ISOLATION OF HEXAVALENT CHROMIUM-REDUCING ANAEROBES FROM HEXAVALENT-CHROMIUM-CONTAMINATED AND NONCONTAMINATED ENVIRONMENTS

Hexavalent chromium [Cr(VI)], is a toxic, water-soluble contaminant pr esent in many soils and industrial effluents. Bacteria from various so ils were examined for Cr(VI) resistance and reducing potential. Microb es selected from both Cr(VI)-contaminated and -noncontaminated soils a nd sediments were capable of catalyzing the reduction of Cr(VI) to Cr( III) a less toxic, less water-soluble form of Cr, demonstrating the ut ility of using a selection strategy for indigenous Cr(VI)-reducing bac teria in a bioprocess. As a result, indigenous Cr(VI)- reducing microb es from contaminated sites should provide the means for developing a b ioprocess to reduce Cr(VI) to Cr(III) in nonsterile effluents such as those from soil washes. This approach also avoids the contamination pr oblems associated with pure cultures of allochthonous microorganisms. In addition the apparent ubiquity of Cr(VI)-reducing bacteria in soil and sediments indicates potential for in situ bioremediation of Cr(VI) -contaminated soils and ground water.