The Mechanism And. Inhibitory Effect Of Hydrogen Peroxide On The Growth Of Microcystis Aeruginosa

Eutrophication of water system is a common environmental problem all over the world. The eutrophication of freshwater lakes led to the explosive growth of algae form blooms. Part of harmful algae also can effect human and other organisms health by release secondary metabolites, such as microcystin.Therefore, it is a hot focus in the field of biological and environmental to inhibit growth of algae and inhibiting the release of microcystins.We selected a common harmful algae Microcystis aeruginosa as experimental objects, to study the toxic mechanism of algaecides, through in the physiological and mRNA abundance levels. The results showed that the inhibitory effect of1.5μM CuSO4,100μM H2O2and1mg L-1PNA were60.8%,93.4%and65.3%. Studing the effects from the antioxidant enzyme activity(SOD, POD, CAT), lipid peroxidation level, chlorophyll level, Reactive oxygen species, and the mRNA abundance level of photosynthesis related genes, we detected the three algaecides can increase reactive oxygen species, trigger the production of Reactive oxygen species, lead to the increased lipid peroxidation level. The real-time polymerase chain reaction assay showed that transcription of psaB, psbD1and rbcL was inhibited by the three algaecides.Microcystins is one of the major hazards caused by algal blooms, H2O2treatment down-regulated mcyD transcription, which indicated a decrease in the microcystin level in the cells. We use HPLC methods for detection for toxin, CuSO4and H2O2treatment would effective control the synthesis of microcystins, the total content of microcystins were20.4%, and40.8%of those of the control, respectively. But the algae treated with PNA was not changed obviously. For it is easy to decomposed, the H2O2will not pollute the environment, have effective inhibition in the growth of algae and microcystins synthesis. Therefore, we make H2O2as an example to study whether it effected through the circadian clock genes, thereby inhibiting the growth of algae.Cyanobacteria endogenous circadian clock regulate many physiological metabolism in the cell, like photosynthetic and toxin synthesis. It is found that40μM H2O2change the rhythm of photosynthesis-related and microcystin-related gene expression, effect the rhythm amplitude and phase during the Light/Dark cycle. Microcystins in algae cell detected by HPLC, H2O2treatment weaken the rhythm. The treatment gene expression and microcystins synthesis during the Light/ Light cycle rhythm were similar with the treatment in Light-Dark, the result show that circadian clock and life activities rhythm didn’t change significant by change the light conditions in a short time.Our results demonstrate that H2O2has the greatest potential as an algaecide because it not only inhibits algae growth but may reduce microcystin synthesis.