Stromatolites as Biosignatures of Atmospheric Oxygenation: Carbonate Biomineralization and UV-C Resilience in a Geitlerinema sp. - Dominated Culture

Abstract

Modern stromatolites are key to the record of past microbial activity preserved in fossil carbonate deposits. Mono-phototrophic cultures dominated by the cyanobacterium Geitlerinema sp. were obtained from a laboratory-maintained, low magnesium-calcite stromatolite originating from Lagoa Vermelha, Brazil. This lagoonal system has been described as a Precambrian analog, illustrating a period of photosynthetically induced atmospheric oxygenation, which created a global sanctuary from shortwave solar radiation and enabled the evolution of modern life on Earth. The enrichment cultures precipitate carbonates in minimal media, suggesting that cyanobacterial photosynthesis and extracellular polymeric substance production may be crucial in the mineralization of the studied stromatolite. We further show that Geitlerinema sp. can build and maintain filamentous mats under long-term UV-C exposure. Our results suggest that present day stromatolites dominated by cyanobacteria may be interpreted as biosignatures of atmospheric oxygenation and have implications for the search for putative biological traces on Mars.

Selective Adsorption of Amino Acids in Crystals of Monohydrocalcite Induced by the Facultative Anaerobic Enterobacter ludwigii SYB1

“…Therefore, the focus of MICP is how the microbes regulate the formation of bioproducts. Whether in the natural environment, in the laboratory, and/or in biomimetic studies, it is widely accepted that the key factor is extracellular polymeric substances (EPS), secreted by microbes ( Cusack and Freer, 2008 ; Krause et al, 2012 ; Perri et al, 2018 ; Huang et al, 2019 ; Popall et al, 2020 ; Yin et al, 2020 ; Zhao et al, 2020c ). It has been demonstrated that negatively charged EPS could serve as nucleation sites; this is mainly caused by the deprotonation of carboxyl components (e.g., amino acids) under high pH conditions ( Katz et al, 1998 ; Deng et al, 2010 ).…”

Biomineralization of ordered dolomite and magnesian calcite by the green alga Spirogyra

“…The accumulation of intracellular Ca 2+ oxalates (Pueschel, 2001) and less commonly aragonite (Mann et al ., 1988) and baryte (Kreger & Boere, 1969) in cells of Spirogyra had been long recognized (Klein, 1877, as cited in Pueschel, 2001), but it is the first time that intracellular dolomite, calcite and minor huntite–magnesite biomineralization has been documented for this alga. Differently, the production of monomineral carbonate inclusions has been described in phylogenetically distant microorganisms (Segovia‐Campos et al ., 2021), including different members of the phyla Cyanobacteria (Couradeau et al ., 2012; Benzerara et al ., 2014; Popall et al ., 2020) and Proteobacteria (Monteil et al ., 2021) and in a microalga (Martignier et al ., 2016). Most of those inclusions consist of amorphous calcium carbonate phases that can contain other alkaline‐earth metals (Segovia‐Campos et al ., 2021).…”

Metabolomics Spatial Survey of Modern Stromatolites from South Africa and Characterization of Ibhayipeptolides

“…These observations motivated us to focus our subsequent analyses on substrate core samples, particularly in light of the known capability of cyanobacteria to produce biologically active metabolites and their central role in structuring microbialite microbial consortia. 16,29,35 Sunburst plots of the CANOPUS output for substrate samples from flag sites 1 (surface) and 7 (submerged) (Fig. S13) display limited divergence of compound superclasses between sites, but revealed significant differences at the class level in metabolites present at each site.…”

“…While they provide insight into the origin, evolution, and distribution of life on Earth and beyond, modern microbialites have elicited interest for their role in global biogeochemical cycling. [14][15][16][17][18][19] Supratidal microbialites on rocky coasts have been described since 2003 20 and these distinct siliciclastic environments are characterized as representative of ancient microbialite beds along Precambrian coastlines. 21 Molecular-based approaches have provided phylogenetic profiles, based on 16S/18S SSU rRNA genes that identified taxonomically diverse consortia, representing different functional guilds, for example, photosynthesis, sulfate reduction, sulfide oxidation, heterotrophy, carbohydrate metabolism, and carbonate accretion.…”