Effects of microbial loading and sporulation temperature on atmospheric plasma inactivation of Bacillus subtilis spores

Abstract

Current inactivation studies of Bacillus subtilis spores using atmospheric-pressure glow discharges (APGD) do not consider two important factors, namely microbial loading at the surface of a substrate and sporulation temperature. Yet these are known to affect significantly microbial resistance to heat and hydrogen peroxide. This letter investigates effects of microbial loading and sporulation temperature on spore resistance to APGD. It is shown that microbial loading can lead to a stacking structure as a protective shield against APGD treatment and that high sporulation temperature increases spore resistance by altering core water content and cross-linked muramic acid content of B. subtilis spores.

Protein destruction by a helium atmospheric pressure glow discharge: Capability and mechanisms

“…Details of the plasma jet have been given elsewhere. 17,18 For this study, the APGD jet was energized with a sinusoidal voltage source with a peak voltage of 4-8 kV and an excitation frequency of 30-45 kHz. Helium ͑99.9999%͒ was used as the working gas with its flow rate fixed at 5 slm, either alone or mixed with oxygen gas of varying flow rates.…”

“…Therefore, the biphasic character of the protein reduction kinetics is largely related to the thickness profile of the surface protein, similar to the microbial loading effect in plasma bacterial inactivation. 11 One important implication of this finding is that a more efficient protein removal would be achieved if localized protein deposits on surgical instruments could be identified, using fluorescence techniques for example, for them to be specifically treated by the APGD jet. Efficiency of protein reduction can be improved if the most lethal plasma species are identified.…”

“…[4][5][6][7][8] A great deal has been learned about how APGD inactivation depends on the plasma operating conditions 9,10 and the physiology of the microbial population. 11,12 These studies have helped establish convincingly the microbiocidal capability of APGD. Today, atmospheric pressure glow discharges are widely regarded as one of the most exciting technology platforms that is likely to impact profoundly on the bio-decontamination practice and policy in both the healthcare service and the food industry.…”

“…101, 074701 ͑2007͒ modes of the microorganism resistance to plasma treatment can be a result of many different factors including the cell wall, 4,6 phase of cell growth, 12 and cell stacking. 17 To understand the factors that contribute to the essentially biphasic kinetics of plasma protein reduction, we took fluorescence images of the FITC-labeled protein sample after different plasma treatment times. These are shown in Fig.…”

Protein destruction by atmospheric pressure glow discharges

“…The ground electrode was essentially the sample holder at 10 mm from the dielectric tube. While its geometric details are given elsewhere, 17,18 its tubular structure and its use of dielectric barriers are different from the atmospheric pressure plasma jet, 19 the plasma needle, 20 and the plasma plume produced from a gas flow through two parallel-plate electrodes. 21 For future reference, it is referred to as the atmospheric dielectric-barrier discharge ͑DBD͒ tube jet or DBD-tube jet.…”