Characterization of host-symbiont molecular interactions and evolutionary relationships in the gutless oligochaete Olavius algarvensis

The marine gutless oligochaete O. algarvensis lives in obligate symbiosis with a chemosynthetic bacterial consortium that exclusively provides it with nutrition. This thesis contributes to a better understanding of how this essential symbiosis is maintained, both on a physiological and immunological level (chapter IV), as well as from an evolutionary perspective (chapter II). This is addressed by using metagenomics, -proteomics and -transcriptomics to better understand symbiont transmission, diversity, co-divergent evolution and the molecular adaptations of the host that allow it to intimately associate with a diverse and physiologically demanding chemosynthetic consortium (anoxia and noxious substances). Furthermore, chapter III provides the first functional genomic description of the spirochaetal symbiont of O. algarvensis, showing that it is most likely a beneficial symbiont involved in the utilization and funneling of environmentally derived organic nutrients into the symbiosis.