Hexavalent chromium (Cr(VI)) has been widely used in a variety of industrial applications including metal plating and finishing, corrosion inhibition, and leather tanning. As a result of its widespread use, considerable amounts of Cr(VI), in the form of either chromate or dichromate, have been released into the environment where it now constitutes a major contaminant of soils and groundwater, and poses a significant health risk to man, plants and animals. One potential way to treat environmental Cr(VI) contamination is through the use of Cr(VI) reducing bacteria. These bacteria have been found by us, as well as other researchers, in a variety of environments around the world, both Cr(VI)-contaminated and pristine. Cr(VI) reducing bacteria, as a normal part of their inherent physiologies, are capable of reducing toxic Cr(VI) (i.e. chromate and/or dichromate) to trivalent chromium (Cr(III)), a much less toxic, less water soluble, and less mobile form. The work reported here focused on the isolation and characterization of Cr(VI) reducing bacteria from both Cr(VI) contaminated and uncontaminated locations in the subsurface of the U.S. Department of Energy (DOE) Hanford site. Enrichments in a minimal, synthetic groundwater medium using subsurface sediments as inocula resulted in several Cr(VI) reducing bacterial consortia. Characterization of the individual Cr(VI) reducing isolates from the Hanford consortia showed that eight of nine were Gram (+) species. Characterization of these isolates using 16S rDNA techniques revealed that a number appeared to be either closely related to, or members of the genus Cellulomonas. This was a novel discovery, since aside from our work with the Hanford consortia, Cellulomonas species have not been previously shown to play a role in Cr(VI) reduction.
展开▼
