The assembly of the flagellar axial structure with tens of thousands of protein subunits always occurs at the distal end of the growing flagellum. The component proteins are selectively exported from the cytoplasm into the narrow central channel of the flagellum by a protein complex attached on the cytoplasmic face of the motor. This flagellar protein export apparatus uses the energy of ATP hydrolysis and is highly homologous to the type III protein secretion system of pathogenic bacteria, by which pathogenic effecter proteins are secreted into host cells. We try to visualize the export process by single molecule technique and understand the mechanism of selective export based on the structure.
Irreducible Complexity
Randall Niles: Michael Behe, a biochemist currently teaching at Lehigh University, coined a term for describing the design phenomenon inherent in molecular machines such as the bacterial flagellar motor — “Irreducible Complexity” — “a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning.”
Like a mechanical motor, each part in the flagellar motor is absolutely necessary for the whole to function. Therefore, I couldn’t logically deduce any naturalistic, gradual, evolutionary explanation for the existence of a bacterial flagellum. Besides, no one would expect an outboard motor, whether mechanical or biological, to be the product of a chance assemblage of parts. Outboard motors are designed and engineered!
Of course, I just picked one example. The bacterial flagellum is only one among many thousands of intricate, well-designed, molecular machines. Furthermore, take these same principles of design and “irreducible complexity” and apply them to marvels such as the human eye, ear, heart, lungs and brain. Seriously, how can we logically explain the gradual and random development of these complex systems?
What about the human heart? It’s a miraculously efficient and durable hydraulic pump that no engineer could dream of producing…
What about the human brain? It’s a legitimate computer system, 1,000 times faster than a Cray supercomputer and with more connections than all the computers, phone systems and electronic appliances on the entire planet…
Wait. I remember Darwin saying something about this…
If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.
OK, using Darwin’s own words, let’s dig in further and look at one of these complex organs – the human eye…
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