Turner, JeffreyO'Donnell, Colin Andrew2024-01-052024-01-052023-08https://hdl.handle.net/1969.6/97726A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Marine BiologyNurdles are the raw material in the manufacture of plastic products. They are mass produced and transported worldwide, but accidental and negligent spills pollute marine environments. In the Gulf of Mexico (GoM), a citizen science initiative, the Nurdle Patrol, revealed that 20 of the highest nurdle-polluted beaches are found in Texas. Microorganisms, including potentially pathogenic bacteria, rapidly colonize nurdles. The purpose of this study was to broaden the understanding of nurdle-bacterial coupling through the following objectives: 1) characterize the microbial diversity of nurdles on a recreational beach compared to a natural substrate and 2) isolate potentially pathogenic members of the nurdle community and further analyze those isolates through whole-genome sequencing (WGS) and antimicrobial resistome analysis. Results show that the nurdles were colonized by a distinct (Faith’s phylogenetic distance, P < 0.001) and more uniform microbial community than beach sand. The nurdle community was dominated by Proteobacteria (69.5%) and Bacteroidota (21.7%) at the phylum level, and Rhodobacteraceae (26.2%) at the family level. Culturable members of the nurdle community included potentially pathogenic Bacillus licheniformis and Bacillus paralicheniformis. Isolates possessed antimicrobial resistance genes (e.g., ATP-binding cassette (ABC) antibiotic efflux pumps and class A Bacillus cereus Bc beta-lactamases), and two B. paralicheniformis isolates appeared to be multidrug resistant (i.e., peptide, macrolide, and penam resistant). Results demonstrate that nurdles were colonized by a distinct community compared to a natural substrate. Additionally, nurdles supported the growth of potentially pathogenic Bacillus species with the genetic potential for antimicrobial resistance. Overall, these results establish a baseline knowledge of nurdle microbial diversity in the northwest GoM.91 pagesen-USAttribution (CC BY)https://creativecommons.org/licenses/by/4.0/16s rRNA sequencingnurdlespathogensplastic pollutionplastic-associated microbial communitiesText