SCT: Bacterial Flagellum Gets Souped Up

New findings show that an icon
of intelligent design is a motor
of motors with enmeshed gears

This article was first published in Science & Culture Today.

Can the Flagellum Get Any Better? Yes! Add Gears
by David Coppedge
Science & Culture Today, February 24, 2026

One of the original icons of intelligent design, the bacterial flagellum continues to astonish viewers shown a complex molecular motor in the “simplest” life-forms. As researchers peer deeper into its operations with super-resolution microscopy, they have revealed many more details since Michael Behe introduced his readers to its outboard-motor function in Darwin’s Black Box (1996), elaborating on it in more detail in his subsequent books. The bacterial flagellum played a starring role in Illustra Media’s film Unlocking the Mystery of Life in 2002. As recently as 2024, Destin Sandlin made a whole episode about it for his channel Smarter Every Day. To watch a modern animation of this elegant device is often enough to convince people of intelligent design. Here is an artifact clearly beyond the reach of unguided natural processes.

Torque Generation

One mystery remained, though: how did it generate torque? Rotating a propeller in fluid that feels more viscous at the nanometer scale requires significant turning force. A recent paper in PNAS by Basarab Hosu and two colleagues at Harvard — the same university where pioneering research was done on it by Howard Berg in the 1990s — helps answer that question: “Torque-generating units of the bacterial flagellar motor are rotary motors.” The flagellum is a rotary motor rotated by smaller rotary motors! Even more amazing, those small motors act like gears. ID advocates leaped on the discovery of planthopper nymphs that use gears to hop, but these are orders of magnitude smaller.

Switching Direction

Another mystery was how the flagellum could switch rotation from one direction to the other almost instantly. The new model by Hosu et al. pictures the inner motors rapidly flipping from inside to outside or back. To visualize this, think of a ring toothed on the inside and outside. Now think of four small motorized gears inside the larger ring, rotating the ring as they turn. If they could flip to the outside and engage the ring’s outer teeth, the ring would reverse direction. Something like that is what Hosu et al. confirmed: “The bacterial flagellar motor is driven by the first set of enmeshed gearwheels that has been described in any living cell.” That’s worth a big “Wow!”

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