CYTOTOXIC AND ANTIBACTERIAL PROPERTIES OF MYTILUS-GALLOPROVINCIALIS, OSTREA-EDULIS AND CRASSOSTREA-GIGAS (BIVALVE MOLLUSKS) HEMOLYMPH

Mussel (Mytilus galloprovincialis) plasma contains cytotoxic activity against both vertebrate (erythrocytes and mouse tumour) and protozoan cells. Procaryotes (Escherichia coli and Vibrio alginolyticus) were no t sensitive to the cytotoxicity. The activity was still present in dia lyzed samples but was inhibited by heating at 45 degrees C. Large indi vidual variability which was not correlated with protein concentration and an increasing number of reactive specimens following injection, s uggested that naive mussels were in various stages of immune response. Purification by anion exchange chromatography followed by gel filtrat ion revealed a 320 kDa cytotoxic polymeric protein that acts through a polymerization process after binding onto target cell membranes as re vealed by ultrastructural observation. European and Pacific oysters (O strea edulis and Crassostrea gigas) expressed antibacterial activity a gainst both Gram negative and Gram positive bacteria which was most pr obably due to small proteins. When tested against the marine pathogeni c Vibrio alginolyticus, hemocyte lysates of both species were more act ive than cell-free plasma. Antibacterial activity showed significant i ndividual variability that was dramatically reduced by stimulation thr ough mechanical stress or injection. The number of spontaneously activ e Pacific oysters increased from 50 to 100% following a single injecti on of bacteria. These results strongly support the view that bivalve m olluscs possess sensitive immune-defense mechanisms that will greatly aid the development of aquaculture systems by employing refined techni ques of transgenesis.