Spin Flagellum, Spin
|September 5, 2008||Posted by idnet.com.au under Intelligent Design|
This month in Current Biology Vol 18 No 16, Howard C. Berg writes a “Quick guide” to the Bacterial Flagellar motor. In it he outlines what is currently known of these amazing structures.
“The flagellar motor is a remarkably small rotary electric motor that includes a stator, drive shaft, bushings, mounting plate, and a switch complex. The motors are powered by protons or sodium ions, that flow through channels from the outside to the inside of the cell. Depending upon the configuration, the rod, hook, and filament are driven clock wise or counter clock wise. Other components include a rod cap, discarded upon rod completion, hook cap, discarded upon hook completion, hook-length control protein, and a factor that blocks late-gene expression.”
As “nothing in biology makes sense except in the light of evolution”, Berg concludes with a few brief comments.
“Is the flagellar motor unique? Yes and no. As a device that powers flagellar rotation, yes. As a device composed of rings, rods, and external filaments, no. There is a homologous structure, called the needle structure, assembled by the same kind of transport apparatus, used by pathogenic species (such as Salmonella) to inject virulence factors into eukaryotic cells. Some argue that the flagellar rotary motor evolved from the needle structure, but it was probably the other way around, since flagellated bacteria existed long before their eukaryotic targets. Perhaps they evolved from a common ancestor. What was the rotary motor doing before the helical propeller was invented, if indeed that was the order of events? Serving as a secretory apparatus that acquired the ability to spin? Packaging polynucleic acids into virus heads? Food for thought.”
Recently Nature Reviews Microbiology volume 6 June 2008 p 455 has a review of the regulation of Flagellar construction, where the authors say “The bacterial flagellum, one of the most remarkable structures in nature: a complex self-assembling nanomachine” where “dozens of proteins, many of which have intrinsic self-assembly properties, need to come together in an ordered assembly process to complete these molecular nanomachines.”
These authors also need to remind us of the inescapable compelling logic of evolutionary biology:
“Finally, it seems that the bacterial flagellum is a structure of great complexity. In an attempt to understand why, it is not necessary to resort to intelligent designers, because surely a designer would have fashioned a simpler structure and gene regulation system. We only need to be reminded that evolution demands that changes occur on the existing structure — no starting from scratch. It is fair to say that we are at long last making a dent in our understanding of how this evolutionary process might have occurred for the reducibly complex bacterial flagellum and the beautiful result it has produced.”
The flagellum is obviously too complex to have been designed. It must have evolved. The logic is inescapable.