Ning Zhang

Defense Date

1-4-2012

Graduation Date

2012

Availability

Immediate Access

Submission Type

thesis

Degree Name

MS

Department

Environmental Science and Management (ESM)

Committee Chair

John F. Stolz

Committee Member

Tobin J. Michael

Committee Member

Skip H.M. Kingston

Keywords

Chromate, Desulfovibrio Desulfuricans ATCC 27774, Reduction

Abstract

Chromium has been used extensively in the industry process of metal refinishing and electroplating. It is also a byproduct of the processing of fissionable materials at United States Department of Energy facilities. Chromate (Cr (VI)) is soluble and readily absorbed by cells, while the reduced form of chromium, Cr (III), is insoluble. Thus means of reducing Cr (VI) to Cr (III) in the environment is a potential means of remediation. Desulfovibrio desulfuricans strain 27774 is a sulfate reducing bacterium that can reduce Cr (VI). It also can respire nitrate to ammonia. As some sites of chromium contamination also contain high concentrations of nitrate, an investigation of Cr (VI) reduction under nitrate reducing growth conditions by D. desulfuricans strain 27774 was conducted. A growth medium that was compatible with the colorimetric assay for Cr (VI) and did not itself reduce Cr (VI) was formulated. Cell assays determined that Cr (VI) reduction was primarily in the supernatant, catalyzed by a secreted secondary metabolite. A genomics investigation identified two pathways as possible mechanisms.

Format

PDF

Language

English

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