Souped-Up Hyperdrive Flagellum Discovered
Get a load of this -- a bacterium that packs a gear-driven, seven-engine, magnetic-guided flagellar bundle that gets 0 to 300 micrometers in one second, ten times faster than E. coli.
If you thought the standard bacterial flagellum made the case for intelligent design, wait till you hear the specs on MO-1, a marine bacterium described by Japanese researchers in the Proceedings of the National Academy of Sciences. Edited by Howard Berg, Harvard's mastermind of flagellum reverse engineering, this paper describes the Ferrari of flagella.
Instead of being a simple helically wound propeller driven by a rotary motor, it is a complex organelle consisting of 7 flagella and 24 fibrils that form a tight bundle enveloped by a glycoprotein sheath.... the flagella of MO-1 must rotate individually, and yet the entire bundle functions as a unit to comprise a motility organelle.To feel the Wow! factor, jump ahead to Figure 6 in the paper. It shows seven engines in one, arranged in a hexagonal array, stylized by the authors in a cross-sectional model that shows them all as gears interacting with 24 smaller gears between them. The flagella rotate one way, and the smaller gears rotate the opposite way to maximize torque while minimizing friction. Download the movie from the Supplemental Information page to see the gears in action.
Electron micrographs included in the paper show that the model is not unrealistic. These flagella really are tightly packed in a sheath, suggesting that the bundle acts like a gear-driven hyperdrive.
Here we have used electron cryotomography to visualize the 3D architecture of the sheathed flagella. The seven filaments are enveloped with 24 fibrils in the sheath, and their basal bodies are arranged in an intertwined hexagonal array similar to the thick and thin filaments of vertebrate skeletal muscles. This complex and exquisite architecture strongly suggests that the fibrils counter-rotate between flagella in direct contact to minimize the friction of high-speed rotation of individual flagella in the tight bundle within the sheath to enable MO-1 cells to swim at about 300 �m/s. (Emphasis added.)At microbial level, that's more than 10 body lengths per second. The authors were clearly excited by this engine, sounding like young men checking out high-performance cars, talking thrust, gear ratios and torque.
MO-1 is a magnetotactic bacterium capable of orienting its cell body along the geomagnetic field lines by using magnetosomes. The MO-1 cell has a flagellar apparatus with two lophotrichous [containing numerous flagella in] bundles. In contrast to peritrichously [flagella all over the cell] flagellated bacteria, MO-1 cells swim constantly in a helical trajectory toward magnetic north, and the trajectory changes from right-handed to left-handed without changes in velocity or direction. The cells are able to swim as fast as 300 ?m/s, which is nearly 10-fold faster than E. coli and Salmonella. Although the flagella of the other types of bacteria usually work individually or by forming a loose bundle to produce thrust, the flagellar apparatus of MO-1 is a tight bundle of seven flagella enveloped in a sheath made of glycoproteins. This unique architecture appears to be essential for the smooth and high-speed swimming of MO-1.They can't see actual gears, of course, but physics demands that the mechanism of rotation must have something like it:
We hypothesize that, whereas each of the seven flagella has its torque-generating motor, the 24 fibrils counter rotate between the flagellar filaments to minimize the friction that would be generated if the flagella were directly packed together in a tight bundle. A schematic diagram representing our hypothesis is presented in Fig. 6. The flagella are represented as large brown gears and the fibrils are represented as small blue-green gears. The flagella and fibrils rotate counterclockwise and clockwise, respectively, as indicated by the arrows, to minimize friction (Movie S1). Although there is no direct evidence that the fibrils can rotate freely in the opposite direction as the flagellar filaments with which they are in direct contact, we think this is the simplest interpretation to explain the superior function afforded by the complex architecture of the MO-1 flagellar apparatus.With powerful evidence of design like this, did the researchers become converts to intelligent design? We can't know, but would PNAS have printed such a paper without an obligatory tribute to unguided materialistic evolution? Evolution is not mentioned until the last paragraph:
Considering the very tight packing of the 7 flagella and 24 fibrils that are in direct physical contact within the sheath, there appears to be no other way for the flagella to rotate at high speed without the counter rotation of the intervening fibrils. Although the fibrils and the surrounding sheath are in direct contact, the friction between them would be small because of the stocking-like flexibility of the sheath. This design must be playing an essential role in the fast, smooth rotation of the flagellar apparatus that allows the rapid swimming of MO-1.
Taken together, these features of the MO-1 flagellar apparatus represent an advanced level of evolution of a motility apparatus. It is also intriguing that the same pattern of an intertwined hexagonal array in two evolutionary distant systems: the basal bodies of flagella and fibrils of the MO-1 flagellar apparatus, and the thick and thin filaments in vertebrate skeletal muscle. Similar architectures of filamentous structures presumably evolved independently in prokaryotes and eukaryotes to fulfill the requirements for two very distinct mechanisms to generate motion: counter rotation and axial sliding.OK, so the Darwinists got their offering, but it leaves a bad aftertaste: now, they have to believe that advanced mechanisms for generating motion evolved not just once, but twice -- completely independent of each other. Thanks a lot, guys. Wait till the intelligent-design movement hears about this.
Oops, too late.