively with the ArsB polypeptide functioning as a chemiosmotic efflux transporter or with two polypeptides, ArsB and ArsA, functioning as an ATPase. The third protein of the arsenic resistance system is an enzyme that reduces intracellular arsenate [As(V)] to arsenite [As(III)], the substrate of the efflux system. In Gram-negative cells, a three polypeptide complex functions as a chemiosmotic cation/protein exchanger to efflux Cd2+, Zn2+ and Co2+. This pump consists of an inner membrane (CzcA), an outer membrane (CzcC) and a membrane-spanning (CzcB) protein that function together.

Publication types

  • Biography
  • Historical Article
  • Lecture

MeSH terms

  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism
  • Awards and Prizes
  • Bacteria / drug effects
  • Bacteria / genetics*
  • Bacteria / metabolism
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Chromosomes, Bacterial / genetics*
  • Drug Resistance, Microbial / genetics
  • Genome, Bacterial
  • History, 20th Century
  • Metals, Heavy / metabolism
  • Metals, Heavy / pharmacology*
  • Mycology / history
  • R Factors / genetics
  • United States


  • Carrier Proteins
  • Metals, Heavy
  • Adenosine Triphosphatases

Personal name as subject

  • C Thom