Biology Forum › Evolution › Inheritance of T3SS pilus
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- August 30, 2007 at 3:23 am #8150
SouthernFriedSkepticParticipantI am not a professional biologist (background in anthropology) but have developed a serious interest in evolutionary biology. I explore topics often as they come up, and debating online have gained enough information to make reasonably competent arguments for evolution from biological evidence. (ERV’s are my favorite)
However, I came across an ID proponent who questioned the speculative path of the evolution of the bacterial flagellum, and presented an idea that I could not immediately recognize as valid or not. A brief search of information did not present an immediate answer and I feel that I am missing some pertinent information. I believe the question would be concerning the inheritance of the T3SS pilus.
Any help explaining whether this point is valid or faulty would be appreciated. His argument goes as follows:
quote :The LOGICAL flow chart for this evolution model should be:Genetic mutation: simple pore
Genetic mutation: association of second protein
Genetic mutation: ATP Synthase associates with pore
Genetic mutation: Type III export apparatus associates with a SecretinSo far, so good. All of these changes are the result of genetic changes. Thus, each new bacteria will inherit the Type III export apparatus. On to the next step:
Adhesive protein gets stuck on Type III export apparatus.
Another adhesive protein gets stuck on Type III export apparatus.
Another adhesive protein gets stuck on Type III export apparatus.
Pilus is eventually formed.
Pilus attaches to inner membrane.CELL DIES
Daughter cells inherit Type III export apparatus
Adhesive protein gets stuck on Type III export apparatus.
Another adhesive protein gets stuck on Type III export apparatus.
Another adhesive protein gets stuck on Type III export apparatus.
Pilus is eventually formed.
Pilus attaches to inner membrane.CELL DIES
Daughter cells inherit Type III export apparatus
Adhesive protein gets stuck on Type III export apparatus.
Another adhesive protein gets stuck on Type III export apparatus.
Another adhesive protein gets stuck on Type III export apparatus.
Pilus is eventually formed.
Pilus attaches to inner membrane.CELL DIES
and so on and so forth
As you can see, the pilus formation is not the result of a genetic mutation. The adhesive proteins don’t randomly grow on the Type III apparatus because of a mutation. They simply stick to it. Thus, when the bacteria dies, the pilus is gone- FOR GOOD.
-SFS
"I never said it. Honest. … I said "billion" many times on the Cosmostelevision series…But I never said "billions and billions". For one thing, it’s too imprecise."
– Carl Sagan - September 1, 2007 at 1:51 pm #75700DarbyParticipant
The issue here is the usefulness of all this "stickiness" – would a mutationally-modified protein that preferentially stuck be advantageous over the ancestral protein that might or might not? Would a mutation in an internal carrier or a variation in expression time help the process?
Since mutational changes in this system are easily heritable, it isn’t much of a leap. And right now, the ancestral proteins for a huge part of the bacterial flagellum are well-established.
I understand that this is part of the religious weakness of Intelligent Design – if the "proof" of the Designer is in the "gaps" between useful intermediates and final form, as more and more intermediates are discovered, the role of the Designer is more and more diminished. Conceivably to nothing, which is problematical to belief.
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