Control of Microcystis aeruginosa with Galla chinensis

Galla chinensis (nutgall), used in traditional Chinese medicine, is a product extracted from nutgall trees in Chinese forests. In this study, Microcystis aeruginosa, a cyanobacterium, was exposed to different concentrations of nutgall extract obtained from Galla chinensis. With increased exposure concentration, and time, the cell density of M. aeruginosa was significantly reduced. After 72 h of exposure, the chlorophyll a content of M. aeruginosa significantly decreased; superoxide dismutase (SOD) activity increased at a low nutgall concentration but decreased at higher concentrations. Cellular ultrastructure was observed by electron microscopy. With increased nutgall concentrations, M. aeruginosa cell walls became wrinkled, collapsed, and ruptured. The photosynthetic thylakoid lamellae were fractured and dispersed, fewer phycobilisomes attached to the photosynthetic thylakoid membrane and were dispersed into the cytoplasm, and the number of lipid particles and cyanophycin granules increased. A large void appeared in the nuclear area and most of the algal cells died. In conclusion, these observations indicate that Galla chinensis has a significant allelopathic effect, and can effectively inhibit the growth of M. aeruginosa