Succinic acid significantly affects the global expression of <i>Oenococcus oeni</i> PSU-1

Oenococcus oeni is the predominant lactic acid bacterium performing malolactic fermentation (MLF) in wine. Succinic acid, produced by yeasts during alcoholic fermentation, can improve the organoleptic properties of wine, but it can have a negative impact on O. oeni and MLF. The levels of succinic acid in wine can increase with the current use of non-Saccharomyces yeasts. In this work, transcriptomic analysis by RNA-seq was performed in wine-like medium supplemented with 2 g/L succinic acid, and a control medium without it, during MLF performed by O. oeni PSU-1. Approximately 25 % of the 1,638 detected transcripts were downregulated, exhibiting half the expression of those in the control or less, and other 29 % were upregulated, with double expression or more. We found that genes of clusters of orthologous groups related to the metabolism of nucleotides, translation, and membrane transport were predominantly downregulated by succinic acid, while those related to the transport and metabolism of carbohydrates, transcription, inorganic ion metabolism and defense mechanisms were predominantly upregulated. Considering the greater upregulation of carbohydrate metabolism genes, we analysed those involved in the phosphotransferase system. In this first transcriptomic study of the effect of succinic acid on O. oeni, we observed a global cell response with many changes in gene expression related to the observed MLF delay by succinic acid.