title: The IStron CdISt1 of Clostridium difficile: molecular symbiosis of a group I intron and an insertion element.
abstract: The IStron CdISt1 was first discovered as an insertion into the tcdA gene of the clinical isolate C34. It combines structural and functional properties of a group I intron at its 5'-end with those of an insertion element at its 3'-end. Up to date four different types could be found, mainly differing in their IS-element portions. Contrasting classical group I introns, CdISt1 is always integrated in ORFs encoding bacterial protein. In case CdISt1 had only the IS-element function such insertion would inactivate the protein encoded by the host gene. It is only due to the self-splicing activity of the group I intron parts that CdISt1 integration does not abolish protein function. Both elements seem to exist in molecular symbiosis and CdISt1 could thus be a prototype of a novel class of genetic elements. Moreover, integration of the CdISt1 into the genome could be advantageous for the bacterium, a motor function for evolution of bacterial proteins is discussed. In clinical practice CdISt1 might well serve as a tool for epidemiological studies of C. difficile infections.
authors.affiliation: Verfügungsgebäude für Forschung und Entwicklung, Institut für Medizinische Mikrobiologie und Hygiene, Johannes Gutenberg-Universität, Mainz 55101, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Hasselmayer
authors.forename: Claudia
authors.initials: C
authors.lastname: Nitsche
authors.forename: Veit
authors.initials: V
authors.lastname: Braun
authors.forename: Christoph
authors.initials: C
authors.lastname: von Eichel-Streiber