Soutenance HDR : Characterization of native enzymes to understand how anaerobic microbes impact biogeochemical cycles

Par Dr Tristan Wagner (IBS/Groupe Extremophiles et grands assemblages moléculaires)

Microbes are actors of the biogeochemical cycles, transforming gases, minerals, and biological matter through enzymatic reaction chains. Among them, anaerobic archaea, namely methanogens and methanotrophs, play a key role in converting planetary carbon, nitrogen, and sulfur, impacting the biosphere and providing green sustainable solutions for our modern society. The last fourteen years of my career were devoted to understanding the molecular basis of these microbial transformations, such as methane production or degradation, CO2 and carbon monoxide conversion to biofuels, N2 fixation, and sulfur cycling. Since these enzymes harbor O2-sensitive complicated metallocofactors, most of my work relies on native protein purification from the microbes themselves under strict O2 exclusion. After a brief presentation of my career and PhD project, the presented work summarizes my most renowned breakthrough regarding the elucidation of molecular tricks in carbon, nitrogen, and sulfur metabolisms in methane-generating microbes, including their regulatory networks. Then, the latest research led by my group is introduced with : (i) how methanogens munch on methylated substrates such as methanol and lignin-degradation products, (ii) how an industrial bacterium turns waste gases into biofuels, (iii) the study of a microbial consortia “that burn” methane and ethane without oxygen via a native approach. Finally, I will present the features of my past group and my future laboratory.