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Mécanisme d'assemblage des enveloppes de la spore en fonction de la température de sporulation : rôle de la protéine morphogénétique CotE chez Bacillus cereus

Abstract : Spores of the pathogenic bacterium Bacillus cereus are widespread in the environment and responsible of foodborne poisonings. Spores are a major concern to public health because of high resistance to treatments applied in food processing operations. Sporulation temperature is a main environmental factor that influences spore resistance properties. The variability of the conditions in which spores are formed during the sporulation process deeply modified their structure and consequently the efficiency of decontamination treatments. The aim of this work was to study the mechanism of spore layers assembly as a function of the sporulation temperature, and more precisely the role of the CotE protein in B. cereus. This morphogenetic protein is more detected in spores formed at 20°C, a suboptimal growth temperature than at 37°C, the optimal growth temperature, of the ATCC14579 strain. Observations in transmission electronic microscopy of DcotE spores revealed an assembly default of the spore exosporium at 37°C and 20°C but also of the spore coat at 20°C, suggesting that CotE has a role in the assembly of both layers, depending of the sporulation temperature. By fluorescence microscopy, we evidenced the kinetics of CotE production during sporulation and its final localization in mature spore, which are not dependent on the temperature of spore formation. Our results suggest that CotE could make a link to maintain the exosporium close to coat and cortex structures. Finally we showed that CotE also plays a role in germination and resistance properties of B. cereus spores to physical and chemical treatments.
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Christelle Bressuire-Isoard. Mécanisme d'assemblage des enveloppes de la spore en fonction de la température de sporulation : rôle de la protéine morphogénétique CotE chez Bacillus cereus. Bactériologie. Université Montpellier, 2015. Français. ⟨NNT : 2015MONTS088⟩. ⟨tel-01954620⟩

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