Inactivation of Bacillus subtilis var. niger of both spore and vegetative forms by means of corona discharges applied in water

Spores are dormant units of bacteria resistant to numerous disinfection methods. Additionally, the effects on bacteria of repetitive electrical discharges in water by used of the socalled corona discharges or streamer are poorly described. In this study vegetative and spore forms of Bacillus subtilis var. niger were subjected to these discharges. To generate corona discharges in water, a Marx generator capable of delivering 60-90 kV was used with a coaxial chamber of treatment. Vegetative and spore form reductions were defined using colony-forming unit counting. Proteins extracts were separated by two-dimensional electrophoresis and spots of interest were characterized by mass spectrometry. Shock waves were assessed by the diminution of liposome size and OD400 nm. The results show a decrease in bacteria viability of 2 log(10) after 1000 discharges on the vegetative form and 4 log(10) after 10,000 discharges on the spores. Two-dimensional electrophoresis showed that the streamers impact the regulation of several proteins in the vegetative forms with UniProt ID: P80861, Q06797, P80244, COZI91, respectively. The reduction appears to be due, in part, to hydrogen peroxide (H2O2) generated by the corona discharges while spore deactivation remained insensitive to these chemicals. The spore eradication was associated to shock waves induced by the discharges but not H2O2. Corona discharges appear as a prospective method for eradication of spores in water. The corona discharges can be an efficient method for decontamination processes of waste water. (C) 2012 Elsevier Ltd. All rights reserved.