Neglected drivers of antibiotic resistance dissemination: promoted the horizontal transfer of antibiotic resistance genes by quorum sensing-mediated filamentous bacterial proliferation in activated sludge process.

内容摘要

Changes in bacterial communities are the main driving factor for influencing the proliferation and dissemination of antibiotic resistance genes (ARGs) in activated sludge systems. However, the underlying effect of filamentous bacterial proliferation-induced changes in the community structure on ARGs proliferation and dissemination in wastewater treatment plants remain unclear. The potential role of quorum sensing-mediated filamentous bacterial proliferation in ARGs proliferation and dissemination in the activated sludge process was investigated in this study. The results indicated that filamentous bacterial (Thiothrix) quorum sensing was triggered by the increase in their population density, which significantly promoted production of extracellular proteins that could directly bind with antibiotics and ARGs, resulting in an increase in antibiotic stress and extracellular polymeric substance (EPS)-associated ARGs concentrations, and subsequently promoting ARGs horizontal transfer. Additionally, Thiothrix proliferation induced the overproduction of reactive oxygen species, leading to a significant increase of 8.35-fold in the Dot/Icm type IV secretion system and an increase in cell membrane permeabilities, which were conducive to ARGs horizontal transfer. Moreover, the absolute abundances of OXA-10 intracellular, EPS-associated, and cell-free obviously increased from 1.80 × 108, 4.71 × 105, and 8.56 × 104 to 2.09 × 109, 1.42 × 107, and 6.80 × 105 copies/g volatile suspended solids, respectively, with EPS becoming the main extracellular ARGs source. Therefore, filamentous bacterial proliferation promoted ARGs proliferation and dissemination by enhancing ARGs horizontal transfer in wastewater treatment plants. The results of this study provide new insight into the proliferation and dissemination of antimicrobial resistance during the activated sludge process.