Selection Of Efficient Algicidal Bacterium And Mechanism Research Of Lytic Effect

In order to control the harmful algal species in bioremediation of eutrophication water bodies, four strain of efficient algicidal bacterium G3, B2, P1 and P2 were isolated from eutrophication water. On the basis of morphology analysis and its physiological characteristics, it may be identified as Aeromonas,Cellulomonas,Micrococcus Cohn and Flavobacterium Bergey. Taking type blue algal species such as Microcystis aeruginosa, Aphanizomeno flas-aquaae and green algal species such as Scenedesmaceae as examples, the algicidal effect and mechanism of four bacterium were studied, furthermore, the universality of algicidal effect of four bacteria was investigated by test in practical eutrophic lake water.The results showed that during logarithmic phase, the bacteria (G3, B2 and P1) which mainly lysed the algal cell by direct contact had the best algicidal effect. Bacterium P2 lysed the algal cell by indirect contact, and released a special dissolved lytic agent(s). During stationary phase and decline phase of P2, no matter adding liquid of bacterium or supernatant, algicidal effect was great.The algicidal effect was influenced by bacterial cell density and algal cell density. The greater the initial bacterial cell density, the greater the alage–lysing effect within certain alage cell density range; the greater the initial algal cell density, the worse the alage–lysing effect. When the bacterial cell density and algal cell density increase simultaneously, it has a stable algicidal effect. Under illumination of natural light and outdoor condition, chlorophyll-a removal efficiency reached 96.74% within 6 days when volume ratio of liquid of bacterium G3 to practical eutrophic lake water was 1%. On the fourth day, the removal of chlorophyll-a highest value was up to 83.1% (volume ratio of liquid of bacterium B2 to practical eutrophic lake water was 2.5%), the mortality of alga reached 77.6%. On the second day, the removal of chlorophyll-a highest value is up to 89.3% (volume ratio of liquid of bacterium P1 to practical eutrophic lake water was 2.5%), the mortality of alga reached 61.4%. On the eighth day, when volume ratio of liquid of bacterium P2 to practical eutrophic lake water was 2.5%, nearly 90% of chlorophyll-a was removed. The mortality of alga was highest, reached 81.6%.The microalgae community structure of eutrophic lake had changed after add the efficient algicidal bacterium, for example, the algae species and the total Shannon's Information index decreased. Therefore, four bacteria have algicidal ability on the multitudinous algal species in eutrophication water and have potential application in bioremediation of eutrophication water body.