Distinct bacterial communities and resistance genes enriched by triclocarban-contaminated polyethylene microplastics in antibiotics and heavy metals polluted sewage environment

Knowledge gaps still surround the question of what biofilms form on contaminated microplastics (MPs) in the antibiotics and (or) heavy metals polluted sewage. In this work, the clean polyethylene microplastics (PE MPs) and triclocarban (TCC)-contaminated PE MPs were cultured in the sewage containing only ampicillin (AMP), only copper (Cu) and both AMP and Cu for 28 days. The results showed that the TCC on PE MPs (with concentration of 2.48 mg/g PE MPs) did not impede the adhesion of the bacteria and the formation of biofilm. Moreover, many potential pathogenic bacteria (Aquabacterium and Pseudoxanthomonas) and potential resistant bacteria (Stenotrophomonas) were more likely to attach on TCC-contaminated PE MPs compared with clean PE MPs. In addition, biofilms of TCC-contaminated PE MPs had highest potential pathogenic functions. TCC-contaminated PE MPs also caused the increases of various resistance genes in both biofilm and sewage. The co-occurrence of TCC, AMP and Cu might exert a stronger selective pressure on bacterial communities and promote the co-selection of resistance genes. In addition, TCC-contaminated PE MPs resulted in higher abundance of five mobile genetic elements (MGEs) (intI1, intI3, tnpA-04, IS613 and trb-C) in sewage, which might further promote the transmission of resistance genes.