TWENTY-FOURTH ANNUAL EASTERN FISH HEALTH WORKSHOP Royal Pavilion Resort, Atlantic Beach, NC MARCH 9-11, 1999 Lipid Metabolism In Perkinsus marinus And Its Relationship To Pathogenicity Fu-Lin E. Chu, Philippe Soudant, Yongqin Huang, and Aswani K. Volety Virginia Institute of Marine Science, School of Marine Science, College of William and Mary, Gloucester Point, VA 23062. Host lipids play a unique role for long term survival and life cycle completion in endogenous parasites. Parasites exploit fatty acids and lipids from the host, not only for membrane synthesis, but also for modification of their surface integrity to avoid host defense. Our study revealed that the content of total lipids increased in the parasite, Perkinsus marinus, parallel to the increase in cell numbers. Depletion of total lipid, different class lipids, and arachidonic acid in media cultured with parasite was also noted. To study lipid utilization by this parasite, we followed the uptake of fluorescent-labeled fatty acid and phospholipid analogs in the merozoite/meront and prezoosporangia stages of P. marinus. After 24 hr incubation at 28°C with fluorescent labeled phosphatidylethanolamine (PE), phosphatidylcholine (PC), and free fatty acid (FFA, C12:0 and C16:0) analogs, yellow-gold fluorescence was present primarily in the discrete lipid droplets throughout the parasite, except those incubated with sphingomyelin, which appeared to be associated with the membrane. Analysis of lipid class composition using thin layer chromatography showed that the merozoite/ meront stage incorporated PC and transformed it into PE, PS, FFA, triacylglycerol (TAG). PE was also metabolized to PS, PC and TAG in meront/merozoite. Incorporation of PC and FFA was observed in prezoosporangia, but there was no conversion of PC to PE or PS, instead PC in prezoosporangia was metabolized into FFAs. The fluorescent-labeled FFAs in prezoosporangia were incorporated in TAG. These results suggest that P. marinus incorporated and modified lipids from exogenous sources and that the metabolic modes of meront differed from prezoosporangia. The effect of salinity and temperature on the uptake and bioconversion of fluorescent lipid analogs in meronts was also examined. Salinity at 3 ppt did not affect the uptake of lipids but drastically reduced the bioconversion of FFA and PC to TAG. The uptake and bioconversion of FFA and PC appeared to be temperature dependent. Return to 24th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page