Senior Honors Projects, 2010-current

Date of Award

Spring 2017

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Department of Biology

Advisor(s)

Morgan M Steffen

Louie L Wurch

James B Herrick

Abstract

One of the primary drivers of cyanobacterial harmful algal blooms (cHABs) in freshwater systems is nutrient loading, particularly of nitrogen and phosphorus. There has been an increased focus on assessing the role of nitrogen (N) in freshwater lakes and rivers that suffer cHABs. Urea, a widely-used, N-rich fertilizer, is a source of interest due to its abundance in freshwater ecosystems, primarily caused by anthropogenic nutrient loading. While recent work has shown that cHAB population succession may favor the toxic cyanobacterium Microcystis in urea-rich waters, the diversity of the associated bacterial community capable of degrading urea has yet to be determined. Therefore, we generated targeted sequence libraries of the gene encoding for the alpha subunit of the urease enzyme, ureC, from samples collected during summer (2015) from two model freshwater systems, Lake Shenandoah (LS) and the Shenandoah River (SR) (Virginia), to reveal potential urea-degrading members in threatened freshwater ecosystems. The total microbial community with urea-degrading capabilities was dominated by Proteobactiera in all samples, while Cyanobacteria was present in low abundance. This may be a result of the physical environment of LS and SR, or the low abundance of Cyanobacteria may be due to limitations in the custom database constructed for ureC amplicon analysis. LS and SR communities were similar overall, with the exception of a higher relative abundance of Acintobacteria ureC sequences in SR. Further analyses will aim to characterize more members with the ureC gene and expand upon the foundation built for community analyses based on ureC. These results provide better insight into the diversity of an important gene involved in bacterial urea degradation needed to resolve the microbial freshwater urea cycle.

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