微囊藻群体形成和群体表型转变的过程和机制对于揭示水华发生的机理起到重要的作用。目前对于微囊藻群体形成的研究主要用铜绿微囊藻单个藻种进行，且室内诱导形成的群体大都为絮团状，没有表现出铜绿微囊藻所具有的典型群体形态。本研究以申请人所在团队发现的胞外多糖溶解诱导微囊藻群体表型转变这一现象为基础，以多糖的组分和结构为切入点，一方面要明确生物及非生物因素对不同藻种群体形成的影响，通过改变培养条件，诱导微囊藻形成典型的群体形态，并进一步观察典型群体形态变化过程和相应的胞外多糖的变化；另一方面比对单细胞及不同群体表型及群体表型变化前后微囊藻胞外多糖的组成，并据此研究群体形态转变的影响因素。通过本项目的研究最终回答下列三个问题：(1) 微囊藻群体和单细胞多糖结构、组分的特征及不同种微囊藻种间有何异同？(2) 多糖结构、组分与群体形成之间的关系如何？(3) 多糖结构、组分对微囊藻表型变化的影响如何？

The processes and mechanisms of colony formation and morphological changes are important to understand the mechanisms of Microcystis blooms formation. Only one species (Microcystis aeruginosa) was used in most previous studies and the colonial morphology of Microcystis induced in laboratory differed significantly from the morphology of M. aeruginosa colony under natural condition. Based on the phenomenon that solubilisation of mucilage induces changes in Microcystis colonial morphology, the composition and structure of extracellular polysaccharide (EPS) will be focused on in this study. The aim of this study is 1) To analyze the morphological responses of different Microcystis species to different environmental factors and to induce flocculent colonies change to the inherent morphology of the special species. The composition and structure of EPS will be also analyzed to explain these processes. 2) To compare the composition and structure of EPS of colonial and unicellular Microcystis and get insight into the influencing factors. This study will answer following questions: 1) What are the differences in the composition and structure of EPS between colonial and unicellular Microcystis? 2) What is the relationship between colony formation of Microcystis and the composition and structure of EPS? 3) How do the composition and structure of EPS influence changes in Microcystis colonial morphology?