Nitrogen gas plasma treatment of bacterial spores induces oxidative stress that damages the genomic DNA

Abstract

Gas plasma, produced by a short high‑voltage pulse generated from a static induction thyristor power supply [1.5 kilo pulse/sec (kpps)], was demonstrated to inactivate Geobacillus stearothermophilus spores (decimal reduction time at 15 min, 2.48 min). Quantitative polymerase chain reaction and enzyme‑linked immunosorbent assays further indicated that nitrogen gas plasma treatment for 15 min decreased the level of intact genomic DNA and increased the level of 8-hydroxy-2'-deoxyguanosine, a major product of DNA oxidation. Three potential inactivation factors were generated during operation of the gas plasma instrument: Heat, longwave ultraviolet-A and oxidative stress (production of hydrogen peroxide, nitrite and nitrate). Treatment of the spores with hydrogen peroxide (3x2‑4%) effectively inactivated the bacteria, whereas heat treatment (100˚C), exposure to UV-A (75‑142 mJ/cm2) and 4.92 mM peroxynitrite (•ONOO‑), which is decomposed into nitrite and nitrate, did not. The results of the present study suggest the gas plasma treatment inactivates bacterial spores primarily by generating hydrogen peroxide, which contributes to the oxidation of the host genomic DNA.

Antibiotic-Resistant and Non-Resistant Bacteria Display Similar Susceptibility to Dielectric Barrier Discharge Plasma

“…Our analysis showed a reduction in the levels of CAT, DNA, and LPS in E. coli after plasma treatment. Previous studies have analyzed gas plasma [ 22 , 23 , 24 , 25 ], which led to oxidation/modification of DNA and protein as well as their degradation. LPS, also termed as endotoxin, is a component of the outer membrane of Gram-negative bacteria and is known to be highly resistant to both physical and chemical treatment [ 26 ].…”

Effect of Nitrogen Gas Plasma Generated by a Fast-Pulsed Power Supply Using a Static Induction Thyristor on Scrapie Prion

“…Previous studies have shown that influenza virus, respiratory syncytial virus, and adenovirus are inactivated within 5 min by BLP–TES applied at 1.5 kpps [ 23 , 24 , 25 ], whereas treatment for more than 15 min is required for the inactivation of bacterial spores [ 22 ]. Overall, these findings are consistent with the notion that prion agent is a more resistant pathogen than viruses or bacteria including bacterial spores.…”

“…Our group previously reported that nitrogen gas plasma causes protein denaturation [ 21 , 22 ]. Roth et al [ 32 ] also reported the same phenomenon of protein inactivation due to oxidation.…”

“…Our previous studies have shown that heat, UV radiation, and oxidative stress are generated during operation of the BLP–TES device [ 21 , 22 , 24 ]; however, reactive chemical species seem to contribute to the main mechanism of inactivation caused by nitrogen gas plasma in the case of bacteria and viruses [ 21 , 22 , 24 ]. Nevertheless, the main chemical and physical factors contributing to inactivation of prions by nitrogen gas plasma have not been clarified.…”

“…Recently, we succeeded in generating nitrogen gas plasma by applying a high-voltage pulse for a short time using an induction energy storage (IES) circuit with a static induction (SI) thyristor to nitrogen using a BLP–TES (bipolar and low-pressure plasma–triple effects sterilization) device (NGK Insulators, Ltd., Nagoya, Japan) [ 20 ]. Interestingly, BLP–TES has shown virucidal and bactericidal activity [ 20 , 21 , 22 , 23 , 24 , 25 ] and been found to be superior to STERRAD ® in terms of endotoxin inactivation efficiency [ 20 ]. Those findings have prompted us to consider the potential use of this technology in the inactivation of prions.…”