Isolation, Identification And Algae-Removing Characteristics Of An Algicidal Bacterium And A Coagulable Bacterium

More and more lakes are facing the problems of uncontrolled microcystin, while eutrophication aggravates and algal blooms occur frequently. But there still lacks an efficient method to control algal blooms so far. This paper investigated bacterial methods to control algal growth, which could provide a new way to prevent blooms and red tides.So far, there haven't been too many papers about algae-removing bacteria, all the algae-removing bacteria reported were algicidal bacteria. Researches on algicidal bacteria mainly focused on the isolations and identifications of algicidal bacteria and classifications of algicidal substances. There were still few studies on algicidal mechanism, which were all presumed in those papers. In addition, there have been no reports about coagulable bacteria up to now.An algae-lysing bacterium W4 and coagulable bacterium T12 were isolated from a lake in Wuhan and SongHuajiang River separately. The algicidal effect and the way of bacterium W4 lysing Microcystis aeruginosa were discussed in this paper. In addition, the influences of the bacterial and algal growth phase on algicidal effect were also investigated. Bacterium W4 was identified by its physiological-biochemical characteristics. Meanwhile, the coagulation effect and the way of bacterium T12 coagulating Microcystis aeruginosa and also the influences of algal and bacterial growth phase on algal coagulation effect were studied, as well as the algicidal effect of bacterium T12. The bacterium T12 was identified by physiological-biochemical characteristics and Molecular Identification.The results showed that bacterium W4 had an excellent algicidal effect that 99.5% of Microcystis aeruginosa were removed after 8 days and 96.5% of Aphanizomenon flos-aquae were removed after 6 days by adding proper bacterial culture. The bacterium W4 lysed Microcystis aeruginosa indirectly and the active algicidal substances were non-proteins. The algicidal effect was influenced by the algal growth phase rather than the bacterial growth phase. Bacterium W4 was identified as Streptomyces sp. according to its morphological and physiological- biochemical characteristics.The coagulable bacterium T12 had a strong effect to coagulate alga that 92.5% of Microcystis aeruginosa were removed from the main liquid and 99.2% of Aphanizomenon flos-aquae were removed from the main liquid by adding proper bacterial culture after 2 days. Although the bacterium T12 had a good effect to coagulate Microcystis aeruginosa, it had no algicidal effect on Microcystis aeruginosa. The algal growth phase influenced the coagulation effect obviously while the bacterial growth phase faintly. Bacterium T12 was identified as Agribacterium tumefaciens according to its morphological and physiological-biochemical characteristics and 16SrDNA sequence analysis.