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Size-specific effects of polyethylene microplastics (100-10,000 nm) on the soil resistome and pathogens revealed via
Xinrui Chang1, Yunxia Ma1, Jiajia Zhang1
1School of Ecology and Environment, Ningxia University, Yinchuan, 750021, PR China.
Abstract:
Microplastics (MPs) and antibiotic resistance genes (ARGs) are widespread, persistent environmental contaminants. However, the influence of MP particle size on ARGs dissemination and soil ecosystem health remains unclear. Herein, polyethylene MPs of three sizes (100, 1,000, and 10,000 nm) were incubated in ARG-contaminated soils for 45 days to evaluate their effects on soil physicochemical properties, microbial communities, ARGs, mobile genetic elements (MGEs), and pathogen abundance. MP exposure significantly increased soil water (up to 4.07-fold), total nitrogen (up to 50.34 %), and ammonium nitrogen (up to 38.54 %) contents. Conversely, soil organic carbon content decreased with increasing MP size. MPs markedly reduced the activities of key enzymes, including alkaline phosphatase (by 87.65 %), sucrase (by 10.96 %), and urease (by 54.17 %). Microbial α-diversity increased; however, the abundance of potentially pathogenic Pseudomonadota increased by up to 41.88 %, whereas that of beneficial Actinobacteria and Chloroflexi declined. MPs promoted the expression of 44 ARGs and 15 MGEs, with smaller MPs exhibiting stronger enrichment. They also increased the expression of virulence factors and the abundance of human- and plant-associated pathogens. Random forest modeling revealed that smaller MPs primarily drove these changes by altering soil physicochemical properties and microbial dynamics. Collectively, these findings demonstrate that MPs, especially smaller particles, simultaneously alter soil chemistry, suppress enzyme activities, reshape microbial communities, and enhance ARGs expression and pathogen proliferation, underscoring their significant ecological and human health risks in agricultural soils.
Insights
Microplastics (MPs) and antibiotic resistance genes (ARGs) contaminate soils. Smaller MPs worsen soil health, increase ARGs, and promote pathogens, posing ecological and human health risks.
Area of Science:
- Environmental Science
- Microbiology
- Soil Science
Background:
- Microplastics (MPs) and antibiotic resistance genes (ARGs) are pervasive environmental pollutants.
- The impact of MP particle size on ARG dissemination and soil health is not well understood.
Purpose of the Study:
- To investigate how different sizes of polyethylene MPs affect soil properties, microbial communities, ARGs, mobile genetic elements (MGEs), and pathogen abundance.
- To determine the role of MP particle size in these environmental changes.
Main Methods:
- Incubation of polyethylene MPs (100, 1,000, 10,000 nm) in ARG-contaminated soils for 45 days.
- Analysis of soil physicochemical properties, enzyme activities, microbial community structure (alpha-diversity, specific phyla), ARG and MGE expression, and pathogen abundance.
- Utilized random forest modeling to identify key drivers of observed changes.
Main Results:
- MP exposure altered soil chemistry, increasing water, total nitrogen, and ammonium nitrogen, while decreasing organic carbon, with effects varying by MP size.
- Enzyme activities (alkaline phosphatase, sucrase, urease) were significantly reduced by MPs.
- Microbial alpha-diversity increased, but potentially pathogenic bacteria (Pseudomonadota) increased, while beneficial bacteria (Actinobacteria, Chloroflexi) decreased.
- MPs, particularly smaller ones, promoted the expression of 44 ARGs and 15 MGEs, alongside virulence factors and pathogens.
- Smaller MPs were found to be the primary drivers of these alterations through impacts on soil properties and microbial dynamics.
Conclusions:
- Microplastics, especially smaller particles, significantly impact soil ecosystems by altering physicochemical properties, reducing enzyme activity, and reshaping microbial communities.
- MP contamination enhances the dissemination of antibiotic resistance genes and promotes the proliferation of pathogens, increasing ecological and human health risks in agricultural soils.
