Research On Community And Abundance Of Ammonia-oxidizing Microorganisms In Sediment Of Biliuhe Reservoir

Ammonia oxidation microorganisms, mainly including ammonia oxidizing bacteria and ammonia oxidizing archaea, play a key role in the process of ammonia oxidation. Meanwhile ammonia oxidation process is the limiting step in the process of nitrification. So to study the diversity and abundance of ammonia oxidation microorganisms has a crucial role in understanding the ability of nitrogen metabolism and ecological stability, and it is also helpful to understand the whole nitrogen cycle. Biliuhe reservoir is an important water source in Dalian. Due to serious soil and water loss, nitrogen, phosphorus, potassium, pesticides and other harmful substances flow into the reservoir every year, which has the potential to cause the eutrophication and pollution in water body, and even destroy the balance of the nitrogen cycle in the reservoir. In order to reduce the speed of eutrophication in Biliuhe reservoir and maintain ecological stability, this experiment mainly studied the abundance and diversity of AOA?AOB in sediments of Biliuhe reservoir and the influence of environmental factors on the ammonia oxidation microorganisms.Sediments were sampled from ten different sites in the upstream, midstream and downstream of the reservoir in two different periods (level period in October 2014, dry season in April 2015). This experiment studied the abundance of the specific amoA gene in ammonia oxidation microorganisms by real time quantitative Polymerase Chain Reaction (RT-PCR), and analyzed the diversity of the gene by cloning sequencing. The result indicated that the copy numbers of AOA amoA gene in sediments were between 2.12×107 copies/g dry sediment and 8.92×108 copies/g dry sediment in October 2014 while they were between 3.58×107 copies/g dry sediment and 1.01×108 copies/g dry sediment in April 2015. The abundance of AOA amoA genes in sediments did not changed significantly in the two seasons. The amoA gene copy numbers of AOB were between 8.07x107 copies/g dry sediment and 1.81×10 copies/g dry sediment in October 2014 while they were between 1.13×10 copies/g dry sediment and 1.18×109copies/g dry sediment in April 2015. There is no big difference between the copy numbers of AOB in the two seasons. As a results, season variation had not great influence on the abundance of ammonia oxidation microorganisms in sediments of Bililuhe reservoir. In general, AOB amoA genes outnumbered AOA obviously in the sediments of Biliuhe reservoir area. Cloning sequencing showed that high diversity ammonia oxidizing bacteria and archaea were found in the ten sampling sites sediments of the Biliuhe reservoir in the two seasons. Nitrosospira and Nitrosomonas were the main AOB while AOA was dominanted by Crenarchaeota.The effect of environmental factors on the ammonia oxidation microorganisms was studied by Pearson's correlation and Redundancy analysis (RDA). The abundance of AOB showed a negative correlation with temperature and conductivity, while it was proportion to water depth, organic carbon, ammonia and nitrite. The abundance of AOA was positively correlated with conductivity and was negatively correlated with nitrate concentration. The community structure of AOA was significantly impacted by ammonia, nitrate concentration, conductivity, organic carbon, water depth and temperature while the community structure of AOB was significantly impacted by ammonia, nitrate, water depth and temperature. In conclusion many environmental factors affected the abundance and community diversity of AOA and AOB.