Aims: The aim of the study was to characterize the effect of various nitrogen sources on Oenococcus oeni growth, carbon source utilization, extracellular protease activity and extracellular proteins. More generally, the goal is to understand how nitrogen-based additives might act to enhance malolactic fermentation in wine. Methods and Results: Five yeast extracts were used. As the amino acid and nitrogen analyses revealed, they were similar in global amino acid composition, except for arginine level. Nevertheless the ratio of amino acids between free/bound, and low/high molecular weight fractions were highly different. One of the yeast extracts led to a significant protease activity in the supernatant and to a poor final biomass of the IOB84(.)13 strain compared to the other ones. For the IOB84(.)13 strain specifically, arginine addition to the arginine poor yeast extract did not restore growth. S-35-methionine-labelled extracellular proteins were separated by SDS-PAGE. Signals were detected in all media early in the growth phase and were maintained during 48 h of culture. Conclusions: A significant protease activity was detected for O. oeni supernatants during growth under nitrogen limitation but only for certain nitrogen sources. Moreover, the activity was strain dependent. Peptides ( 0(.)5-10 kDa) seemed to be more favourable for growth of wine bacteria than < 0(.)5 kDa nitrogen sources. The extracellular protein signal patterns differed more greatly between the bacterial strains tested than between the nitrogen molecules in the medium. Significance and Impact of the Study: This is the first study extensively considering the role of the nitrogen source composition and level upon O. oeni growth and metabolism.