Date of Award

5-1-2015

Degree Name

Master of Science

Department

Molecular Biology Microbiology and Biochemistry

First Advisor

Bender, Kelly

Abstract

Acid mine drainage (AMD) is an environmental hazard across the world. Passive bioreactors utilizing sulfate-reducing bacteria to remediate AMD impacted sites are a promising solution due to their low cost and minimal maintenance. This study profiled the microbial community associated with six in situ, pilot scale bioreactors that were constructed with varying ratios of simple and complex organic substrate and exposed to AMD. Samples were analyzed nine and fourteen months post assembly to ascertain long-term performance. The overall microbial and sulfate-reducing communities were analyzed by 16S rRNA gene and dsrA gene sequencing, respectively. Over the fourteen-month experiment, the results indicated that the microbial community shifted from one dominated by heterotrophic and fermentative microorganisms utilizing the available substrates to one commonly found in untreated AMD. Thus suggesting a decrease in bioreactor performance over time. The data also indicated that the overall microbial communities within the test bioreactors possessed similar members, but in different abundance. Thus it is unlikely that substrate composition played a significant role in community diversity. At the end of the study period, sulfide measurements suggested that the bioreactor containing the highest amount of complex substrate (Barrel 6) resulted in the greatest stimulation of sulfate reduction. Analysis of the dsrA genes from the community in Barrel 6 suggested that bacteria related to thermophilic sulfate-reducers were responsible for the increased sulfate reduction in this bioreactor.

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