The chemical species of mercury accumulated by Pseudomonas idrijaensis, a bacterium from a rock of the Idrija mercury mine, Slovenia

• Published in: Chemosphere
• Main Authors: Bourdineaud, Jean-Paul, Durn, Goran, Režun, Bojan, Manceau, Alain, Hrenović, Jasna
• Other Authors: Microbiologie Fondamentale et Pathogénicité (MFP), Université Bordeaux Segalen - Bordeaux 2-Centre National de la Recherche Scientifique (CNRS), University of Zagreb, Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement IRD : UR219-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), Croatian Science Foundation (project no. IP-2014-09-5656).The French National Research Agency (ANR).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Mercury; mer operon; Pseudomonas idrijaensis; Tn5041; Idrija mine; XANES spectroscopy; [SDV.MP.BAC]Life Sciences [q-bio]/Microbiology and Parasitology/Bacteriology; [SDE]Environmental Sciences; permafrost
• Online Access: https://hal.science/hal-02469580; https://hal.science/hal-02469580/document; https://hal.science/hal-02469580/file/Article%20Chemosphere%202020-version%20Hal.pdf; https://doi.org/10.1016/j.chemosphere.2020.126002

International audience A mercury-resistant bacterial strain has been isolated from a rock of the Idrija mercury mine in Slovenia. The rock had 19 g carbon and 2952 mg mercury (Hg) per kg. Mass spectrometry and DNA sequencing showed that the bacterium belongs to the Pseudomonas genus. It is called Pseudomonas idrijaensis. This bacterial strain is sensitive to methylmercury (MeHg) like the reference P. aeruginosa strain PAO1, and is resistant to divalent mercury (Hg(II)) in contrast to PAO1. This difference could be attributed to the presence of the mer operon yet deprived of the merB gene encoding the organomercurial lyase, on the basis of whole genome sequencing. The P. idrijaensis mer operon displays the RTPCADE organization and is contained in the Tn5041 transposon. This transposon identified here occurs in other Gram-negative Hg-resistant strains isolated from mercury ores, aquatic systems and soils, including Pseudomonas strains from 15,000 to 40,000 years old Siberian permafrost. When P. idrijaensis was exposed to mercury chloride, two intracellular Hg species were identified by high energy-resolution XANES spectroscopy, a dithiolate Hg(SR)2 and a tetrathiolate Hg(SR)4 complex. P. idrijaensis had a much higher [Hg(SR)2]/[Hg(SR)4] molar ratio than bacteria lacking the mer operon when exposed to 4 µg Hg2+/L - resulting in an intracellular accumulation of 4.3 µg Hg/g dw. A higher amount of the Hg(SR)2 complex provides a chemical signature for the expression of the dicysteinate Mer proteins in response to mercury toxicity.