BACTERIAL-RESISTANCE TO HEAVY-METALS AND METALLOIDS

Bacteria have evolved various types of resistance mechanisms to toxic metals and metalloids including mercury, cadmium/zinc, copper/silver a nd arsenic/antimony. Active efflux of the metal is a frequently utiliz ed stratagem, lowering the intracellular concentration to subtoxic lev els. Reduction to a less toxic form or to a form recognized by an effl ux system also occurs. Sequestration of metals has also been observed. In bacteria, each of these resistance systems is transcriptionally re gulated by the metal.