Polymer-specific toxicity of microplastics to Microcystis aeruginosa: Growth inhibition, physiological responses, and molecular mechanisms

Microplastics (MPs), as emerging contaminants, are increasingly prevalent in the environment, posing significant threats to ecosystems and human health. However, the ecological risks associated with different polymer types, particularly their toxic effects and underlying molecular mechanisms on cyanobacteria, remain poorly understood. This study comprehensively investigated the toxicological impacts of four common MPs—polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and polytetrafluoroethylene (PTFE)—on Microcystis aeruginosa ( M. aeruginosa ) over a 12-day exposure period. Results showed that all four MPs significantly inhibited M. aeruginosa growth, with maximum inhibition rates of 68.3 % (50 mg/L PE, day 6), 61.0 % (50 mg/L PS, day 4), 68.2 % (200 mg/L PVC, day 8), and 63.3 % (100 mg/L PTFE, day 6), respectively. Additionally, MPs exposure led to reduced chlorophyll content, impaired photosynthetic activity, and induced oxidative stress, though these effects exhibited temporal dynamics and partial reversibility. Integrated transcriptomic and physiological analyses revealed polymer-specific mechanisms: PE, PVC, and PTFE primarily disrupted M. aeruginosa growth by targeting ABC transporter and oxidative phosphorylation pathways, whereas PS affected ABC transporter and amino sugar and nucleotide sugar metabolism pathways. This study elucidates the toxicological mechanisms of different MP polymer types and provides critical insights for assessing their ecological risks. • First evidence of PTFE's unique ecotoxicity at the molecular level. • ABC transporters identified as a common target for MPs toxicity. • PE/PVC/PTFE impaired oxidative phosphorylation, PS disrupted sugar metabolism. • Provides molecular evidence for polymer-specific risk assessment.