title: A model for endosymbiosis: interaction between Tetrahymena pyriformis and Escherichia coli.
abstract: Endosymbiosis in ciliates is a common and highly diverse phenomenon in nature, but its development at the mechanistic level and the origins are not easy to understand, since these associations may have arisen at any time during evolution. Therefore a laboratory model is helpful. It could be provided by the interaction of Tetrahymena pyriformis and Escherichia coli. Microscopic analyses with a genetically manipulated fluorescent strain of E. coli show single bacteria leaving food vacuoles and escaping digestion, an important prerequisite for further experiments. Under selective conditions, beneficial for T. pyriformis, the ciliate was shown to internalize E. coli cells. After feeding, bacteria, transformed with the plasmids pBS-neoTet or pNeo4, provide T. pyriformis with the ability to handle toxic conditions, caused by the aminoglykoside antibiotic paromomycin. Axenic cultures or cocultures with untransformed bacteria show lower cell numbers and survival rates compared to cocultures with transformed bacteria after transfer to paromomycin containing media. PCR detects bacterial DNA inside T. pyriformis cells. Additionally, microscopical analysis of selectively grown cocultures reveals fluorescing particles in the cytoplasm of T. pyriformis containing DNA and lipids, corresponding in size to E. coli. This system could be a reasonable model for understanding mechanisms of endosymbiosis establishment in ciliates.
authors.affiliation: Institut für Mikrobiologie, Lehrstuhl für Allgemeine Mikrobiologie und Mikrobengenetik, Friedrich-Schiller-Universität Jena, Neugasse 24, D-07743 Jena, Germany. Electronic address: Lisa.Siegmund@uni-jena.de.
authors.forename: Lisa
authors.initials: L
authors.lastname: Siegmund
authors.forename: Anke
authors.initials: A
authors.lastname: Burmester
authors.forename: Martin S
authors.initials: MS
authors.lastname: Fischer
authors.forename: Johannes
authors.initials: J
authors.lastname: Wöstemeyer
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D010303:Paromomycin / Q000494:pharmacology; D013194:Staining and Labeling; D013559:Symbiosis / Q000502:physiology*; D013769:Tetrahymena pyriformis / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D010303:Paromomycin
keywords: Ciliates; Endosymbiosis; Model system; Paromomycin; Tetrahymena