title: Effect of TiO2 nanoparticles and UV radiation on extracellular enzyme activity of intact heterotrophic biofilms.
abstract: When introduced into the aquatic environment, TiO2 NP are likely to settle from the water column, which results in increased exposure of benthic communities. Here, we show that the activity of two extracellular enzymes of intact heterotrophic biofilms, β-glucosidase (carbon-cycling) and l-leucin aminopeptidase (nitrogen-cycling), was reduced following exposure to surface functionalized TiO2 NP and UV radiation, depending on the particles' coating. This reduction was partially linked to ROS production. Alkaline phosphatase (phosphorus-cycling) activity was not affected, however in contrast, an alkaline phosphatase isolated from E. coli was strongly inhibited at lower concentrations of TiO2 NP than the intact biofilms. These results indicate that enzymes present in the biofilm matrix are partly protected against exposure to TiO2 NP and UV radiation. Impairment of extracellular enzymes which mediate the uptake of nutrients from water may affect ecosystem function.
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , 8600 Dübendorf, Switzerland.
authors.forename: Hannah
authors.initials: H
authors.lastname: Schug
authors.forename: Carl W
authors.initials: CW
authors.lastname: Isaacson
authors.forename: Laura
authors.initials: L
authors.lastname: Sigg
authors.forename: Adrian A
authors.initials: AA
authors.lastname: Ammann
authors.forename: Kristin
authors.initials: K
authors.lastname: Schirmer
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D018441:Biofilms / Q000187:drug effects / Q000528:radiation effects; D017753:Ecosystem; D004926:Escherichia coli; D052836:Heterotrophic Processes; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D053768:Metal Nanoparticles / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013472:Sunlight; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification; D001617:beta-Glucosidase / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium; D000469:Alkaline Phosphatase; D001617:beta-Glucosidase; D007931:Leucyl Aminopeptidase