title: Effects of TiO2 and Ag nanoparticles on polyhydroxybutyrate biosynthesis by activated sludge bacteria.
abstract: Manufactured nanomaterials (MNMs) are increasingly incorporated into consumer products that are disposed into sewage. In wastewater treatment, MNMs adsorb to activated sludge biomass where they may impact biological wastewater treatment performance, including nutrient removal. Here, we studied MNM effects on bacterial polyhydroxyalkanoate (PHA), specifically polyhydroxybutyrate (PHB), biosynthesis because of its importance to enhanced biological phosphorus (P) removal (EBPR). Activated sludge was sampled from an anoxic selector of a municipal wastewater treatment plant (WWTP), and PHB-containing bacteria were concentrated by density gradient centrifugation. After starvation to decrease intracellular PHB stores, bacteria were nutritionally augmented to promote PHB biosynthesis while being exposed to either MNMs (TiO2 or Ag) or to Ag salts (each at a concentration of 5 mg L(-1)). Cellular PHB concentration and PhyloChip community composition were analyzed. The final bacterial community composition differed from activated sludge, demonstrating that laboratory enrichment was selective. Still, PHB was synthesized to near-activated sludge levels. Ag salts altered final bacterial communities, although MNMs did not. PHB biosynthesis was diminished with Ag (salt or MNMs), indicating the potential for Ag-MNMs to physiologically impact EBPR through the effects of dissolved Ag ions on PHB producers.
authors.affiliation: Bren School of Environmental Science & Management, Earth Research Institute, and UC Center for the Environmental Implications of Nanotechnology (UC CEIN), University of California , Santa Barbara, Santa Barbara, California 93106, United States.
authors.forename: John H
authors.initials: JH
authors.lastname: Priester
authors.forename: Laurie C
authors.initials: LC
authors.lastname: Van De Werfhorst
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ge
authors.forename: Adeyemi S
authors.initials: AS
authors.lastname: Adeleye
authors.forename: Shivira
authors.initials: S
authors.lastname: Tomar
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Tom
authors.forename: Yvette M
authors.initials: YM
authors.lastname: Piceno
authors.forename: Gary L
authors.initials: GL
authors.lastname: Andersen
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Holden
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D018533:Biomass; D059013:Microbial Consortia / Q000187:drug effects / Q000235:genetics; D053758:Nanoparticles; D011091:Polyesters / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S; D012722:Sewage / Q000382:microbiology*; D012834:Silver / Q000494:pharmacology*; D014025:Titanium / Q000494:pharmacology*; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater
chemical_list: D011091:Polyesters; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D012834:Silver; D014025:Titanium; D062065:Wastewater; C107955:poly(4-hydroxybutanoate); C009495:titanium dioxide