Date Thesis Awarded

5-2019

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Biology

Advisor

Kurt Williamson

Committee Members

Douglas Young

Mark Forsyth

Abstract

As the most ubiquitous biological entities on earth, viruses have important impacts on aquatic microbial ecology and have been studied at length in the global ocean. However, the role of bacteriophage in lotic ecosystems, particularly in benthic biofilms, have been largely under studied. Streams and rivers play crucial roles in global carbon cycling, with over 2 x 1015 g C turned over each year, and benthic biofilms appear to be hotspots of microbial activities like organic carbon transformations. Given this importance of lotic ecosystems and the known impacts of viruses in other aquatic systems, investigating the ecology of viruses in streams is likely to illuminate the specific roles viruses play in these ecosystems. The main goals of my work were to: 1) determine whether viruses (detectable as extracellular particles) are consistent members of natural mixed biofilm communities; 2) determine whether temperate phage are present and active in multispecies bacterial biofilms collected from streams; and 3) to determine whether community profiling approaches like RAPD-PCR can be adapted to biofilm virus communities/samples. Firstly, epifluorescence microscopy was used to verify that viruses were present in biofilm communities procured from the Crim Dell Creek, White Clay Creek, and experimental flumes. To investigate the potential importance of lysogeny in benthic biofilms, prophage induction experiments were carried out on samples of both naturally occurring and laboratory grown biofilms. Both field and laboratory experiments revealed evidence of prophage induction in the majority of the biofilm samples investigated. Interestingly, prophage induction was statistically significant but only a small percentage of the total bacterial population appeared to harbor prophage or engaged in induction. Finally, use of the community level profiling approach RAPD-PCR was optimized for use in analyzing the viral communities of lotic biofilms. This approach is an effective and more cost-efficient alternative to other viral community composition analyses such as metagenomics. Our results suggest that bacteriophage are consistent members of lotic biofilm communities, and that lysogenic interactions may be particularly important, though the specific implications for stream ecology have yet to be determined. The RAPD-PCR optimization should aid in future studies for resolving spatial and temporal changes in biofilm viral community composition in response to different variables.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Share

COinS