Heavy metals induce cellular damage through competition with optimal metals for vital protein binding sites or through oxidative stress, which can damage DNA and other cellular components. With the increase in heavy metal pollution in the environment since the Industrial Revolution, there has been a mounting need for effective remediation methods.

Bioremediation of heavy metals

Bioremediation is the use of either naturally-occurring or deliberately-introduced organisms to consume and break down environmental pollutants and clean up a polluted site. Microbes have been utilized for large-scale bioremediation since the 1960s and 1970s, when researchers first began using mixtures of bacterial species to help clean up oil spills.

While much research, thus far, has focused primarily on the bioremediation possibilities of singular species, some studies have found that mixed cultures of microbial species may have more advantages. Recently, research into the role of microbes in the bioremediation of heavy metals has become a topic of considerable interest due to the expense and toxicity of other remediation methods.

Metal resistance mechanisms

Understanding how microbes withstand exposure to heavy metal concentrations that are toxic to humans and other organisms is foundational to the development of effective bioremediation techniques. While most bacteria have evolved some mechanisms for metal tolerance, metallophiles (metal-lovers) have adapted to survive in extremely high concentrations. This enables them to avoid the toxic effects of exposure, which would normally lead to cell death through oxidative damage and binding of suboptimal metal cofactors to protein binding sites. There are several mechanisms by which microbes can tolerate high levels of metals: