A combination of direct cell count and fluorescein diacetate hydrolysis to evaluate the viability of algae cell

Knowing the algae cell viability would be helpful in answering ecological or physiological questions. In this study, the direct cell count was combined with fluorescein diacetate hydrolysis to evaluate the of viability algae cell. The direct cell count was performed under light-field by a microscope equipped with CCD camera, and then an image processing program was used to calculate the cell count. Fluorescein diacetate is hydrolyzed into fluorescein by nonspecific intracellular esterases, and the fluorescence of fluorescein was simultaneously measured by spectrofluorometer. A linear regression analysis was used to determine the fluorescence intensity slope against time. Finally, we have chosen to use the ratio of fluorescence intensity slope and direct cell count result to make an evaluation of algae cell viability. The result shows that the combination of direct cell count with fluorescein diacetate hydrolysis can provide a sensitive and rapid method to detect algae cell viability.