** Outboard Motor **
The E-Coli Flagellum
The E-Coli Flagellum
Let us now look at an example of the kind of complexity we find in micro-organisms. The E-coli bacterium is considered a "primitive" form of life due to its relatively simple structure. As such it is one of the most thoroughly and intensely studied micro-organisms.The flagellum which drives the E. Coli bacterium, is essentially an outboard motor. The structure comprises a hook with filament or propeller rotating up to 100,000 rpm, a rotor, stator, drive shaft, U-joint, bushings and engine casing (inner and outer membranes). If just one of 40 structural components of the engine is missing, it does not work and the bacterium dies.
Studies of the bacterial flagellum reveal that the parts have to be assembled in a certain order, as with a car engine. Chemicals cannot do this, there has to be information orchestrating the construction - and there is, on the DNA strand. Molecular machines construct the bacterial flagellum in the correct order for it to work. If one piece is mislaid or put in the wrong place, the engine won't work, so the system is said to be irreducibly complex. And the machines which make the flagella are in turn made by other machines, which are themselves constructed by further systems which are also irreducibly complex. Such mind-boggling complexity goes all the way "down" [1] to levels beyond our ability to understand.
Furthermore, besides the rotary motor type flagella in bacteria, there are also various types of flagella out there, such as those in eukaryotes (ex. sperm cells) which beat back and forth. Here's what researchers from Brandeis University [2] say about those:
Eukaryotic flagella, whip-like organelles that elegantly propel microorganisms and pump fluid, seem to embody simplicity on the microscopic scale. But appearances can be deceptive: Flagella are composed of 650 different types of proteins.Six hundred and fifty components to get this tiny filament to beat with the proper rythm! Scientists tried to produce a synthetic one but eventually gave up and settled for a simple string of beads computer model.
Their jobs are vitally important. Flagella help sperm swim, sponges eat, and sweep mucus from the lungs, among other functions. Their length depends on their purpose but flagellas' structure and rhythmic, beating movement remain the same across functions and species (though they necessarily arose independently).
That fluid movement is a highly sought-after capability in small-scale devices, such as microrobots. But scientists have struggled to build a simple, controllable model that can recreate it.
Let us now look a bit at how scientists are faring in reverse-engineering the "primitive" E-Coli bacterium. The authors of the article on E. coli in the "Annual Review of Microbiology" (Riley and Serres 2000) wrote:
Even though the entire sequence of the E. coli K-12 chromosomal DNA has been known for [over] two years, we are still far from knowing all of the details of how the cell operates, lives, replicates, coordinates, and adapts to changing circumstances . . . the number of experimental journal articles on aspects of the basic biology of E. coli has increased from an average of 78 per month in 1996 to an average of 94 per month today . . . new biological information about this well-studied organism continues to roll in. New metabolic capabilities are discovered and are connected to underlying genes. There are new regulation systems, new transport systems, and more information on cellular constituents and cellular processes.Regulation systems? Transport systems? Looks like scientists are learning the hard way just how unbelievably complex even "simple" life forms truly are.
. . . but how many regulators are needed to maintain coordination of expression of the genes and correct interaction among the gene products? Regulation systems are not the same in all bacteria, and we still do not have all of the information for the regulatory networks of even one bacterial species . . . the minimal set of genes and proteins necessary for life of an independently replicating cell does not have an easy answer.
Experimentation into details of the biology of E. coli continues unabated today, and the numbers of papers published annually continues to increase . . . not all enzymes and pathways in E. coli are known . . . besides genes for unknown enzymes, we have data for enzymes that don't have genes. There are 55 enzymes of E. coli that have been isolated, purified and characterized over the years, but their genes have never been identified.
The advent of massive DNA-sequencing technology and the completion to date of [more than] 20 microbial genomes that are now available to the public have not brought us (yet) to a complete understanding of exactly how a single free-living cell functions and adapts to changing environments.[3]
There is another class of Bacteria, even "simpler" than E-Coli called Mycoplasma. Like E-Coli, mycoplasma bacteria are one of the most thoroughly and intensely studied microorganisms. In 1979 T.D. Brock's biology textbook stated mycoplasmas are "of special evolutionary interest because of their extremely simple cell structure". Sure enough though in 1996 Dybvig and Voelker stated, "Mycoplasmas can no longer be thought of as a simple organism." Scientists used the word simple. Notice also, that with more time and research, the 'simple' turned out to be awfully complex!
This pattern we are seeing in everything. Down to the "simple" electron and quark, etc, which turns out to be a bottomless world of mathematical complexity. G-d is giving the poor scientists a heck of a run for their money!
Let us now look a bit at the mind boggling complexity of cells, a complexity which is almost unbelievable.
>> Next: The Amazing Cell
Footnotes