Shuffling genes around in hotenvironments


The DNA translocator of Thermus thermophilus as model system for macromolecuar transport machineries

Natural genetic transformation, also referred to as “natural competence”, permits the exchange of free DNA among organisms of different domains and, therefore, is suggested to be a driving force for bacterial adaptation and genome evolution. Both, induction of competence and the physiology of natural transformation have been intensively studied in mesophilic bacteria and there is a considerable body of literature.  In contrast, much less is known about the mechanism of DNA transport and the structure and function of the DNA transport machineries. Moreover,  information with respect to natural transformation systems in thermophilic bacteria is even more scarce.The latter is of prime interest since thermophilic bacteria clearly stand out in terms of interdomain DNA transfer and massive interdomain gene transfer between hyperthermophilic archaea and bacteria is suggested to play a major role in adaptation to hot environments. To get insights into the transformation machinery of extremely thermophilic bacteria we chose Thermus thermophilus HB27. This strain exhibits highest natural transformation frequencies known to date. We performed broad physiological, molecular, biochemical, immunological and electron microscopical studiesandidentified genes, proteins and macromolecular complexes of the DNA translocator. We unravelled the structure and function and the interplay of subunits of the DNA translocator and the data have culminated in a model of a highly complex DNA translocator spanning the whole cell periphery of T. thermophilus. Currently we focuss on the elucidation of the atomic structure and the molecular mechanism of DNA uptake and analyze the in vivo dynamics and regulation of the DNA transporter system. These questions are addressed by modern state of the art techniques such as cryo electronmicroscopy, tomography, crystallisation and in vivo labeling techniques.


Model of the DNA translocator of Thermus thermophilus.





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