Molecular mechanism of DNA uptake during transformation

Heike Gangel, Christof Hepp



Watching DNA import by the bacterium Neisseria gonorrhoeae. The development of segmentation tools enabled us to automatically depict the contour of the bacterium (white line) and to quantify the spatial distribution of imported DNA. False colors encode for the amount of DNA imported by the bacterium.



Bacterial gene transfer constitutes an important medical problem since antibiotic resistance and virulence traits are transferred between bacteria. In a process called transformation, bacteria take up naked DNA from the environment. The first step to transformation is the transport of DNA through the cell envelope. Macromolecular translocation through nanometer-sized pores is a ubiquitous theme in cell biology and a challenging problem in physics. For efficient transport, we suggest, that a molecular machine pulls the DNA molecule through the cell envelope. We are using a combination of single molecule techniques and genetic manipulations for deciphering the molecular mechanism of DNA import. We have developed two different techniques that allow us to watch how a bacterium takes up a single DNA molecule. Using laser tweezers, the import kinetics is accessible at well-defined external forces. Time-lapse fluorescence microscopy allows quantification of the spatio-temporal dynamics of fluorescently labeled DNA during import.

Main collaborators:
Michael Koomey, Oslo

Review articles:
Allemand, J.-F., Maier, B. Bacterial translocation motors investigated by single molecule techniques,  FEMS Mircobiol. Rev. 33(3), 593-610 (2009)
Allemand, J.-F., Maier, B., Smith, D.E. Molecular motors for DNA translocation in procaryotes,  Curr. Opin. Biotechnol., 23(4), 503 (2012)
Maier, B. Wie Gene wandern,  Physik Journal, 11(10), 33 (2012)