Other phage use bacterial appendages in an even more clever way. These φCb13 siphophage take advantage of the cell’s motility to hitch a ride to the cell. They have a filament on their head that wraps into the helical groove of the Caulobacter crescentus flagellum. Remember that flagella can spin either clockwise or counter-clockwise. If this single polar flagellum spins clockwise, pushing the cell body, the attached phage would unscrew like a nut off the end of the flagellum. But if the flagellum spins counter-clockwise, the nut will instead spin down to the cell body, where its tail fibers will find their receptors and its tail will inject the genome (⇩).