Membrane vesicles of Oenococcus oeni: A tool for adaptation to wine-related stresses?

Abstract

Membrane vesicles (MVs) are nanoscale structures derived from the cytoplasmic membrane that are involved in a wide range of biological functions, including cell–cell communication, molecular transport and biofilm formation [1]. In Gram-positive bacteria, MVs are now recognized as key players in stress responses, although their precise roles remain insufficiently characterized [2]. The lactic acid bacterium Oenococcus oeni represents a relevant model for investigating stress adaptation mechanisms, as this species is able to survive and maintain metabolic activity in wine, a highly constraining environment characterized by low pH, presence of ethanol and limited nutrient availability [3]. In this context, the aim of this work was to investigate the impact of different environmental stresses on MV production and properties in O. oeni, and to evaluate their potential role in bacterial survival under adverse conditions. MVs were isolated by ultracentrifugation from a standard O. oeni culture and from cultures subjected to different stresses, including ethanol stress (13%), acid stress (pH 3) and mitomycin C–induced stress (1µg/mL). The resulting vesicular fractions were characterized using complementary approaches, including particle size and concentration analysis by MA-DLS, protein quantification, protein profile analysis by SDS-PAGE, and morphological observation by transmission electron microscopy (TEM). TEM observations confirmed the presence of structures morphologically compatible with MVs. While no major differences in particle size or concentration were observed between the experimental conditions, clear variations were detected in MV protein concentrations and protein profiles, suggesting stress-dependent modulation of vesicular cargo. From a functional perspective, assays performed under ethanol stress conditions showed that the addition of MVs derived from control or stressed cultures improved bacterial survival in a dose-dependent manner. To further investigate the molecular mechanisms underlying this protective effect, the fluorescent probe Laurdan is being used to assess the impact of MVs on membrane fluidity. Overall, the study of membrane vesicles provides new insights into how O. oeni withstands environmental stresses and adjusts its membrane properties to preserve survival and metabolic activity.

References

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