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Microplastics enhanced the resistant genes spread under disinfectant replacement exposure in partial nitrification-anammox systems
Summary
Researchers investigated how alternating disinfectant exposure affects the spread of antibiotic resistance genes on microplastic biofilms in wastewater treatment systems. They found that switching between different disinfectants increased the risk of resistance gene transmission, with PET and polyethylene microplastics serving as vectors for both resistant bacteria and nitrogen-removing microorganisms. The study raises concerns that microplastics in wastewater systems may accelerate the spread of antimicrobial resistance under common disinfection practices.
• Disinfectant replacement exposure increased the risk of RGs transmission. • Different disinfectant pre-exposure increased different types of QRGs . • PET MPs enriched with more nitrogen removal functional bacteria than PE MPs. • MPs selected for RGs differently under different disinfectant pre-exposure. • Multidrug RGs expressed strongly under disinfectant replacement exposure. There is a concern that continuous alternating exposure to disinfectants will affect microbial colonization and exacerbate the spread of resistance genes (RGs) on microplastics (MPs) biofilms. In this study, polyethylene (PE) and polyethylene glycol terephthalate (PET) MPs were investigated as vectors for microbial and RGs in partial nitrification-anammox (PNA) systems under different disinfectant exposure modes. Results showed that ammonia-oxidizing bacteria Nitrosomonas and anammox bacteria Candidatus Kuenenia were enriched on PE MPs and PET MPs. Meanwhile, the abundance of Nitrosomonas decreased after dioctadecyldimethylammonium chloride (DODMAC) exposure in the CD system (DODMAC exposure only), but was instead enriched after disinfectant replacement exposure in the PD system (successively exposed to chloroxylenol (PCMX) and DODMAC) and TD system (successively exposed to triclosan (TCS) and DODMAC). Oligotyping analyses showed that disinfectant replacement exposure leads to differentiation of nitrogen removal functional bacteria and pathogenic bacteria into distinct oligotypes. The RGs were found to be enriched in PD and TD systems than in CD system, which suggested that PCMX/TCS and DODMAC replacement exposure increased the risk of RGs spread. In addition, quaternary ammonium compounds RGs (QRGs), tended to be enriched more on PE MPs in the PD system, whereas in the TD system, QRGs were enriched more on PET MPs. In summary, the MPs increased risk of RGs spread with different disinfectant replacement exposure in PNA systems.