Screening And Low-nutrient Characteristics Of The Oligotrophic Bacteria On Water Purification

Three sections about the oligotrophic bacteria included in this research: isolation, screening on water purification and the characteristics of low-nutrient conditions. The main results were as follows:1. Thirty-eight facultative oligotrophic bacteria were isolated from different environment with low-nutrient medium, and their 16S rDNA sequences were analyzed. All of the strains belonged to eighteen genera, most of which were closely related to genera Acinetobacter (23. 68%), Porphyrobacter (18. 42%), Brevibacterium (10. 53%) and Bacillus (7. 89%). Among them, Acinetobacter almost existed in the water samples from nature, and Porphyrobacter were in the ascendant quantitatively from the soil.2. Among thirty-eight oligotrophic bacteria, a strain Y11 was screened because of its efficient purification on micro-polluted water. Treating with Y11, the COD_Mn and TOC of the treated water reduced 48. 01% and 46. 83% respectively, and the water became much clearer compared with the blank control. Y11 was identified to be Bacillus pumilus after biochemical characteristics' experiments. Brevibacterium 31 was the secondly efficient strain on micro-polluted water. Because of its spores, Bacillus pumilus Y11 had more advantage in application on a large scale.3. The study about low-nutrient characteristics of Y11 and 31 were carried through. The results showed that the oligotrophic bacteria had high tolerances for starvation, and remained viable after long time compared with the eutrophic bacteria. Furthermore, the oligotrophic bacteria utilized more substances including several poisonous and hurtful pollutants. The researches also found that the phosphate played an important role in the growth of the oligotrophic bacteria on low-nutrient medium. Besides, the charges of resistance appeared after long-term cultivation as well as on low-nutrient medium.