Chongming Dongtan Ammonia Oxidation, A Preliminary Study Of Denitrifying Microbial Community

Located in Changjiang estuary, Eastern Chongming Shoal is the main tidal flat in China. It plays an important role in eliminating the nitrate, ammonium as well as other organic compounds from Changjiang River. Most of domestic researches on nitrogen-cycling microorganisms focus on activated sludge and sewage processor. There is a lack of analysis on community structure in soil, especially in wetland.This study selected twenty-six soil samples from Eastern Chongming estuary, using a set of main methods, including soil activity determination, fluorescence quantitative PCR (RT-PCR), clone libraries construction, phylogenetical analysis, biostatistics calculation, and terminal restriction fragment length polymorphism (T-RLFP), by utilizing the molecular markers of bacterial amoA gene, archaeal amoA gene, and bacterial nosZ gene, to research the relationships among physical and chemical characteristics, soil activity, ammonium oxidizing and denitrifying microorganisms in conditions of different soil development stage, salinity, plants, and seasons.The research showed that the physical and chemical factors had obvious influence on soil activity and related microorganisms. The impact of salinity on nitrifiers and denitrifiers was clear, that high salinity restrained soil activity. The predominant soil microorganisms were different under high salinity, and the diversity of both nitrifiers and denitrifiers was lower under low salinity. The extreme pH values restrained soil activity. The adaptable pH value of nitrifiers and denitrifiers was neutral and alkaline. The influence of plants was evident. The soil activity at rhizosphere of Phragmites australis was higher than that in Spartina alterniflora. The functional genes of nitrifiers distributed differently in soils with different plants. Plant was selective for predominant microbial community. The amount of denitrifiers was the highest in summer. There was difference for nitrifiers from soil of tidal flat and waste land in seasonal distribution. For different type of soil inning, the species and distribution of nitrifiers and denitrifiers were different in tidal flat, waste land and crop land. There was similarity of microbial distribution between waste land and crop land. In addition, all of the reference sequences similar to sequences we had detected were isolated from soil or sediments. And the difference in three type of inning was obvious. This finding is significant for building nitrogen-cycling model of estuary. Thus further it has meaning for the research of global nitrogen-cycling and environmental protection.