Speaker
Description
Bacteria of the family Cand. Midichloriaceae (Rickettsiales, Alphaproteobacteria) like Aquarickettsia spp. or Grellia spp. are common intracellular symbionts in a wide range of aquatic protists and animals, such as euglenozoans, placozoans or cnidarians. They have been detected in almost 10% of all aquatic microbiomes, but their pathogenic or beneficial roles in the associations remain unclear. To better understand the ecophysiology and the molecular mechanisms behind these symbioses, we combine RNASeq data from experiments with high-resolution imaging techniques such as immunofluorescence and fluorescence in-situ hybridization in a 3D context and at sub-cellular resolution. A special focus of our work are effector proteins of the symbionts that are secreted into the host cells and that appear to modulate host cell biology to create and stabilize the intracellular niche of the symbionts. We use structural modelling, phylogenetic analyses and recombinant expression-based experiments for the characterization of these effectors and the validation of their function. Based on our preliminary results, the Midichloriaceae symbionts in our protist and animal models are in mutualistic rather than parasitic interactions and likely support their hosts with the digestion of energy rich and commonly available fungal and algal carbohydrates.
