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LIPID BIOMARKER ANALYSIS OF THE TOXIC DINOFLAGELLATENPFIESTERIA PISCICIDA: DISTRIBUTION OF STEROLS AND FATTY ACIDS WITHIN THE CLASS DINOPHYCEAE
Citation:
Leblond, J. D. AND P J. Chapman. LIPID BIOMARKER ANALYSIS OF THE TOXIC DINOFLAGELLATENPFIESTERIA PISCICIDA: DISTRIBUTION OF STEROLS AND FATTY ACIDS WITHIN THE CLASS DINOPHYCEAE. Presented at Phycological Society of American Annual Mtg, Madison, WI, Aug 3-8, 2002.
Description:
Within United States waters, regular blooms of harmful dinoflagellates occur in the Gulf of Mexico and Chesapeake Bay regions. Although the causes of blooms are not fully understood, events in Gulf of Mexico waters have been recorded for over thirty years, and are almost exclusively caused by the photosynthetic dinoflagellate, Karenia brevis. Conversely, blooms in the Chesapeake Bay region, caused by the heterotrophic dinoflagellate Pfiesteria piscicida, appear to be a relatively new phenomenon, and are hypothesized to be linked to an increase in nutrient-rich runoff from chemical plants and livestock farms along tributaries leading into the Chesapeake. Despite the environmental, economic, and human health relevance of
P. piscicida, there appears to be no published work on the characterization of its lipid composition. The objective of this study was, therefore, to examine the sterol and fatty acid composition of cultured P. piscicida isolates as a precursor to eventual field studies of blooms of this organism. GC/MS analysis of trimethylsilyl ether derivatives of sterols in free sterol and sterol ester fractions revealed that the overwhelming majority of sterols was found as free sterols. Furthermore, free sterols were found to resemble those of other dinoflagellates, with the dominant compound being the common dinoflagellate sterol, dinosterol; a number of
other 4-methyl sterols common to other dinoflagellates were also identified. The fatty acids of P. piscicida were found to be primarily associated with a fraction containing cellular membrane phospholipids; small amounts of the recently described highly-unsaturated fatty acids, octacosaoctaenoic acid [28:8(n-3)] and octacosaheptaenoic acid [28:7(n-6)], were observed in this fraction. The dominant fatty acid (approximately 40-60% of the phospholipid fatty acids) were docosahexaenoic acid [22:6(n-3)]. Unlike K. brevis (see accompanying poster), P. piscicida does not appear to possess significant amounts of unusual sterols or fatty acids which may serve as potential biomarkers for this organism.