Toxicity Test of Various Surfactants in Resting Cysts and Vegetative Cells Reveals Tolerance of Resting Cysts to Surfactants in Protist, Colpodid Ciliates

Encystment (resting cyst formation), a state of dormancy with extreme tolerance of environmental stresses, is the standard survival strategy used by protists in response to unfavorable environmental changes. Here, we investigated the relative tolerances of resting cysts and vegetative cells of the colpodid ciliate Colpoda cucullus to exposure to surfactants. The effects of four different types of surfactant, namely, anionic surfactant (SDS), cationic surfactant (benzalkonium chloride), zwitterionic surfactant (CHAPS), and non-ionic surfactant (NP-40), were tested on Colpoda resting cysts and vegetative cells. We found that resting cysts showed tolerance levels to the surfactants that were more than 100 times higher than those of vegetative cells. This study provides updated information on the tolerance of resting cysts with regard to how they can adapt to environmental stresses and human influences. Additionally, our results highlight the importance of considering resting cysts when using detergents for cleaning, which is crucial for preventing infectious diseases and promoting the One Health initiative in our daily lives.