| Because microorganisms can live in all kinds of extreme environment and the barren habitat with the widespread ecological adaptability, they have close link with the life, the survival and the development of the humanity, yet the ways to the humanity activities also have influence on desertification. So there are close relationship between microorganisms and desertification. The thermophilic, psychrophilic, acidophilic, haloalkalophilic, and oligotrophic bacteria are possessed of the stable special functions and genes through the long-term natural selection to adapt the adverse circumstances. Therefore the species resources and molecular biology of those bacterial strains have been extensively researched in domestic and abroad, and more and more importance has been attached to them. By looking up the quantity and the newest literatures, the findings indicate that at present the oligotrophic bacteria have mainly been conducted the research from the aquatic environment, but the study of the oligotrophic bacteria, which growth for C-source need is only 1% of the normal strains, in the arid desert area has not been done much in the national and international publications.In this paper, five bacteria with obvious oligotrophic characteristics had been isolated from Gobi, Flaming Mountain, Aydingkol Lake, Gurbantonggut Desert, etc. in Xinjiang, and a series of the physical and biochemical characteristic research to them had been conducted. Among them one isolated with capsule not only grew better under the conditions of low C-source and without N-source but also secreted massive adhesive during the growing process. The electron microscopic observation and indoor sand fixation experiment also showed that it could form the microbial crust (2-8mm) in the drift sand surface after this oligotrophic bacterium was inoculated on the surface of sand and incubated for a period of time. The microbial crust's formation resulted in the obvious distinction of the sandy soil in terms of physical, chemical, and biological characteristics, which were quite different from loose sandy soil. And it had the stronger anti-wind erosion function and the important ecological and geographical effects, also important foundation of vegetation succession in the arid desert area. Hence, the experiment had undertaken the study on the individual morphology, the main physical and biochemical characteristics about the isolated oligotrophic bacterium, which was preliminarily identified as a member of Azotobacter Beijerinck.At the same time, this paper had ascertained the relationship between the main factors such as strain, growth, nutrition demand, and the yield and viscosity of extracellular polysaccharide (EPS) by carrying on the experiment of single factor optimized culture medium (C-source, inorganic salts, etc.); the experiment of optimized conditions for shaking culture (temperature, time, the initial pH, dissolve oxygen); the experiment of the chemical composition about the adhesive; preparing the oligotrophic bacterial reagent for sand treatment. The indoor and outdoor experiments showed that the reagent had the function of sand fixation and improvement of water retention and seedling survival.The desertification not only worsens the regional ecological environment but also simultaneously brings the potential risks for other environmental issue. Therefore, it is high time that increased the investment that controls desertification. Owing to what the oligotrophic microorganisms need C-source only is 1% of normal microorganisms, it can greatly reduce the cost if the oligotrophic microorganisms are... |
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