Discrimination of Three Highly Toxic Alexandrium tamarense (Dinophyceae) Isolates Using FITC-conjugated Lectin Probes

A lectin binding assay was conducted on three Alexandrium tamarense isolates (AT-A, AT-2 and AT-6). The fatty acid composition of all three isolates was analyzed, and the total carotenoid content andβ-carotene were 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 bind the lectin Dolchis biflorus agglutinin (DBA), regardless of growth phase, but conjugated concanavalin A (ConA), peanut agglutinin (PNA), Ricinus communis agglutinin (RCA), soybean agglutinin (SBA), Ulex europaeus agglutinin (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 high abundance in AT-6 compared with AT-A and AT-2. However, carotenoid content and β-carotene did not contribute to the discrimination of each isolate. Owing to variability in the biochemical composition of different isolates, possibly DBA and 22:6 (n-3) polyunsaturated fatty acid provide good information for the discrimination of AT-6.