Temporal Variation of General and Rare Bacterial Taxa in an Activated Sludge Bioreactor


Temporal Variation of General and Rare Bacterial Taxa in an Activated Sludge Bioreactor


Hee-Deung Park


School of Civil, Environmental and Architectural Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul, 136-713, South Korea



Bacterial communities vary with time in activated sludge bioreactors. Although the temporal variation is believed to affect the performance and stability of biological treatment, it is not well characterized how the variation is generated and maintained. Particularly, the temporal variation of rare bacterial taxa is not well studied. In order to address the issue, temporal variation of general and rare bacterial taxa was investigated using pyrosequencing of 16S rRNA gene retrieved from activated sludge samples collected bimonthly for a two-year period. A total of 4,999 operational taxonomic units (OTUs) were retrieved from 35,856 sequences at a 3% cutoff. Most of OTUs were allocated to rare taxa (89.6%), but the rare taxa comprised a small portion of the community in terms of abundance of sequences analyzed (28.6%). Rare taxa exhibited a log series distribution, while the distribution of general taxa had a log normal pattern. Temporal variations in OTUs richness significantly differed between the two taxa groups in which the rare taxa showed a higher diversity and a more fluctuating pattern than the general taxa. Furthermore, the two taxa groups were constrained by different explanatory variables. Over the test period, the general taxa persisted for a longer time in the bioreactor than the rare taxa. In conclusion, this study demonstrated clear differences in temporal dynamic patterns for the general and rare bacterial taxa in an activated sludge bioreactor, which would be a foundation for better understanding the bacterial ecology of activated sludge.