| Algae blooms caused by eutrophication of water bodies occur frequently in the world,causing serious damage to the aquatic environment.The cyanobacteria blooms almost every year.The harm and pollution caused are immeasurable.Exploring effective algae-killing techniques is imminent.In recent years,the ecological restoration technology based on the interaction of bacteria and algae has attracted much attention due to its low cost and good ecological compatibility,and has broad application prospects.Algicidal bacteria are a general term for bacteria that directly or indirectly inhibit algae growth,or kill algae and dissolve algae cells.Algicidal bacteria can effectively regulate the structure and function of biological populations in aquatic ecosystems and play an important role in maintaining the biomass balance of microalgae.However,indigenous algicidal bacteria have strong adaptability to local environmental and nutritional conditions,and the degradation of aseptic species has no biological invasion compared with exogenous algicidal bacteria.Therefore,the screening of indigenous algicidal bacteria from the outbreak of algal blooms has become a hot spot in the research field of algicidal bacteria.Based on this,this paper isolates a indigenous algicidal bacteria with high-efficiency algae-dissolving activity by using the dominant algae species,Microcystis aeruginosa,in the Taihu Lake Basin.In the mechanism research,the fermentation medium and culture conditions of the strains with potential application potential were optimized by response surface methodology.Through research,the following conclusions were obtained:1.A Gram-positive bacterium with high-efficiency and stable algae-dissolving effect was isolated from the Taihu Lake watershed,and the colony was light yellow,round,regular,smooth and Wet.The V-P test and the gelatin liquefaction test of the strain WS8 were all negative,and the hydrogen peroxide and methyl red tests were positive,and the nitrate was reduced.The 16S rDNA molecule was identified as Bacillus sp.,and the 16S rDNA sequence similarity to Bacillus amyloliquefaciens(GenBank Accession No.KC441776)was 99%.2.Algicidal bacteria WS8 has obvious inhibitory effect on Microcystis aeruginosa.In the various growth stages of Algicidal bacteria WS8,the algae-dissolving effect was the strongest in the stable period,and the algae-dissolving rate was as high as 91.7%in 4 days.The algae-dissolving effect of the bacterial liquid increased with the increase of the dosage ratio,but the dosage was 5 There was no significant difference in the algae-dissolving effect between the%and the treatment group with 10%dosage.The algae-dissolving rate in the 4 days was 91.3%and 93.3%,respectively.The inhibition of the high concentration of the algae was slower than that of the low concentration of water.The inhibitory effect of algae was rapid,but there was no significant difference in the algae-dissolving rate in 4 days,91.5%and 96.4%,respectively.The bacterial solution of algicidal bacteria WS8 had strong adaptability to temperature and pH,and had good engineering application value.At the temperature of 30? and pH 8,the algae rate was the highest,98.1%and 90.8%,respectively.3.Algicidal bacteria WS8 inhibit algae indirectly by secreting extracellular active substances having algae-dissolving properties.The active substance causes the algal cell cycle to be arrested to the pre-DNA replication stage,and thereby causing the algae cells to fail to perform DNA replication and division normally;the active substance oxidative damage to the algae cells,destroying the algae cell antioxidant enzyme system;reducing algal cell photosynthetic electrons Transfer efficiency,which in turn affects its normal photosynthesis.4.In order to develop the algicidal bacteria as a high-efficiency biological algaecide,the culture parameters of the algicidal bacteria WS8 were optimized by shake flask experiment under the condition of laboratory,and the algicidal WS8 was obtained.The optimum medium and culture parameters were:bran 24.00 g/L,soybean meal 10.10 g/L,NaCl 1.00g/L,KH2P04 0.20 g/L,MgS04 0.20 g/L,MnS04 0.03 g/L,pH 7.00,temperature 28.96 0C,shaker speed 150.00 r/min,liquid volume 40%(V/V),inoculum 1%.It was verified by fermentation experiments that the concentration of the bacteria reached 1.11×109 CFU/mL.Compared with the beef paste peptone medium,the bacterial concentration was greatly improved,which could be used to guide the fermentation production of the algae WS8.In summary,it is believed that the indigenous algicidal bacteria in the Taihu Lake Basin obtained in this study have the potential to be developed into biological algaecide,which can provide technical alternatives for local water bloom control. |
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