Congratulations to Aina Astorch-Cardona (MEB), who defended her thesis on October 30.

On the following topic: "Influence of environmental variations on the dynamics of microbial communities in iron-rich marine mats".

The jury was composed of :


- Mme Maria Soledad GONI URRIZA (Maîtresse de conférences), Université de Pau et des Pays de l'Adour
- M. Karim BENZERARA (Directeur de recherche), IMPMC
- Mme Valérie CHAVAGNAC (Directrice de recherche), GET
- Mme Patricia BONIN (Directrice de recherche), MIO

- Mme Céline ROMMEVAUX (Chargé de Recherche), MIO
- M. David EMERSON (Professor), Bigelow Laboratory for Ocean Sciences

Summary :

This thesis aims to understand how environmental variations influence the microbial communities’ dynamics in marine iron-rich microbial mats. To achieve this objective, we have studied the microbial communities of mats developing in two different environments in terms of iron origin and concentration, the Lucky Strike Hydrothermal Field (LSHF) and the EMSO-Western Ligurian Sea Observatory (EMLIG), together with those of microbial colonizers. In order to analyze this diversity, we have used 16S rRNA gene metabarcoding and we have quantified the abundance of different taxonomic groups (including Zetaproteobacteria) using qPCR or dPCR approaches. Moreover, we have coupled these analyses with geochemical data from the end-member hydrothermal fluids associated with the mats at the LSHF, and we have studied the different Fe-oxyhydroxide morphologies produced by Zetaproteobacteria using SEM. Our results suggest that the microbial communities of iron-rich mats from hydrothermal environments are influenced by the type of diffuse fluids that nourish them, which vary depending on the composition of their associated end-member hydrothermal fluids and the lithology of the substratum on which they develop. In non-hydrothermal contexts, the bacterial communities depend completely on the type of substratum in which they form. The communities from Fe-bearing metals or minerals resemble more to those associated with biocorrosion or to mineral weathering environments, respectively. Finally, our findings show that Zetaproteobacteria are key taxa in the creation of communities associated with Fe-bearing materials or Fe-rich environments, and that they are also mostly influenced by the type of substratum in which they develop and the age of the mats