title: Utilization of low-pressure plasma to inactivate bacterial spores on stainless steel screws.
abstract: A special focus area of planetary protection is the monitoring, control, and reduction of microbial contaminations that are detected on spacecraft components and hardware during and after assembly. In this study, wild-type spores of Bacillus pumilus SAFR-032 (a persistent spacecraft assembly facility isolate) and the laboratory model organism B. subtilis 168 were used to study the effects of low-pressure plasma, with hydrogen alone and in combination with oxygen and evaporated hydrogen peroxide as a process gas, on spore survival, which was determined by a colony formation assay. Spores of B. pumilus SAFR-032 and B. subtilis 168 were deposited with an aseptic technique onto the surface of stainless steel screws to simulate a spore-contaminated spacecraft hardware component, and were subsequently exposed to different plasmas and hydrogen peroxide conditions in a very high frequency capacitively coupled plasma reactor (VHF-CCP) to reduce the spore burden. Spores of the spacecraft isolate B. pumilus SAFR-032 were significantly more resistant to plasma treatment than spores of B. subtilis 168. The use of low-pressure plasma with an additional treatment of evaporated hydrogen peroxide also led to an enhanced spore inactivation that surpassed either single treatment when applied alone, which indicates the potential application of this method as a fast and suitable way to reduce spore-contaminated spacecraft hardware components for planetary protection purposes.
authors.affiliation: Ruhr University Bochum (RUB) , Institute for Electrical Engineering and Plasma Technology (AEPT), Bochum, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Stapelmann
authors.forename: Marcel
authors.initials: M
authors.lastname: Fiebrandt
authors.forename: Marina
authors.initials: M
authors.lastname: Raguse
authors.forename: Peter
authors.initials: P
authors.lastname: Awakowicz
authors.forename: Günther
authors.initials: G
authors.lastname: Reitz
authors.forename: Ralf
authors.initials: R
authors.lastname: Moeller
mesh_terms: D001407:Bacillus / Q000502:physiology*; D008855:Microscopy, Electron, Scanning; D058626:Plasma Gases; D013171:Spores, Bacterial; D013193:Stainless Steel
chemical_list: D058626:Plasma Gases; D013193:Stainless Steel