March 20, 2002 | David F. Coppedge

Bacterial Flagellum Can Tune Its Swim Speed with Network-Controlled Brakes

51; What’s new with flagella?  These are the favorite toys of intelligent design supporters, because they are irreducibly complex molecular machines that evolutionists rarely attempt to explain by a Darwinian process.  More fodder for their position comes from a paper in Cell1 that finds that bacteria can fine-tune their swimming velocity by means of a molecular brake under network control: “This behaviour is governed by a molecular motor-brake protein that upon binding of the bacterial second messenger cyclic dimeric GMP interacts with a specific subunit of the flagellar nano-motor and thereby curbs motor output.  The intracellular concentration of cyclic dimeric GMP is controlled by a network of signaling proteins” – at least five of them.
    The authors, hailing from Switzerland and Germany, said: “These experiments demonstrate that bacteria can modulate flagellar motor output and thus swimming velocity in response to environmental cues.”  Noting that “E. coli directs its movement in an aqueous environment via phosphorylation-mediated control of motor reversals.”  That led them to ask, “Why would bacterial cells, in addition to this sophisticated motor control, modulate their swimming speed?” and answered that this mechanism may work best when nutrient supply is low: “Switching to a fuel-conserving locomotion regime is particularly important under low nutrient conditions….one function of the mechanism described here might be to adjust bacterial velocity to the energy status of the cell.”  The flagellar system, therefore, has good brakes as well as reversible gears.
    The research team said nothing about evolution.  Their paper was summarized by Science Daily and PhysOrg from information supplied by the University of Basel.  Science Daily threw in a biomimetic angle: “the discovery of flagellar motor curbing could be exploited for biotechnological applications, for example to engineer nanopumps in microfluidics or to build cell-based microrobots.”  Here’s what the paper said about that: “The discovery of flagellar motor curbing might have implications beyond the biology of bacterial locomotion.  On the basis of our findings, one could for example imagine to exploit the flagellar motor to engineer a rotary nanomachine that can be fine-tuned ad libitum.”  Driving your machine ad lib; that’s cool.


1.  Boehm, Kaiser et al, “Second Messenger-Mediated Adjustment of Bacterial Swimming Velocity,” Cell, doi:10.1016/j.cell.2010.01.018.

How many mousetraps does it take to establish irreducible complexity?  Just one.  Here we see mousetraps controlling mousetraps, and other mousetraps signalling those mousetraps to control the first mousetraps.  It’s irreducible complexity all the way down, all the way up, all the way in, and all the way out.  Then it’s biomimetic mousetraps coming in for inspiration.  Darwinian mice should be running scared.

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