Evaluation of Berberine's Algicidal Effects on Toxic Microcystis aeruginosa Growth using a Double Fluorescein Staining Method

An accurate and convenient method for determining Microcystis cell viability is necessary to control blooms in small aquaculture water bodies. The fluorescein diacetate-propidium iodide (FDA-PI) staining method was developed to determine the viability of toxic Microcystis aeruginosa (FACHB905). Live M. aeruginosa 905 cells, stained with FDA, emitted bright green fluorescence after excitation at 470 nm. Dead cells, stained with PI, produced bright red fluorescence after excitation at 540 nm. Berberine inhibited M. aeruginosas 905 growth and the inhibition rate determined by FDA-PI fluorescein staining and counting on a dark field was much higher than when determined by counting on a bright field because some berberine-killed cells were misidentified as live cells. Thus, less berberine is needed to control Microcystis bloom when the accurate and reliable FDA-PI fluorescein staining method is used to judge the viability of the algae cells.