Response of extracellular and intracellular alkaline phosphatase inMicrocystis aeruginosato organic phosphorus

Cyanobacterial blooms caused byMicrocystishave become a menace to public health and water quality in the global freshwater ecosystem. Alkaline phosphatases (APases) produced by microorganisms play an important role in the mineralization of dissolved organic phosphorus (DOP) into orthophosphate (Pi) to promote cyanobacterial blooms. However, the response of extracellular and intracellular alkaline phosphatase activity (APA) ofMicrocystisto different DOP sources is poorly understood. In this study, we compared the growth ofM. aeruginosaon two DOP substrates (beta-glycerol-phosphate (beta-GP) and lecithin (LEC)) and monitored the changes of P fractions and the extra- and intracellular APA under different P sources and concentrations.M. aeruginosacan utilize both beta-GP and LEC to sustain its growth, and the bioavailability of LEC was greater than beta-GP. For the beta-GP treatment, there was no significant difference in the algal growth at different concentrations (P> 0.05), while the algal growth in the LEC treatment groups was significantly affected by concentrations (P< 0.05). The results showed that intracellular APA ofM. aeruginosacould be detected in all DOP treatment groups and generally higher than extracellular APA. In addition, the intracellular APA per cell increased first and then decreased in all DOP treatment groups. Compared with the beta-GP treatment,M. aeruginosain the LEC groups could secret more extracellular APA.