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Tracking early metabolisms in the rock record with metals

Thursday 12 November - 4 PM

Marie Sforna

University of Liège

ABSTRACT: The metallome of an organism corresponds to the set of elements present in a cell. Among these elements, around 15 are transition metals. These metals are involved in all aspects of cell life, such as, DNA production, energy production and transport, detoxification processes. The requirement in metals changes based on the domain of life, the taxon, the metabolism and the environment. Microorganisms have developed different processes that allow them to make available the metals they need. For example, they can dissolve the metals trapped in the mineral phases or immobilize them in order to make them bioavailable. In modern environments, the mobilization, immobilization or detoxification processes can be traced by observing the enrichment or depletion of certain metallic species as well as their oxidation states. Thus, these processes are likely to have been recorded in the fossil record and our ability to identify them in the Precambrian rock record could allow us to better constrain the evolution and metabolism of the first organisms.

Through a fine coupling of the study at different scales (sedimentary series → microfossil) of the distribution of metals (X-ray fluorescence applied to the synchrotron), organic matter (Raman, FT-IR, TEM) and the mineral matrix (Raman, SEM, LA-ICPMS), it is possible to identify different metal/mineral/organic matter associations corresponding to different biological and abiotic processes that control the accumulation of metals within traces of life.

Here, we will present the results of this type of approach on Archean stromatolites of the Tumbiana formation (2.72 Ga, Pilbara Craton, Australia) and on Proterozoic eukaryotic microfossils from the Mbuji-Mayi Supergroup (1 Ga, Congo Basin, DRCongo). We will show the potential of this approach on several types of typical Precambrian objects to highlight accumulations of metals which can be attributed to metabolic processes. This study therefore shows the potential of this type of approach to provide new fundamental information on the metabolisms of organisms living during the Precambrian and then on the co-evolution of Life and Earth.

BIO: Marie Catherine Sforna is currently is a FNRS fellow researcher at the University of Liege in Emmanuelle Javaux’s Lab “Early Life and Traces – Astrobiology”. She obtained her PhD in Geochemistry in 2014 at the Institut de Physique du Globe de Paris in France, under the direction of Pascal Philippot and Mark van Zuilen. During her PhD, she developed the use of metals to track biologic processes and their preservation through time in Archean and modern stromatolites. Then, she did a postdoctorate with Daniele Brunelli in the Department of Geology at the University of Modena in Italy. She characterized condensed carbonaceous material formed abiotically during the progressing serpentinization of mantellic material at different oceanic ridges and within ophiolites. She arrived in Liege in 2016 with a Marie Curie Postdoc In Grant and since 2018 she has a FNRS grant. She developed her approach based on metals on Proterozoic eukaryotic microfossils in order to reconstruct their metabolisms.