Abstract
Polyphosphate-accumulating organisms (PAOs), which can store high levels of phosphate (Pi) in the form of polyphosphate (polyP), are employed to engineer enhanced biological P removal (EBPR) from wastewaters. Co-localization of Mg and K in polyP granules of PAOs has been reported, and higher abundance of Mg-polyP granules relative to other metal complexes was correlated positively with EBPR performance stability. However, the underlying mechanism remains unknown. Here, we obtained molecular structural information of hydrated polyP complexes with four physiologically relevant metal cations (Na+, K+, Ca2+, and Mg2+) using computational and experimental techniques. Molecular dynamics simulations revealed that Mg-polyP and K-polyP complexes were the most and least stable of the complexes, respectively, suggesting that the co-occurrence of these complexes facilitates variable polyP bioavailability. The relative thermodynamic stability reflected the strength of metal chelation whereby the coordination distance between the polyP ligand O and the metal was 1.71-2.01 Å for Mg2+ but this distance was 2.64-2.70 Å for K+. Pair distribution function analysis of X-ray scattering data obtained with a Mg-polyP solution corroborated the theoretical Mg-polyP coordination geometry. These findings implied a possible mechanistic role of metal complexation in the P cycling traits of PAOs in engineered and natural systems.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 14185-14193 |
| Number of pages | 9 |
| Journal | Environmental Science and Technology |
| Volume | 55 |
| Issue number | 20 |
| DOIs | |
| State | Published - Oct 19 2021 |
Funding
This research was funded by a research grant awarded to L.A. from the U.S. National Science Foundation (NSF CHE-1709626). This work made use of the IMSERC Crystallography facility at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633) and Northwestern University. Purchase of the Ag-microsource diffractometer used to obtain results included in this publication was supported by the Major Research Instrumentation Program (NSF CHE-1920248). The SAXS measurements were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, The Dow Chemical Company, and DuPont de Nemours, Inc. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The SAXS data were collected using an instrument funded by the National Science Foundation (NSF-DMR 0960140).
Keywords
- X-ray scattering
- molecular modeling
- phosphorus removal
- polyphosphate
- wastewater
ASJC Scopus subject areas
- General Chemistry
- Environmental Chemistry
