Isolation And Identification Of Photosynthetic Bacteria From Nansi Lake And Preliminary Study On Water Purification

Nansihu Lake is the largest freshwater lake in Shandong Province, it plays an important role in economic development and utilization of water resources. But in recent years, because of the high-speed economic development in the region surrounding and human factors, the wetlands ecosystem has been seriously damaged and the lake is becoming eutrophic. PSB has a special physiological and biochemical property which is able to degrade pollutants in water. Therefore we can screen out a variety of PSB which have water purification functions to improve the current situation.This thesis separates 22 photosynthetic bacteria from Nansihu Lake sediment, we select GH-5 and GH-12 as the research object which have typical characteristics. We identify them separately, optimize the culture conditions and improve the media formulations. In the end, we attempt to treat the degradation in the aquaculture wastewater with regard to TN, TP and COD.By morphological identification, physiological and biochemical identification and molecular identification, we can confirm that GH-5 belongs to Rhodobacter capsulatus and GH-12 belongs to Rhodobacter sphaeroides.Considering the culture conditions of GH-5 and GH-12, the optimum culture conditions of GH-5 are obtained as follows: inoculation is 5%, culture temperature is25℃, the initial pH is 7.0; the optimum culture conditions of GH-12 are obtained as follows: inoculation is 5%, culture temperature is 30℃, the initial pH is 8.0. Through the improvement of ATYP medium, the optimal medium compositions of GH-5 are obtained as follows: the content of NaHCO3 is 2000mg/L, the content of yeast extract is 1000mg/L, the content of CH3 COONa is 1000mg/L; the optimal medium compositions of GH-12 are obtained as follows: the content of NaHCO3 is1500mg/L, the content of yeast extract is 1000mg/L, the content of CH3 COONa is2000mg/L.GH-5 and GH-12 are both able to purify aquiculture water. The best degradation conditions of GH-5 are obtained as follows: light and microoxygen, treatment temperature is 25℃, added amount of the strain is 2mg/L, the treatment efficiency of TN、TP and COD respectively are 66.8%、58.1%、62.7%; the best degradation conditions of GH-12 are obtained as follows: light and microoxygen, treatmenttemperature is 30℃, added amount of the strain is 5mg/L, the treatment efficiency of TN、TP and COD are 62.1%、59.2%、60.7% respectively. The degradation of mixed strains is better than the single strain, when adding amount of the strain between GH-5 and GH-12 is 2:1, the treatment efficiency of TN 、 TP and COD respectively are 68.2%、58.8%、64.3% respectively.These results indicate that the photosynthetic bacteria screened from the Nansihu Lake sediment have water purification functions, which provide theoretical data for microbial diversity and ecological environment of Nansihu Lake.