On the following topic: "Influence of environmental variations on the dynamics of microbial communities in iron-rich marine mats".
The jury was made up of :
- Ms Maria Soledad GONI URRIZA (Associate Professor), Université de Pau et des Pays de l'Adour
- Mr Karim BENZERARA (Research Director), IMPMC
- Ms Valérie CHAVAGNAC (Research Director), GET
- Ms Patricia BONIN (Research Director), MIO
- Ms Céline ROMMEVAUX (Research Fellow), MIO
- Mr David EMERSON (Professor), Bigelow Laboratory for Ocean Sciences
Summary:
This thesis aims to understand the influence of environmental variations on the dynamics of microbial communities in iron-rich marine mats. To do this, we studied the microbial communities of mats developing in two environments that differ in terms of origin and iron concentration, the Lucky Strike hydrothermal field (LSHF) and the EMSO-Ligure West observatory (EMLIG), as well as those of the microbial colonisers. To analyse this diversity, we used metabarcoding of the 16S rRNA gene and quantified the abundance of different taxonomic groups (including Zetaproteobacteria) using qPCR or dPCR approaches. We coupled these analyses with geochemical data from hydrothermal fluids associated with LSHF mats, and studied the different morphologies of iron oxyhydroxides produced by Zetaproteobacteria using SEM. Our results suggest that the communities of iron-rich microbial mats in hydrothermal environments are influenced by the diffuse fluid that feeds them, which varies according to the composition of the associated hydrothermal fluids and the lithology of the bedrock on which they develop. In a non-hydrothermal context, bacterial communities are completely dependent on the type of substratum on which they form. Communities on metals or iron-containing minerals more closely resemble those associated with biocorrosion or mineral alteration, respectively. Finally, our results show that Zetaproteobacteria are key taxa in the creation of communities associated with iron-rich materials or environments, and that they are also influenced by the type of substrate on which they develop and by the age of the mats.