Bryan Crable

Defense Date

6-22-2007

Graduation Date

Spring 2007

Availability

Immediate Access

Submission Type

thesis

Degree Name

MS

Department

Biological Sciences

Committee Chair

John F. Stolz

Committee Member

Partha Basu

Committee Member

Jana Patton-Vogt

Keywords

Microbial Transformation of 3-Nitro-4-Hydroxybenzene Arsonic Acid (Roxarsone)

Abstract

Land application of chicken litter from production houses that use the organoarsenical 3-nitro-4-hydroxybenzenearsonic acid (roxarsone) results in deposition of significant quantities of arsenic into United States soil each year. Used widely as a feed additive in the poultry industry, roxarsone was originally thought to be stable in the environment. However, recent evidence from our lab, as well as others, has established that this benign compound is readily transformed via several intermediates into inorganic arsenate. While microbial activity has been implicated in this process, there is no direct evidence suggesting the specific processes or the organisms involved.

Using a physiological and proteomic approach, this study demonstrates increased anaerobic growth of the arsenate respiring Clostridium species strain OhILAs in the presence of roxarsone using two different carbon sources, as well as provides evidence to suggest the respiratory arsenate reductase (Arr) system may be constitutively expressed. Increased growth of Clostridium OhILAs was coupled to a loss of roxarsone as determined by spectrophotometric assays. Similar results have been obtained with the structurally similar ortho-nitrophenol. Additionally, arsenate reductase activity assays of OhILAs grown in the presence of lactate alone or in the presence of lactate and either roxarsone, ortho-nitrophenol or sodium arsenate have suggested that the respiratory arsenate reductase is constitutively expressed.

Format

PDF

Language

English

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