Skip to content Skip to navigation

Article: Diverse communities of Bacteria and Archaea flourished in Palaeoarchaean (3.5–3.3 Ga) microbial mats

Palaeontology - Vol. 63 Part 6 - Cover Image
Publication: Palaeontology
Volume: 63
Part: 6
Publication Date: November 2020
Page(s): 1007 1033
Author(s): Keyron Hickman‐Lewis, Frances Westall, and Barbara Cavalazzi
Addition Information

How to Cite

HICKMAN‐LEWIS, K., WESTALL, F., CAVALAZZI, B. 2020. . Palaeontology, 63, 6, 1007-1033. DOI: /doi/10.1111/pala.12504

Author Information

  • Keyron Hickman‐Lewis - Dipartimento Biologiche, Geologiche e Ambientali Università di Bologna via Zamboni 67 I‐40126 Bologna Italy
  • Keyron Hickman‐Lewis - CNRS Centre de Biophysique Moléculaire Rue Charles Sadron 45071 Orléans France
  • Frances Westall - CNRS Centre de Biophysique Moléculaire Rue Charles Sadron 45071 Orléans France
  • Barbara Cavalazzi - Dipartimento Biologiche, Geologiche e Ambientali Università di Bologna via Zamboni 67 I‐40126 Bologna Italy
  • Barbara Cavalazzi - Department of Geology University of Johannesburg PO Box 524, Auckland Park 2006 Johannesburg South Africa

Publication History

  • Issue published online: 25 November 2020
  • Manuscript Accepted: 15 July 2020
  • Manuscript Received: 09 April 2020

Funded By

INACMa (Inorganic Nanoparticles in Archaean Carbonaceous Matter – a key to early life and palaeoenvironmental reconstructions) project. Grant Number: 618657

Online Version Hosted By

Wiley Online Library
Get Article: Wiley Online Library [Pay-to-View Access] |

Abstract

Limited taxonomic classification is possible for Archaean microbial mats and this is a fundamental limitation in constraining early ecosystems. Applying Fourier transform infrared spectroscopy (FTIR), a powerful tool for identifying vibrational motions attributable to specific functional groups, we characterized fossilized biopolymers in 3.5–3.3 Ga microbial mats from the Barberton greenstone belt (South Africa). Microbial mats from four Palaeoarchaean horizons exhibit significant differences in taxonomically informative aliphatic contents, despite high aromaticity. This reflects precursor biological heterogeneity since all horizons show equally exceptional preservation and underwent similar grades of metamorphism. Low methylene to end‐methyl (CH2/CH3) absorbance ratios in mats from the 3.472 Ga Middle Marker horizon signify short, highly branched n‐alkanes interpreted as isoprenoid chains forming archaeal membranes. Mats from the 3.45 Ga Hooggenoeg Chert H5c, 3.334 Ga Footbridge Chert, and 3.33 Ga Josefsdal Chert exhibit higher CH2/CH3 ratios suggesting mostly longer, unbranched fatty acids from bacterial lipid precursors. Absorbance ratios of end‐methyl to methylene (CH3/CH2) in Hooggenoeg, Josefsdal and Footbridge mats yield a range of values (0.20–0.80) suggesting mixed bacterial and archaeal architect communities based on comparison with modern examples. Higher (0.78–1.25) CH3/CH2 ratios in the Middle Marker mats identify Archaea. This exceptional preservation reflects early, rapid silicification preventing the alteration of biogeochemical signals inherited from biomass. Since silicification commenced during the lifetime of the microbial mat, FTIR signals estimate the affinities of the architect community and may be used in the reconstruction of Archaean ecosystems. Together, these results show that Bacteria and Archaea flourished together in Earth's earliest ecosystems.

PalAss Go! URL: http://go.palass.org/l7e | Twitter: Share on Twitter | Facebook: Share on Facebook | Google+: Share on Google+