Nanoplastic stress drives cyanobacterial secondary metabolism and taste-and-odor production

Abstract

The convergence of nanoplastic pollution and cyanobacterial blooms presents a complex threat to aquatic ecosystems, yet the molecular mechanisms governing their interaction remain poorly understood. This is particularly critical for taste-and-odor compounds (T&Os) like geosmin (GSM) and 2-methylisoborneol (2-MIB), which compromise global water security. Here, we investigated the impact of positively charged amino-modified polystyrene nanoplastics (PS-NH₂) on the T&O-producing cyanobacterium Microcystis aeruginosa (M. aeruginosa). We found that low-concentration (1 μg mL⁻¹) exposure significantly inhibited T&O production, whereas high-concentration (20 μg mL⁻¹) exposure dramatically stimulated it, increasing total GSM and 2-MIB yields by 5.40- and 6.16-fold, respectively. An integrated transcriptomic and metabolomic analysis revealed that the high-dose effect is driven by a catastrophic cellular cascade. Severe oxidative stress and membrane damage cause a collapse of the photosynthetic apparatus, triggering a system-wide metabolic reprogramming that diverts carbon precursors overwhelmingly toward T&O biosynthesis. Conversely, the low-dose inhibition occurs without significant transcriptional changes, suggesting a rapid, adaptive resource allocation trade-off. These results reveal an unconventional toxicological pattern and provide a fundamental molecular blueprint for how nanoplastic stress can dysregulate cyanobacterial secondary metabolism, highlighting the critical need to consider non-linear responses in environmental risk assessment.