| Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD50 value of 3.3 mu g/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of hemocytes to live bacteria induced... |
