Isolation, Identification And Application Of A Strain Of Denitrifying Bacterium Pseudomonas Mendocina

Water is the most critical resource of human production and life. With the content of nitrogen in water increasing, the water eutrophication is enhanced. The increasing of nitrogen content is a serious problem to be solved.The nitrate is reduced into N2by denitrification and released into the air, which is the final process of nitrogen cycle.The physiological and biochemical character of the denitrifying bacteria and the effects on Microcystis aeruginosa were investigated in this study. The main contents are as follows:(1) Denitrifying bacterium was isolated from Xinyang city of Henan Province. The results by Gram staining and aerobic type analysis suggested that the bacteria was facultative anaerobic G" bacteria, and the analysis to16S rDNA sequence showed that the bacteria was Pseudomonas mendocina. The optimum growth temperature, pH and the optimum denitrification temperature were also studied. The results showed that Pseudomonas mendocina has an optimum pH of6～8and an optimum of28℃～31℃.(2) Denitrification efficiency in the treatment of nitrate wastewater was studied. The role of bacteria in wastewater treatment was identified by measuring the changes of NO3--N and COD concentrations in water. The results showed that the denitrifying bacteria had an significant effect on the nitrate w astewater, which provided a theoretical basis for water denitrification.(3) Microcystis aeruginosa was isolated from eutrophication pond in Xinyang city of Henan Province by enrichment, separation and purification of the bacteria. In experimental conditions, different concentrations of Pseudomonas mendocina were added into the culture medium of Microcystis aeruginosa and the biomass of Pseudomonas mendocina and Microcystis aeruginosa in the system of co-culture were measured. At the same time, we also studied the changes of microcystin photosynthetic system and antioxidant system affects by Pseudomonas mendocina through surveying the changes of the concentrations of Chlorophyll a, Fv/Fm values, the rate of photosynthetic oxygen evolution, CAT activity, POD activity, SOD activity. The concentrations of Chlorophyll a, Fv/Fm value and the rate of photosynthetic oxygen evolution reduced significantly; the CAT activity, POD activity, SOD activity increased significantly in the beginning of the experiment, but they remained at a downward trend as the time passed. Moreover, the highest concentration of denitrifying bacteria caused the strongest destruction of the Microcystin photosynthetic system and antioxidant system. In the end, a large number of algal cells split and died, the results suggested that denitrifying bacteria had an obvious effect of inhibition on Microcystis aeruginosa cells.The metabolization process of the denitrifying bacterium was studied, which provided a theoretical reference for the removal of the sewage from chemical plant and control of water blooms where Microcystis is the dominant algal group.