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In this study, one high-effect algae-lysing bacterium was isolated and purified from Lake Dianchi, which was tabled as the strain DC-L5. The effect, host range, biosafety, lysing mechanism and lysing phenomenon of the algae-lysing bacteria were analyzed. Results were as the followings: The strain was identified as Bacillus pumilus by means of morphological observation and 16S rDNA sequence analysis in the CCTCC (China Center for Type Culture Collection). Toxicity test with mouse primarily showed that the strain was non-toxic. 4 kinds of DC-L5 cultures of different growth phases were added to Microcystis aeruginosa, and the strongest algae-lytic ability was found in the log phase of DC-L5 cultures, Chlorophyll a contents in culture of Microcystis aeraginosa reduced by 83.33% in 5 days. For the host range experiment, 4 kinds of dominant cyanobacteria in Lake Dianchi was researched, and average reduction rates of Chlorophyll a of 62.25% in cultures of Microcystis viridis, Microcystis wesenbergii, Aphanizomenon flos-aquae and Anabaena flos-aquae was observed with the highest 67.6% and the lowest 58.5% in 4 days respectively. After centrifugation and sedimentation, both the cells of bacteria and the cell-free suspension had strong algae-lytic activity, but the bacteria culture had the strongest algae-lytic activity, so it maybe showed the strain DC-L5 could directly cause the cyanobacterial cells agglomerated, sinked down and further lysed while the strain could excrete extra-cellular substances able to lyse cyanobacterial cells. In order to improve the algae-lytic activity of the strain DC-L5 to nature bloom, the bacteria cultures were added to nature cyanobacterial bloom dominant with Microcystis aeruginosa, which were sampled from Lake Dianchi and cultured in the lab. The result of nature bloom experiment showed the strain DC-L5 firstly disaggregated the cyanobacterial colony, reduced the floatability, degraded the pigments and then released inclusions of algal cells. |
