Date of Award

Spring 2015

Document Type

Restricted Thesis

Terms of Use

© 2015 Randall C. Burson. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts

Department

Biology

First Advisor

Amy Cheng Vollmer

Abstract

Triazole fungicides are a common class of xenobiotic compounds used in both agricultural and horticultural environments, and are persistent in the soil. While these fungicides are intended to target fungal cell wall synthesis, in high concentrations they have been shown to have negative health consequences in other biota, including humans. Prior research observed bioremediation of the triazole fungicides by environmental microbial communities with a prior history of exposure to these fungicides. This research focuses on the isolation of bacteria capable of metabolizing the triazole fungicide, myclobutanil. Bacteria consortia were isolated from soil regularly exposed to triazole fungicides; the Holiday lab has shown that soil sample DCC005, taken from the Newark, DE Country Club, demonstrated significant degradation of the fungicide during initial time trials. Metabolic assays were conducted to determine the nutritional and enzymatic characteristics of DCC005. Using increasingly stringent conditions, DCC005 was plated on Pseudomonas minimal medium enriched with 50ppm myclobutanil, and supplemented carbon or nitrogen sources. To test for co-metabolism of the fungicide, permissive trials utilized four concentrations of nutrient broth media (NB) (1X, 1/10X, 1/100X, 1/1000X). Optical density data of resuspended samples indicated bacterial growth over the course of time trials, but no visible differences in media with or without fungicide. 16S rRNA identification of bacterial consortia members and spotting assays grown on fungicide-containing media indicate that myclobutanil does not have universal bacteriostatic effects and a diverse consortia of bacteria are maintained when grown in the presence of fungicide, including Pseudomonas/Stenotrophomonas sp., Delftia sp., and Enterobacter sp. Future research will further characterize fungicide degradation by DCC005, and explore the effects of fungicide exposure and degradation on the bacterial soil consortium.

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