Gradual Deformation of Bacterial Cell Morphology Due to the Effect of Nonthermal Atmospheric Pressure Plasma Jet-Treated Water (PTW)

Treatment of distilled water by plasma jet in atmospheric air results the plasma treated water (PTW) which has the bactericidal properties. To improve the understanding and the methodology of the inactivation process, PTW has been applied on bacteria cell (
E. coli
) as the bacteria inactivation tool. PTW of different chemical strength is produced by changing the plasma irradiation time (1–20 min) on distilled water. The pH of distilled water decreases with plasma irradiation time and reaches below 4 after 10 min plasma irradiation. The correlation between the pH value of PTW and the concentration of different chemical species in it is shown in this paper. HNO
₃
is the main acidic compound of this PTW. Different chemical species (NO
_x
, OH, H
₂
O
₂
) in the PTW have been identified and the effect of this PTW on bacteria cell is discussed in this paper. The cell inactivation increases with the increase of the ratio of bacteria cell suspended liquid volume to be treated to the PTW volume (tested for the ratio of 1:05 and 1:10) and the chemical strength of PTW. Moreover, gradual deformation of bacteria cell morphology due to the effect of PTW and the change of the cell morphology after direct plasma treatment have been observed by using scanning electron microscope.