ABSTRACT
Abstract In recent years the contribution of anaerobic processes to in situ contaminant transformation has been recognized as an increasingly important if not dominant process during the natural attenuation of groundwater contaminants. Microbial processes coupled to Fe(III) reduction have been viewed as of particular importance because upon the depletion of dissolved oxygen, Fe(III) is generally the most abundant potential electron acceptor within subsurface sediments. A wide diversity of Fe(III)-reducing bacteria are known but relatively few are found to be important for in situ contaminant transformation. Members of the Geobacteraceae have been detected in situ in association with contaminant degradation consistent with the known physiology of these organisms. Geobacteraceae are known to utilize aromatic hydrocarbons as growth substrates, remove important metal contaminants from groundwater and have been associated with halogenated solvent degradation. Geobacter species are also known to utilize electrodes as electron acceptors, a consequence of respiring solid phase Fe(III). Recent insights into the mechanism of metal reduction in Geobacter species may explain the prevalence of this group in sediments. Further genomeenabled studies of Geobacteraceae physiology are likely to lead to gene expression assays for monitoring in situ metabolism and suggest ways to promote contaminant degradation in situ.
