Study On Microbial Diversity And Anammox Bacteria Identification In Lake Sediments

Nitrogen is one of the essential nutrients for organisms, and it’s also the main nutrient elements of eutrophication. There are a large number of nitrogen reaction to maintain the global nitrogen balance and biological growth in natural water bodies. Many lakes in China are now facing a more serious threat of nitrogen pollution, nitrogen removal in lakes rely on microbial nitrification, denitrification and anaerobic ammonium oxidation in sediment. Therefore, the discussion of species diversity and importance of microorganisms in freshwater sediments clarifies the seasonal changes of the anammox bacteria, and provides a scientific basis for enriching the nitrogen cycle theory of lakes and repairing eutrophic water. It will be more conducive to give us an in-depth understanding the nitrogen cycle of land water, and it also has a practical significance for water pollution control of nitrogen.Lake Donghu, Lake Nanhu and two ponds surrounding Nanhu was selected as our study area. We studied the microbial community structure and biodiversity of freshwater sediment by extraction of bacteria DNA, PCR, DGGE and other molecular ecology methods. And sequencing and phylogenetic analysis of anammox bacteria in sediments was discussed at large in this paper. The main results of research are as follows:(1) The bacterium in sediments of Lake Donghu, Lake Nanhu and the two ponds have a very rich biodiversity and a complex community structure. Summer bacterial richness and diversity index is generally higher than the winter. We speculated that temperature is one of the reasons for this result.(2) The biodiversity has a trend of increase with the reduction of pollutants concentration. It shows that water quality conditions would produce a certain negative impact on bacterial community structure in shallow lake sediments.(3) The community structure of Lake Nanhu is more complex than Lake Donghu, which declares that the relatively stable sediment microbial communities’structure is diverse in different areas. The reason is related with the physical and chemical properties of water quality and sediment in various lakes. The similarities between each sampling point in the lake are even bigger, which explains that each lake has formed a unique microbial community structure. The abundance and diversity index of fish pond is higher than lotus root pool. The lotus root pool is similar to the bacterial community structure of Lake Donghu, and the fish pond’s sediment bacterial community structure is similar to Lake Nanhu, which states that similar human activities make assimilated microbial communities.(4) The biodiversity indices of sediments in Lake Donghu and Lake Nanhu centre increases firstly and then begins decreasing from surface to the deep that the maximum is in the depth of6-12cm, and an obvious change of bacterial community structure is in the depth of6-8cm, which relates the disturbance of wind waves and sediment oxygen content.(5) Sequencing and phylogenetic analysis of36typical bands showed that the recovery bands are α-proteobacteria, β-proteobacteria,δ-proteobacteria, y-proteobacteria, a few of flavobacterium, bacilli and bacillus. Massilia, methylotenera and pseudomonas are at dominant position.(6) Anammox bacteria was found from Lake Donghu, Lake Nanhu and the two ponds successfully by nested PCR, while the biodiversity of anammox bacteria is low after Blast analysis. It shows that Candidatus Brocadia fulgida occupies an absolutely dominant position. In the fish pond we fond an new strain belongs Brocadia, but its functions and features need to be further studied.