Impact of the surrounding environment on antibiotic resistance genes carried by microplastics in mangroves

The pollution of antibiotic resistance genes (ARGs) carried by microplastics (MPs) is a growing concern. Mangroves are located at the intersection of land and sea and are seriously affected by MP pollution. However, few studies have systematic research evaluating the transmission risk of ARGs carried by MPs in mangroves. We conducted in situ experiments by burying five different MPs (polypropylene, high-density polyethylene, polystyrene, polyethylene glycol terephthalate, and polycaprolactone particles) in mangroves with different surrounding environments. A total of 10 genes in the MPs of mangroves were detected using quantitative real-time polymerase chain reactions, including eight ARGs and two mobile genetic elements (MGEs). The abundance of ARGs in Guanhai park mangroves in living areas (GH) was higher than that of Gaoqiao mangroves in protected areas (GQ) and Beiyue dike mangroves in aquaculture pond areas (BY). Pathogenic bacteria, such as Acinetobacter, Bacillus, and Vibrio were found on the MP surfaces of the mangroves. The number of ARGs carried by multiple drug-resistant bacteria in the GH mangroves was greater than that in the GQ and BY mangroves. Moreover, the ARGs carried by MPs in GH mangroves had the highest potential transmission risk by horizontal gene transfer. Sociometric and environmental factors were the main drivers shaping the distribution characteristics of ARGs and MGEs. Polypropylene and high-density polyethylene particles are preferred substrates for obtaining diffuse ARGs. This study investigated the drivers of ARGs in the MPs of mangroves and provided essential guidance on the use and handling of plastics.