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 and arsenic/antimony. Active efflux of the metal is a frequently utilized stratagem, lowering the intracellular concentration to subtoxic levels. Reduction to a less toxic form or to a form recognized by an efflux system also occurs. Sequestration of metals has also been observed. In bacteria, each of these resistance systems is transcriptionally regulated by the metal.