Date of Award

Summer 2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Committee Director

Fred C. Dobbs

Committee Member

P. Dreux Chappell

Committee Member

Dayle Daines

Abstract

Since plastics degrade very slowly, they remain in the environment on much longer timescales than most natural substrates and can thus provide a novel habitat for colonization by bacterial communities. The full spectrum of relationships between plastics and bacteria, however, is little understood. The objective of this study was to examine marine plastic pollution as a substrate for bacteria, with particular focus on Vibrio spp., including the human pathogens, Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus.

Colonization experiments were set up in a tributary of the lower Chesapeake Bay to follow Vibrio spp. colonization and total bacterial community composition over time. Microplastics and paired seawater samples were also collected and examined for the presence and abundance of Vibrio spp. In many instances, vibrios were enriched on plastics by at least two orders of magnitude compared to paired seawater samples. Antibiotic-resistance profiles for Vibrio spp. isolates revealed no differences between the antibiotic susceptibilities of vibrios isolated from plastics compared to those from the surrounding water column. There was, however, a significant difference in antibiotic susceptibility between isolates from colonization experiments and microplastics, with more resistance overall seen in the former.

Bacterial colonization on plastics was detected with DNA sequencing as early as day two and communities on plastic were consistently distinct and more diverse than surrounding seawater. Fifteen different bacterial classes were found in water and biofilms and 171 genera were identified. Among all samples, Gammaproteobacteria (30%) constituted the majority of the total sequences with the next most retrieved bacterial classes being Bacteroidetes (28%) and Alphaproteobacteria (20%). Colonization rates and community structure varied temporally and among substrate types, suggesting that numerous factors should be considered when characterizing microbial communities on plastic. This is the first study to culture V. cholerae, V. parahaemolyticus, and V. vulnificus from marine plastics, demonstrates that plastic pollution serves as a habitat for Vibrio species, and confirms the conjecture of Zettler et al. (2013) that plastics may serve as a vector for these and other potentially pathogenic bacteria.

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DOI

10.25777/qwn2-3r85

ISBN

9780438455948

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