title: Bacterial responses to Cu-doped TiO(2) nanoparticles.
abstract: The toxicity of Cu-doped TiO(2) nanoparticles (NPs, 20nm), synthesized by a flame aerosol reactor, to Mycobacterium smegmatis and Shewanella oneidensis MR-1, is the primary focus of this study. Both doped and non-doped TiO(2) NPs (20nm) tended to agglomerate in the medium solution, and therefore did not penetrate into the cell and damage cellular structures. TiO(2) particles (<100mg/L) did not apparently interfere with the growth of the two species in aqueous cultures. Cu-doped TiO(2) NPs (20mg/L) significantly reduced the M. smegmatis growth rate by three fold, but did not affect S. oneidensis MR-1 growth. The toxicity of Cu-doped TiO(2) NPs was driven by the release of Cu(2+) from the parent NPs. Compared to equivalent amounts of Cu(2+), Cu-doped TiO(2) NPs exhibited higher levels of toxicity to M. smegmatis (P-value<0.1). Addition of EDTA in the culture appeared to significantly decrease the anti-mycobacterium activity of Cu-doped TiO(2) NPs. S. oneidensis MR-1 produced a large amount of extracellular polymeric substances (EPS) under NP stress, especially extracellular protein. Therefore, S. oneidensis MR-1 was able to tolerate a much higher concentration of Cu(2+) or Cu-doped TiO(2) NPs. S. oneidensis MR-1 also adsorbed NPs on cell surface and enzymatically reduced ionic copper in culture medium with a remediating rate of 61microg/(liter x OD(600) x hour) during its early exponential growth phase. Since the metal reducing Shewanella species can efficiently "clean" metal-oxide NPs, the activities of such environmentally relevant bacteria may be an important consideration for evaluating the ecological risk of metal-oxide NPs.
authors.affiliation: Department of Energy, Environmental and Chemical Engineering, One Brookings Drive, Campus Box 1180, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Wu
authors.forename: Rick
authors.initials: R
authors.lastname: Huang
authors.forename: Manoranjan
authors.initials: M
authors.lastname: Sahu
authors.forename: Xueyang
authors.initials: X
authors.lastname: Feng
authors.forename: Pratim
authors.initials: P
authors.lastname: Biswas
authors.forename: Yinjie J
authors.initials: YJ
authors.lastname: Tang
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D003300:Copper / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D014025:Titanium / Q000378:metabolism*
chemical_list: C009495:titanium dioxide; D003300:Copper; D014025:Titanium