Comparison between sequences of band pairs with identical migrating patterns but from different environmental samples resulted in identical sequences for one pair and a total of two mismatches for the other pair of bands (data not shown).
Although environmental conditions in the reactors were considerably different, practically all amoA DGGE profiles showed the same two dominant bands (bands 1 and 2). Band 3 was particularly strong in virtually all amoA DGGE profiles of reactor C (0.5 h:1.5 h) and was occasionally present in the other reactors. Bands 4 and 5 were only occasionally detected in all reactors and usually with faint signals, except for Fig. 1h and j, which show band 4 as a major band. Throughout the experiment, amoA DGGE profiles showed a total of nine different bands, with increasing AOB species diversity (based on the number of bands) toward the end of the experiment.
High ammonia and TKN removal efficiencies were observed for samples with various amoA DGGE profiles, including samples with high and low AOB species diversity. Similarly, amoA DGGE profiles showing high AOB diversity, as well as amoA DGGE profiles with low AOB diversity, were shown for days with poor ammonia and TKN removal performance