THE EFFECT OF LABELING INTENSITY, ESTIMATED BY REAL-TIME CONFOCAL LASER SCANNING MICROSCOPY, ON FLOW CYTOMETRIC APPEARANCE AND IDENTIFICATION OF IMMUNOCHEMICALLY LABELED MARINE DINOFLAGELLATES

Two different fluorescein isothiocyanate (FITC) conjugates were used t o analyze the effect of labeling intensity on the flow cytometric appe arance of marine dinoflagellates labeled with antibodies that specific ally recognized the outer cell wall. Location of the labeling was reve aled by epifluorescence and real-time confocal laser scanning microsco py using an anti-rabbit IgG/FITC-conjugated secondary antiserum. Flow cytometric measurements showed that cells of Prorocentrum species labe led this way could not always be distinguished from unlabeled cells. T he labeling intensity increased several times when a biotinylated anti -rabbit IgG secondary antiserum was used in combination with a strepta vidin/FITC conjugate. Flow cytometry indicated that the labeling inten sity had increased 50%, which resulted in an improved separation of cl usters of labeled and unlabeled cells.