Physical Virology: Direct Measurement of Phage phi29 Stiffness Provides Evidence of Internal Pressure (Small 15/2012)

A 3D AFM topography rendition of a phage phi29 (red) adsorbed on mica (blue) is shown by P. J. de Pablo and coworkers, where part of the viral DNA (yellow) has been ejected through the tail. The phi29 bacteriophage translocates part of its DNA into the host by releasing the elastic energy arising from the internal pressure created during the DNA-packing process. Pushing with the AFM tip on the phage enables the direct measurement of the stiffness to estimate its internal pressure, just as a tyre may be pressed with fingers.