Balancing flagellum assembly and energy consumption

Halte, M., Popp, P.F., Hathcock, D., Severn, J., Fischer, S., Goosmann, C., Ducret, A., Charpentier, E., Tu, Y., Lauga, E., Erhardt, M., Renault, T.T. (2025). Bacterial motility depends on a critical flagellum length and energy-optimised assembly. PNAS 122, e24134881.

The bacterial flagellum is a complex structure made of ~24 different proteins, with flagellin as its main component. The flagellar type-III secretion system can secrete flagellin at rates up to 10,000 amino acids per second. This study shows that this high rate is evolutionarily optimized - a minimum flagellar length of 2.5 μm is needed for bacterial swimming, and the rapid secretion rate allows efficient flagellum construction while balancing energy costs.