Structure and function of the microbial community in a full-scale enhanced biological phosphorus removal plant

The structure and function of the microbial community in a full-scale enhanced biological phosphorus removal wastewater treatment plant (WWTP; Skagen) were investigated using the full-cycle rRNA approach, combined with ecophysiological studies. A total of 87 16S rRNA gene sequences were retrieved, and 78 operational taxonomic units were identified. Novel oligonucleotide probes were designed, and quantitative fluorescence in situ hybridization revealed that six hitherto undescribed probe-defined groups within the phylum Bacteroidetes (two groups), and classes Betaproteobacteria (two groups) and Gammaproteobacteria (two groups), were relatively abundant (>1% of total biovolume) in the Skagen WWTP and 10 other full-scale WWTPs with biological P removal. The most abundant was a group of rod-shaped Bacteroidetes attached to filamentous bacteria, which is distantly related to the genus Haliscomenobacter of the family Saprospiraceae, and comprised 9-19% of the bacterial biovolume in all the WWTPs investigated. The other five probe-defined groups were found in all WWTPs, but they were less abundant (1-6%). Two groups had a glycogen-accumulating phenotype and one Dechloromonas-related group had a polyphosphate-accumulating phenotype, and they were potentially all involved in denitrification. In total, about 81% of all bacteria hybridizing with the general eubacterial probe were detected in the Skagen WWTP by using clone- or group-specific probes, indicating that most members of the microbial community had been identified.