Research On Ecological Characteristics And The Retrieve Of Emerging Pathogenic Bacteria In Urban Water Body

The pathogenic microorganism in the urban water body, which is a latent risk of biological pollution and harmful to public health, has aroused the widespread attention. However, little is known about the pathogenic microorganism in the urban water body. In this thesis, the microorganism population structural feature in the water body was investigated by constructing bacterium's 16S rRNA gene library, and then the massive pathogenic microorganism was discovered. So the pathogenic microorganism's ecological characteristics were studied, including the population structure, space-time distribution characteristic and community's biodiversity of the pathogenic microorganism. Then the origin of the dominant microflora in the water body was explored and the effect had been appraised in removing the pathogenic microorganisms by the existing sewage treatment process. All the research provided the essential data for control the pathogenic microorganism pollution in the urban water body and also indicated the direction for the source control Arcobacter. The research mainly obtained the following conclusion:(1)The 16S rDNA gene bank was constructed by extracting the total bacterial DNA in the water body and amplifying 16S rRNA gene fragment using PCR. The sequence alignment was carried on after cloning and sequencing, and then bacterium population structure was analyzed. The bacterium in Neijiang water body belongs to 9 bacterium class groups. The 16S rDNA gene bank constructed by molecular biology method fully manifests the bacterium population's multiplicity of the water body. The Neijiang water body had many kinds of pathogenic microorganisms outside the water quality biological monitor index, in which Proteobacteria was the main bacterium class group and Arcobacter was the superiority bacteria colony. Arcobacter was presumably from the urban sewage.(2)According to the result by the molecular and biological method, the main pathogenic bacteria in Neijiang water body were isolated and identified by traditional bacteria isolation and identification method, specific and selective medium method and morphological and biochemical method. The isolated strains were identified as Alcaligenes faecalis, Providencia stuartii, Aeromonas hydrophila,Aeromonas salmonicida , Acinetobacter junii,Acinetobacter rhizosphaera, and so on. The activity of pathogenic Arcobacter spp. was detected through PCR amplification technique using species-specific primers, which amplify the most variable areas of 23S rRNA gene. The result proved that pathogenic Arcobacter spp. in the water had the potential proliferative ability.(3) The diversity estimators S_ACE and S_Chaol were carried on computation for the progressive construction of 16S rDNA gene bank of the microorganisms in Neijiang water body. The best library size for analyzing bacterial diversity could been achieved when one of both index reached stable or both simultaneously. The research result showed that the species richness estimators reached the maximum when the number of clones sequenced in bacterial 16S rDNA library of Neijiang water body was about 100.(4)The characteristics of bacterial space-time distribution of main pathogenic microorganisms from Neijiang water body were studied by population structure analysis method constructed in the study. The result showed that that the bacterium gross structure didn't have the obvious difference in the region Proteobacteria was the main class group and pathogenic Arcobacter was the the dominant bacteria colony in which Arcobacter cryaerophilus held the high proportion. The type and proportion of the main pathogenic bacteria at different position were related with the orientation and the distance between the urban sewage overflow site and other monitoring sites. The result indicated that the main pathogenic microorganisms probably originated from the urban sewage.(5) Through the analysis of bacterial space-time distribution characteristics and bioinformatics of the main pathogenic bacteria, it proved that the characteristic of the microorganism population structure in Neijiang water body was the same as that of in the effluent from the wastewater treatment plant. The dominant genus Arcobacter in Neijiang water body came from the hospital sewage and the resident sanitary sewage. Trichococcus pasteuri mainly came from the hospital sewage. Clostridium spp.mainly came from the food market sewage and the hospital sewage. Other pathogenic microorganisms in the Neijiang water body was not obviously related with the sewage from different places.(6) The microorganisms in the influent of wastewater treatment plant and the effluents from treatment process I and II were investigated by molecular and biological methods and bioinformatics methods. The analysis results showed that there were no significant difference of the community structure of total bacterial population between the influents and the effluents, but partial main microorganisms were removed by treatment process I, and the effect of the treatment process to control the dominant genera Arcobacter cryaerophilus was related to the water temperature. It is guessed that partial bacteria are removed by an adsorption precipitation process in the treatment method. And in treatment process II some other bacterial species decreased except the dominant genus Arcobacter cryaerophilus by ultraviolet irradiation, which meaned Arcobacter cryaerophilus was not sensitive with ultraviolet irradiation.