In the framework of the 2022 proposals call ‘Diversity of biological mechanisms’ from the CNRS Institute of Biological Sciences (INSB), the team led by Alain Lescure is one the fifteen teams selected. This program rewards studies to identify and/or develop new models to answer important and specific biological questions that cannot be answered by research conducted on currently available model organisms, such as mice, Drosophila, Caenorhabditis, Arabidopsis, yeast or cell cultures. The selected project concerns the study of symbiotic bacteria living in symbiosis with the sponge Aplysina aerophoba to better characterize the function of SelenoN, a selenium-containing protein involved in a hereditary muscle disease in humans. This sponge being endemic on the French Mediterranean coast, this project is conducted in collaboration with the team of Marcelino Suzuki of the Observatoire Océanologique in Banyuls-sur-Mer. This study provides for the first time a chance to analyze the SelenoN activity in a particular but natural biological and ecological context.