title: Use of combined microscopic and spectroscopic techniques to reveal interactions between uranium and Microbacterium sp. A9, a strain isolated from the Chernobyl exclusion zone.
abstract: Although uranium (U) is naturally found in the environment, soil remediation programs will become increasingly important in light of certain human activities. This work aimed to identify U(VI) detoxification mechanisms employed by a bacteria strain isolated from a Chernobyl soil sample, and to distinguish its active from passive mechanisms of interaction. The ability of the Microbacterium sp. A9 strain to remove U(VI) from aqueous solutions at 4 °C and 25 °C was evaluated, as well as its survival capacity upon U(VI) exposure. The subcellular localisation of U was determined by TEM/EDX microscopy, while functional groups involved in the interaction with U were further evaluated by FTIR; finally, the speciation of U was analysed by TRLFS. We have revealed, for the first time, an active mechanism promoting metal efflux from the cells, during the early steps following U(VI) exposure at 25 °C. The Microbacterium sp. A9 strain also stores U intracellularly, as needle-like structures that have been identified as an autunite group mineral. Taken together, our results demonstrate that this strain exhibits a high U(VI) tolerance based on multiple detoxification mechanisms. These findings support the potential role of the genus Microbacterium in the remediation of aqueous environments contaminated with U(VI) under aerobic conditions.
authors.affiliation: CEA, DSV, IBEB, SBVME, LIPM, F-13108 Saint-Paul-lez-Durance, France; CNRS, UMR 7265, F-13108 Saint-Paul-lez-Durance, France; Université d'Aix-Marseille, F-13108 Saint-Paul-lez-Durance, France; IRSN/PRP-ENV/SERIS/L2BT, bat 183, B.P. 3, F-13115 Saint Paul-lez-Durance, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Theodorakopoulos
authors.affiliation: CEA, DSV, IBEB, SBVME, LIPM, F-13108 Saint-Paul-lez-Durance, France; CNRS, UMR 7265, F-13108 Saint-Paul-lez-Durance, France; Université d'Aix-Marseille, F-13108 Saint-Paul-lez-Durance, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Chapon
authors.affiliation: IRSN/PRP-ENV/SERIS/L2BT, bat 183, B.P. 3, F-13115 Saint Paul-lez-Durance, France.
authors.forename: Fréderic
authors.initials: F
authors.lastname: Coppin
authors.affiliation: IRSN/PRP-ENV/SERIS/L2BT, bat 183, B.P. 3, F-13115 Saint Paul-lez-Durance, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Floriani
authors.affiliation: CEA, DEN, DANS, DPC SEARS, LANIE, F-91191 Gif-Sur-Yvette Cedex, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Vercouter
authors.affiliation: Univ Bordeaux, CENBG, UMR5797, F-33170 Gradignan, France; CNRS, IN2P3, CENBG, UMR5797, F-33170 Gradignan, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Sergeant
authors.affiliation: IRSN/PRP-ENV/SERIS/L2BT, bat 183, B.P. 3, F-13115 Saint Paul-lez-Durance, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Camilleri
authors.affiliation: CEA, DSV, IBEB, SBVME, LIPM, F-13108 Saint-Paul-lez-Durance, France; CNRS, UMR 7265, F-13108 Saint-Paul-lez-Durance, France; Université d'Aix-Marseille, F-13108 Saint-Paul-lez-Durance, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Berthomieu
authors.affiliation: IRSN/PRP-ENV/SERIS/L2BT, bat 183, B.P. 3, F-13115 Saint Paul-lez-Durance, France. Electronic address: laureline.fevrier@irsn.fr.
authors.forename: Laureline
authors.initials: L
authors.lastname: Février
mesh_terms: D039903:Actinobacteria / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D000327:Adsorption; D058491:Bacterial Load; D047852:Chernobyl Nuclear Accident; D046529:Microscopy, Electron, Transmission; D010710:Phosphates / Q000032:analysis / Q000378:metabolism; D012988:Soil Microbiology; D012990:Soil Pollutants, Radioactive / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D014455:Ukraine; D014501:Uranium / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D010710:Phosphates; D012990:Soil Pollutants, Radioactive; D014501:Uranium
keywords: Bioaccumulation; Efflux; Microbacterium; Phosphate; Uranium