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A molecular machine drives DNA uptake during horizontal gene transfer

Detecting the import of a single DNA molecule. A DNA molecule (red) is attached to a bead (green) at one end. The bead is trapped within a laser trap (blue). The other end of the DNA is allowed to bind to a bacterium (grey). As the bacterium imports DNA, the bead is deflected from the center of the laser trap. The optical restoring force pulling the bead back into the center increases linearly with the deflection. This setup enables characterizing the bacterial DNA uptake machine because it provides access to both force and speed of the machine.

Transport of macromolecules through nanometer-sized membrane pores is a ubiquitous theme in cell biology and an interesting problem in physics. For example, during gene transfer by transformation, bacteria take up micrometer-long DNA from the environment through nanometer-sized pores into the cell envelope. To make DNA uptake efficient, an energy consuming molecular machine powers the uptake process. How does the DNA uptake machine work? How does it use chemical energy to generate directed movement of the DNA molecule? We tackle these questions by combining laser tweezers technology with molecular biology.

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