Polysphaeroides filiformis, a proterozoic cyanobacterial microfossil and implications for cyanobacteria evolution
Catherine F. Demoulin,
Marie Catherine Sforna,
Yannick J. Lara,
Yohan Cornet,
Andrea Somogyi,
Kadda Medjoubi,
Daniel Grolimund,
Dario Ferreira Sanchez,
Remi Tucoulou Tachoueres,
Ahmed Addad,
Alexandre Fadel,
Philippe Compère,
Emmanuelle J. Javaux
Affiliations
Catherine F. Demoulin
Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, 4000 Liège, Belgium
Marie Catherine Sforna
Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, 4000 Liège, Belgium; Centre de Biophysique Moléculaire, (UPR CNRS 4301), 45071 Orléans, France
Yannick J. Lara
Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, 4000 Liège, Belgium
Yohan Cornet
Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, 4000 Liège, Belgium
Andrea Somogyi
Synchrotron Soleil, 91190 Saint-Aubin – BP 48, France
Kadda Medjoubi
Synchrotron Soleil, 91190 Saint-Aubin – BP 48, France
Daniel Grolimund
Paul Scherrer Institut, Swiss Light Source, 5232 Villigen PSI, Switzerland
Dario Ferreira Sanchez
Paul Scherrer Institut, Swiss Light Source, 5232 Villigen PSI, Switzerland
Remi Tucoulou Tachoueres
ESRF-The European Synchrotron, 38000 Grenoble, France
Ahmed Addad
Unité Matériaux et Transformations (UMR CNRS 8207), Université Lille 1 - Sciences et Technologies, 59650 Villeneuve d'Ascq, France
Alexandre Fadel
Unité Matériaux et Transformations (UMR CNRS 8207), Université Lille 1 - Sciences et Technologies, 59650 Villeneuve d'Ascq, France
Philippe Compère
Functional and Evolutive Morphology, UR FOCUS, and Center for Applied Research and Education in Microscopy (CAREM-ULiege), University of Liège, 4000 Liège, Belgium
Emmanuelle J. Javaux
Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, 4000 Liège, Belgium; Corresponding author
Summary: Deciphering the fossil record of cyanobacteria is crucial to understand their role in the chemical and biological evolution of the early Earth. They profoundly modified the redox conditions of early ecosystems more than 2.4 Ga ago, the age of the Great Oxidation Event (GOE), and provided the ancestor of the chloroplast by endosymbiosis, leading the diversification of photosynthetic eukaryotes. Here, we analyze the morphology, ultrastructure, chemical composition, and metals distribution of Polysphaeroides filiformis from the 1040–1006 Ma Mbuji-Mayi Supergroup (DR Congo). We evidence trilaminar and bilayered ultrastructures for the sheath and the cell wall, respectively, and the preservation of Ni-tetrapyrrole moieties derived from chlorophyll in intracellular inclusions. This approach allows an unambiguous interpretation of P. filiformis as a branched and multiseriate photosynthetic cyanobacterium belonging to the family of Stigonemataceae. It also provides a possible minimum age for the emergence of multiseriate true branching nitrogen-fixing and probably heterocytous cyanobacteria.
