As you know, the book Why Intelligent Design Fails:A Scientific Critique of the New Creationism edited by our own Matt Young and Taner Edis http://www2.truman.edu/~edis/books/id/ has just been published. I am one of the authors, with a chapter on the evolution of bacterial flagella. So I feel particularly honoured that one of the first responses to the book is to my chapter.
Unfortunately, the response shows the author is somewhat unclear on the concepts involved.
In the chapter “Evolution of the Bacterial Flagellum” I try, amongst other things, to show a motility system can be built up by cooption of the components of a secretory system to motility functions, it also helps to know that that there are multiple bacterial motility systems, some simple (but now out of date) background can be found at my Evolution of the Bacterial Flagellum page, and an excellent and more exhaustive work is Nic Matzke’s Evolution in (Brownian) space.
For the purposes of this blog though, it is enough to point out that while Dembski and Behe characterize the eubacterial flagella, a swimming motility system, as an “outboard motor”, it is also a secretory system. The secretory system is a key part of flagella function. The flagellar secretory system is also the structure that rotates, and the flagellar secretory system is homologous to the type III secretion system (TTSS) that pathogenic bacteria use to secrete proteins necessary to invade eukaryotic cells. Indeed, place flagella side by side with TTSS and it is hard to tell them apart. In many ways, a TTSS is a flagellum without a motor. Phylogenetic analysis show that TTSS and flagella share a common ancestor, and most workers in the field think that flagella evolved from a primitive secretory system.
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One of these is a secretory TTSS, one is a flaellum, but which one?
The question is why would a motor be added to a TTSS that is secreting without it? It turns out that the motor of the flagellum, MotAB, is a proton pump and is part of a family of proton pumps (TolPQ) that drive secretion in a number of systems. Interestingly, the advential gliding motility system of Myxococcus xanthus (where bacteria glide along surfaces rather than swim freely), is a secretory system driven by a TolPQ family proton pump. It is also of interest that flagella are required for a form of gliding motility called swarming. This suggests a pathway for evolving a swimming motility system from a secretion system via functionally intermediate steps.
Secretion system -> secretion system + proton pump -> gliding motility (via secretion) -> swimming motility
This is in clear contrast to the “flagella poofed in one go” model used by Dembski in his calculations. But back to the question, “why would a motor be added to a TTSS that is secreting without it”? Because the proton motor increases secretion efficiency. If you knock out the flagella motor then the flagella is paralysed and flagellar secretion continues, but at reduced rate. This suggests that adding a proton pump to a proto-flagellar TTSS-like secretion system would increases secretion, so that association of a proton pump with the proto-flagella secretion system would be beneficial (and result in a system that could be co-opted for motility).
Now in this paper Wilharm G, et al., Yersinia enterocolitica type III secretion depends on the proton motive force but not on the flagellar motor components MotA and MotB. Infect Immun. 2004 Jul;72(7):4004-9.
a non-flagellar TTSS has been described which also uses a proton-pump to help drive secretion. This is completely consistent with the scenario above, where a proton motor is not essential for secretion, but addition of a proton motor is beneficial as it increases secretion.
Also consistent with my model is the distribution of functional motility systems, which show the functional intermediates postulated by my model.
E. Coli TTSS- ATP pump drives secretion
Y. enterocolitica TTSS - ATP pump and proton pump drives secretion, proton pump not essential for secretion
Myxococcus TolPQ related transporter proteins and proton gradient necessary for adventital gliding motility, not clear if secretion is reduced or abolished by deletion of TolPQ proteins.
Cytophaga - ATP pump and proton pump, proton gradient essential for gliding motility via rotatory structure. Not clear if secretion is reduced or abolished by deletion of proton pump.
E. coli flagella. ATP dependent transporter and proton pump, proton pump not essential for secretion but essential for swimming motility.
Hmmm, can you see a pattern here?
The Yersina non-flagella TTSS doesn’t use MotAB (and wouldn’t it be cool if it did), but I am willing to bet a copy of Gould’s brick that the proton pump turns out to be a TolPQ related protein (heck what if it turns out to be a homolog of MotAB, wouldn’t that be cool).
