Proteome dynamics during sporulation and heat resistance in Bacillus subtilis spores

Bacterial spores are one of the common concerns for the food industry. Sources of contamination by bacterial spores in the food chain may include, but are not limited to, water, soil, food ingredients and the processing chain itself. The extreme thermal resistance exhibited by the spores favors their survival of food processing and long-term persistence in foods. Beside the problems caused in the food chain, some species of Bacillus and Clostridium are causative agents of several serious human diseases. Therefore, the investigation of the sporulation (spore formation) characteristics at the molecular physiological level and thus, among others the spore proteome, are crucial to further our understanding of spore physiology and to ensure the most efficient control of the problems caused by spores. In the current thesis, the proteome changeover during a synchronized sporulation, as well as the proteome of spores of a lab strain and a high heat resistant spore forming food isolate, was extensively studied using high resolution mass spectrometry-based proteomics. The effect of synchronized sporulation by kinA overexpression on spores was clarified. Additionally, this thesis details the protein co-expression network during sporulation and reveals the proteome difference of spores of two strains exhibiting different heat resistance. Finally, the thesis describes the application of a novel protein extraction method that allows one to use SDS in proteome extraction protocols facilitating membrane protein analysis. This will be of use in more detailed time resolved germination protein analyses aimed at resolving some of the outstanding mechanistic details of spore protein biogenesis.