水华铜绿微囊藻影响细菌溶藻效应的机制研究

The application of algicidal bacteria to control cyanobacterial bloom is a potential and environmentally friendly method. A large number of researches have been carried out to make the inhibition mechanism of algicidal bacterium on cyanobacteria clear. However, the phenomenon that cyanobacterial bloom influences low-density algicidal bacteria and thus interferes its algae-lysing effect is present. The mechanism is not yet clear, which leaves unknown interference potential for algicidal bacteria application in the future. To solve this problem, this project was presented from the perspective of ecological niche and algal life cycle with full consideration of population characteristics of the dominant cyanobacteria-Microcystis aeruginosa. The coupling response of algicidal bacteria distribution to the gradient changes of the water microenvironment mediated by groups of Microcystis aeruginosa would be explored. The effects of physiological and biochemical characteristics of Microcystis aeruginosa in different growth cycles on the proliferation of algicidal bacteria would be also probed into. In stress to the growth of algicidal bacteria below the density threshold, the differential response characteristics of the transcriptional expression of cyanobacterial gene pathways would be further delved. The results of the research would help us to get the mechanism of the algicidal effect interfered by Microcystis aeruginosa, and grasp the inflection point of bacteria reaching the algicidal density threshold. Combined with existing researches, a better understanding of the interrelationship between Cyanobacteria and algicidal bacteria would be got. It will have important environmental, physiological and ecological significance and provides a scientific basis for the rational application of algicidal bacteria.

应用溶藻细菌控制蓝藻水华是一种很有发展潜力和环境友好的方法。已开展的大量研究，使溶藻细菌对水华蓝藻抑制的机理已经明确。但水华蓝藻反过来对低密度溶藻细菌影响、进而对溶藻效应干扰的现象现实存在，而机制还不明确，这为溶藻细菌未来的应用留下了未知的干扰隐患。针对这个问题，本研究结合水华优势蓝藻——铜绿微囊藻的群体特性，从生态位和生命周期的角度，研究群体铜绿微囊藻介导的水体微环境的梯度变化与溶藻细菌数量和分布的耦合响应关系；不同生长周期铜绿微囊藻的生理、生化特性对溶藻细菌增殖的影响规律；在对低于密度阈值的溶藻细菌生长干扰时，群体铜绿微囊藻基因通路转录表达的差异响应特征。研究的成果将有助于我们获得水华铜绿微囊藻影响细菌溶藻效应的机制，把握溶藻细菌达到溶藻密度阈值的拐点时机，结合已有的研究，更好的理解水华蓝藻与溶藻细菌的相互关系，具有重要的环境与生理生态学意义，为溶藻细菌的合理应用提供一定的科学依据。

应用溶藻细菌控制蓝藻水华是一种很有发展潜力和环境友好的方法。已开展的大量研究，使溶藻细菌对水华蓝藻抑制的机理已经明确。但水华蓝藻反过来对低密度溶藻细菌影响、进而对溶藻效应干扰的现象现实存在，而机制还不明确，这为溶藻细菌未来的应用留下了未知的干扰隐患。针对这个问题，本研究结合水华优势蓝藻——铜绿微囊藻的群体特性，研究群体铜绿微囊藻介导的水体微环境的梯度变化与溶藻细菌数量和分布的耦合响应关系；不同生长周期铜绿微囊藻的生理、生化特性对溶藻细菌增殖的影响规律；在对低于密度阈值的溶藻细菌生长干扰时，群体铜绿微囊藻基因通路转录表达的差异响应特征。研究结果表明：群体态铜绿微囊藻在水体中的分布呈现垂向分层的特点，导致水体DO、DOC也出现上高下底的垂向分层现象。溶藻细菌受碳源的驱动，也呈现垂向分层的变化。在水体上层，溶藻细菌未能突破溶藻的密度阈值，反而促进了群体态铜绿微囊藻密度的上升。中层和下层水体中，藻细胞数显著下降，有利于溶藻细菌突破溶藻的密度阈值，促进藻细胞数的进一步下降。对于不同数量的蓝藻，细菌起溶藻作用时的菌藻比例也并不是固定的。溶藻细菌达到溶藻密度阈值的拐点可能受其分泌的溶藻物质的浓度影响，而细菌的数量与分泌的溶藻物质可能并不成正比。相较于对数生长早、后期蓝藻，生长平稳期的蓝藻可以显著提升溶藻细菌的生长，提高溶藻细菌的碳代谢途径的关键酶活，并且显著降低对溶藻细菌的氧化损伤水平。低密度溶藻细菌尚不足以引发对数生长早期的蓝藻细胞的程序死亡，但激发了对数生长早期蓝藻细胞的免疫防御，增加了某些次生代谢物的合成和某些物质的跨膜运输，抑制溶藻细菌的生长。而低密度溶藻细菌与平稳期蓝藻细胞共培养后，能够快速扩增群体，抑制生长平稳期的蓝藻细胞的生长，减少次生代谢物的合成，促进其进一步衰退。研究结果将有助于更好的理解水华蓝藻与溶藻细菌的相互关系，为溶藻细菌的合理应用提供一定的科学依据。