Mechanism analysis of combined acid-and-ethanol shock on Oenococcus oeni using RNA-Seq

Acid-and-ethanol tolerance plays an important role in the cell viability of Oenococcus oeni and affects the enological characteristics of malolactic fermentation in wine. To reveal the mechanism of the response to acid-and-ethanol in O. oeni , we analyzed the changes to its gene expression profile after acid-and-ethanol shock for the first time using RNA-Seq. Some physiological indicators related to this stress response were also characterized. Bioinformatic and physiological analyses showed that the O. oeni strengthened the biosynthesis of peptidoglycan as a response to ethanol toxicity, and the cell membranes altered their fatty acid compositions for keeping the acidic H + outside when the cells were shocked with acid-and-ethanol. When H + entered the cytoplasm, the F 0 F 1 -ATPase system began discharging H + (producing ATP), and the cells increased their expression of rec N and mut T genes for minimizing the DNA damage. The cells also used two-component systems to communicate between same-species cells for improving the overall population survival rate. Genes encoding spermidine and putrescine transport were also upregulated to increase resistance to the acid-and-ethanol environment. This study fills important gaps in the current understanding of the bacterial acid-and-ethanol stress response mechanism, and it may be beneficial to screen more robust O. oeni strains in future works.