Now, over to our friends at ARN
The abstract of the paper is quoted and then they say that it
. . … shows that, protein secretion by the flagellar system of Yersinia is not affected by a mutation in motAB. This indicates that motility and protein secretion are not linked as they appear to be in bacteria that exhibit gliding motility.
Now, this shows they don’t grasp the model (or indeed what the paper says). The paper confirms an expectation from the flagellar secretion system that addition of a proton motor to a TTSS increases, but is not essential for, secretion. Thus addition of a proton pump to a primitive TTSS would be beneficial, and provide a pre-adaptation which later could be co-opted to provide motility.
The key mistake made is not reading the paper (or abstract) carefully. The secretion is via a non-flagella TTSS, not the flagella, as the ARN author says. The experiment was to find out if non-flagella TTSS co-opted flagella MotAB to help drive secretion. The non-flagella TTSS doesn’t use MotAB, rather some other proton pump. As I said, I’ll bet a copy of Gould’s brick they use a TolPQ derived system. Again, this finding is entirely consistent with my model.
So the entire objection arises because the ARN author didn’t understand the difference between a flagellar TTSS and the non-flagella Ysc TTSS. Lets hope further comments on the book don’t make such basic mistakes.
Note also the discover of proton pump involvement was driven by the hypothesis that flagella non-flagella TTSS share a common ancestor. This is a fruitful hypothesis, and several discoveries have come form investigations based on it (see Blocker A, Komoriya K, Aizawa S. Type III secretion systems and bacterial flagella: insights into their function from structural similarities.Proc Natl Acad Sci U S A. 2003 Mar 18;100(6):3027-30). Compare this to the sterility of the Paleyist hypothesis, which has given us no insights to TTSS structure of function at all.
48 Comments
charlie wagner · 23 July 2004
Dave S · 23 July 2004
I've often wondered just how closely these flagella are to an "outboard motor" in design. I mean the outboard motor on my boat has hinge upon which the propeller can be turned to steer it. No steering mechanism for the flagella as far as I know. My outboard motor has a reverse gear and the boat can move as readily (if not as quickly) backwards as forwards. Although the flagella can be reversed, it results in a wild random tumbling motion instead. My motor prop has 3 blades balanced around the central shaft, a flagella just one.
I know this sounds a bit picky, but since the same crowd who uses this analogy is so very stringent when it comes to other analogous terms like "junk" DNA, I have to wonder why they're so forgiving here.
Dave S · 23 July 2004
charlie wagner · 23 July 2004
Eddie Rios · 23 July 2004
Charlie wrote: "That's not the claim at all. The claim is that this evolution could not have occurred without intelligent guidance i.e. it could not have occurred by random, accidental processes."
Which is irrelevent, Charlie. No one claims that that evolution happened via a random accidental process. Evolution happened via natural selection which is not a random accidental process.
You need to get a grasp of the concept.
Eddie
Pim van Meurs · 23 July 2004
Charlie is still confused about evolutionary processes even after having being corrected countless times.
Sigh...
steve · 23 July 2004
At some point it's no longer ignorance.
Ian Menzies · 23 July 2004
Eddie Rios · 23 July 2004
I think Charlie's problem is the same as other creationists' - no imagination. I.e. Charlie cannot imagine how something can happen, hence it cannot happen.
It's the old argument from personal incredutlity.
Great White Wonder · 23 July 2004
Dave S., I agree with your criticsm re the "outboard motor" as an analog to the bacterial flagella. I have no idea who first proposed it as an analogy, but I agree that it isn't a very useful one at the end of the day except to show that both engineers and evolution have discovered that corkscrew shaped objects can provide a propulsive force in a liquid medium.
If you look at an image of a bacteria with its flagella (or even a sperm with its very different flagella), a motorboat is not the first thing that comes to my mind. It's more like a snake with a giant head.
