Discrimination of three highly toxic Alexandrium tamarense (Dinophyceae) isolates using FITC-conjugated lectin probes

A lectin binding assay was conducted an three Alexandrium tamarense isolate s (AT-A, AT-2 and AT-6). The fatty acid composition of all three isolates w as analyzed, and the total carotenoid content and beta -carotene mere also determined. When treated with different lectins in this study, AT-A and AT- 2 showed a positive response, whereas the potentially toxic AT-6 did not bi nd the lectin Dolchis biflorus agglutinin (DBA), regardless of growth phase , but conjugated concanavalin A (ConA), peanut agglutinin (PNA), Ricinus co mmunis agglutinin (RCA), soybean agglutinin (SBA), Ulex europaeus agglutini n (UEA) and wheatgerm agglutinin (WGA). It is possible that the use of DBA is a desirable method for rapid and easy discrimination of highly toxic A. tamarense. AT-A, AT-2 and AT-6 comprised saturated fatty acids (49.0-61.9%) , monounsaturated fatty acids (8.0-20.5%) and polyunsaturated fatty acids ( 23.2-30.5%). In particular, 22:6 (n-3) polyunsaturated fatty acid had a hig h abundance in AT-6 compared with AT-A and AT-2. However, carotenoid conten t and beta -carotene did not contribute to the discrimination of each isola te. Owing to variability in the biochemical composition of different isolat es, possibly DBA and 22:6 (n-3) polyunsaturated fatty acid provide good inf ormation for the discrimination of AT-6.