Research On The Isolation And Identification,Algicidal Characteristics And Mechanism Of Efficient Algicidal Bacteria

In this study,bacteria with high efficient algicidal characteristics of the M.aeruginosa were isolated and purified from Xi'an eutrophic water.The physiological and biochemical characteristics algicidal characteristics,algicidal mechanism,algicidal product characteristics,biological denitrogenation and microcystins degradation characteristics of algicidal bacteria,raw water bodies in chlorophyll and nitrogen removal were discussed.Suggesting that:1.Two strains with high efficient algicidal effect of bacteria R11 and J25 were isolated and screening from eutrophic water.Combined with morphological characteristics and 16S r RNA gene sequence analysis,were identified as Raoultella sp.and Acinetobacter sp.When inoculation of bacteria R11 and J25 was 10%,15%,20%,25%,30%,the removal ratio of chlorophyll-a of was 40.00%,40.82%,90.38%,90.70%,94.00%for R11 after 8 days,respectively.Meanwhile,the removal ratio of chlorophyll-a was 36.67%,44.50%,86.54%,90.70%,96.00%for J25 after 8 days,respectively.When M.aeruginosa cell density of OD₆₈₀was 0.615,0.517,0.417,0.301,0.220,0.120,the removal ratio of chlorophyll-a of was 90.36%,81.97%,84.21%,86.67%,93.55%,95.24%for R11 after 6 days,respectively.Meanwhile,the removal ratio of chlorophyll-a was 80.72%,81.97%,85.97%,86.67%,87.10%,90.48%for J25after 6 days,respectively.Under the full illumination and darkness conditions,strain R11 had a good effect on the removal of chlorophyll-a,and removal of chlorophyll-a for strain J25 was not significant in the darkness conditions.When the inoculation(v/v)of R11 and J25 was greater than 10%at replacement of BG11 content,the removal ratio of chlorophyll-a was more than 80%.2.Strain R11 could reduce NO₃^--N from initial concentration of 5.59mg/L to 0mg/L within 36h.Meanwhile,nitrate could be removed completely.And,the denitrification rate was 0.155mg·L^-1·h^-1.Besides,M.aeruginosa can be used as carbon source and nitrogen source for biological denitrification by R11 and J25.When pure algae powder used as carbon source and nitrogen source with inoculation(v/v)of 10%,the maximum removal ratio of nitrate and ammonia nitrogen for strain R11 was 70.77%and 65.71%from 0 days to 4 days,respectively.And,the removal ratio of nitrate and ammonia nitrogen for strain J25 was 69.15%and 20.21%,respectively.3.Soluble active substances released by strain R11 and J25 were mainly found in extracellular substances.Therefore,it should be indirectly lysing algae.Meanwhile,the maximum absorption wavelength 680nm between 400nm and 800nm was determined for M.aeruginosa.The relationship between the number of M.aeruginosa cells and OD₆₈₀was measured by the flow cytometry.When the inoculation(v/v)of strain R11was 10%,15%,20%,25%and 30%comparing with the control group,the SOD activity values was 1.78-,1.91-,2.23-,2.30-,2.95-fold after 8 days,respectively.The trend of SOD activity values for strain J25 was consistent with strain R11.Besides,the morphological changes of strain R11(25%;v/v)were observed by scanning electron microscopy in different periods.4.Using fourier infrared spectroscopy and three-dimensional fluorescence spectroscopy technology,the composition and characteristics of algicidal product characteristics of strain R11 were studied.After 6 days,5 peaks appeared in EEM spectra.Ex/Em of 280/315,230/310,240/430 represent the dissolved metabolites,protein and fulvic acid,respectively.And,Ex/Em of 415/380 and 355/430 represent humic acid.After treatment with acid and alkali,released metabolites of strain R11 and J25 could resist the acid and alkali.When the inoculation(v/v)of strain R11 and J25 was more than 20%,the chlorophyll-a removal ratio reached over 80%within 4 days.5.In the experiment of dissolving algae and biological denitrification for R11(v/v=20%),the removal efficiency of chlorophyll-a and nitrate was 73.12%and84.03%within 6 days,respectively.And,the removal rate of nitrate was1.57mg NO₃^--N·L^-1·h^-1.When the inoculation dosage of strain R11 was 10%,15%,20%,25%and 30%,the removal ratio of chlorophyll-a of was 38.52%,57.63%,71.64%,85.13%and 93.58%,respectively.However,the Zeta potential values of the surface of M.aeruginosa cells was increased gradually.6.When the inoculation(v/v)of 28.20%,M.aeruginosa cells density(OD₆₈₀)of0.31,temperature of 31.40?,the maximum chlorophyll-a removal ratio of 77.81%could be obtained for strain R11.The immobilized strain J25 had a higher removal efficiency than R11 for chlorophyll-a.When the number was more than 30 for strain J25,the removal ratio of chlorophyll-a was more than 80%after 8 days.The initial M.aeruginosa cells density(OD₆₈₀)was 0.504,0.401,0.300,0.201,0.102 for strain R11and J25 mixture(v/v=30%),the removal ratio of chlorophyll-a was 92.68%,92.17%,96.00%,96.29%,97.01%after 4 days,respectively.When strain R11 was added to the raw water,the removal ratio of chlorophyll-a and nitrate was 74.59%and 99.74%after24 days,respectively.However,strain J25 was added to the raw water,the removal ratio of chlorophyll-a and nitrate was 87.76%and 100%after 24 days,respectively.The environmental microbial diversity for the eutrophic raw water reactor was analyzed by high throughput sequencing technology.