| Red Tide is one of the serious ecological marine disasters. Its prevention and control research has been wide concern. Now more attemions have focused on the issue that algae-lysing bacteria act as a possible factor to mitigate the adverse effects of HABs.Especially the found of algicidal substances provides new methods and ideas for the red tide control. As a result, it has more application value and is also the focus of the current study and the difficulty to break. 4 marine algicidal bacterialstrains against Skeletonema costatumand isolated from a HABs area of Mirs Bay, but only one marine bacterial strain named HSQAY1 could produce algicidal substances. In this study, more research were couducted on the strain HSQAY1.We studied the bacterial growth phase; the effects on algicidal activity by salt concentration and p H. The environmental stability and physicochemical properties of algicidal substances in the supernatants were also investigated. The objective of this study is to find a safe and feasible biological method to control HABs. The results were as follows:1. The growth curve of algicidal bacteria HSQAY1 were determined by plate colony method, the results show that 0-8 h is a slow period, 8-40 h as the logarithmic phase, 40-72 h entered a stable period, after 72 h into the decline phase. The strain HSQAY1 gave effectively on S. costatumand by means of extracellular products,which were secreted from the logarithmic phase and reached the peak value at the stable period.The extracellular products made the removal of to 80.4% after 12 hours and then the algicidal rate remained stable at between 80.4% and 93.4%.2. Medium environment of different p H had effects on the amount of algicidal substances and algicidal effect of algicidal bacteria HSQAY1. The algae lysing of sterile filtrate increased along with the medium environment p H. The algicidal rate were 20.62%, 46.10%, 61.14%, 62.99%, 74.41% when the p H were 5.5, 6.5, 7.5, 8.5 and 9.5. Alkaline environment were more conducive to bacterial synthesis or producing algicidal substances than weakly acidic environment. Changes of salinity in bacterial culture environment had effects on the amount of algicidal substances and algicidal effect of algicidal bacteria HSQAY1. The algicidal rate were 53.03%, 88.13%, 87.94%, 41.91% and 17.25% when the salinities were 20, 25, 30, 35 and 40. It was more conducive to bacterial producting algicidal substances when the range of salinity(25~30). But high salinity(salinity 40) could inhibit the production of algicidal substances.3. The results showed that although the algicidal substance lost algicidal activity under acid treatment(p H=3), it still kept stable under wide range of p H(5~11) and temperature(30~110 ℃) withand 71.7%~94.5%, respectively. In addition, it’s activity was also stable under repeated freeze-thaw cycles treatment(-20 ℃).4. The algicidal substance can be precipitated in ethanol. Ethanol precipitation phase of the algae lysing rate as high as 65.6%, while the ethanol extraction phase algicidal activity. The algicidal substance can be also precipitated in ammonium sulfate, and was proteinaceous, which were greater than 10 k Da in molecular weight. Algicidal substances were separated out in ammonium sulfate saturation between 60%-80%.5. The crude algicidal protein extract showed three protein bands in SDS-PAGE corresponding to a range of molecular weight 15 ~ 40 k Da. HPLC analysis indicated that the sample group appeared 3 obvious peaks, which were different from the control group. |
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