Effects of the resistive barrier discharge on bacterial viability, biochemical pathways, and morphology

Summary form only given, as follows. The Resistive Barrier Discharge (RBD) has been shown to be an effective bio-decontamination device by Laroussi, Dobbs and co-workers (2000). In previous presentations, we examined the killing efficacies as a function of various helium-oxygen mixtures. In these preliminary works, we found the optimal gas mixture for killing bacteria with the RBD to be 3% oxygen and 97% helium. Helium was selected as the carrier gas mainly for discharge stability. This "optimal gas mixture" was used for all experiments presented. First we present data from viability experiments employing standard cultural techniques with gram-positive Bacillus subtilis (ATCC 6051) and gram-negative Escherichia coli (ATCC 25922). For both strains of bacteria, cells in suspension and on a surface (cellulose nitrate membrane filters) were tested for their viability following various exposure times. Second, the biochemical impacts of RBD exposure on E. coli were addressed with sole carbon substrate utilization (SCSU) experiments, using Biolog GN2/sup TM/ 96-well microtiter plates. The purpose of the SCSU experiments was to determine if any enzyme activities were altered in E. coli subjected to sub-lethal doses of RBD. Finally, the effects of plasma on bacterial cell morphology were evaluated using evidence from electron microscopy.