Oenococcus oeni, the lactic acid bacterium primarily responsible for malolactic fermentation in wine, is able to grow on a large variety of carbohydrates, but the pathways by which substrates are transported and phosphorylated in this species have been poorly studied. We show that the genes encoding the general phosphotransferase proteins, enzyme I (EI) and histidine protein (HPr), as well as 21 permease genes (3 isolated ones and 18 clustered into 6 distinct loci), are highly conserved among the strains studied and may form part of the O. oeni core genome. Additional permease genes differentiate the strains and may have been acquired or lost by horizontal gene transfer events. The core pts genes are expressed, and permease gene expression is modulated by the nature of the bacterial growth substrate. Decryptified O. oeni cells are able to phosphorylate glucose, cellobiose, trehalose, and mannose at the expense of phosphoenolpyruvate. These substrates are present at low concentrations in wine at the end of alcoholic fermentation. The phosphotransferase system (PTS) may contribute to the perfect adaptation of O. oeni to its singular ecological niche.

<p style="text-align: justify;"><strong>Aims</strong>: The aim of this study was to develop a colorimetric test to determine <em>Oenococcus</em> carbohydrate consumption profile.</p><p style="text-align: justify;"><strong>Methods and results</strong>: A semi-defined growth medium which enabled efficient bacterial growth and medium acidification in the presence of glucose was developed. The inoculum size and the presence of citrate in the medium were optimized. Acidification of the medium was revealed by adding bromocresol green and was shown to be perfectly correlated with D-glucose, D-fructose, L-arabinose, D-xylose, L-rhamnose, D-cellobiose or D-trehalose consumption by 23 distinct <em>O. oeni</em> strains and one <em>O. kitaharae</em> strain (confirmed with HPLC analysis).</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: Efficient bacterial growth is essential before malic acid degradation occurs in wine. The method developed here will facilitate the comparison of numerous <em>O. oeni</em> strains and their ability to grow by using the various carbohydrates present in wine prior to malolactic fermentation.</p>