海洋硅藻胞外多聚物研究

Extracellular Polymeric Substances (EPSs) of diatoms are mucilaginous substances secreted eternal to the plasmalemma by diatom cells during their growth period. These mucilaginous EPSs encompass a wide variety of morphological forms and complex compositions, which is a crucial part of their biological success. Recently, studies of EPSs are caused more and more attention with the development of marine science and the implement of large projects, such as LOICZ，JGOFS etc. Many researches have proved that EPSs play important roles in aquatic carbon cylces, energy flow in aquatic food webs, aglag-bacterial interactions, and the nutritional roles of EPS in creating a "microenvironment' around the diatom cell. Moreover, EPS is also an important filed of biofouling studies, which plays essential roles in adhesion process of diatoms, formation of biological membrane, vertical structure and stability of the habitat.This study was focused on EPSs and investigated 1). the influences of environmental factors, such as nutrients and light/dark cylce on extracellular polysaccharid in planktonic diatoms; 2). morphology, fine structure and biochemical compositions of EPSs of diatoms; 3). the progress and mechanism of EPS secretion using A. javanica as the model species,and the influence of the herbicides on adherison and production of EPSs, discussed the formation process of algal membrane of A. javanica and variation of nutrients, and got many valuable results. Significant results include:a) Influences of light-dark cycle on production of extracellar Polysaccharide in three marine planktonic diatom speciesThe results showed that the influences of light-dark cycle on production of extracellular polysaccharide were species specific, and dependent on the growth phase. The extracellular polysaccharide contents of T. reticulum and P. triconutum was higher under long light cycle (L/D, 16/8h), however the highest content was found at the exponential phase in T. reticulumn and at the late growth phase in P. triconutum. The content of extracellular olysaccharide in Skeletonema spp was higher under longer dark cycle (L/D, 8/16h) and peaked at the late growth phase. Among the three species, the production of extracellular polysaccharide (mg/106cells) was the highest in T. reticulumn, upto 103-104mg/106cells, while the production of P. triconutum and Skeletonema spp was very low. Light-dark cycle might affect the total amount of light absorption, cell division pattern and synthesis of organic materials, which inversely influenced the extracellular polysaccharide production of algal cells.b) Process and mechanism of adhesion The adhesion process of A. javanica was divided into four phases, froamtion of single cell and reorientation of cells (4-5 hours after inoculation), .formation of pad (6-8 hours), formation of shaft (8-10 hours) and cell division phase (10-12 hours)。In the process of shaft formation, chloroplast varied significantly, and active vesicle movements were observed in cells, which might involve in secretion of EPS..c) Chemical composition and physiological-chemical characteristics of EPS The majority componet of EPSs is polysacchride, upto 80% of total EPS with a little amount of protein, about 10% of total EPS, no lipid was found.EPS of A. javanica composed of eight onosaccharides, among of them, Gal and Fuc were two main components, upto 60% of total EPS. The results from fluorescent marker indicated that the whole shaft contained Fuc, pad and collor of shaft contained b-Glycan, and pad and core of shaft contained anionic carbohydrates. The IR analysis indicated the presence of sulfate ester.. This project is the first study on EPSs of diatoms in China, which will not only push forward the development of oceanographic ecology, phycology and biofouling biology of our country, and also provide usful information for other related studies in EPSs of diatoms.

海洋硅藻胞外多聚物形态、超微结构、化学组成及分子量大小，胞外多聚物合成机制、分泌机理，环境因子对硅藻分泌胞外多聚物的影响胞外多聚物对海区溶解有机碳贡献及其在硅藻附着过程中的作用，硅藻附着机制，阐明胞外多聚物的生物学功能及其在生态系统中的作用将对海洋生态学和污损生物学业的发展具有重要学术意义并为污损硅藻防治提供科学依据。