Side note: many years ago I remember wandering the basement of Barker Hall and passing Julius Adler's lab http://www.biochem.wisc.edu/adler/. Someone had posted an eyebrow-raising quote from him on the door: "Cocaine, LSD, morphine, amphetamine ... I've tried them all." Of course, the quote was referring to compounds Adler had tested to see whether they had attractant or repellent effects on E.coli chemotaxis!
Dave S. · 23 July 2004
rubble · 23 July 2004
RBH · 23 July 2004
steve · 23 July 2004
RBH, that is just glorious.
Great White Wonder · 23 July 2004
RBH: That is the most coherent discussion of "design theory" I've ever read. I have been converted. Hereinafter, I will refer only to multiple designers when discussing the alleged intelligent beings who allegedly designed all the "irreducibly complex" (sic) living organisms that ever existed on Earth.
charlie wagner · 23 July 2004
charlie wagner · 23 July 2004
RBH · 23 July 2004
RBH · 23 July 2004
steve · 23 July 2004
G3 · 23 July 2004
RBH · 23 July 2004
Bob Flynn · 23 July 2004
I don't think I'm a Creationist lurker (in fact, I know I'm not), but I find Charlie Wagner to be interesting and imaginative, and, well, a lot less insufferable than some of you other folks. Good job, Charlie.
Barley Zagner · 23 July 2004
Finally somebody rediscovers my theory! I've long held that Bacterial Flaggellums went backwards in time in order to evolve, so entropy would go in the necessary direction. One day I'll be recognized as having seen through the mysteries which so perplexed my lesser peers at Caltech and MIT, and I will be as a giant.
steve · 23 July 2004
RBH, no one can argue your contributions are not equal to that of the leading crea-I mean, Intelligent Design Theorists. I think you should submit articles to their magazines, and request a spot on their lecture circuit.
steve · 23 July 2004
Maybe you just haven't seen it enough Bob. It's the same tired old shit. SLOT arguments? That's not even entertainingly stupid anymore.
Pim van Meurs · 23 July 2004
Charlie: They gain information, rather than lose it over time.
Yes, and natural selection and variation can at least in principle be shown to be able to increase information.
Sigh
Russell · 24 July 2004
Wouldn't the inevitability of a candle burning out be an illustration of the First Law, and actually say nothing about the Second?
(Sorry, Bob, if this sort of pedantry is insufferable. I'll try to come up with a refreshingly wacky hash of some other physical law to keep you entertained)
Nick · 24 July 2004
Plus, charlie must have heard about the origin by frameshift mutation of the nylonase protein from a non-protein-coding DNA sequence. A whole new gene, just like that. A bit of variation and selection on the originally crudely-functioning protein, and voila, a much more specific and effective protein that meets the criteria most ID advocates employ.
A more popular version
Ohno S. (1984). "Birth of a unique enzyme from an alternative reading frame of the preexisted, internally repetitious coding sequence." PNAS 81(8):2421-5. Online: PubMed -- Free online -- Related articles.
Thwaites, W., 1985. New Proteins without God's Help. Creation/Evolution 5(2), Issue 16: 1-3. Free online
Nick · 24 July 2004
Also:
Prijambada ID, Negoro S, Yomo T, Urabe I. (1995). Emergence of nylon oligomer degradation enzymes in Pseudomonas aeruginosa PAO through experimental evolution. Appl Environ Microbiol. 61(5):2020-2. PubMed Free online Related article
G3 · 24 July 2004
Joe McFaul · 24 July 2004
No, Charlie's tactic is ultimately a loser because even honest and upfront creationists acknowledgge the the 2nd law is not invalidated by evolution, see here:
http://www.answersingenesis.org/home/area/magazines/docs/v24n2_moving_forward.asp
Joe McFaul · 24 July 2004
No, Charlie's tactic is ultimately a loser because even honest and upfront creationists acknowledgge the the 2nd law is not invalidated by evolution, see here:
http://www.answersingenesis.org/home/area/magazines/docs/v24n2_moving_forward.asp
Bob Flynn · 24 July 2004
Feel Free to call me Bob.
