Study On The Isolation And Lysing Effects Of Algicidal Bacteria To The Microcystis Aeruginosa

In order to get algicidal bacteria which can dissolve the harmful cyanobacteria in bloom water effectively, the Microcystis aeruginosa was selected as the research object in this paper and isolated the algicidal bacteria from soil. The algicidal bacteria was identified by physiology and biochemistry experiments and 16S rDNA analysis, the effect of adding dosage of bacteria liquid, temperature, initial density of algae broth, and the adding methods on aldicidal efficiency were studied, then the mechanism of algae-lysing was preliminarily investigated. COD, ammonia nitrogen, total nitrogen and total phosphorus were determined to study the influence of water quality after adding the bacteria liquid, then the algicidal bacteria was applied to the treatment of the actual broom water samples, and the changes of algae cell were observed by neutral red dyeing and scanning electron microscope.Three strains of high performance algicidal bacteria were obtained from the soil after the isolation, purification and screening. They were identified as Ochrobactrum intermedium, Brevundimonas diminuta and Brevundimonas olei, respectively. Then their accession number were named as NR₀42447, NR₁17188 and NR₁17268.When AA06 was applied to study the algae-lysing effect, the lethal concentration was achieved at 3.94×106 CFU/mL as the cell density was 1.0-3.0×109 cells/L;when the bacterial density was 1.08×108 CFU/mL, added 10 mL bacterial liquid to 100 mL algae broth can attain above 95% algicidal efficiency. When the algae were dissolved at temperature of 30℃,22℃and15℉, the algae-lysing effect was in yurn down. When the algae density was 1.04×109 cells/L,8.56×109 cells/L �'� 7.02×1010 cells/L respectively, the algae-lysing rate can attain 87.4%、89.7%and98.2%. The algae-lysing effect of the bacterial fluid was added in 5 batches was better than the one-time adding method of bacteria liquid.The algicidal bacteria, supernatant without bacteria cells, the mixed solution of bacteria cells with distilled water, and the mixed solution of bacteria cells with medium were used to study the algae-lysing efficiency separately. It found that the mixture of bacterial andmedium, supernatant, bacteria liquid can achieve better algae-lysing efficiecncy, while the bacteria cells had no algae-lysing effect. These results showed that the algae-lysing efficiency of AA06 was obtained through the secretion of algicidal substance into the supernatant. Due to the determination three dimensional fluorescence determination （3D-Scan） and analysis, the substance may belong to the category of humic substances.It was very obvious of the change of water quality as added 10 mL bacterial solution into the algae broth, the concentration of COD increased to 1800 mg/L as the bacterial organic matter in the bacterial culture medium. However, as the growth of algicidal bacteria, most of the organic matters could be consumed and the concentration of COD decreased to 330 mg/L immediately. Although the concentration of total nitrogen （TN） and ammonia nitrogen also increased at a wide margin, the TN concentration can still droped to 227 mg/L 8 days later. The concentration of ammonia nitrogen will continue to rise as the transformation of bacteria until it rises to 300 mg/L. However, the concentration of total phosphorus （TP） was rised slightly, which ranged from 2.1 mg/L to 2.9 mg/L.The Algicidal bacteria had good algae-lysing effect on the Microcystis of the natural water. The Microcystis which sampled from the water bloom substance, after adding 10 mL、30 mL and 50 mL AA06 bacteria liquid into the algae broth 10 days later, the removal efficiency of Chla were 77.9%、 89.1% and 92.0%, respectively; after adding the same volume of AA10 bacteria solution, the removal efficiency of Chla were varied to 55.6%、92.6% and 98.7%, which means the bacteria liquid also had a good lysing effect to Microcystis in nature water. In the algae-lysing process, the algae cells which float onto the surface of the water will sink into central of the water, then sink into the bottom of the lake. They become etiolated gradually in the lake bottom, the cell aggregates to cluster and will not disperse into individual cells, but they will die as a whole form. The algae cell membrane was damaged until it dissolved into the fragment aggregates.