Physiological and multi-omics studies of microbial sulfur metabolisms present in hydrothermal ecosystems

• Main Author: Allioux, Maxime
• Other Authors: Laboratoire de Microbiologie des Environnements Extrêmophiles (LM2E), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne occidentale - Brest, Karine Alain, Mohamed Jebbar
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2021
• Subjects: Sulfur cycle; Disproportionation; Comproportionation; Organic sulfur compounds; Hydrothermal; Cycle du soufre; Dismutation; Comproportionnement; Composés organiques soufrés; Composés organiques soufrés Hydrothermal; [SDV.MP]Life Sciences [q-bio]/Microbiology and Parasitology; Kerguelen; Kerguelen Islands
• Online Access: https://theses.hal.science/tel-03789624; https://theses.hal.science/tel-03789624/document; https://theses.hal.science/tel-03789624/file/These-2021-SML-Microbiologie-ALLIOUX_Maxime.pdf

Hydrothermal vents host a vast microbial diversity, both at the taxonomic and metabolic levels. These ecosystems are qualified as extreme, because they harbor harsh physico-chemical gradients. Sulfur is omnipresent in these environments, and it can be used by a large diversity of microorganisms for oxidation or reduction reactions.However, the sulfur cycle remains partially unknown in these ecosystems. The objective of this thesis was to study the poorly documented or thermodynamically predicted metabolisms of the sulfur cycle in hydrothermal ecosystems, namely the dismutation of inorganic sulfur compounds, the catabolism of organosulfur compounds and the comproportionation of sulfur. Four new inorganic sulfur compound disproportionating taxa were discovered during this study and extensive genomic analyses were conducted to decipher the pathways of inorganic sulfur compound dismutation. Comparative genomics analyses identified a gene cluster potentially involved in elemental sulfur dismutation in marine hydrothermal bacteria, but this result will need to be confirmed by functional approaches.Finally, the microbial communities of the geographically isolated hot springs from the Kerguelen Islands were studied by metagenomics, revealing the presence of many new lineages of bacteria and archaea in these previously unstudied habitats. Les cheminées hydrothermales hébergent une vaste diversité microbienne, tant au niveau taxonomique qu’au niveau métabolique. Ces écosystèmes sont qualifiés d’extrêmes, en raison des très larges gradients physicochimiques qu’ils abritent. Le soufre y est un élément omniprésent, il peut être utilisé par une large diversité de microorganismes pour des réactions d’oxydations ou de réductions. Cependant, le cycle du soufre reste partiellement méconnu au sein de ces écosystèmes. L’objectif de cette thèse était d’étudier les métabolismes du cycle du soufre peu documentés ou simplement prédits par la thermodynamique, au sein des écosystèmes hydrothermaux, à savoir la dismutation des composés ...