Evolution of the the Bacterial Flagellum

[Kim]

So I'm pretty sure most of us are well aware of the ID camp using the Bacterial Flagellum as a key "irreducibly complex" system. This issue was also greatly discussed and studied, but I always cared about the _details_.

The famous argument made between Miller and Behe in court demonstrated that there is similarity between the flagellum and what is called the type III secretory system which is presumed to be the precursor of the flagellum. Furthermore, the idea is to show homologies exists among the proteins of the bacteria flagellum and others that preexisted before the evolution of the flagellum. A very good explanation of the evolution of the bacterial flagellum is found on CDK007 Youtube video:

CDK007 Youtube video

However, I found a video response and also a blog post titled The Bacterial Flagellum and Homology that claims that roughly ~52% of the proteins in the Salmonella flagellum are not homologous to any known precursors using sources from a peer reviewed journal.

Wouldn't that pose a serious problem to the proposed evolutionary model? I tried to find responses to this claim online but couldn't find any, any ideas?

[Minimalist]

I always found it amusing that Behe had to put a disclaimer on his own bio at Lehigh U.

http://www.lehigh.edu/~inbios/faculty/behe.html

My ideas about irreducible complexity and intelligent design are entirely my own. They certainly are not in any sense endorsed by either Lehigh University in general or the Department of Biological Sciences in particular. In fact, most of my colleagues in the Department strongly disagree with them.

and that the Biology Department sees fit to denounce this horse's ass even further.

http://www.lehigh.edu/bio/news/evolution.htm

The faculty in the Department of Biological Sciences is committed to the highest standards of scientific integrity and academic function. This commitment carries with it unwavering support for academic freedom and the free exchange of ideas. It also demands the utmost respect for the scientific method, integrity in the conduct of research, and recognition that the validity of any scientific model comes only as a result of rational hypothesis testing, sound experimentation, and findings that can be replicated by others.

The department faculty, then, are unequivocal in their support of evolutionary theory, which has its roots in the seminal work of Charles Darwin and has been supported by findings accumulated over 140 years. The sole dissenter from this position, Prof. Michael Behe, is a well-known proponent of "intelligent design." While we respect Prof. Behe's right to express his views, they are his alone and are in no way endorsed by the department. It is our collective position that intelligent design has no basis in science, has not been tested experimentally, and should not be regarded as scientific.

[Kim]

Thanks Minimalist for the reply, however, what does it have to do with the blog post I cited in my original post? Any biologists here that can shed light on this?

[Doubting Thomas]

In other words, "we all think he's a kook."

"Irreducible complexity" is just a fancy way of saying "Goddidit."

[LeoVonFrost]

In my humble opinion the homology of appendages of reptiles and mammals holds a lot more water than the lack of homology of bacterial flagellum.

[pineapplebunnybounce]

ok i looked at the blog, and then i looked at the scientific paper it cited.

the writer of the blog dishonestly represented the data. On the original paper, it doesn't say no homolog, it says "none yet known". I assume he does this because most people do not have access to scientific papers? Have you tried to search google scholar for this? Or is it behind a paywall?

Haven't read the entire paper (as it's long and i'm in the middle of something), but i think it just means the scientists haven't found homologs yet, which is not surprising because there are a lot of proteins in a bacteria, these things take time and you may want to search for follow up research, since the paper he quoted is 2006.

[Minimalist]

Right, D/T. He can't convince his own colleagues. They must have some interesting departmental luncheons at Lehigh.

[Kim]

the writer of the blog dishonestly represented the data. On the original paper, it doesn't say no homolog, it says "none yet known".

Isn't that the same as saying that AS OF TODAY, we don't know of any homologous proteins? So in essence, the conclusion that ~52% of the bacteria flagellum having no homologs is still a valid assertion given the data available now.

My problem with this is if that's the case, then the proposed evolutionary model for the bacteria flagellum still suffers from serious issues until the remainder, not necessarily 100%, of the proteins are shown to have homologs.

I assume he does this because most people do not have access to scientific papers? Have you tried to search google scholar for this? Or is it behind a paywall?

Yeah most papers are behind a paywall. A followup paper is Bacterial flagellar diversity and evolution: seek simplicity and distrust it?

Flagella are the chief organelles of motility in bacteria. In recent years, several new findings have illuminated the evolution of bacterial flagella, including cut-down versions of the organelle in Buchnera, a dispensable ATPase and structural evidence for homology between FliG (a component of the flagellar motor) and MgtE (a magnesium transporter). However, a fresh examination of the phylogenetic distribution of flagellar genes warns against a simplistic model of early flagellar evolution.

Interestingly, Behe DID read that paper! and even made an interesting post on it on UncommonDecent.

Behe concludes with:

Snyder et al (2009) think Buchnera’s derived structure “illuminates flagellar evolution by providing an example of what a simpler precursor of today’s flagellum might have looked like – a precursor dedicated solely to protein export rather than motility”. I think that simplicity should be distrusted. The activity of a protein export system has no obvious connection to the activity of a rotary motor propulsion system. Thus the difficulty of accounting for the propulsive function of the flagellum and its irreducible complexity remains unaddressed. In regard to the flagellum’s evolution, Snyder et al’s (2009) advice to distrust simplicity is sound and should be followed consistently.

So what I gather from all of this is that some advances have been made to illustrate possible pathways for the evolution of the bacteria flagellum. However, over half the flagellum proteins as of today have no known homologs. Furthermore, claims that protein export was a precursor to a flagellum rotary motor propulsion system cannot be made without showing at least the theoretical evolutionary pathway that led from the former to the latter.

I must say that this issue irks me and sometimes I wish I had a degree in biology to understand more!

[The Grand Nudger]

-Nor are we likely to find much in the way of fossilized bacteria from which something we can sequence is going to be pulled. You know what I think happened, I think that alien waffles genetically engineered the other half of those proteins. That's going to keep you up at night, earnestly wondering, isn't it? It'd take a degree in biology to work that one out, wouldn't it?

[Kim]

-Nor are we likely to find much in the way of fossilized bacteria from which something we can sequence is going to be pulled. You know what I think happened, I think that alien waffles genetically engineered the other half of those proteins.

So don't make claim that the bacteria flagellum can be completely explained TODAY by evolution. Say it's a work-in-progress or whatever. Easy enough.