A Novel Glycogen Accumulating Organism Abundant in Enhanced Biological Phosphorus Removal Plants

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A Novel Glycogen Accumulating Organism Abundant in Enhanced Biological Phosphorus Removal Plants

Abstract

Enhanced biological phosphorus removal (EBPR) is widely used to remove phosphorus from wastewater. The process relies on polyphosphate accumulating organisms (PAOs) that are able to take up phosphorus in excess of what is needed for growth, whereby phosphorus can be removed from the wastewater by wasting the biomass. However, glycogen accumulating organisms (GAOs) may reduce the EBPR efficiency as they compete for substrates with PAOs, but do not store excessive amounts of polyphosphate. PAOs and GAOs are thought to be phylogenetically unrelated, with the model PAO being the betaproteobacterial “ Candidatus  Accumulibacter phosphatis” (Accumulibacter) and the model GAO being the gammaproteobacterial “ Candidatus  Competibacter phosphatis”. Here, we report the discovery of a GAO from the genus  Propionivibrio , which is closely related to Accumulibacter.  Propionivibrio  sp. are targeted by the canonical fluorescence  in situ  hybridization probes used to target Accumulibacter (PAOmix), but do not store excessive amounts of polyphosphate  in situ . A laboratory scale reactor, operated to enrich for PAOs, surprisingly contained co-dominant populations of  Propionivibrio  and Accumulibacter. Metagenomic sequencing of multiple time-points enabled recovery of near complete population genomes from both genera. Annotation of the  Propionivibrio  genome confirmed their potential for the GAO phenotype and a basic metabolic model is proposed for their metabolism in the EBPR environment. Using newly designed fluorescence  in situ  hybridization (FISH) probes, analyses of full-scale EBPR plants revealed that  Propionivibrio  is a common member of the community, constituting up to 3% of the biovolume. To avoid overestimation of Accumulibacter abundance  in situ , we recommend the use of the FISH probe PAO651 instead of the commonly applied PAOmix probe set.

Source:  Front. Microbiol., 04 July 2016 | http://dx.doi.org/10.3389/fmicb.2016.01033

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