| Land Desertification refers to the processes of soil degradation in arid, semi-arid and sub-humid, which is a major environmental and ecological security issues. China is one of the countries that the most serious affected by Land desertification harm in the world, which is serious threat to the development of China’s ecological security; economic and social. Drought; high saline-alkali; high UV radiation are the most important survival test of biological in desert habitats faced, in which high UV radiation can cause the organism to form more reactive oxygen species(ROS), will damage the cells’ DNA and RNA, eventually leading to damage even death of the biological cell, whichis extremely unfavorable for organism’s survival. Microcoleus vaginatus Gom. is a filamentous cyanobacterium that belongs to Oscillatoriales, Microcoleus, which is one of the dominant species of biological crusts in desert habitat. The alga gets a strong ability to resist UV radiation in the long process evolution, and this ability is closely related to its extracellular polysaccharide. The recent research mainly in that the role of the algae played in the process of desertification control and its mechanism, etc. The research on biological activity of its extracellular polysaccharide is also fewer, especially that the research on its resist ultraviolet radiation activity.Polysaccharide is the third category of natural macromolecules in addition to the nucleic acid and protein, mainly in form of glycoproteins, glycolipids and proteoglycans, which is an important part of most living organisms. Polysaccharide, as a new antioxidant, has variety of biological effects including anti-radiation; anti-cancer; anti-viral; anti-oxidation; anti-aging and promote organism immunity.The paper studies the protective effect of extracellular polysaccharide from Microcoleus vaginatus Gom. to E.coli by UV radiation. The first experiment of the paper is to recovery cultivate Microcoleus vaginatus Gom. and expand it, then extracting and purifying extracellular polysaccharide, making extracellular polysaccharide solution of Microcoleus vaginatus Gom. Secondly, adding different concentrations of extracellular polysaccharide solution into E.coli bacterial suspension to be mixed bacterial suspension, computing UVsurvival rate of E.coli as well anti-ultraviolet radiation rate of polysaccharide by cultivation and counting, to study the enhancement effect of Extracellular polysaccharide to the ability of E.coli anti-ultraviolet radiation under different UV intensity. The results show that: the UV survival rate of E. coli under 20 W UV light irradiation conditions is lower than the 15W’s. The anti-ultraviolet radiation rate under the condition of 20 W UV lamp irradiation for 40 s is 41%of the polysaccharide solution of 400mg/L, which is 1.71 times and 1.47 times more the polysaccharide solution anti-radiation rate than 200mg/L and 800mg/L; the anti-ultraviolet radiation rate under the condition of 15 W UV lamp irradiation for 40 s is 29%of the polysaccharide solution of400mg/L, which is 1.38 times and 1.32 times than the polysaccharide solution anti-radiation rate of 200mg/L and 800mg/L. The experimental results show that the extracellular polysaccharide from Microcoleus vaginatus Gom. can enhance the ability of E.coli anti-UV radiation, and the radiation resistance of 400mg/L polysaccharide solution is better than others. Polysaccharides can clear excessive free radicals due to ultraviolet radiation, reduce cell damage and enhance cellular immunity, as well as help cells against damage caused by UV radiation. The results of this experiment can provide material and the basic data for future research on biologically active of polysaccharides anti-UV radiation, and to promote the research on Microcoleus vaginatus Gom. and other dominant cyanobacteria in desert, further promote desertification control. |
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