Abstract
A protocol is described for the PCR-DGGE analysis of nirS nitrite reductase genes and its application to analyzing the denitrifying bacterial populations in activated sludge biomass samples from eight plants treating wastewater. A degenerate primer set designed by Braker et al (1998) was modified as 24 primer sets for this purpose. The method uses the 24 primer sets for the PCR analysis of these genes, and was validated against Ralstonia eutropha. With the activated sludge samples, six of the primer sets produced no PCR products under the given conditions. The multidimensional DGGE profiles obtained suggest that similar bacterial populations harboring the nirS gene exist in different plants treating the same type of wastewater. Some of the bands detected by DGGE were common to all biomass samples obtained from different plants, suggesting the presence of common denitrifying populations.
