AimsThe aim of this study was to investigate the effect of ethanol exposure on the expression level of geranylgeranyl pyrophosphate synthase gene involved in the metabolism of Oenococcus oeni to probe the mechanisms of ethanol tolerance correlated with adaptive changes. Methods and ResultsThe evaluation of ten potential internal control genes and the comparative study of their stability were performed to select the most stable internal controls for the normalization of expression data. The expression level analysis by qPCR and changes after exposure to ethanol stresses highlighted a significant increase in the presence of higher ethanol concentrations. ConclusionsThe analysis of results suggest that O.oeni adjusts the expression of genes to adapt to stress conditions and the high expression level of ggpps would allow a flow of isoprenoid precursors towards the carotenoids and related pathways to stabilize bacterial cell membranes, improving the cell membrane disturbances and preventing cell death induced by ethanol. Significance and Impact of the StudyThe involvement of ggpps gene in physiological changes of bacterial behaviour confirmed the exposure to stress requires the activation of defence mechanism to be more tolerant to adverse conditions. Improving the knowledge of stress tolerance and adaptation mechanisms of O.oeni is essential to enhance the efficiency of the malolactic starter in wine and to obtain the development of starters able to survive to direct inoculation with a large benefit for wine technology.