title: Metabolic Response of "CandidatusAccumulibacter Phosphatis" Clade II C to Changes in Influent P/C Ratio.
abstract: The objective of this study was to investigate the ability of a culture highly enriched with the polyphosphate-accumulating organism, "CandidatusAccumulibacter phosphatis" clade IIC, to adjust their metabolism to different phosphate availabilities. For this purpose the biomass was cultivated in a sequencing batch reactor with acetate and exposed to different phosphate/carbon influent ratios during six experimental phases. Activity tests were conducted to determine the anaerobic kinetic and stoichiometric parameters as well as the composition of the microbial community. Increasing influent phosphate concentrations led to increased poly-phosphate content and decreased glycogen content of the biomass. In response to higher biomass poly-phosphate content, the biomass showed higher specific phosphate release rates. Together with the phosphate release rates, acetate uptake rates also increased up to an optimal poly-phosphate/glycogen ratio of 0.3 P-mol/C-mol. At higher poly-phosphate/glycogen ratios (obtained at influent P/C ratios above 0.051 P-mol/C-mol), the acetate uptake rates started to decrease. The stoichiometry of the anaerobic conversions clearly demonstrated a metabolic shift from a glycogen dominated to a poly-phosphate dominated metabolism as the biomass poly-phosphate content increased. FISH and DGGE analyses confirmed that no significant changes occurred in the microbial community, suggesting that the changes in the biomass activity were due to different metabolic behavior, allowing the organisms to proliferate under conditions with fluctuating phosphate levels.
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water EducationDelft, Netherlands; Department of Biotechnology, Delft University of TechnologyDelft, Netherlands.
authors.forename: Laurens
authors.initials: L
authors.lastname: Welles
authors.affiliation: Department of Biotechnology, Delft University of Technology Delft, Netherlands.
authors.forename: Ben
authors.initials: B
authors.lastname: Abbas
authors.affiliation: Department of Biotechnology, Delft University of TechnologyDelft, Netherlands; Winogradsky Institute of Microbiology, Research Center of Biotechnology, Russian Academy of Sciences (RAS)Moscow, Russia.
authors.forename: Dimitry Y
authors.initials: DY
authors.lastname: Sorokin
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education Delft, Netherlands.
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Lopez-Vazquez
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education Delft, Netherlands.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Hooijmans
authors.affiliation: Department of Biotechnology, Delft University of Technology Delft, Netherlands.
authors.forename: Mark C M
authors.initials: MC
authors.lastname: van Loosdrecht
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water EducationDelft, Netherlands; Department of Biotechnology, Delft University of TechnologyDelft, Netherlands.
authors.forename: Damir
authors.initials: D
authors.lastname: Brdjanovic
keywords: glycogen-accumulating organisms (GAO); metabolic response; microbial population dynamics; phosphate limitation; polyphosphate-accumulating organisms (PAO)