Multifactorial spore resistance of Bacillus subtilis to low-pressure plasma sterilization: addressing the roles of structural spore components and DNA repair mechanisms

Kurzfassung

Common sterilization techniques for labile and sensitive materials have farreaching applications to the medical, pharmaceutical and industrial fields. Heat inactivation, chemical treatment and radiation are established methods to inactivate microorganisms, but may be hazardous for humans and the environment or may damage susceptible materials. Earlier studies showed that cold low-pressure plasma (LPP) treatment is an efficient alternative to common sterilization methods. To adjust the plasma composition, different process gases, such as oxygen, nitrogen or argon can be used. Depending on the composition of the plasma, microorganisms have to deal with several active agents like (V)UV radiation, charged particles, radical species, excited atoms and molecules as well as the electric field. To verify the detrimental effects of LPP treatment, the Grampositive bacterium Bacillus subtilis was used as a model organism. In this work, spores of B. subtilis were tested for their susceptibility towards LPP as control, and then contrasted to strains lacking major DNA repair mechanisms such as nonhomologous end-joining (NHEJ), or abasic endonucleases, protective proteins like α/β-type small acid soluble spore proteins (SASP) and structural protection by the outer spore coat layer. In this study, the knowledge of multifactorial resistance of Bacillus subtilis spores to LPP, addressing the roles of spore structural components as well as DNA repair mechanisms should be advances. The results of this study demonstrated that LPP-treatment leads to significant DNA damage. To withstand LPP sterilization the interaction of efficient DNA repair during spore germination and other protection mechanisms such as oxygen radical detoxification via KatX catalase activity is needed. Due to impact of multiple lethal factors LPP is a suitable method to sterilize efficiently.