Effects Of DOM Originated From Livestock Manure On The Physiological And Toxin-producing Characteristics Of Microcystis Aeruginosa FACHB905

China is an agricultural country.The livestock and poultry breeding industry can produce a large number of dissolved organic matter(DOM)which contain lots of C,N,P and other elements.With DOM emission and migration to water,it causes water eutrophication and other water quality problems.On the other hand,cyanobacteria frequently dominate in eutrophic fresh water and form cyanobacterial blooms.In China,microcystis is the main genus responsible for cyanobacterial blooms.In this paper,the effects of DOM on the physiological and biochemical as well as toxin-producing characteristics of M.aeruginosa FACHB905 were studied.Furthermore,the structure of DOMwascharacterizedbyFouriertransformspectroscopy(FTIR)and Tetramethylammonium hydroxide thermochemolysis-gas chromatography-mass spectrometry(TMAH-GC-MS),and then the impacts of two kinds of pure compound isolated from DOM on M.aeruginosa FACHB905 had been investigated.The main results are as follows:1.The CM-DOM(cattle manure originated DOM)slightly improved the growth rate of M.aeruginosa FACHB905 as well as Chl-a synthesis,the maximum growth rate presented in the treatment of 90 mg/L CM-DOM,and it was 107.54%of the control.While its impact on the carotenoid was not significant.The performance of PSII can restore with the extension of exposure time.Although the activity of E-APA was inhibited treated with CM-DOM,the cell activity had been promoted,and the maximum increased rate was 1.1times of the control at 60 mg/L CM-DOM exposure.Additionally,the CM-DOM increased the concentration of the Microcystin-LR(MC-LR).The highest level of MC-LR presented in the treatment of 120 mg/L CM-DOM on day 2 and 30 mg/L on day 4,6.And it was126.04%,114.94%,164.83%of the control respectively.However the synthesis of Dha~7-Microcystin-LR(Dha~7-MC-LR)was suppressed.2.The effects of MC-DOM(manure compost originated DOM)on the growth of M.aeruginosa FACHB905 was firstly promoted,and then inhibited,while the synthesis of intracellular pigments was not affected by MC-DOM.When the MC-DOM concentrations were between 60-120 mg/L,it decreased reduction rate of the PQ pool in the PS?and caused the block of electron transfer in the process of photosynthesis.Under the stress of MC-DOM,hormetic effects was observed in the cell activity and the E-APA activity.However,the concentration of microcystins in M.aeruginosa FACHB905 were inhibited by MC-DOM.3.The BL-DOM(biogas liquid originated DOM)inhibited the growth of M.aeruginosa FACHB905 at the concentrations of 60-120 mg/L.The minimum growth rate presented in the treatment of 120 mg/L BL-DOM,and it was 26.48%of the control.In contrary,the concentrations of Chl-a and carotenoid in M.aeruginosa FACHB905 increased of BL-DOM concentration.In the same case,although the E-APA activity was inhibited,the cell activity was increased by 1.6,2.0,2.3 times of the control at 2,4,6 d in the treatment of120mg/L BL-DOM.The performance of PSII was not affected under the exposure of the low BL-DOM concentration(15-30 mg/L),but it could be depressed by BL-DOM under higher concentrations.Furthermore,the inhibitory effects of BL-DOM on the synthesis of intracellular Dha~7-MC-LR was much more significant then MC-LR.For Dha~7-MC-LR,its highest inhibition rate was up to 64.38%at 6d.4.The constituents of DOM were characterized by FTIR and TMAH-GC-MS.The results indicated that phenol and benzene derivatives originated from lignin were the primary constituents of DOM,followed by alkane compounds,N/P containing compounds,and some fatty acids compounds.With the further fermentation,the degree of carboxylation of organic compounds in DOM was deeper and the lignin compounds,fatty acids were further biodegraded,however the lignin compounds were still the primary constituents in the DOM.5.Indole isolated from DOM could inhibit the growth of M.aeruginosa FACHB905,but this inhibition was not caused by an increase of intracellular ROS.The reason for cell density reduction may refer to the depression of PSII performance and ATP synthesis reducing.Besides,the synthesis of intracellular microcystins were inhibited in the presence of indole.6.The increase of carboxylic acid salt in DOM(simulated by sodium acetate)significantly promoted the growth of M.aeruginosa FACHB905,PS?performance,and concentration of intracellular microcystins.But it did not affect the intracellular Chl-a or carotenoid synthesis.