Nanoparticles Formed by Microbial Metabolism of Metals and Minerals

Microorganisms produce a wide variety of metallo-nanoparticles. These are deposited in the cytoplasm, periplasm, extracellular area, or on the surface of the cell. These nanoparticles may be the result of energy-conserving dissimilatory metal reduction processes, cell-building assimilatory activities, or co-metabolism. This formation of metal or metalloid nanoparticles from soluble cations and anions generally result in the lowering of the concentration of toxic chemicals in the environment. While the reduction of metals and metalloids is observed with growing cultures, the reduction also occurs with bacteria in the stationary growth phase, or with enzymes isolated from bacteria. As the industrial use of metallo-nanoparticles increases, the use of microorganisms is preferred over some of the chemical processes, as they can have a lower impact on the environment. This chapter focuses on the cellular systems, enzymes, and electron transport proteins of microorganisms contributing to the production of metallo-nanoparticles.