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Abstract:
The essential role that symbioses between bacteria and animals play for life on
earth has been a major topic of scientific research for the past fifty years. We now
understand that eukaryotic life could not have evolved without the intricate influence of
bacteria, which impact physiological, metabolic, nutritional, developmental and
evolutionary processes in many eukaryotic phlya.
One model system for such associations is the well-studied symbiosis between the gutless
oligochaete Olavius algarvensis, from the island of Elba, Italy, and its obligate
consortium of chemoautotrophic sulphide-oxidizing γ -proteobacteria and sulphatereducing
δ -proteobacteria. The complete nutritional dependency of the host to its
symbionts has led to the reduction of the digestive tract and the excretory system. The
aim of this thesis is to investigate how this symbiosis is maintained over consecutive
generations. In particular I examine whether symbionts are transmitted into the next host
generation vertically – by smearing from the parent worm during oviposition,
horizontally – by uptake from the environment, or by both these modes.
