ENVIRONMENTAL RESPONSE OF SPORE FORMING BACTERIA: MOLECULAR STUDIES OF FOOD ASSOCIATED CLOSTRIDIA

For several reasons, including their specific growth requirements, the diagnosis of infections and food contamination caused by clostridia still presents much difficulty at the clinical, bacteriological and molecular levels. The main purpose of this work is to learn more about clostridia and their interactions with environment. First, new microscopy techniques have been used to study the germination process in Clostridium tyrobutyricum, an anaerobic bacterium responsible for late blowing defects during cheese ripening; meanwhile, the application of real-time PCR methods have been employed to enumerate C. tyrobutyricum cells and spores in milk. Then, a molecular genotyping has been set in order to identify the most common clostridia in a agro-dairy production aimed to detect the possible ways of diffusion of these microbial species. The last part concerns the study of expression patterns of Clostridium sporogenes, an apathogenic gram positive clostridium usually involved in food damage and frequently isolated from late bowled cheese; Clostridium sporogenes is genetically indistinguishable from Clostridium botulinum and is often used as a model for the toxic subtypes. The objective of this study is to use an array-based large-scale transcriptional analysis in order to study gene expression in four different steps of Clostridium sporogenes life cycle: vegetative cells, sporulating cells, dormant spores and germinating ones. Our aims includes being able to relate gene-expression patterns to specific phenotypes and to discover gene expression divergences between the different phases of living, germination and outgrowth of spore-forming bacteria. An important aim is to assign functions to groups of or individual C. sporogenes genes and use this information to formulate specific hypotheses for further testing also on pathogenic clostridia types.