Establishing a model system to unravel metabolic interactions in the Bathymodiolin symbiosis

Abstract

Chemosynthetic symbioses represent a fascinating ecological adaptation of animals, wherein animals rely on chemosynthetic bacteria to tap into chemical energy sources otherwise inaccessible to them. In deep-sea habitats, such as hydrothermal vents or hydrocarbon seeps, this form of nutritional symbiosis allows vast colonies of invertebrates to thrive. Mussels of the genus Bathymodiolus are among the most common species found in these environments. In this thesis, I explored the use of model organisms as tools in Bathymodiolus research. As a model for the host, I applied the related shallow water mytilid Mytilus edulis, which is aposymbiotic but shares a similar body plan and evolutionary history with Bathymodiolus, and the more distantly related pacific oyster Crassostrea gigas.Matrix-assisted laser desorption/ionization (MALDI)-MSI in combination with liquid chromatography/mass spectrometry (LC/MS²) was used to identify and localize phosphonolipids in both species. Methyloprofundus sedimenti strain WF1 was chosen as a model organism for the methanotrophic symbionts of the same genus, which was cultivated for transcriptomic and metabolic analysis. In a pangenomic analysis of 35 genomes, it was found that while genome reduction is evident in some symbiotic species, the overall metabolic capabilities and chemosynthetic potential is maintained.