Nitrogen metabolism plays an important role in the nitrogen cycle and transformation in Dianchi Lake. Not only do eukaryotes participate in nitrogen transformation but prokaryotes, as the main drivers of the nitrogen cycle, also play an extremely important role in the nitrogen cycle. Based on 16S rDNA high-throughput sequencing technology, 13 sites in Caohai and Waihai of Dianchi Lake were monitored, and PICRUSt function analysis method was adopted to analyze the microbial community diversity and key genes of nitrogen metabolism in Dianchi Lake. Bacteria belonging to 35 phyla and 427 genera were found in Dianchi Lake water and mainly included Proteobacteria and Bacteroidetes. Archaea had 14 phyla and 61 genera and mainly belonged to Euryarchaeota. The overall bacterial richness index of Dianchi Lake was higher than that of archaea, and the bacterial diversity index of Caohai was higher than that of Waihai. Functional prediction showed functional richness of bacteria and archaea. There were 35 KO pathways involved in nitrogen metabolism in bacteria, including key genes such as nitrogenous nitrate-reducing gene nirB, nitric oxide reductase gene norB in denitrification, and nitroreductase gene nasK. There were 23 KO pathways involved in nitrogen metabolism in archaea, involving nifH, nifK, and nifD nitrogenase genes in nitrogen fixation. The copy number of nitrogenase genes was significantly higher than that of other nitrogenase genes. The copy number of nitrogen-fixing genes of archaea was higher than that of bacteria, the nitrogen metabolism capacity of archaea in Caohai was higher than that in Waihai, and the potential of nitrogen-fixation of archaea in Dianchi Lake water was higher than that of bacteria. From the perspective of community structure and function prediction of bacteria and archaea, this study discussed the differences of nitrogen cycle in bacteria and archaea in different areas of Dianchi Lake and provided a decision basis for water environment management in Dianchi Lake.
Keywords: Dianchi Lake; functional genes; nitrogen metabolism; prokaryote; spatial distribution.