Bacillus and other spore-forming genera: variations in responses and mechanisms for survival.

The ubiquity of Bacilli endospores in soils facilitates their easy transfer routes to other environments, including cleanrooms and low-biomass sites required by many industries such as food production and processing. A bacterial endospore is a metabolically dormant form of life that is much more resistant to heat, desiccation, lack of nutrients, exposure to UV and gamma radiation, organic chemicals, and oxidizing agents than is a vegetative cell. For example, the heat tolerance of endospores depends on multiple factors such as sporulation temperature, core dehydration, and the presence of minerals and small, acid-soluble proteins (SASPs) in the core. This review describes our current understanding of the persistence mechanisms related to sporeformers' biochemical properties and discusses in detail spores' heat, radiation, and reactive chemical resistance. In addition, it discusses the impact of contamination with spores on many areas of human activity, spore adhesive properties, and biofilm contribution to resistance.

Protection of Bacillus pumilus spores by catalases.

Bacillus pumilus SAFR-032, isolated at spacecraft assembly facilities of the National Aeronautics and Space Administration Jet Propulsion Laboratory, is difficult to kill by the sterilization method of choice, which uses liquid or vapor hydrogen peroxide. We identified two manganese catalases, YjqC and BPUM_1305, in spore protein extracts of several B. pumilus strains by using PAGE and mass spectrometric analyses. While the BPUM_1305 catalase was present in six of the B. pumilus strains tested, YjqC was not detected in ATCC 7061 and BG-B79. Furthermore, both catalases were localized in the spore coat layer along with laccase and superoxide dismutase. Although the initial catalase activity in ATCC 7061 spores was higher, it was less stable over time than the SAFR-032 enzyme. We propose that synergistic activity of YjqC and BPUM_1305, along with other coat oxidoreductases, contributes to the enhanced resistance of B. pumilus spores to hydrogen peroxide. We observed that the product of the catalase reaction, gaseous oxygen, forms expanding vesicles on the spore surface, affecting the mechanical integrity of the coat layer, resulting in aggregation of the spores. The accumulation of oxygen gas and aggregations may play a crucial role in limiting further exposure of Bacilli spore surfaces to hydrogen peroxide or other toxic chemicals when water is present.