The bacterial flagellum is important in bacterial pathogenesis and biofilm formation. It is a rotary nanomotor that allows bacteria to propel themselves through liquids and across surfaces. Researchers interested in nanoscale robotics use the bacterial flagellum as a model for a machine that self-assembles on the nanoscale. Cohen et al. examined exactly how the flagellum precisely measures its shaft so that it spans, but does not extend beyond the edge of, the periplasm. The growing flagellum uses a mechanism by which it “senses” when it hits the outer membrane and stops growing. Changing the width of the periplasmic space by remodeling a particular lipid changed the length of the flagellar shaft.
Science, this issue p. 197
The bacterial flagellum exemplifies a system where even small deviations from the highly regulated flagellar assembly process can abolish motility and cause negative physiological outcomes. Consequently, bacteria have evolved elegant and robust regulatory mechanisms to …