Does doping with aluminum alter the effects of ZnO nanoparticles on the metabolism of soil pseudomonads?

Doping of ZnO nanoparticles (NPs) is being used to increase their commercialization in the optical and semiconductor fields. This paper addresses whether doping with Al alters how ZnO NPs at nonlethal levels modifies the metabolism of soil-borne pseudomonads which are beneficial in performing bioremediation or promoting plant growth. The differences in X-ray diffraction (XRD) patterns, observed between commercial ZnO and Al-doped ZnO NPs indicated the aluminum was present as Al NPs. Both particles aggregated in the bacterial growth medium and formed colloids of different surface charges. They had similar effects on bacterial metabolism: rapid, dose-dependent loss in light output indicative of temporary toxicity in a biosensor constructed in Pseudomonas putida KT2440; increased production of a fluorescent pyoverdine-type siderophore, and decreased levels of indole acetic acid and phenazines in Pseudomonas chlororaphis O6. Solubilization of Zn and Al from the NPs contributed to these responses to different extents. These findings indicate that Al-doping of the ZnO NPs did not reduce the ability of the NPs to alter bacterial metabolism in ways that could influence performance of the pseudomonads in their soil environment.