Genomic surveillance of the two available genome sequences from Oenococcus oeni indicated the presence of a 480-bp ORF, encoding a 18.7-kDa protein named DpsA, whose deduced amino acid sequence was in significant homology with the Dps proteins from Escherichia coli and various lactic acid bacteria. Consistent with the role of Dps proteins as a key component in response to oxydative stress, the cloned dpsA gene complemented the dps- mutant of E. coli and conferred resistance to hydrogen peroxide. More interestingly, the oenococcal gene also protected E. coli from the deleterious effects of wine, copper and ferric ions, three stressors encountered by O. oeni in its environment. The dpsA gene was flanked by IS-related elements. The entire region was characterized by an anomalously high GC content compared to those reported for complete PSU-1 and ATCC-BAA-1163 oenococcal genomes. In the O. oeni species, the dpsA gene was present in 15 of the 38 tested isolates. Positive strains were apparently unrelated, as they originated from different geographical areas and types of wines. No change in tolerance to wine was observed between strains harbouring dpsA and those not harbouring this gene. Our results suggest that some O. oeni have acquired the dpsA gene as part of a mobile element. DpsA probably increases the O. oeni fitness in response to environmental challenges. However, the physiological condition under which it adds a selective advantage to O. oeni during winemaking remains to be found.