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

Wippler, Juliane

English

E-LIB Dokumentserver - Staats und Universitätsbibliothek Bremen

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

State and University Library Bremen

Once thought to be a curiosity, it has now become increasingly recognized that beneficial symbioses between animals and microbes are common and wide-spread in nature. Animalmicrobe interactions had mostly been studied from a medical perspective. However, thanks to major advances in sequencing technology that allowed the genomic study of non-cultivable microorganisms, it has become apparent that not only most (if not all) animals are colonized by microbes, but that the majority of these microbes is harmless or even beneficial to the host animal and often contributes integral functions to the biology of these animals. In some cases, animals form such highly intimate associations with bacteria that the association becomes obligate for their survival. One such example is the obligate symbiosis between marine gutless oligochaete worms (Annelida, Phallodrilinae) and their chemosynthetic bacterial symbionts. Over the course of evolution, gutless oligochaetes have lost their entire digestive system, including mouth, gut, and anus, as well as their excretory organs, becoming entirely dependent on their symbionts to provide all necessary nutrients and to remove the waste products of the host. Each gutless oligochaete host harbors its own highly species-specific consortium of bacteria. Among the gutless oligochaetes, the model species Olavius algarvensis is one of the best studied. This Mediterranean species lives in symbiotic association with multiple bacterial phylotypes, including two gammaproteobacterial sulfur-oxidizers (OalgG1 and OalgG3), two deltaproteobacterial sulfate-reducers (OalgD1, OalgD4) and a spirochaete symbiont of unknown function (OalgS1). Although this species is one of the best studied gutless oligochaetes, many aspects of this symbiosis remain unresolved, in particular with regard to the evolutionary history of host and symbionts, their population level diversity, the transmission of symbionts from parent to offspring, the molecular mechanisms that enable the symbiosis to be functional and maintained across all life stages and across host generations, and the function of the spirochaete symbiont within the symbiosis

Wippler, J.

MPG.PuRe