About

My main research interest is to better understand the behaviour, history and evolution of natural systems at both the local and global scales. A significant part of this research is dedicated to explicitly take into account, when present, the biological compartment of these systems by modeling their advanced thermodynamics, including non-equilibrium thermodynamics and thus de facto the kinetics. Determining these thermodynamics and kinetics requires experimental practice on analogs of these systems at the submicron scale  through the structure of complex interfaces between different media (e.g.  biological and mineral), compositional gradients or deciphering phase assemblages in tiny experimental setups (e.g.  micro-reactors). For this I systematically apply advanced structural and chemical visualization of these analog microsystems by (mostly electron) microscopies and spectroscopic techniques.

I am currently mainly applying this approach to hydrothermal systems, whether in the deep ocean or at the surface of continents. Those are privileged interfaces between the Earth’s chemically reduced interior and the often more oxidized external fluid envelopes. An important research question, that remains mysterious to this day, is the level of contribution of living organisms to the geochemical functioning of these systems. For this reason, over the past few years, in close collaboration with my colleague Aurore Gorlas of Université Paris Saclay -the major advances that we made together in this field should be largely credited to her-, I developed a research project about life of hyperthermophilic microoganisms at extreme temperatures in highly mineralized hydrothermal environments. This research has major implications for biogeochemical cycles, for search of life limits on Earth and in other planets and for discussions about the conditions of emergence of life. I believe that this particular area of science also has the potential, in the more or less long term, to provide decisive solutions to current health and energy issues in an unstable world.

In the course of this quest to identify the limits and impact of life at high temperatures, I came across the concept of habitability and, with my colleagues Antonin Affholder and Régis Ferrière, I developed thermo-kinetic models of the limits of living organisms. As phosphorus is the main biogeochemical marker of living organic matter and therefore likely the major limiting nutrient for determining the qualitative and quantitative boundaries of the biosphere, this logically, but only very recently, led me to an in-depth study of phosphorus and phosphorylation in current and ancient natural systems, What was merely a side project is now becoming central in my research.

In parallel, I am involved in several research projects, for which I am not the principal investigator, helping colleagues with my skills in microscopy, spectroscopy and thermokinetic modelling. in the fields of

• High-pressure mineralogy of planetary interiors,
• Thermodynamics of  biomineralization by prokaryotic microorganisms 
• Environmental biomineralogy with special emphasis on hydrogen production and consumption by microorganisms,
• Medical biomineralogy with special emphasis on interactions between minerals and macro-organisms.