Mechanism of E. coli Inactivation by Direct-in-liquid Electrical Discharge Plasma in Low Conductivity Solutions

• Published in: Scientific reports Vol. 9; no. 1; p. 2326
• Main Authors: Estifaee, P., Su, X., Yannam, S. K., Rogers, S., Thagard, S. Mededovic
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20-02-2019; Nature Publishing Group
• Subjects: 639/166/898; 704/172/169/896; Cell walls; Conductivity; Deoxyribonucleic acid; DNA; E coli; Electric fields; Humanities and Social Sciences; Inactivation; Microorganisms; multidisciplinary; Plasma; Radicals; Rods; Scanning electron microscopy; Science; Science (multidisciplinary); Ultraviolet radiation
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-38838-7

This work investigates and reveals the main mechanism(s) responsible for inactivation of
E
.
coli
by in-liquid pulsed electrical discharge plasma in low conductivity solutions. Experiments were designed and performed to explore the effects of plasma-emitted UV light, oxidative radicals, and electric field on
E
.
coli
inactivation curves, rate of DNA leakage and visual appearance of the treated microorganisms. Results showed that electric field had the main role in inactivation; scanning electron microscopy images revealed that both plasma and the isolated electric field result in extensive cell wall disruptions. While this damage in the case of plasma treatment was extensive and distributed randomly along the envelope, the electric field-induced damage resulted in disruption primarily at the poles of the bacterial rods. Subsequent experiments conducted with an oxidative radical scavenger suggested that plasma-generated radicals do not contribute directly to the inactivation but assist in cell wall deterioration and extension of the ruptures first generated by the electric field.