Evolutionarily conserved mucus-mediated nanoplastic bioflocculation in Tetrahymena.

Nanoplastics (NPs), pervasive environmental pollutants with elevated toxicity and stability, present critical remediation challenges due to the inefficiency of conventional methods. Here, we reveal a protozoan bioflocculation pathway in Tetrahymena that effectively sequesters NPs and fundamentally reshapes their environmental fate. Upon NP exposure, Tetrahymena activates a Ca2+-dependent mucus secretion mechanism, driving nano-scale aggregation that reduces aqueous NP concentrations by 41.6%-44.8% and enriches sedimentary sinks. Critically, this biotic process mitigates atmospheric dispersion risks, compelling revision of current NP fate models that neglect biological interactions. Multi-omics analyses identify Ca2+-mediated GRL secretion dynamics associated with this bioflocculation response in Tetrahymena. This mechanism represents a Ca2+-mediated defensive response observed in Tetrahymena, which may also occur in related species but requires further investigation across other protist taxa. These findings underscore the critical, underappreciated role of protozoa in pollutant mitigation and necessitate updates to global frameworks for projecting NP transport, abundance and ecological risk.