Double-edged sword of microbial self-adaptive mechanisms in biofilm systems under non-antibiotic bisphenol stress: Promoting contaminant degradation and antibiotic resistance genes propagation.

Biofilm systems demonstrate significant potential for the efficient degradation of persistent organic pollutants and serve as a crucial reservoir for antibiotic resistance genes (ARGs) due to the widespread misuse of antibiotics. However, the role of biofilm systems under non-antibiotic bisphenol stress in contaminant removal and ARGs dissemination remains uncertain. This research investigates the removal performance of bisphenol S (BPS) as a representative bisphenol and its impact on ARG dynamics in biofilm systems. The results indicate that biofilm systems can achieve nearly 100 % BPS removal, accompanied by a 17.1 % enrichment in the relative abundance of ARGs. Hydrogen bonding with -6.9 kJ/mol binding energy played a major role in the interactions between the hydroxyl groups of BPS and the biofilm. This interaction promotes the secretion of extracellular polymeric substances, which provide habitats for mobile genetic elements (MGEs), leading to 64.3 % enrichment in their abundance. Meanwhile, microbial communities shift towards BPS-degrading microorganisms and are also potential ARG hosts. Additionally, the presence of BPS triggers microbial self-adaptive mechanisms, including SOS responses, quorum sensing, and two-component systems, enhancing bisphenol degradation pathways for BPS removal. Unfortunately, these activated microbial adaptation mechanisms lead to ARG proliferation by increasing membrane permeability, enhancing biofilm formation, and improving microbial connectivity.