Isolation And Identification Of Three Algae-Lysing Bacteria And Their Lytic Effects On Blue-Green Algae

In recent years, eutrophication of freshwater and occurrence of harmful algal blooms have affected the ecological balance of environment seriously and also did harm to human health. At present, in order to control cyanobacterial blooms, techniques such as physical method, chemical method and biological method have been put forward. The physical method to control cyanobacterial blooms needs high-energy inputs and chemical method can cause secondary pollution to the water environment. Whereas, the biological method is efficient and environmental friendly. Therefore, through various and comprehensive consideration, biological method is more ideal and biological control methods show great potential. In this study, Microcystis aeruginosa, as the common algae during harmful algae blooms was regarded as the research object. Three strains of algae-lysing bacteria were isolated from different water bodies. The algae-lysing mechanisms were discussed initially and the bacterium strains were identified by the sequence analysis of16S rDNA. The main contents and achievements of this study are as follows.At first, the algae-lysing bacteria were isolated respectively from lakes in algae blooms, activated sludge aeclimated by Microcystis aeruginosa and yellowish Microcytis aeruginosa. Among these algae-lysing bacterias, the three strains numbered WM4, WM5and FS1had good algae-lysing effects and were studied in detail. The three strains were identified by the sequence analysis of16S rDNA. Using the BLAST analysis and followed by comparison of sequences in the GenBank nucleotide database. The sequence is available in GenBank under the Accession number of WM4, WM5and FS1are KC523391, KC523392and KC523393. The Phylogenetic tree of sequences was made by the MEGA5.2program. The phylogenetic tree showed that the three strains were closely related to Bacillus sp.Second, the algicidal effect and algicidal mode of three strains algae-lysing baeteria on Microcystis aeruginosa were studied. The results showed that the phytoplankton-lytic activity of WM4, WM5and FS1are64.1%,45.7%and54.8%respectively after four days. And WM4, WM5and FS1all removed algae by secreting extracelluar matter.At last, the influence of bacterial growth phases, temperature, illumination, and pH on algae-lysing effects was studied. The results showed that the bacterial culture in stationary phase and decline phase have the higher algicidal activity than the bacterial culture in lag phase and exponential phase. The best temperature for three strains of algae-lysing baeteria on Microcystis aeruginosa was30℃. The results of illumination showed the algae-lysing effects in darkness were better than in illumination. And the best algae-lysing effects of three strains occured when pH value was10. In addition, the phytoplankton-lytic activity of three strains showed a downward trend with the increasing of generation.