Effects And Mechanisms Of Sanguinarine On Physiological Characteristics Of Microcystis Aeruginosa Involved In Ecological Competition Advantages

Our previous studies showed that sanguinarine had strong inhibitory effect against Microcystis, wheras, the effects of sanguinarine on the ecological competitive advantages remain unknown. In order to elucidate this issue, the effects of sanguinarine on the cellular phenotype, microcystins synthesis, activities of antioxidant enzymes, and the uptake of nutrients were investigated in this thesis. The results presented in this thesis would provide important information on further understanding the effects of sanguinarine on ecological competitive advantages of cyanobacteria and their effects on aquatic microbial ecosystem in algae control. The main results are as follows:（1）Sanguinarine has strong inhibitory effects on the growth of M. aeruginosa EH-S1 and chlorophyll content. The contents of protein, phycocyanin and allophycocyanin of M. aeruginosa EH-S1 were also inhibited by sanguinarine. The size of the colony of M. aeruginosa EH-S1 increased under the stress of sanguinarine. Sanguinarine has no effect on M. aeruginosa EH-S1 cell buoyancy.（2） Sanguinarine stress resulted in the increase of the activities of alkaline phosphatase （ALP）, catalase（CAT）, superoxide dismutase enzyme（SOD） and Malondialdehyde （MDA） content in the cells of M. aeruginosa EH-S1, whereas the activities of nitrate reductase （NR）, carbonic anhydrase （CA） decreased. These results suggested that oxidative stress was one of inhibitory mechanism of sanguinarine on M. aeruginosa EH-S1.（3） The effects of sanguinarine on the synthesis and release of microcystins in M. aeruginosa EH-S1 were studied by ELISA and HPLC. The results showed that the concentrations of extracellular microcystins were lower than the control at a sanguinarine addition level from 10 to 80 μg/L on 1 days. After 3 days exposure, the concentrations of extracellular microcystins were significantly higher than the control at the sanguinarine concentration of 10 μg/L, whereas, the they were obviously lower than the control at the concentration of 40、80μg/L. After 5 days exposure, the concentrations of extracellular microcystins in all sanguinarine stress treatments were higher than the control. For the MC-LR concentrations of intracellular microcystins, sanguinarine inhibits the secretion of MC-LR in the 1 days, after then the microcystins content rose again; Another intracellular microcystins DAH7-LR, in addition to the 80 μg/L treatment for sanguinarine inhibitory effect, other groups have no significant effect on the DAH7-LR content.（4） Results of nutrition absorption test showed that, at the initial P concentration of 6,10, and 20 μmol/L, sanguinarine showed no obvious effect on the uptake of P at the addition level of no more than 20μg/L. When the concentration of sanguinarine increased to 40、80μg/L, the uptake efficiencies of P by M. aeruginosa EH-S1 were depressed by sanguinarine. Results of iron absorption test showed that, at the initial Fe³⁺ concentration of 1、10 μmol/L, sanguinarine showed no obvious effect on the uptake of iron at the addition level of no more than 20μg/L. When the concentration of sanguinarine increased to 40、80μg/L, the uptake efficiencies of Fe³⁺ by M. aeruginosa EH-S1 were improved by sanguinarine.