Different microplastics distinctively enriched the antibiotic resistance genes in anaerobic sludge digestion through...

Area of Science:

• Environmental Science
• Microbiology
• Environmental Engineering

Background:

• Microplastics (MPs) and antibiotic resistance genes (ARGs) are prevalent in waste activated sludge (WAS).
• The specific effects of different MP types on ARGs and their dissemination mechanisms in sludge are not well understood.

Purpose of the Study:

• To investigate the impact of polyethylene (PE) and polyvinyl chloride (PVC) microplastics on ARGs and antibiotic-resistant bacteria (ARB) dynamics in anaerobic sludge digestion.
• To elucidate the mechanisms by which MPs influence ARG emergence and dissemination.

Main Methods:

• Long-term semi-continuous anaerobic digesters were used to treat sludge contaminated with PE and PVC MPs.
• Metagenomic sequencing was employed to analyze ARG profiles and bacterial communities.
• Network analysis was performed to understand ARG-host interactions and horizontal gene flow (HGF).

Main Results:

• Both PE- and PVC-MPs increased ARG abundance (14.8% and 23.6%, respectively) and enriched ARB, with Acinetobacter sp. and Salmonella sp. being dominant.
• PVC-MPs, but not PE-MPs, stimulated ARG acquisition by human pathogen bacteria (HPB) and functional microorganisms (FMs).
• MPs exposure enhanced genes associated with HGF, including reactive oxygen species (ROS) production, cell membrane permeability, extracellular polymeric substances (EPS) secretion, and ATP synthesis, promoting ARG dissemination.

Conclusions:

• Different MPs exert distinct effects on ARG fate and dissemination in anaerobic sludge digestion.
• PVC-MPs pose a greater risk by facilitating ARG transfer to pathogens and other key microorganisms through enhanced HGF.
• Understanding MP-specific impacts is crucial for managing ARGs in sludge treatment systems.