Being the most resistant form of a biological system, spores of
Bacillus subtilis are very resistant against a broad spectrum of
sterilization methods and, therefore, are commonly used as a
biological indicator in order to verify the functionality of a
sterilization procedure. The process of low-pressure plasma
sterilization is a promising alternative to conventional sterilization
methods as it is extremely fast, efficient and gentle to heatsensitive
materials. Active plasma species contain a high degree
of sporicidal UV/VUV-radiation, as well as charged particles and
free radicals, which exert detrimental effects on microorganisms.
In this study we present novel insights into the key factors
involved in spore inactivation by low pressure plasma sterilization
using a double inductively-coupled plasma reactor.
In order to standardize the assessment of spore inactivation
efficiencies by plasma discharges, an electrically operated
deposition device was developed, allowing fast, reproducible, and
homogeneous preparation of B. subtilis spore in monolayers on
surfaces leading to more reliable investigations. We demonstrate
that low-pressure plasma discharges of argon and oxygen
discharges cause significant physical damage to spore surface
structures as visualized by atomic force microscopy. A systematic analysis of B. subtilis spores lacking individual coat and crust
layers - the first barrier to environmental influences – revealed the
coat to be a major factor in spore resistance towards plasma
treatment (Raguse et al., 2016).
In order to gain a better understanding of the complex molecular
mechanisms involved in the inactivation by plasma sterilization
processes, we analyzed plasma-induced DNA lesions in vitro,
identified general and spore-specific DNA lesions, and
characterized different DNA repair mechanisms during spore
revival after plasma treatment
