Basic Study On Microorganism Community Structure In Constructed Wetlands

Many experiments proved that the constructed wetlands are effective in degradation of pollutants, particularly nitrogen treatment. Microorganisms played very important role in constructed wetlands. The species and quantity of the microorganism in the constructed wetland are extremely abundant, which offered enough decomposer for sewage disposal system of constructed wetland. Mengqing park bulrush wetland located beside the downstream Suzhou Creek, Shanghai, China was studied in this research. Under hydraulic loading of 60-70 cm/d, the mean removal rate of ammonia, BOD and SS could reach to about 30 %, 50% and 60% respectively in wetland. To elucidate the roles of microorganisms on pollutants degradation in bulrush wetland, molecular methods, such as ERIC-PCR, PCR-SSCP and PCR-DGGE were used to explore the microbial communities strucutrue and funcational microbacteria(ammonia-oxidizing bacteria). The conclusions were drawn as follows:1, Among DNA extracted methods, it is found that using the method combined ultrasonication, SDS, phenol with Proteinase K to lyses cells could successfully extract DNA from sediments. Moreover, the fragments of DNA could be decreased effectively by controlling ultrasonic frequency and using shaking with intermission. The purification methods all cause DNA losing. However, low melting temperature agrose was better than others.2, The ERIC-PCR fingerprints of exogenous microorganism were legibility and good reproducibility, which showed that the exogenous microorganism products were changeless. Meanwhile, we compared the fingerprints of the addition to the pure culture and DNA extracted directly from the microorganism products and found that they were quite different. The reason was that the bacteria cultivated were limited.3, Many factors, such as the gel-concentration, the dilution of the PCR products, the sample quantity of the PCR products, the electrophoresis temperature, voltage etc, can influence the results of SSCP. The optimal conditions were as followed : the gel-concentration is 10 %( acrylamide-bisacrylamide[49:1], 5% urea, no glycerol), the dilution of the PCR products is 1 : 4(total vol. 20 μl), the sample quantity of the PCR products applied in electrophoresis is 4 μl , during electrophoresis, the voltage is 150V, with constant temperature.