Study On The Screening Of Algicidal Bacteria And Their Algae-lytic Effects

In recent years, using micro-biological method to control harmful algae has become the hotspot, especially mechanism of on effect of algicidal bacteria on the growth of algae, has gradually aroused the concern of people, and algicidal bacteria has a huge potential and prospect in controlling breakout of water bloom.The method of algicidal bacteria screening in the present stage is not very perfect and still has many shortcomings. This paper mainly studies how to improve the effects of original foundation algicidal bacteria in the screening method. From the culture medium angle, we alter glucose and the sodium chloride ingredient into citric acid sodium. In the research, we discovered the glucose has the suppressive effects to algae's growth. By the modified medium, four strains algicidal bacteria A,B1,B2,B3 were obtained from the pond of Fujian Agriculture and Forestry University, Nanping music square and Xiamen South Putuo, and four strains A,B1,B2,B3 has higher algicidal ability. But no one strain was obtained from the water samples by using the routine medium. After the improvement screening method obviously surpasses the conventional method and removed the disturbing factors in medium, and also has no influence for bacterial extracellular exudates. One rapid and efficient screening way was provided for algicidal bacteria especially using extracellular exudates algae-lysing.According to the studies on Gram's staining, the morpHological characters and the pHysiological, biochemical characters, it was identified as a Bacillus. The experimental result indicated that: the bacteria strains A could effectively inhibit the growth of Anabaena sp.PCC595 and Microcystis aeruginosa, when the concentration of strain A was l0⁶cftu·mL^-1, most of algae cells were dissolved after 3～4 days, but other bacteria strains have certain selectivity and just could kill some of algae cells, and only inhibit the growth of algae in certain degree; The bacteria strain A lyses the algae by the indirect way, and other three bacteria strains lyses the algae by the direct way; The algicidal ranges of strain A was broadly, other three bacteria strains were narrower; In the algicidal bacteria preservation aspect, algicidal bacteria and the etiolated algae together preserved was easy to maintenance algicidal bacteria activity and preserve much longer. This paper also study the mixed algae-lytic effect of different algicidal bacteria strains to get more efficient mixed strains. The experiment indicated: the lytic effects of mixed strains of A and B1 excelled that of any single strains. At the same time, the lytic effects were consistent in any proportion mixed strain. Through taking count of colony of bacteria indicated: strain A and B1 after the different proportion mixed, the two strains were approached ten to one. The experimental result indicated that: mixed strains of A and B1 have certain stability. In different illumination and temperature, the lytic effects of mixed strains of A and B1 excelled that of any single strains. The bacteria strain A lyses the algae by the indirect way , The bacteria strain B1 lyses the algae by the direct way, but the mixed strains occurred change, since they lyses the algae by the direct way, also secreting certain extracellure substances lyses the algae, and the substances was steady in the temperature.