Tuesday, March 4, 2008

The wheel business

“It’s a really interesting question, Why do animals beat their wings?” Dr. Spedding said. “One reason is, they don’t have wheels. They don’t have parts that rotate.” No wheels, no propellers, no jet engines to give them thrust. Nature never did get into the wheel business, he said, but “the flapping-wing thing works pretty well.”

Never is a sttong word for nature. Which this writer should have avoided. There is Nannosquilla decemspinosa, a shrimp that rolls when on land to get back to the water.

The place where nature did get into the wheel business, so to speak, is at the nano level:

The Prokaryotic Flagellum

Bacteria invented the wheel! The bacterial flagellum is a helical structure that drives the cell through the media like a propeller. The structure is rigid and turned by a rotatory motor at the base where it connects to the bacteria's body. The rotary motor consist of several wheel-like discs one of which the M-ring (and/or possibly the S-ring) interact with the C-ring and studs to rotate the whole structure. The rotary motor is very like a stepping motor! The flagella is composed of a protein called flagellin which is synthesized in the cell body and transported through the narrow lumen of the growing flagella itself to polymerise at the tip as it is about to exit the bacteria! This system has evolved into a syringe –like mechanism to inject toxins into the cells of vertebrates during infection (this is called "type 3 secretion"). There are two main type of prokaryotic flagella, those belonging to gram positive (one membrane) and gram negative (two membranes) bacteria (Figure 1). The bacterial flagellum is driven by a proton motive force resulting from a gradient of protons. Bacterial chemotaxis is brought about by alterations in the direction that the motor rotates in, this in turn is controlled by phosphorylation.

So there you ahve it... nature does get into the wheel business... just one that we aren't in yet.


  1. I have seen the The bacterial flagellum used as an argument that evolution has some questions to answer. Some argue that it is too complex to be arrived at by random chance.

  2. Cory used to have the flying spaghetti monster as his avatar...

    More seriously, the anti-evolutionary argument always amounts to saying that because we don't know, we can't know. I'm a really big non-believer in the idea that just because something hasn't been done, it is some kind of proof it can't be done.

  3. Unfortunately the anti-evolutionary arguments end up being anti-science. Evolution at a theory is still the very best we have.

    Personally, I think the truth is still out there - and it will astound us.

  4. Great post, Lillie ... I hoped you were going there, and you did. And, from my perspective, folks that think something is "too complex to be arrived at by random chance" just aren't paying adequate attention.

    Annie Dillard, one of my favorite nature writers, once wrote that nature will try anything once.

  5. Evolution isn't random chance, but instead a process of taking the breath of the world and forging a strand upon which is written in faint but simple letters, the code that wraps around it.