Prokaryotic Diversity Of Sediments In Dianchi Lake And Evaluation Denitrification Capacities Of Aerobic Denitrifiers

Lake eutrophication seriously affects not only aquatic ecosystems, while is also a threat to the social economic development and human health. The sediments are the reservoir of nutrients for the water body, playing an important role to the biogeochemical cycles of carbon, nitrogen, phosphorus, potassium, sulfur and other elements in the water, and are important part of the ecosystem of a lake. Sediment microorganisms drive the exchange of nutrients and energy between sediments and water, and they can directly affect the level of water nutrients. Therefore, investigations of community structure, functions and their relationships with abiotic environmental factors, can reveal the basic laws of ecology of microbial communities in lake ecosystems, and have an important role for pollution control to lake ecosystem.The objective of the research was Dianchi, a plateau freshwater lake and eutrophic. The next-generation high-throughput sequencing technologies and bioinformatics were used to study the prokaryote diversity of Dianchi sediments, analyzed the prokaryotes community compositions, structure and phylogeny, and preliminarily discussed the influence of abiotic environmental factors on prokaryotic microorganisms. Moreover, some aerobic denitrifiers were isolated from Dianchi lake sediments by using BTB selective medium and explored the characteristics of screened efficient aerobic denitrifiers. The main results were shown as follows:High-throughput sequencing results indicated there are abundant prokaryotes in Dianchi sediment. Community composition analysis showed that 65,2007 effective tags were obtained from 23 sediments samples of Dianchi. Proteobacteria Euryarchaeota、Nitrospirae、Firmicutes、 Chlorobi、 Chloroflexi、Parvarchaeota、 Crenarchaeota、Acidobacteria、Bacteroidetes and Actinobacteria were the major components of sediment prokaryotic communities. Proteobacteria was the largest phylum, the average relative abundance about 46.40%. In addition, Euryarchaeota was also an important part of prokaryote in Dianchi sediment, which was the most abundant archaea taxa, relative abundance about 16.20%. UPGMA cluster tree showed that there was a significant difference of the prokaryotic communities between Caohai and Waihai. RDA results demonstrated that TOC, NH4+-N and water depth were the main abiotic environmental factors affecting prokaryote community composition in Dianchi sediment.269 strains isolated from fourteen samples in Waihai of Dianchi belonged to three phyla(Proteobacteria、Firmicutes、Bacteroidetes), thirteen families, seventeen genera. Through qualitative and quantitative detection of denitrification ability, YIM DC15 and YIM DC 16, two effective aerobic denitrifiers were screened. Combined with morphological characteristics, physiological and biochemical characteristics, and 16S rRNA gene sequence analysis, it were identified as the genus Pseudomonas and named Pseudomonas brassicacearum subsp.neoaurantiaca YIM DC 15 and Pseudomonas plecoglossicida YIM DC 16.Based on denitrification medium, explored the influence of five factors on strains denitrification capacity, which are carbon sources, C/N, temperature, dissolved oxygen and pH. Results showed that the optimum denitrifying carbon source, temperature, C/N, pH and rotational speed for YIM DC15 was sucrose,30-35℃,12,6.0-7.0,0-50 rpm, and for DC16 was glucose,20℃,15,7.5,100 rpm, respectively. After 48 h,99% of nitrate and 97% of TN can remove with YIM DC15 treated simulated high nitrate wastewater at low C/N, the nitrate and TN degradation rate is 100% and 86% for YIM DC 16.