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Preservatives induced succession of microbial communities and proliferation of resistance genes within biofilm and plastisphere in sulfur autotrophic denitrification system
Summary
Researchers studied how the preservatives methylparaben and benzethonium chloride affect microbial communities and antibiotic resistance genes on microplastic surfaces in wastewater denitrification systems. They found that microplastics formed a unique ecological niche (the plastisphere) that harbored pathogenic bacteria and accumulated resistance genes, with preservative exposure significantly altering microbial community structures. The study suggests that mobile genetic elements drive the horizontal transfer of resistance genes between biofilm and plastisphere communities.
Methylparaben (MeP), Benzethonium chloride (BZC) and microplastics (MPs) as emerging contaminants are frequently detected in the environment. Furthermore, MPs can be colonized by microorganisms to form a unique ecological niche known as the "plastisphere". In this study, three biofilm-based sulfur autotrophic denitrification (SAD) reactors were established, which were exposed to 0.5-5 mg/L MeP and BZC individually and in combination, while polyamide 6 bags were added to cultivate plastisphere within the three SAD systems. The results found that BZC had a more serious inhibition effect than MeP. Besides, MeP mitigated the toxicity of BZC on SAD, and the observed inhibition gradually diminished over time. The incorporation of preservatives significantly changed the microbial community structures and induced the proliferation of resistance genes (RGs) in both biofilm and plastisphere. Enrichment of functional bacterium like Thiobacillus and the colonization of pathogenic bacterium like Desulfovibrio were found in plastisphere. The proliferation of intracellular RGs in biofilm might drive the recovery of SAD performance. In addition, mobile genetic elements were recognized as the key drivers of horizontal gene transfer responsible for the dissemination of RGs. This research guided the efforts to control the risks associated with preservatives and MPs in wastewater treatment.