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Orr Misrepresents Science

by Krauze

I usually consider myself a pretty circuitous guy, couching my statements in qualifying if’s and maybe’s . But sometimes, something just needs to be said, and needs to be said bluntly: In his recent ID-critical article, Allen Orr’s mouth is writing checks the evidence can’t cash.

Alluding to a molecular pump known as the type three secretory system (TTSS), used by bacteria for injecting poisons into other cells, Orr claims that “there’s now strong evidence that several flagellar proteins once played roles in a type of molecular pump found in the membranes of bacterial cells.” OK, here’s the facts: There’s strong evidence that the bacterial flagellum exists. There’s strong evidence that the TTSS also exists. And there’s strong evidence that the two systems are related, as evidenced by the many similarities between them. But as far as the majority of scientists studying this relationship is regarded, the TTSS is descended from the flagellum, not, as Orr claims, the other way around.

Robert Macnab, writing in the Journal of Bacteriology, noted that, since “[f]lagella are very ancient organelles, predating by far the targets for bacterial pathogenesis”, it’s reasonable to conclude that “the rest of the type III pathways must have evolved from the flagellar one.” (1999, 7152) Mecsas and Strauss write: “The bacterial flagellum exists in a wide range of eubacteria and some archaebacteria, which indicates that it probably emerged well before gram-negative bacteria, the hosts of the type III virulence factor secretion systems identified thus far.” (1996, 280) Other researchers taking this position are Stephens and Shapiro (1996) and Nguyen, et al. (2000). In fact, the only dissenting voices comes from Gohpna, Ron and Graur (2003), and they’re arguing that the TTSS and the bacterial flagellum are both descended from a third system.

ID critics often seek to portray themselves as Defenders of Science, protecting the public against falsehoods from the “ID creationists”. But Orr, in claiming “strong evidence” for a claim that is at best controversial and at worst universally rejected in the scientific community, is himself engaging in what can only be described as a case of gross misrepresentation (whether comitted knowingly or not). Also, it is often said that ID proponents should get off their lazy butts and do the scientific research necessary to test their claims. Well, where’s Allen Orr doing research to test his non-consensus claim that the flagellum is descended from the TTSS?

PS. William Dembski at Uncommon Descent has a longer reply, though more overbearing of Orr’s misrepresentation.

References

Macnab R.M., 1999, “The Bacterial Flagellum: Reversible Rotary Propellor and Type III Export Apparatus”, Journal of Bacteriology 181(23):7149-53

Mecsas J. & Strauss E.J., 1996, “Molecular Mechanisms of Bacterial Virulence: Type III Secretion and Pathogenicity Islands”, Emerging Infectious Diseases 2(4):271-88

Nguyen L., et al., 2000, “Phylogenetic analyses of the Constituents of Type III Protein Secretion Systems”, Journal of Molecular Microbiology and Biotechnology 2(2):125-44

Stephens C. & Shapiro L., 1996, “Delivering the payload”, Current Biology 6(8):927-30

2 Responses to “Orr Misrepresents Science”

KC Says:
May 31st, 2005 at 9:21 am
A recent paper agrees with Gophna et al’s view:

Pallen MJ, SA Beatson and CM Bailey (2005). Bioinformatics, genomics and evolution of non-flagellar type-III secretion systems: a Darwinian perspective. FEMS Microbiol Rev 29(2):201-29.

From the abstract:

We review the biology of non-flagellar type-III secretion systems from a Darwinian perspective, highlighting the themes of evolution, conservation, variation and decay. The presence of these systems in environmental organisms such as Myxococcus, Desulfovibrio and Verrucomicrobium hints at roles beyond virulence. We review newly discovered sequence homologies (e.g., YopN/TyeA and SepL). We discuss synapomorphies that might be useful in formulating a taxonomy of type-III secretion. The problem of information overload is likely to be ameliorated by launch of a web site devoted to the comparative biology of type-III secretion

Here is the pertinent passage:

If we accept the above analysis, then parsimony demands that we also accept the notion that the flagellar and non-flagellar systems have evolved from a common ancestor, rather than the idea that non-flagellar systems have evolved from flagellar systems. The reasoning for this assertion is as follows. To get from the common ancestor of all type-III secretion systems via a flagellar system to a non-flagellar system would require seven steps: gain of the motor, acquisition of the chemotaxis apparatus and recruitment of the sigma/anti-sigma mechanism during the evolution of the flagellar system, and then, in the lineage leading to the NF-T3SSs, loss of the motor, uncoupling from the chemotaxis apparatus and demise of the sigma/anti-sigma mechanism, followed by gain of the translocation apparatus. However, if the flagellar and non-flagellar systems diverged from a common ancestor, then we need posit only four steps: gain of the motor, gain of the chemotaxis apparatus and gain of the sigma/anti-sigma mechanism in the flagellar lineage, and gain of the translocation apparatus in the non-flagellar lineage.

As for Orr’s remarks, I’m not sure you can justify saying he is ‘misrepresenting science’. If the modern TTSS and the flagellum are descended from a common ancestor, then that ancestor may very well have been a TTSS-like secretion system. If so, then Orr’s remarks are well within that interpretation.

KC

Comment by KC — May 31, 2005 @ 9:21 am
Krauze Says:
May 31st, 2005 at 10:14 am
Hi KC,

Nice to see you here. Also, thanks for the reference, which I hadn’t seen when I wrote my post. However, my point that Orr was misrepresenting the research on this area still stands. I took account of the “flagellum and secretory system both evolving from a common ancestory” position when I wrote, “Orr, in claiming “strong evidence” for a claim that is at best controversial and at worst universally rejected in the scientific community, is himself engaging in what can only be described as a case of gross misrepresentation (whether comitted knowingly or not).”

Comment by Krauze — May 31, 2005 @ 10:14 am