title: Microbial mediated formation of Fe-carbonate minerals under extreme acidic conditions.
abstract: Discovery of Fe-carbonate precipitation in Rio Tinto, a shallow river with very acidic waters, situated in Huelva, South-western Spain, adds a new dimension to our understanding of carbonate formation. Sediment samples from this low-pH system indicate that carbonates are formed in physico-chemical conditions ranging from acid to neutral pH. Evidence for microbial mediation is observed in secondary electron images (Fig. 1), which reveal rod-shaped bacteria embedded in the surface of siderite nanocrystals. The formation of carbonates in Rio Tinto is related to the microbial reduction of ferric iron coupled to the oxidation of organic compounds. Herein, we demonstrate for the first time, that Acidiphilium sp. PM, an iron-reducing bacterium isolated from Rio Tinto, mediates the precipitation of siderite (FeCO3) under acidic conditions and at a low temperature (30°C). We describe nucleation of siderite on nanoglobules in intimate association with the bacteria cell surface. This study has major implications for understanding carbonate formation on the ancient Earth or extraterrestrial planets.
authors.affiliation: Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, 28850 Madrid, Spain.
authors.forename: Mónica
authors.initials: M
authors.lastname: Sánchez-Román
authors.affiliation: Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, 28850 Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Fernández-Remolar
authors.affiliation: 1] Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, 28850 Madrid, Spain [2] Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Amils
authors.affiliation: Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, 18002 Granada, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Sánchez-Navas
authors.affiliation: Department of Chemistry and Applied Biosciences, ETH-Zurich, CH 8093 Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmid
authors.affiliation: Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, 28850 Madrid, Spain.
authors.forename: Patxi
authors.initials: P
authors.lastname: San Martin-Uriz
authors.affiliation: Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, 28850 Madrid, Spain.
authors.forename: Nuria
authors.initials: N
authors.lastname: Rodríguez
authors.affiliation: Geological Institute, ETH-Zurich, CH 8092 Zurich, Switzerland.
authors.forename: Judith A
authors.initials: JA
authors.lastname: McKenzie
authors.affiliation: Geological Institute, ETH-Zurich, CH 8092 Zurich, Switzerland.
authors.forename: Crisogono
authors.initials: C
authors.lastname: Vasconcelos
mesh_terms: D002254:Carbonates / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*
chemical_list: D002254:Carbonates; D008903:Minerals; D007501:Iron
references.citation: Anal Chem. 2000 Nov 15;72(22):5529-34
references.pmid: 11101227
references.citation: Nature. 2004 Jun 17;429(6993):707-8
references.pmid: 15201892
references.citation: Proc Natl Acad Sci U S A. 2012 Sep 18;109(38):15146-51
references.pmid: 22949693
references.citation: Nature. 2004 Sep 23;431(7007):423-6
references.pmid: 15386004
references.citation: Science. 2009 Jan 9;323(5911):218-9
references.pmid: 19131619
references.citation: J Colloid Interface Sci. 2008 Jul 15;323(2):317-25
references.pmid: 18471824
references.citation: Adv Dent Res. 1987 Dec;1(2):306-13
references.pmid: 3504181
references.citation: Biochim Biophys Acta. 1997 Apr 17;1335(1-2):199-208
references.pmid: 9133657
references.citation: J Bacteriol. 2011 Oct;193(19):5585-6
references.pmid: 21914891
references.citation: Nature. 2004 May 27;429(6990):395-9
references.pmid: 15164058
references.citation: Proc Natl Acad Sci U S A. 2009 Jun 16;106(24):9548-55
references.pmid: 19515817
references.citation: Proc Natl Acad Sci U S A. 2006 Jun 20;103(25):9440-5
references.pmid: 16772379
references.citation: Geochim Cosmochim Acta. 1989;53:859-71
references.pmid: 11539784
references.citation: Astrobiology. 2008 Oct;8(5):1023-47
references.pmid: 19105758
references.citation: ISME J. 2010 Jul;4(7):922-32
references.pmid: 20182524
references.citation: FEMS Microbiol Ecol. 2012 Aug;81(2):303-14
references.pmid: 22385317
references.citation: FEMS Microbiol Ecol. 2007 Aug;61(2):273-84
references.pmid: 17535298
references.citation: Geochim Cosmochim Acta. 1993 Oct;57(19):4619-25
references.pmid: 11539579
references.citation: Proc Natl Acad Sci U S A. 2010 Apr 6;107(14):6316-21
references.pmid: 20308589