ABSTRACT
Bacteria have been interacting with heavy metals since their early evolutionary history. Bacterial interactions with heavy metals have been best studies in ex treme environments where the emphasis has been to assess bacterial adaptation, metabolism, tolerance, and resistance to heavy metals. In general, the types of interactions are directly dependent on the biological role of the heavy metal spe cies in the bacteria: some heavy metals are required as essential cofactors for protein activity or to stabilize protein conformations, while most heavy metals tend to be toxic at high concentrations (reviewed in 1). Under these extreme environments, a selective advantage is conferred to those organisms that have adopted resistance mechanisms to withstand the toxic effects of high concentra tions of heavy metals.
