PVC Microplastics Inhbit the Degradation of Intracellular and Extracellular Antibiotic Resistance Genes in Wastewater Sludge during Anaerobic Digestion Roles of Microbial Hosts and Gene transfes
Microplastics (MPs) have been extensively acknowledged for their role in influencing antibiotic resistance genes (ARGs) through the formation of a plastisphere via microbial adsorption. Anaerobic digestion (AD), a prevalent technology employed in wastewater treatment plants (WWTPs), has demonstrated the potential to degrade both MPs and ARGs. Despite this, there remain substantial gaps in the understanding of the dynamics of ARGs during the AD, and the potential inhibitory effect of MPs on ARG degradation has emerged as a critical area of inquiry. This study utilized a sequential batch reactor (SBR) experiment to simulate the AD, systematically examining the impact of polyvinyl chloride (PVC) microplastics (0, 0.04, 1.0 g/kg VS) on intracellular ARGs (iARGs) and extracellular ARGs (eARGs) in sludge across various digestion stages (D12, D22, D70). The finding reveal that the D70 significantly reduces both iARGs and eARGs in sludge, a reduction attributed to the low nutrient levels and high acidification at this stage, which suppress microbial activity. Additionally, their was a noted decrease in the abundance of functional genes associated with reactive oxygen species production (ROS), T4SS secretion systems, and mobile genetic elements (MGEs). Conversely, an increase in DNA replication levels was observed, indicating a shift in gene transfer pathways from horizontal gene transfer (HGT) to vertical gene transfer (VGT) during AD. Specifically, MPs can adsorb microorganisms and eARGs, enhancing gene transfer frequency to inhibit AD efficiency. Similarly, AD promotes host potential, functional contribution transfer, and pathogenicity enrichment. Based on these findings, the study provides new insights into the distribution and transmission of iARGs and eARGs in sludge during AD.