Fig 4. The colony assays showing effect of scavengers on rescue of plasma charged aerosol post-treated E. coli wildtype and mutants.

(A) Catalase, the specific scavenger of H₂O₂ was able to significantly protect mutant (ΔkatE) from inactivation. (B) A non-enzymatic ROS scavenger, D-mannitol was significantly able to rescue wildtype and ΔkatE cells from inactivation as compared to their corresponding non-scavenged conditions. (C) Thiourea, a wildly used ^.OH scavenger was able provide significant protection to deletion mutant (ΔkatE) but not the wildtype E. coli, suggesting that intracellular ^.OH pool created in hydroperoxidase deficient cells during post-exposure to plasma charged aerosols are effectively scavenged, and possibly inhibit further Fenton chemistry generating hydroxyl radicals. This also demonstrates that katE is an important mediator of survival in bioaerosolized E. coli under such condition. (* indicates p <0.05 against their corresponding conditions without scavenger. ** indicates p <0.05 against remaining concentrations of catalase).