Present knowledge on the molecular basis of cytotoxicity, antibacterial activity and stress response in marine bivalves

Abstract

Mussel hemolymph possessed naturally occurring cytotoxic activity. Vertebrate erythrocytes, mouse tumor cell line and parasite Bonamia were killed, but not bacteria. Two step chromatography revealed a complex multimeric protein of 320 kDa, acting through a polymerization process on the target cell membrane. Of naive animals from the two oyster species Crassostrea gigas and Ostrea eclulis, a low proportion of plasmas and hemocyte lysates presented naturally occurring antibacterial activity. Induction assays by injection of saline solution or bacterial suspensions resulted in increased activity in virtually all oysters. Identification of active polypeptides included acidic solubility followed by reverse phase chroma‐tographies. Oyster hemocytes responded to heat‐shock by the synthesis of particular proteins. Treated in the same way, the protozoan parasite Perkinsus marinus also synthesised long‐lasting 70 to 30 kDa proteins which are different from the oyster ones. The question arises of the biological significance of heat‐shock proteins in coelomate invertebrates with regard to stress and immune response.

Key words:

• Marine bivalves
• Molluscs
• Cytolysis
• Cytotoxicity
• Antibacterial activity
• Stress proteins