Abstract 2402 Novel bacteria A5 Isolated from LDPE Demonstrates Antimicrobial Activity Against a Unique Class of Bacterial Strains

The plastisphere, an increasingly studied ecological concept, refers to the complex microbial communities that colonize and thrive on the surfaces of plastic debris in aquatic environments. Due to humans' continuing reliance on plastic, these synthetic materials persist in marine and freshwater ecosystems, leading to the formation of unique microbial ecosystems. The plastisphere represents a novel frontier in environmental microbiology, offering insights into the microbial diversity and functions associated with plastic pollution. Bacteria of the genus Cobetia are Gram-negative, aerobic, and halotolerant. They are marine bacteria that had been found present on low density polyethylene (LDPE) plastic material and have been proposed for their potential to degrade plastic or oil spills. Similar to soil, the plastisphere is characterized by both resources and competition. As soil is a major source of antibiotics, we wanted to explore ocean plastic bacteria as potential sources of novel antimicrobials. We had previously adapted Tiny Earth framework, a crowdsourced approach to isolate antibiotic producing bacteria from the soil (https://tinyearth.wisc.edu/) to ocean plastic samples and obtained numerous promising candidates. Here we describe A5, closely related to Cobetia marina, which was obtained from LDPE after a 90-day incubation at 5m deep in water near Scripps Pier in La Jolla, CA. After culture on Marine Agar, colonies were selected by testing their antimicrobial activity against Gram positive and negative bacterial strains using the spread-patch technique. Bacterial targets included safe ESKAPE relatives and antibiotic resistance strains from the CDC AR Bank# 0637. Producers were subsequently isolated and characterized by 16S metabarcoding. Furthermore, whole genome sequencing, assembly, and annotation was completed. A5 has a wide range of activity via spread/patch technique against both Gram positive (B.subtilis, S.aureus, E. raffinosus) and Gram negative (E.coli, A, bayley, C. salexigens) strains. In addition, organic extracts using either ethyl acetate or heptane/ethyl acetate were obtained and tested against bacterial strains. Extracts were resuspended in methanol, added to 96-well flat-bottomed plate at different dilutions, and let dry. Bacterial test strains were added to the wells, and OD600 nm was measured after 18-24 hours. The heptane fraction of A5 was effective against antibiotic-resistant Citrobacter freundii and Enterococcus faecalis strains. Genome-wide analysis of A5 using antiSMASH revealed several biosynthetic clusters for natural products, including potential antimicrobials such as bacteriocins and polyketides. No antimicrobial resistance genes were detected using the Abricate software. Notably, while Cobetia species have been known for secondary metabolite production and antibiofilm activities, our study marks the first report of their effectiveness against antibiotic-resistant pathogenic strains. Ongoing investigations aim to elucidate the chemical nature of A5's antibiotic compounds, emphasizing its significance in combating antibiotic-resistant pathogens.