| dc.description.abstract | Because plastic products are superbly durable and cheap, they quickly become practical items in life. Yet, massive increases in plastic production have resulted in plenty of waste plastics accumulated in natural habitats. Once the plastic enters the environment, the pits generated after weathering make the surface rough and reduce the hydrophobicity, which enables bacteria to colonize the surface and form biofilms. Bacteria in biofilms can share and spread antibiotic resistance genes (ARGs) through horizontal gene transfer (HGT). In addition, a biofilm on plastic particles can significantly enrich most heavy metals, including copper (Cu) that is widely used in industrial processes and animal husbandry. Hence, the spread of ARGs in biofilms on plastic debris may be affected by Cu through co-selection. In this study high-density polyethylene (HDPE) films were selected for biofilm formation; once biofilms formed on HDPE, HDPE films were exposed to buffer solution containing varying levels of Cu ions; biofilms were then collected from surfaces of HDPE films, and the related genes (including the β-lactam, tetracycline, macrolide, sulfonamide ARGs, Cu resistance genes (CRGs), class 1 integron-integrase gene intI1 and 16S rRNA gene) and Cu concentrations in biofilm were quantified to probe whether the generation of resistance genes would be regulated by extracellular Cu speciation. Results show that compared with controls, pcoA relative abundance on day 2 was increased in LC, LC + EDTA and HC + EDTA. Intracellular Cu concentrations on day 5 were decreased in LC, LC + EDTA and HC + EDTA compared with day 2, indicating concentration gradients of bioavailable Cu ions between intracellular and extracellular regions can be the driving force of HGT related to mobile genetic element (MGE) carrying pco operon. Furthermore, the correlation between blaCTX-M and pcoA was higher than that between other ARGs and pcoA, suggesting the spread of blaCTX-M could be affected by Cu due to co-existing of ARGs and CRGs in MGEs like plasmid. The spread of sul1 also could be affected by Cu through class 1 integron because sul1 and intI1 relative abundance on day 2 were simultaneously increased in LC compared with controls. This study provides preliminary evidence and insights into co-selection of antibiotic resistance driven by concentration gradients of bioavailable Cu ions in HDPE biofilm. | en_US |