The problem, as I see it, is that some of you sound like my car mechanic, Jim.
Jim's a great guy, but he'll start yapping about "the fetzer valve near crankshaft is out of line, so you may want a new fuel injector, but for 383 models, this means ..blah, blah, blah."
So, I say, "Jim, Jim -- don't tell me how the watch was made, just give me the time."
1. Can you fix it?
2. How much will it cost me?
Every other nano-bit of "car-talk" is superfluous information in which I dare not dwell.
Same phenomenom I see with you folks. Minutiae and terminology substituting for useful analysis.
I'm an agnostic on both God and Darwin. My science background is a few classes in College. That's it. I was taught evolution, it makes sense to me. I accept it.
But almost all science, even most of life is a series of Cause & Effect. If our DNA evolved overtime from simple DNA in a swamp, that's fine. But how did the FIRST DNA originate?
Moreover, if energy cannot be created or destroyed, how did we get the first Erg? (proper terminology?)
Obviously, those questions don't prove or disprove anything and may have easy answers. But I don't know the answers, and they interest me. That's it
So, I see Charlie taking all this flak and, I'm like, Why?
G3 · 24 July 2004
Russell · 24 July 2004
And I'm still, like, what does that candle have to do with the 2nd law - let alone the first DNA molecule?
Jim Harrison · 24 July 2004
Years ago on Talk.origins i pointed out to a creationist that his argument about the 2nd Law was so general it would rule out the possibility of building a refrigerator. As i recall, he replied that refrigerators don't count because human beings make 'em.
steve · 24 July 2004
Next time you encounter that, Jim, switch to 'your argument about the second law is so general is would rule out the possibility of ice freezing at night', ice of course being lower entropy than water. It's a good thing creationists don't apply their anti-complexity arguments to anything other than evolution, or they'd be totally verklempt. The sun produces heavy elements from simple hydrogens. Iridium is much more complicated than hydrogen. I guess god must have assembled each one, in Creationland.
Besides, everyone knows the answer is, ice uses the opposite-time-sense solutions to physical laws to run in the direction with increasing entropy. ;-)
steve · 24 July 2004
Mike Hopkins · 25 July 2004
Mike Hopkins · 25 July 2004
Steve · 25 July 2004
Actually it is quite true. Iron is a heavy element, so my first sentence is correct. Iridium is much more complicated than hydrogen, so my second sentence is correct.
Steve · 25 July 2004
In any case it's beside the point. The principal thing going on in the sun is fusion from hydrogen to helium, with a smattering of trace heavier elements due to the thermal distribution. At various stages in star life, they fuse various nuclei to get more complex nuclei. If I wanted to be more specific, I would hang out with the Astro guys over in the Bureau of Mines, but I don't. The point is, it's another example of a natural process which converts simple things to more complex things, there are a hundred such examples, and yet creationists usually argue no such thing can happen.
Frank J · 25 July 2004
rdb · 25 July 2004
For Dave S, Life at Low Reynolds Number - E.M. Purcell is worth reading.
It helps to imagine under what conditions a man would be swimming at, say, the same Reynolds number as his own sperm. Well you put him in a swimming pool that is full of molasses, and the you forbid him to move any part of his body faster than 1 cm/min. Now imagine yourself in that condition; you're under the swimming pool in molasses, and now you can only move like the hands of a clock. If under those ground rules you are able to move a few meters in a couple of weeks, you may qualify as a low Reynolds number swimmer.
Evan Swanson · 28 July 2004
I wonder if someone might direct me to some good reading on common ID arguments, why they fail, etc.
steve · 28 July 2004
http://www.millerandlevine.com/km/evol/
http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=yR4YQdl9zy&sourceid=&isbn=081353433X&itm=1
http://www.physicstoday.org/vol-55/iss-6/p48b.html
http://www.ncseweb.org/default.asp
http://www.talkorigins.org/origins/faqs-qa.html
More importantly, learn about evolution itself. Carl Zimmer's book is great for intelligent laypeople--there are many good books.
Pim van Meurs · 28 July 2004