Cargando…

Characterisation of iron oxide encrusted microbial fossils

Robust methods for the characterisation of microbial biosignatures in geological matrices is critical for developing mineralogical biosignatures. Studying microbial fossils is fundamental for our understanding of the role microorganisms have played in elemental cycling in modern and ancient environm...

Descripción completa

Detalles Bibliográficos
Autores principales: Levett, Alan, Gagen, Emma J., Rintoul, Llew, Guagliardo, Paul, Diao, Hui, Vasconcelos, Paulo M., Southam, Gordon
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group UK 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7303173/
https://www.ncbi.nlm.nih.gov/pubmed/32555223
http://dx.doi.org/10.1038/s41598-020-66830-z
_version_ 1783547994253033472
author Levett, Alan
Gagen, Emma J.
Rintoul, Llew
Guagliardo, Paul
Diao, Hui
Vasconcelos, Paulo M.
Southam, Gordon
author_facet Levett, Alan
Gagen, Emma J.
Rintoul, Llew
Guagliardo, Paul
Diao, Hui
Vasconcelos, Paulo M.
Southam, Gordon
author_sort Levett, Alan
collection PubMed
description Robust methods for the characterisation of microbial biosignatures in geological matrices is critical for developing mineralogical biosignatures. Studying microbial fossils is fundamental for our understanding of the role microorganisms have played in elemental cycling in modern and ancient environments on Earth and potentially Mars. Here, we aim to understand what promotes the fossilisation of microorganisms after the initial stages of biomineralisation, committing bacteriomorphic structures to the geological record within iron-rich environments. Mineral encrusted cell envelope structures were routinely identified within a goethite-rich vein that cross-cut the saprolite (iron ore) of a weathered banded iron formation (BIF) system in the Quadrilátero Ferrífero, Brazil. The preservation of potential organic and mineralogical biosignatures associated with these fossils was characterised using the following high-resolution analytical techniques: scanning and transmission electron microscopy, focused ion beam scanning electron microscopy, nanoscale secondary ion mass spectrometry, synchrotron-based Fourier transform infrared spectroscopy and Raman spectroscopy. Electron microscopy demonstrated that mineral nucleation associated with a range of cell envelope structures typically followed the extant cell templates. These biologically-influenced iron-rich minerals are microcrystalline with minimal secondary growth. In contrast, intracellular mineralisation formed larger minerals that grew inward from the cell membrane to infill intracellular voids after cell death. A three dimensional reconstruction of encrusted cell envelopes in a fossilised biofilm suggests that microorganisms may be able to replicate, during the initial stages of mineralisation. Carbon and nitrogen signatures are preserved associated with the cell envelope structures; however, there were no conclusive mineralogical biosignatures associated with the mineralised cell envelopes highlighting the classical importance of morphology and elemental biosignatures in determining the biogenicity of bacteriomorphic structures.
format Online
Article
Text
id pubmed-7303173
institution National Center for Biotechnology Information
language English
publishDate 2020
publisher Nature Publishing Group UK
record_format MEDLINE/PubMed
spelling pubmed-73031732020-06-22 Characterisation of iron oxide encrusted microbial fossils Levett, Alan Gagen, Emma J. Rintoul, Llew Guagliardo, Paul Diao, Hui Vasconcelos, Paulo M. Southam, Gordon Sci Rep Article Robust methods for the characterisation of microbial biosignatures in geological matrices is critical for developing mineralogical biosignatures. Studying microbial fossils is fundamental for our understanding of the role microorganisms have played in elemental cycling in modern and ancient environments on Earth and potentially Mars. Here, we aim to understand what promotes the fossilisation of microorganisms after the initial stages of biomineralisation, committing bacteriomorphic structures to the geological record within iron-rich environments. Mineral encrusted cell envelope structures were routinely identified within a goethite-rich vein that cross-cut the saprolite (iron ore) of a weathered banded iron formation (BIF) system in the Quadrilátero Ferrífero, Brazil. The preservation of potential organic and mineralogical biosignatures associated with these fossils was characterised using the following high-resolution analytical techniques: scanning and transmission electron microscopy, focused ion beam scanning electron microscopy, nanoscale secondary ion mass spectrometry, synchrotron-based Fourier transform infrared spectroscopy and Raman spectroscopy. Electron microscopy demonstrated that mineral nucleation associated with a range of cell envelope structures typically followed the extant cell templates. These biologically-influenced iron-rich minerals are microcrystalline with minimal secondary growth. In contrast, intracellular mineralisation formed larger minerals that grew inward from the cell membrane to infill intracellular voids after cell death. A three dimensional reconstruction of encrusted cell envelopes in a fossilised biofilm suggests that microorganisms may be able to replicate, during the initial stages of mineralisation. Carbon and nitrogen signatures are preserved associated with the cell envelope structures; however, there were no conclusive mineralogical biosignatures associated with the mineralised cell envelopes highlighting the classical importance of morphology and elemental biosignatures in determining the biogenicity of bacteriomorphic structures. Nature Publishing Group UK 2020-06-18 /pmc/articles/PMC7303173/ /pubmed/32555223 http://dx.doi.org/10.1038/s41598-020-66830-z Text en © The Author(s) 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
spellingShingle Article
Levett, Alan
Gagen, Emma J.
Rintoul, Llew
Guagliardo, Paul
Diao, Hui
Vasconcelos, Paulo M.
Southam, Gordon
Characterisation of iron oxide encrusted microbial fossils
title Characterisation of iron oxide encrusted microbial fossils
title_full Characterisation of iron oxide encrusted microbial fossils
title_fullStr Characterisation of iron oxide encrusted microbial fossils
title_full_unstemmed Characterisation of iron oxide encrusted microbial fossils
title_short Characterisation of iron oxide encrusted microbial fossils
title_sort characterisation of iron oxide encrusted microbial fossils
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7303173/
https://www.ncbi.nlm.nih.gov/pubmed/32555223
http://dx.doi.org/10.1038/s41598-020-66830-z
work_keys_str_mv AT levettalan characterisationofironoxideencrustedmicrobialfossils
AT gagenemmaj characterisationofironoxideencrustedmicrobialfossils
AT rintoulllew characterisationofironoxideencrustedmicrobialfossils
AT guagliardopaul characterisationofironoxideencrustedmicrobialfossils
AT diaohui characterisationofironoxideencrustedmicrobialfossils
AT vasconcelospaulom characterisationofironoxideencrustedmicrobialfossils
AT southamgordon characterisationofironoxideencrustedmicrobialfossils