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Polystyrene nanoparticles and phosphorus sources jointly modulate antibiotic resistance gene enrichment in microalgae-bacteria systems
Summary
Scientists found that tiny plastic particles (nanoplastics) combined with certain phosphorus nutrients in water can help bacteria become more resistant to antibiotics, especially at low plastic concentrations that let algae and bacteria communities keep growing while swapping resistance genes. This matters because antibiotic-resistant bacteria are already a growing public health threat, and this research shows that plastic pollution in lakes and rivers—not just antibiotic overuse—could be quietly fueling the problem in ways we didn't fully understand before.
The regulatory mechanisms of antibiotic resistance genes (ARGs) in freshwater microalgae-bacteria systems under combined nutrient-nanoplastic stress remain poorly understood. Herein, we investigated the combined effects of phosphorus (P) sources (inorganic phosphate (IP), adenosine monophosphate (AMP), and phytic acid (PA)) and polystyrene nanoplastics (PS-NPs; 10 and 100 mg/L) on the Chlorella pyrenoidosa‑bacteria system. Results showed that P utilization efficiency followed the order IP > AMP > PA. PS-NPs exerted concentration-dependent effects: low concentrations activated adaptive pathways (including glutathione metabolism) to maintain homeostasis, whereas high concentrations disrupted photosynthesis and membrane integrity, reducing chlorophyll a levels by 20.84%-58.89% and suppressing algal growth. Quantitative PCR and microbial sequencing confirmed that P supplementation increased ARG abundances by 37.58%-59.34%, with organic phosphorus groups harboring higher ARG levels than those of IP groups. Low PS-NP concentrations further promoted ARGs by 16.21% via mobile genetic elements (intI1 and tnpA-04) that mediate horizontal gene transfer, whereas high PS-NP concentrations reduced ARGs by 2.70% through diversity suppression. Proteobacteria dominated, with Brevundimonas and Aquimonas identified as potential ARG hosts. Microbial community assembly was a primary driver of resistome profiles, alongside mobile genetic elements and P metabolism. These findings highlight that nutrient-nanoplastic interactions accelerate ARG propagation in microalgae-bacteria systems, providing insights for managing environmental antibiotic resistance.