Extracellular Electron Shuttles for the Anaerobic Oxidation of Tar Oil Contaminants

Coal tar is a complex mixture; its aromatic and phenolic constituents are amongst the most worrisome substances from an environmental viewpoint. Understanding abiotic and enzymatically mediated pollutant transformation processes, involving complex contaminant, geochemical and microbial matrices, is required to control and, if desired, enhance biogeochemical reactions that contribute to site detoxification. In this context, one of the aspects less well understood is the role of poorly soluble electronacceptors, including Fe(III) and Mn(IV) minerals, in anaerobic contaminant transformation processes. Despite their poor aqueous solubility and thus poor bio-accessibility, these species participate in microbe-driven geochemical cycles. Several mechanisms, including electrochemically conductive pilus-like assemblages expressed by Geobacter species, or Shewanella's chelatingagents, enable for extracellular electron transport to practically insoluble Fe(III) surfaces serving as terminal electron acceptors in contaminant oxidation, have been 'devised' by nature.