title: Extracellular production of tellurium nanoparticles by the photosynthetic bacterium Rhodobacter capsulatus.
abstract: The toxic oxyanion tellurite (TeO3(2-)) is acquired by cells of Rhodobacter capsulatus grown anaerobically in the light, via acetate permease ActP2 and then reduced to Te(0) in the cytoplasm as needle-like black precipitates. Interestingly, photosynthetic cultures of R. capsulatus can also generate Te(0) nanoprecipitates (TeNPs) outside the cells upon addition of the redox mediator lawsone (2-hydroxy-1,4-naphtoquinone). TeNPs generation kinetics were monitored to define the optimal conditions to produce TeNPs as a function of various carbon sources and lawsone concentration. We report that growing cultures over a 10 days period with daily additions of 1mM tellurite led to the accumulation in the growth medium of TeNPs with dimensions from 200 up to 600-700 nm in length as determined by atomic force microscopy (AFM). This result suggests that nucleation of TeNPs takes place over the entire cell growth period although the addition of new tellurium Te(0) to pre-formed TeNPs is the main strategy used by R. capsulatus to generate TeNPs outside the cells. Finally, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) analysis of TeNPs indicate they are coated with an organic material which keeps the particles in solution in aqueous solvents.
authors.affiliation: Dept. of Pharmacy and Biotechnology, University of Bologna, Italy. Electronic address: roberto.borghese@unibo.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Borghese
authors.affiliation: Institute for the Study of Nanostructured Materials (CNR-ISMN), Rome, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Brucale
authors.affiliation: Dept. of Pharmacy and Biotechnology, University of Bologna, Italy.
authors.forename: Gianuario
authors.initials: G
authors.lastname: Fortunato
authors.affiliation: Dept. of Industrial Chemistry "Toso Montanari", University of Bologna, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Lanzi
authors.affiliation: Institute for the Study of Nanostructured Materials (CNR-ISMN), Rome, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Mezzi
authors.affiliation: Institute for the Study of Nanostructured Materials (CNR-ISMN), Bologna, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Valle
authors.affiliation: Institute for the Study of Nanostructured Materials (CNR-ISMN), Bologna, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Cavallini
authors.affiliation: Dept. of Pharmacy and Biotechnology, University of Bologna, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Zannoni
mesh_terms: D005632:Fructose / Q000494:pharmacology; D019344:Lactic Acid / Q000494:pharmacology; D008293:Malates / Q000494:pharmacology; D053758:Nanoparticles / Q000378:metabolism*; D009285:Naphthoquinones / Q000494:pharmacology; D010788:Photosynthesis; D019289:Pyruvic Acid / Q000494:pharmacology; D016354:Rhodobacter capsulatus / Q000187:drug effects / Q000378:metabolism*; D013691:Tellurium / Q000378:metabolism*
chemical_list: D008293:Malates; D009285:Naphthoquinones; D005632:Fructose; D019344:Lactic Acid; C030298:malic acid; D019289:Pyruvic Acid; D013691:Tellurium; C005090:lawsone
keywords: Lawsone; Nanoprecipitates; Photosynthetic bacteria; Rhodobacter capsulatus; Tellurite