MEB - Topic 1

Dynamics in complex microbial systems : relationships and interactions between organisms

 

Moderator : Cécile Militon

 

Interactions among community members (including symbionts) could produce endogenous dynamics in composition and activities, even in the absence of environmental changes. Our aim is to take into account these endogenous dynamics in combination with environmental factors to reach a more integrated understanding of the functioning of the complex microbial systems. In our programs, we will not only focus on direct and indirect microbial interactions (prokaryotes, viruses and unicellular eukaryotes) but also between macro- and microorganisms (macrobenthos, macrophytes, metazoan plankton).

Our main scientific issues concern (i) the transfer of metabolic products (metabolic coupling), (ii) the sharing of metabolic pathways and (iii) the horizontal gene transfer (HGT) throughout the ecological network of microbial communities. The role of the physical and chemical signals in the establishment of these interactions (e.g. bioluminescence) is also studied. Data from environmental genomics are integrated by developing several bioinformatics tools like the OGA web site (Ocean Gene Atlas).

 

Examples of studies

Interspecific hydrogen transfer : microorganisms in hydrogen biogeochemical cycle at marine hydrothermal vents

 

Within the anaerobic ecosystems, either terrestrial or marine, it is well established that molecular hydrogen (H2), which could be an intermediate metabolite as produced by some microorganisms and consumed by others, plays an important role in the regulation and functioning of the microbial trophic network. Research studies are focused on the mechanisms of interspecies H2 transfer between H2-producing anaerobic and H2-consuming microaerobic hyperthermophilic microorganisms.

Biotechnical projects linked to bioenergy production are also developed using the capability of hyperthermophilic bacteria to produce H2 from various sugars. (topic 5).

Electronic mutualisms : the electroactive microorganisms from deep-sea hydrothermal vent systems

 

 

It has been recently shown that some microorganisms are able to exchange electrons with an insoluble electrical conductor. The team is studying the electroactivity of thermophilic and hyperthermophilic microorganisms linked to extreme and/or hydrothermal vent ecosystems.

Especially, we focus on electroactive microbial communities (electrotrophic or electrogenic) as well as on electronic mutualism (Direct Interspecies Electron Transfer (DIET). These researches are also in relationship with the production of electrofuel and electric power (see topic 5).

Importance of diazotrophic cyanobacteria in food web

 

Within some subtropical marine ecosystems in the South-West Pacific, a paradoxical bloom of phytoplanktonic microorganisms is observed in oligotrophic water zones (SPOT -South Pacific Ocean Time Series- program). We search to identify these microorganisms and to understand the impact of their metabolism on the trophic network, the last levels being exploited by human beings. In that way, we study their biodiversity, metabolism (see topic 5) and their interaction with virus, micro- and macro components of plankton and nekton. This research project is developed in partnership with the Kanak civil society.

 

Bioluminescence

 

Our goal is to understand the role of bioluminescence in the marine geochemical processes by using Photobacterium phosphoreum ANT-2200 (bioluminescent bacterium isolated at the ANTARES site (Astronomy with a Neutrino Telescope and Abyss environmental RESearch project) at 2200m depth).

This research is based on the multi-domain skills developed in the laboratory (physiology at atmospheric and high pressures, genetics, transcriptomics, etc.). It also has an applied aim through the collaboration with the company “TANGRAM Architectes” for the implementation of bioluminescence in a sustainable mediterranean habitat model (collaboration labeled CapEnergie Pole, Pole Sea, recognized by the PACA Region and awarded by the Rougerie Foundation).