MEB - Topic 2

Microbial metabolisms involved in the functioning and coupling of the biogeochemical cycles in the climate change context

 

Moderator : Valerie Michotey

 

The team has a great expertise in microbial ecology of anaerobic environments, specially concerning the Carbon, Nitrogen and Sufur biogeochemical cycles. Our goal is now to focus on their coupling with respect to the global climate change and related episodes of hypoxia. 

A particular interest is focused on :

  1. Relationship between N cycle and either metals cycle (anaerobic nitrification coupled with Mn cycle or Fe-Ammox), S cycle (H2S oxidation and nitrate reduction) or CH4 cycle (anaerobic CH4 oxidation and Nitate/sulfate reduction).
  2. Impact of anaerobic metabolisms (sulfate reduction and methanogenesis) on the Mercury cycle (methylation/demethylation) through an active collaboration with Marine Environmental Chemistry team.

The originality of our approach consists in coupling C, N and S fluxes with the measurement of the bacterial metabolic activities responsible for these fluxes to the structure of the associated communities. The metabolisms identified, based on analytical expertise both in situ and in controlled microcosms, are confirmed at the molecular level by genomics and transcriptomics. The new metabolic pathways are elucidated by physiological and post-genomic approaches on model strains isolated from environments of interest.

 

Examples of studies

 

Methane cycle

Study of the methane cycle (production and oxidation) in Arctic and sub-Antarctic ecosystems exposed to climate change: measurement of emission flux, dissolved methane concentration profiles, characterization of the microbial actors involved (methanogens and methanotrophs, aerobes and anaerobes)

 

The diversity and activity of methanogenic and methanotrophic microorganisms are analyzed both in situ (especially in climate change-sensitive ecosystems such as permafrost, Arctic / Antarctic wetlands and tropical reservoirs) and in microcosms, in response to temperature variations. This microbial characterization is coupled with the geochemical evaluation of fluxes and profiles of dissolved methane and CO2, in order to evaluate their impact on the regulation of greenhouse gas emissions.

Nitrogen Cycle

Our project focuses on the aerobic / anaerobic interfaces and episodes of hypoxia. We are particularly interested in unconventional processes recently discovered (comammox) and the coupling between the N cycle and those of metals (Mn / Fe), S or methane

.

Iron cycle

The dynamics of ferro-oxidative bacteria (FeOB) within microbial mats that are rich in iron oxides depending on the environmental conditions and their variations, will allow to understand their role in the formation of its mats and how they impact the geochemical cycles of iron but also those of Carbon, Nitrogen, and less importantly those of methane and sulfur.