The aim of that studywas to explore the hypothesis that a quorumsensingmechanismmodulatesmetalloprotease gene expression of two Vibrio species pathogenic for oyster, at intraspecific (Vibrio splendidus) and interspecific (V. splendidus affecting V. aestuarianus) levels. Metalloprotease activities (Vsm for V. splendidus LGP32 and Vam for V. aestuarianus 02/041) and growth curves obtained by real-time PCR assay revealed cell density-dependent metalloprotease inductions triggered between 12 h and 16 h of culture. A quorum sensing assay was then developed using a conditioned medium prepared from supernatant of a mutant strain of V. splendidus LGP32 unable to produce metalloprotease. Specific real-time qPCR assays targeting metalloprotease genes vsm and vam were performed. A relative increase in expressionwas observed for vsm and, particularly, vam in the presence of the conditioned medium, probably controlled by a quorumsensing system. The study revealed intraspecific and interspecific modulation of expression in metalloprotease genes vsm and vam in V. splendidus and V. aestuarianus. Our experiments showed for the first time that V. splendidus is able to produce an autoinducer-like substance that displays intra- and interspecific effects on the expression of two different metalloprotease genes: vsm and vam