PhD : Chloé Truong (Directors : François Guyot IMPMC, Aurore Gorlas I2BC, Sylvain Bernard IMPMC – Grant ED 227). 

Sulfur-rich hydrothermal vents are ecosystems characterized by extreme conditions of life. Yet numerous hyperthermophilic microorganisms adapted to hydrothermal conditions have been isolated from there. This hot biosphere still constitutes a little-known part of biodiversity, whether in terms of their ecosystem contribution or their evolution during the Earth history. This project aims to identify the organic and mineral traces left by those organisms and to look for them in rocks of various ages, in order to better constrain their evolution. The microorganisms are cultivated in simulated hydrothermal conditions and the culture residues are tested by multiscale analyses such as ATP-Metry, X-Ray Diffraction, Electronic Microscopy (SEM / TEM) and X-ray Absorption Spectroscopy based on synchrotron. Finally, the biogeochemical traces are placed under diagenesis conditions in order to determine their preservation/degradation through geological times. This work may offer a new vision on the thermal limits of life and on the signals potentially preserved in rocks.

Figure: Pyrite spherules formed in the presence of hyperthermophilic archaea (T. kodakaraensis)

© Chloé Truong