Evidence for metabolic diversity in Meso-Neoproterozoic stromatolites (Vazante Group, Brazil)

Abstract

Deciphering the evolution of ecological interactions among the metabolic types during the early diversification of life on Earth is crucial for our understanding of the ancient biosphere. The stromatolites from the genus Conophyton cylindricus represent a datum for the Proterozoic (Meso to Neoproterozoic) on Earth. Their typical conical shape has been considered a result of a competition between microorganisms for space, light and nutrients. Well-preserved records of this genus from the “Paleontological Site of Cabeludo”, Vazante Group, São Francisco Craton (Southern Brazil) present in situ fossilized biofilms, containing preserved carbonaceous matter. Petrographic and geochemical analyses revealed an alternation between mineral laminae (light grey laminae) and fossilized biofilms (dark grey laminae). The dark grey laminae comprise three different biofilms recording a stratified microstructure of microbial communities. These three biofilms composing the dark grey laminae tend to be organized in a specific pattern that repeats through the stromatolite vertical section. Iron and manganese are distributed differently along the dark and light grey laminae; X-ray absorption and luminescence data showed possible different areas with authigenic iron and iron provided from diagenetic infiltration. Cryptocrystalline apatite in the lowermost biofilms in each dark grey laminae may suggest past metabolic activity of sulfide-oxidizing bacteria. These findings suggest that the microorganisms reached a complex metabolic diversification in order to maintain an equilibrium situation between the three different biofilms along the vertical section of the structures, thus benefiting the whole microbial community. This means that the stromatolites from the Conophyton genus may have formed as a result of a greater complexity of interactions between microorganisms, and not only from competition between photosynthesizers.

State-of-the-art multimodal scanning hard X-ray imaging and tomography sheds light at multiple length-scales on biomineralization related processes

“…From a methodological point of view, simultaneous measurement of all modalities has particular importance in producing overlay imaging with the same probing spatial resolution. Such integrative multimodal imaging approach is still in its infancy (Callefo et al, 2022;Graziotto et al, 2023). It permits to combine all information to study highly heterogenous systems in a more quantitative manner and with higher sensitivity.…”

“…Emerging analytical tools, such as multi-modal scanning hard X-ray imaging (e.g. (Somogyi et al, 2015;Schroer et al, 2016;Yan et al, 2016;Martínez-Criado et al, 2017;Parsons et al, 2017;Suuronen and Sayab, 2018;Yan et al, 2018;Chu et al, 2020;Quinn et al, 2021;Callefo et al, 2022;NANOSCOPIUM, 2024)) can provide invaluable pieces of information about these highly heterogenous hierarchical structures at multiple length-scales in 2D and/or 3D, offering new insights on biomineral formation pathways. Here, we provide an overview of the possibilities offered by such multimodal and multi-length-scale scanning X-ray imaging and tomography methods, through research examples performed at the NANOSCOPIUM beamline at synchrotron SOLEIL.…”

Chimera of fossil biomolecules found in Pleistocene fossil in tropical cave: Fossil biofilm characterization by micro Raman spectroscopy

“…Fossilized bacteria bio lms have been reported in various places on the earth. For example, from banded iron-formation 7,8 to the stromatolite rocks 9 . Recent studies demonstrated the bio lms have an important role on fossil preservation.…”