Mécanismes d’adaptation de Moorella thermoacetica/thermoautotrophica sur les lignes de production de produits alimentaires appertisés

Abstract : Moorella thermoactica is a spoilage anaerobic and thermophilic spore-former producing the most highly heat-resistant spores isolated so far in food industry, which enables the bacteria to survive the sterilization process applied in cannery. M. thermoacetica is the main cause of low acid canned food spoilage after incubation at 55 °C. Little is known about sporulation mechanisms and spore properties according to environmental conditions.In this work, we aimed at characterizing the impact of environmental conditions on sporulation and spore resistance properties, as well as describing the molecular mechanisms underlying sporulation. We showed that sporulation capacities are higher when sporulation is performed at the optimal temperature (55 °C) that at limit temperatures (45 °C and 65 °C). Besides, spores are less resistant to wet heat and biocides when formed at 45 °C than at 55 °C. We showed that the ultrastructure and spore protein composition varied according to sporulation temperature. Moreover, the study of gene expression by RNAseq during sporulation in optimal regulated conditions showed that most of the 167 genes involved in the sporulation process and identified in silico in M. thermoacetica ATCC 39073 genome, were up-regulated during sporulation, suggeting that the mechanisms described in other endospore-formers are conserved in Moorella.Altogether, our results showed that sporulation temperature strongly impacts sporulation and spore properties of M. thermoacetica and that sporulation mechanisms tend to be conserved in Moorella considering data available on other endospore-formers.
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Tiffany Malleck. Mécanismes d’adaptation de Moorella thermoacetica/thermoautotrophica sur les lignes de production de produits alimentaires appertisés. Bactériologie. Université d'Avignon, 2017. Français. ⟨NNT : 2017AVIG0339⟩. ⟨tel-02275777v2⟩

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