Author name: Anhuai Lu

A synergistic reaction pathway has been identified between semiconducting minerals and bacteria. Such reactions sustain electron and energy flow from light to nonphototrophic bacteria via semiconducting minerals, which act as a catalytic shuttle. Understanding this pathway may shed light on a unique ecosystem that potentially carries out phototrophic metabolism without the involvement of phototrophic organisms. Four key natural elements of this system are sunlight, semiconducting minerals, nonphototrophic bacteria, and water. This pathway also suggests a “selfcleansing” mechanism that may exist in nature, whereby both oxidative and reductive degradation of contaminants can occur.

Minerals and microbes have coevolved throughout much of Earth history. They interact at the microscopic scale, but their effects are manifested macroscopically. Minerals support microbial growth by providing essential nutrients, and microbial activity alters mineral solubility and the oxidation state of certain constituent elements. Microbially mediated dissolution, precipitation, and transformation of minerals are either directly controlled by microorganisms or induced by biochemical reactions that usually take place outside the cell. All these reactions alter metal mobility, leading to the release or sequestration of heavy metals and radionuclides. These processes therefore have implications for ore formation and the bioremediation of contaminated sites.