Lipid class composition of the protozoan Perkinsus marinus, an oyster parasite, and its metabolism of a fluorescent phosphatidylcholine analog

Perkinsus marinus is one of two important protozoan parasites of the easter n oyster, Crassostrea virginica. The other is Haplosporidium nelsoni. Lipid s extracted from 7-d-old in vitro cultured P. marinus meronts, incubated wi th fluorescent-labeled phosphatidylcholine (FL PC) and nonincubated P. mari nus meronts, were analyzed by a high-performance liquid chromatography (HPL C) system equipped with a diol phase column, in combination with thin-layer chromatography coupled with a flame-ionization detector (TLC/FID), and hig h-performance thin-layer chromatography (HPTLC). Various polar and neutral lipid classes were separated by HPLC using a two-gradient solvent system. F ive polar lipid classes-phosphatidylcholine (PC), phosphatidylethanolamine (PE), cardiolipin (CL), sphingomyelin (SM), and phosphatidylserine (PS)-wer e identified from P. marinus extracts. Four neutral lipid classes-triacylgl ycerol (TAG), steryl ester (SE), cholesterol (CHO), and fatty alcohol-were distinguished. TLC/FID analysis of meront lipids showed that the weight per centages of PC, PE, CL, SM, PS/PI, TAG, SE, and CHO were 21, 10.7, 4, 2.3, 4.3, 48.7, 7.8, and 1.2%, respectively. HPLC and HPTLC analyses revealed th e presence of two SM and PS isomers in P. marinus extracts. Perkinsus marin us effectively incorporated FL PC acquired from the medium and metabolized it to various components (i.e., free fatty acid, monoacylglycerol, diacylgl ycerol, TAG, PE, and CL). Uptake and interconversion of FL PC in P. marinus meronts increased with time. After 48 h the total uptake of fluorescence ( FL) was 28.9% of the FL PC added to the medium, and 43% of the incorporated FL resided in TAG.