Does Bacteriophage φ29 Pack Its DNA with a Twist?

You probably never tried to put toothpaste back into the tube, but if you did, you’d have a good idea of what the Bacillus subtilis bacteriophage ϕ29 experiences as it crams its DNA into a protein capsid shell following replication. Scientists have speculated that this bacteria-infecting “phage” accomplishes this energy-intensive task by rotating a connector complex at the opening that feeds the DNA into the capsid as it turns, and that this process is fueled by the breakdown of ATP by an associated ring of ATPases. But until now there has been no way to show whether that’s really what happens.