title: Rhodococcus aetherivorans BCP1 as cell factory for the production of intracellular tellurium nanorods under aerobic conditions.
abstract: BACKGROUND
  Tellurite (TeO32-) is recognized as a toxic oxyanion to living organisms. However, mainly anaerobic or facultative-anaerobic microorganisms are able to tolerate and convert TeO32-into the less toxic and available form of elemental Tellurium (Te0), producing Te-deposits or Te-nanostructures. The use of TeO32--reducing bacteria can lead to the decontamination of polluted environments and the development of "green-synthesis" methods for the production of nanomaterials. In this study, the tolerance and the consumption of TeO32-have been investigated, along with the production and characterization of Te-nanorods by Rhodococcus aetherivorans BCP1 grown under aerobic conditions.
  
  
  RESULTS
  Aerobically grown BCP1 cells showed high tolerance towards TeO32-with a minimal inhibitory concentration (MIC) of 2800 μg/mL (11.2 mM). TeO32-consumption has been evaluated exposing the BCP1 strain to either 100 or 500 μg/mL of K2TeO3(unconditioned growth) or after re-inoculation in fresh medium with new addition of K2TeO3(conditioned growth). A complete consumption of TeO32-at 100 μg/mL was observed under both growth conditions, although conditioned cells showed higher consumption rate. Unconditioned and conditioned BCP1 cells partially consumed TeO32-at 500 μg/mL. However, a greater TeO32-consumption was observed with conditioned cells. The production of intracellular, not aggregated and rod-shaped Te-nanostructures (TeNRs) was observed as a consequence of TeO32-reduction. Extracted TeNRs appear to be embedded in an organic surrounding material, as suggested by the chemical-physical characterization. Moreover, we observed longer TeNRs depending on either the concentration of precursor (100 or 500 μg/mL of K2TeO3) or the growth conditions (unconditioned or conditioned grown cells).
  
  
  CONCLUSIONS
  Rhodococcus aetherivorans BCP1 is able to tolerate high concentrations of TeO32-during its growth under aerobic conditions. Moreover, compared to unconditioned BCP1 cells, TeO32-conditioned cells showed a higher oxyanion consumption rate (for 100 μg/mL of K2TeO3) or to consume greater amount of TeO32-(for 500 μg/mL of K2TeO3). TeO32-consumption by BCP1 cells led to the production of intracellular and not aggregated TeNRs embedded in an organic surrounding material. The high resistance of BCP1 to TeO32-along with its ability to produce Te-nanostructures supports the application of this microorganism as a possible eco-friendly nanofactory.
authors.affiliation: Microbial Biochemistry Laboratory, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada. alessandro.presentat@ucalgary.ca.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Presentato
authors.affiliation: Microbial Biochemistry Laboratory, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: Elena
authors.initials: E
authors.lastname: Piacenza
authors.affiliation: Department of Chemistry, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: Max
authors.initials: M
authors.lastname: Anikovskiy
authors.affiliation: Department of Pharmacy and Biotechnology, Unit of General and Applied Microbiology, Via Irnerio 42, Bologna, 40126, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Cappelletti
authors.affiliation: Department of Pharmacy and Biotechnology, Unit of General and Applied Microbiology, Via Irnerio 42, Bologna, 40126, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Zannoni
authors.affiliation: Microbial Biochemistry Laboratory, Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada. turnerr@ucalgary.ca.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Turner
mesh_terms: D000332:Aerobiosis; D043942:Nanotubes / Q000032:analysis*; D012240:Rhodococcus / Q000378:metabolism*; D013691:Tellurium / Q000378:metabolism*
chemical_list: D013691:Tellurium
keywords: Biogenic nanostructures; Elemental tellurium; Nanorods biosynthesis; Rhodococcus aetherivorans; Tellurite; Tellurium nanorods