Microbial community structure of ammonia-oxidizing enrichments from urban river sediments in Wenzhou City

Abstract:

[Background] Urban river sediments are rich in microbial resources, and the surface sediment is a major site for nitrification. Microorganisms in surface sediment play an important role in nitrogen transformations of river ecosystems. [Objective] To compare and analyze the microbial communities of ammonia-oxidizing microorganism enrichments from sediments under different environmental conditions, sediment samples were collected at four sampling sites at the Shunao and Hengjiang Rivers, which are tributaries of the Wen-Rui Tang River located in Wenzhou. [Methods] Ammonia-oxidizing microorganism enrichments were obtained through field sampling and laboratory cultivation. The microbial composition, abundance and diversity of ammonia-oxidizing microorganism enrichments were studied by high-throughput sequencing. [Results] Proteobacteria and Bacteroidetes were the two dominant phyla in enrichments. The microbial communities in four samples contained three genera of ammonia-oxidizing bacteria (Nitrosomonas, Nitrosospira and Nitrosococcus) and one genus of ammonia-oxidizing archaea (Nitrososphaera), of which the genus Nitrosomonas was dominant in each sample. There were marked differences in the composition of ammonia-oxidizing microorganism OTUs (operational taxonomic units) among different enrichments. The number and relative abundance of ammonia-oxidizing bacteria OTUs were highest in the sample DA2 from the site that has many aquatic plants, while those of ammonia-oxidizing archaea OTUs were highest in the sample DA4 from the site where untreated municipal wastes are often dumped there. The number and relative abundance of ammonia-oxidizing microorganism OTUs were higher in the enrichment samples DA2 and DA4 from lotic-dominated sites compared to those from lentic-dominated sites. [Conclusion] The results revealed microbial diversity in enrichments from urban river sediments under four different environments, and described the dominant phyla in enrichments. Such data provides a reference for selecting the culture source of ammonia-oxidizing microorganism, and provides fundamental knowledge for isolation and further study of ammonia-oxidizing microorganism in urban river sediments.