Toxic dinoflagellate Prorocentrum lima and its associated bacteria

An immunoflorescence method, using a monoclonal antibody against okadaic acid (OA) toxin and DNA staining, was used to visualize the toxin and extranuclear DNA which could possibly be of intracellular bacterial origin, in the dinoflagellate species Procentrum lima Ehrenberg (Dodge). Okadaic acid (OA) was detected within the cytoplasm oi the dinoflagellate cell, frequently near the cytoplasmic membrane in the cell periphery and occasionally close to the nuclear membrane in the center of the cytoplasm. These results suggest that OA production could be related to the peripheral chloroplast and that OA accumulation may be associated with membrane lipids. OA is not co-localized with extranuclear DNA, implying that intracellular bacteria do not contain or accumulate the toxin. Comparison between axenic and non-axenic dinoflagellate cultures showed no differences in immunolabelling, suggesting that extracellular associated bacteria are not essential to okadaic acid production by the P. lima culture. These results tend to show that the dinoflagellate cell is able to produce OA autonomously.