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RESEARCH PRODUCT

Molecular mechanisms involved in the regulation of stress response in Oenococcus oeni and experimental evolution

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description

Oenococcus oeni is the main bacterium responsible of malolactic fermentation in wine. This lactic acid bacteria grow in the stressful wine environment (high ethanol content, sulfites, low pH and low temperatures….). To maintain its cellular homeostasis, O. oeni has established mechanisms of resistance to its ecological niche. This research work focuses on the adaptative response of O. oeni to its environment and especially to acidity. Two approaches have been implemented (1) First, a targeted approach to characterize the molecular actors involved in regulating the general stress response. The RNA interference technique made possible the characterization of the repressor CtsR as well as two genes encoding proteins of the Clp-ATPAses family: ClpL1 and ClpL2. Inhibition of the expression of these two genes suggests that ClpL1 acts with an accessory protein to maintain CtsR under active conformation and that ClpL2 is involved in the repressor degradation by forming a proteolytic complex with the ClpP subunit. (2) The second approach of this work consists of a global approach using an experimental evolution process. Four clones of ATCC BAA-1163 strain were propagated for 20 months (approximately 550 generations) into an increasingly acidic environment (pH 5.3 to 2.9). Genomic sequencing of the 4 independent populations allowed the identification of five locus, systematic target of mutations (deletion, insertion, substitution), potentially implicated in the adaptation of O. oeni to the extreme acidity of its environment.