[Denitrifying bacteria of constructed wetland system based on nitrous oxide reductase gene (nosZ)]

A horizontal subsurface flow constructed wetland was used to treat micro-pollution surface water and its effluent flowed into a landscape river as the water supplement. The abundance of the nitrous oxide reductase gene nosZ and 16S rDNA was investigated for the rhizosphere soil of the constructed wetland and the sediment of the landscape river by quantitive PCR. The diversity and similarity of denitrifiers were studied by using PCR-DGGE technique targeting the functional gene nosZ. The quantitive PCR results showed that the copy number of 16S rDNA and nosZ gene of the rhizosphere soil of the constructed wetland and the sediment of the landscape river were 1.91E + 07, 1.26E + 06 and 2.68E + 07, 8.37E + 05 copies x ng(-1) (by DNA), and 1.45E + 11, 9.31E + 09 and 5.31E + 11, 1.45E + 10 copies x g(-1) (by dry soil), respectively. Generally, the total bacterial count and denitrifiers in the sediment of the landscape river was higher than that of the constructed wetland, but the relative abundance of nosZ of the latter (3.8% - 10.1%) was significantly higher than that of the former (1.7% - 4.1%). There was low similarity between the two niches in cluster analysis. The predominant species of rhizosphere soil were mainly contained Rhodobacearales, Rhizobiales and Burkholderiales, although the predominant species of sediment were uncultured bacteria.