title: Mechanisms of gold biomineralization in the bacterium Cupriavidus metallidurans.
abstract: While the role of microorganisms as main drivers of metal mobility and mineral formation under Earth surface conditions is now widely accepted, the formation of secondary gold (Au) is commonly attributed to abiotic processes. Here we report that the biomineralization of Au nanoparticles in the metallophillic bacterium Cupriavidus metallidurans CH34 is the result of Au-regulated gene expression leading to the energy-dependent reductive precipitation of toxic Au(III)-complexes. C. metallidurans, which forms biofilms on Au grains, rapidly accumulates Au(III)-complexes from solution. Bulk and microbeam synchrotron X-ray analyses revealed that cellular Au accumulation is coupled to the formation of Au(I)-S complexes. This process promotes Au toxicity and C. metallidurans reacts by inducing oxidative stress and metal resistances gene clusters (including a Au-specific operon) to promote cellular defense. As a result, Au detoxification is mediated by a combination of efflux, reduction, and possibly methylation of Au-complexes, leading to the formation of Au(I)-C-compounds and nanoparticulate Au(0). Similar particles were observed in bacterial biofilms on Au grains, suggesting that bacteria actively contribute to the formation of Au grains in surface environments. The recognition of specific genetic responses to Au opens the way for the development of bioexploration and bioprocessing tools.
authors.affiliation: Centre for Tectonics, Resources and Exploration, School of Earth and Environmental Sciences, University of Adelaide, North Terrace, SA 5000, Australia. frank.reith@csiro.au
authors.forename: Frank
authors.initials: F
authors.lastname: Reith
authors.forename: Barbara
authors.initials: B
authors.lastname: Etschmann
authors.forename: Cornelia
authors.initials: C
authors.lastname: Grosse
authors.forename: Hugo
authors.initials: H
authors.lastname: Moors
authors.forename: Mohammed A
authors.initials: MA
authors.lastname: Benotmane
authors.forename: Pieter
authors.initials: P
authors.lastname: Monsieurs
authors.forename: Gregor
authors.initials: G
authors.lastname: Grass
authors.forename: Christian
authors.initials: C
authors.lastname: Doonan
authors.forename: Stefan
authors.initials: S
authors.lastname: Vogt
authors.forename: Barry
authors.initials: B
authors.lastname: Lai
authors.forename: Gema
authors.initials: G
authors.lastname: Martinez-Criado
authors.forename: Graham N
authors.initials: GN
authors.lastname: George
authors.forename: Dietrich H
authors.initials: DH
authors.lastname: Nies
authors.forename: Max
authors.initials: M
authors.lastname: Mergeay
authors.forename: Allan
authors.initials: A
authors.lastname: Pring
authors.forename: Gordon
authors.initials: G
authors.lastname: Southam
authors.forename: Joël
authors.initials: J
authors.lastname: Brugger
mesh_terms: D018441:Biofilms / Q000254:growth & development; D049921:Cupriavidus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004785:Environmental Pollutants / Q000493:pharmacokinetics / Q000633:toxicity; D005798:Genes, Bacterial; D006046:Gold / Q000493:pharmacokinetics* / Q000633:toxicity; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000633:toxicity; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008903:Minerals / Q000493:pharmacokinetics / Q000633:toxicity; D005810:Multigene Family
chemical_list: D004785:Environmental Pollutants; D008903:Minerals; D006046:Gold