Objective: We compared the microbial communities of two denitrifying bioreactors acclimated by quinoline and indole under identical condition.
Methods: We acclimated two reactors by using the same seeding sludge and acclimating conditions. When both reactors reached steady stage with a high pollutant removal capacity after 6 weeks adaptation, we constructed the 16S rDNA clone libraries to analyze the structure of microbial communities of those 2 bioreactors.
Results: Despite the same seeding sludge and identical acclimating condition, molecular ecological analysis showed distinctly different communities of two reactors. All operational taxonomic units (OTUs) of 16S rDNA clone library of quinoline acclimated bioreactor were affiliated to Betaproteobacteria, whereas in library of indole acclimated bioreactor, the percentage of Betaproteobacteria was only 56.3%. Results showed that microbial diversity in indole acclimated community was higher. Clones (73%) in quinoline acclimated community were Thauera related OTUs from the Rhodocyclaceae family. But OTUs from the families of Comamonadaceae, Alcaligenaceae and Rhodocyclaceae were dominant OTUs in indole acclimated community. The most dominant OTU from Comamonadaceae was 28.7% in clone library.
Conclusion: The type of pollutants in the wastewater had a strong effect on the selection of population in microbial community. Our study was the first report comparing the microbial structure of two effective denitrifying communities which could efficiently degrade quinoline and indole.