Abstract
The continuous introduction of cleaning products containing benzalkonium chloride (BAC) from household discharges can mold the microbial communities in wastewater treatment plants (WWTPs) in a way still poorly understood. In this study, we performed an in vitro exposure of activated sludge from a WWTP in Costa Rica to BAC, quantified the changes in intI1, sul2, and qacE/qacEΔ1 gene profiles, and determined alterations in the bacterial community composition. The analysis of the qPCR data revealed elevated charges of antibiotic resistance genes in the microbial community; after BAC's exposure, a significant increase in the qacE/qacEΔ1 gene, which is related to ammonium quaternary resistance, was observed. The 16S rRNA gene sequences' analysis showed pronounced variations in the structure of the bacterial communities, including reduction of the alpha diversity values and an increase of the relative abundance of Alphaproteobacteria, particularly of Rhodospseudomonas and Rhodobacter. We confirmed that the microbial communities presented high resilience to BAC at the mg/mL concentration, probably due to constant exposure to this pollutant. They also presented antibiotic resistance-related genes with similar mechanisms to tolerate this substance. These mechanisms should be explored more thoroughly, especially in the context of high use of disinfectant.
Highlights
The use and release of antimicrobial substances into the environment from urban uses and agricultural activities cause concern and require urgent attention
This study explores the impact of a higher benzalkonium chloride (BAC) exposure to a bacterial community from activated sludge from a municipal WWTP in Costa Rica, regularly exposed to low BAC concentrations
Significant changes occurred in antibiotic resistance-associated genes present in the sludge after treatment with BAC (Figure 2, Table S1). qacE/qacEΔ1 was significantly higher in the treated sludge (T1) compared to the T0 and T2 (ρ1⁄40.0066)
Summary
The use and release of antimicrobial substances into the environment from urban uses (houses, hospitals, factories, for example) and agricultural activities (horticulture, aquaculture, and livestock production) cause concern and require urgent attention. Large amounts of disinfectants were released into the environment before the COVID-19 pandemic. The primary mechanism of action involves a general perturbation of lipid bilayers of membranes leading to a generalized and progressive leakage of cytoplasmic materials to.
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