title: "Use of acidophilic bacteria of the genus Acidithiobacillus to biosynthesize CdS fluorescent nanoparticles (quantum dots) with high tolerance to acidic pH".
abstract: The use of bacterial cells to produce fluorescent semiconductor nanoparticles (quantum dots, QDs) represents a green alternative with promising economic potential. In the present work, we report for the first time the biosynthesis of CdS QDs by acidophilic bacteria of the Acidithiobacillus genus. CdS QDs were obtained by exposing A. ferrooxidans, A. thiooxidans and A. caldus cells to sublethal Cd2+concentrations in the presence of cysteine and glutathione. The fluorescence of cadmium-exposed cells moves from green to red with incubation time, a characteristic property of QDs associated with nanocrystals growth. Biosynthesized nanoparticles (NPs) display an absorption peak at 360nm and a broad emission spectra between 450 and 650nm when excited at 370nm, both characteristic of CdS QDs. Average sizes of 6 and 10nm were determined for green and red NPs, respectively. The importance of cysteine and glutathione on QDs biosynthesis in Acidithiobacillus was related with the generation of H2S. Interestingly, QDs produced by acidophilic bacteria display high tolerance to acidic pH. Absorbance and fluorescence properties of QDs was not affected at pH 2.0, a condition that totally inhibits the fluorescence of QDs produced chemically or biosynthesized by mesophilic bacteria (stable until pH 4.5-5.0). Results presented here constitute the first report of the generation of QDs with improved properties by using extremophile microorganisms.
authors.affiliation: Universidad Andres Bello, BioNanotechnology and Microbiology Lab, Center for Bioinformatics and Integrative Biology (CBIB), Facultad de Ciencias Biológicas, Republica # 239, Santiago, Chile; Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingstone Pohlhammer 1007, Santiago, Chile.
authors.forename: G
authors.initials: G
authors.lastname: Ulloa
authors.affiliation: Universidad Andres Bello, BioNanotechnology and Microbiology Lab, Center for Bioinformatics and Integrative Biology (CBIB), Facultad de Ciencias Biológicas, Republica # 239, Santiago, Chile.
authors.forename: B
authors.initials: B
authors.lastname: Collao
authors.affiliation: Departamento de Ingeniería Química y Biotecnologia, Facultad de Ciencias Fisicas y Matematicas, Universidad de Chile, Beauchef 851, Santiago, Chile.
authors.forename: M
authors.initials: M
authors.lastname: Araneda
authors.affiliation: Departamento de Ingeniería Química y Biotecnologia, Facultad de Ciencias Fisicas y Matematicas, Universidad de Chile, Beauchef 851, Santiago, Chile.
authors.forename: B
authors.initials: B
authors.lastname: Escobar
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingstone Pohlhammer 1007, Santiago, Chile.
authors.forename: S
authors.initials: S
authors.lastname: Álvarez
authors.affiliation: Laboratorio de Microbiología Oral, Facultad de Odontología, Universidad de Chile, Chile.
authors.forename: D
authors.initials: D
authors.lastname: Bravo
authors.affiliation: Universidad Andres Bello, BioNanotechnology and Microbiology Lab, Center for Bioinformatics and Integrative Biology (CBIB), Facultad de Ciencias Biológicas, Republica # 239, Santiago, Chile. Electronic address: jose.perez@unab.cl.
authors.forename: J M
authors.initials: JM
authors.lastname: Pérez-Donoso
mesh_terms: D042763:Acidithiobacillus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D013856:Acidithiobacillus thiooxidans / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D001709:Biotechnology; D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology; D019187:Cadmium Compounds / Q000737:chemistry* / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D005453:Fluorescence; D005978:Glutathione / Q000378:metabolism; D055772:Green Chemistry Technology; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D036103:Nanotechnology; D045663:Quantum Dots / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D013440:Sulfides / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D019187:Cadmium Compounds; D013440:Sulfides; D002104:Cadmium; C034939:cadmium sulfide; D005978:Glutathione; D003545:Cysteine
keywords: Acid-tolerant quantum dots; Bioleaching bacteria; Biosynthesis of nanoparticles; Quantum dots