Temporal dynamics of pathogenic bacterial consortia on the plastics in shallow-water hydrothermal vents

Plastics provide persistent substrates for microbial colonization, including potentially pathogenic taxa, in marine environments, a distinct ecological niche that supports microbial biofilm development called the plastisphere,. While plastisphere research is extensive in coastal and pelagic systems, their composition and functional potential in geochemically extreme environments, such as shallow water hydrothermal vents (SW-HTVs), remains largely uncharacterized. SW-HTVs are characterized by elevated temperatures, sulfur-rich emissions, and reduced pH, creating selective pressures that may uniquely structure plastisphere associated bacterial communities. In this study, plastic substrates (drinking bottles and fishing nets) were deployed at a sulfur dominated hydrothermal vent system off Kueishan Island, Taiwan, and retrieved at three time points (Day 0 (1 h), Day 8, and Day 16) to assess bacterial succession and pathogen enrichment. Alpha diversity, including richness and evenness, was initially higher on plastics (PB, PN) than in seawater (SW, BSW) but this difference diminished by Day 16, suggesting increased within-substrate stabilization over time. Using Oxford Nanopore long read 16S rRNA sequencing, we uncovered a clear transition from early colonizers, primarily sulfur oxidizing bacteria such as Sulfurimonas lithotrophica, to a more diverse bacterial consortium. Notably, substrate-specific enrichment of potential pathogens including Thiothrix eikelboomii and Desulfuromusa bakii was observed on plastic nets. These findings underscore the role of plastics as reservoirs for potentially pathogenic microbes in extreme marine environments, with implications for bacterial dispersal, sulfur cycling, and marine ecosystem health. As SW-HTVs represent natural laboratories of future ocean acidification scenarios, this study provides critical insights into how acidified marine conditions may shape plastic-associated bacterial biodiversity dynamics and pathogenic persistence.