Oenococcus oeni is the most important lactic acid bacteria of the winemaking process involved in malolactic fermentation. Most O. oeni strains are able to catabolyze arginine via the arginine deiminase (ADI) pathway. The arcR, A, B, C, D1, and D2 cluster of O. oeni bacteria has been characterized. Here, we completed the ADI locus sequence. Downstream of arcD2 gene, we found an additional gene which encodes a putative arginyl-tRNA synthetase (argS2). It is not the same arginyl-tRNA synthetase which was sequenced in O. oeni MCW strain. Transcriptional analyses have shown that argS2 was induced by arginine. In addition, systematic polymerase chain reaction amplification of each arc gene and argS2 has provided a characteristic feature of the ADI locus within the O. oeni species: all genes of ADI locus are present or absent according to the strains.