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Buoyant polyethylene rope fragments may enhance pathogenic bacteria dispersion in aquaculture water
Summary
Researchers examined how pathogenic bacteria colonize polyethylene rope fragments preconditioned with biofilms in marine aquaculture systems. The study found that Vibrio parahaemolyticus, Vibrio harveyi, Vibrio alginolyticus, and Pseudomonas plecoglossicida readily colonized the microplastic surfaces and expressed virulence genes, suggesting that buoyant rope fragments may enhance pathogen dispersal in aquaculture waters.
Microplastics (MPs), as emerging contaminants, are increasingly recognized for their widespread presence in marine aquaculture systems and potential role in facilitating pathogen transmission. This study examined the colonization dynamics and virulence gene expression of four representative aquatic pathogens: Vibrio parahaemolyticus , Vibrio harveyi , Vibrio alginolyticus and Pseudomonas plecoglossicida on polyethylene rope fragments (PE-Frags) preconditioned with in situ biofilms. A 10-day simulated PE-Frags drift experiment was conducted, during which pathogen load and virulence gene expression were quantified using TaqMan real-time PCR and RT-qPCR. Results revealed distinct species-specific responses. Between days 4 and 6, V. harveyi and P. plecoglossicida exhibited significant surface enrichment on PE-Frags, reaching 11.6-fold and 12.8-fold higher than the control, whereas V. parahaemolyticus and V. alginolyticus showed more than 99 % reduction V. parahaemolyticus upregulated tlh and toxR by 7.791-fold and 7.031-fold on day 8. V. harveyi showed sustained elevation of chiA and vhpA from days 6 to 10. P. plecoglossicida maintained high ompA and sigX expression throughout. In V. alginolyticus , toxS remained upregulated, while fur and FlaA showed moderate increases. These findings indicate that PE-Frags serve not only as physical substrates for microbial attachment but also as environmental stimuli capable of triggering virulence expression, providing molecular-level insight into pathogen activation mechanisms. The upregulation of virulence genes induced by PE-Frags may enhance the pathogenic potential of aquatic pathogens, thereby increasing the likelihood of disease outbreaks in aquaculture systems. Moreover, the potential transfer of pathogen-associated PE-Frags into the food chain poses an additional risk to seafood safety and public health. • Polyethylene rope fragments selectively enriched or suppressed aquatic pathogens. • A dynamic drift experiment revealed species-specific colonization trends on PE-Frags. • PE-Frags significantly induced virulence gene expression in Vibrio and Pseudomonas . • Expression of toxR , vhpA , ompA and sigX was markedly upregulated on PE-Frags. • PE-Frags serve both as microbial vectors and as stimulatory platforms for virulence regulation.