Hydra as a model for screening ecotoxicological effects of plasma-treated water

Atmospheric cold plasma (ACP) has been widely researched to generate function-alized solutions for decontamination of liquids and wastewater treatment. The focus of this work was to study the ecotoxicological effects of plasma-treated water (PTW) using a free-living brown Hydra as an important and prevalent component of freshwater ecosystems. We obtained PTW by subjecting 25 mL of sterile deionized water to high-voltage (80 kV) contained ACP treatment for 15 (PTW15) and 25 (PTW25) min. Toxicity measurements were based on the progressive changes in Hydra morphology through a scoring procedure. The effects of PTW on Pseudomo­nas aeruginosa, Escherichia coli, and Bacillus atrophaeus cells were determined using a broth microdilution method that estimated minimum inhibitory concentration (MIC) and minimum bac­tericidal concentration (MBC). Results demonstrated that PTW is potentially toxic to biological systems. In Hydra tests, toxic effects were observed for PTW15 and PTW25 at concentrations above 50% and 25%, respectively. Similarly, PTW25 at a concentration of 25% is lethal for P. aeruginosa and E. coli, whereas an MBC of 37.5% was obtained for B. atrophaeus. The present investigation demonstrates that Hydra can be used as an additional in vivo tool to monitor the impact of plasma-processed solutions on the aquatic environment.