Why stop at a quarter turn when you can twist your cell into a full wave or even a corkscrew? Just as a corkscrew penetrates its target, helical pathogenic bacteria like this Campylobacter jejuni can burrow efficiently into the tissue of their target.
It can be tempting to group species based on a common characteristic, but appearances are often deceiving about relatedness. Undulating shape, for instance, was not a one-shot invention; it evolved independently multiple times. This is true of other bacterial and archaeal cell shapes as well. For wavy shape, these independent origins are reflected in different mechanisms of creating it. Some species, including C. jejuni, use dedicated proteins to regulate the pattern of peptidoglycan insertion–a continuation of the theme we have been discussing. Other species take different approaches (⇩).