Phylogenetic diversity of nirS-type denitrifying bacteria in Jiulong River estuary

Abstract:

[Objective] To understand the microbial community of denitrifying bacteria in Jiulong River estuary. [Methods] The sampling site was in Jiulong River estuary that was characterized by eutrophication. The water sample and sediment sample were collected and the environmental physicochemical factors were analyzed. The 16S rRNA gene and nirS gene clone libraries were constructed based on water sample and sediment sample respectively. [Results] In the 16S rRNA gene clone library, 86 valid sequences were grouped into 53 OTUs based on 97% sequence similarity and clustered into 6 different bacterial groups on the phylum level: Proteobacteria (Alpha, Beta, Gamma and Delta), Planctomycetes, Bacteroidetes, Actinobacteria, Firmicutes and Chloroflexi. Among these groups, Proteobacteria was the predominant member (62.9%). Of the nirS gene clone library 190 valid sequences were translated to conceptual amino acid sequences and group into 60 OTUs based on 82% similarity for genus identification. Among the 190 sequences, 71.6% were clustered into Proteobacteria phylum, including Alphaproteobacteria (5.8%), Betaproteobacteria (49.0%) and Gammaproteobacteria (16.9%). The most abundant OTU shared 100% sequence similarity to sequences from the nitrite reductase of Thauera sp. R-26906, a species of cultured denitrifier. [Conclusion] High diversity of the microbial community as well as nirS genes were found in the Jiulong River estuary. Most of the NirS sequences of this study shared quite high similarity to known sequences from various similar environments such as estuary and gulf.

Key words:Denitrifying bacteria, nirS gene, Diversity of microbial community, Estuary, Phylogenetic analysis