Evolution Intelligent design/creationism Medicine Pseudoscience Science Skepticism/critical thinking

Once more into the muck: Creationists and the evolution of antibiotic resistance

ResearchBlogging.orgI’m not sure why, but it’s been a while since I’ve delved into the cesspit of pseudoscience that is the Discovery Institute’s propaganda organ, Evolution News & Views. Perhaps it was because I simply got tired of diving into the depths of stupid. Of course, that then begs the question of why I’ve been spending so much time diving into the Age of Autism website or the sophisticated-sounding yet ultimately vacuously pseudoscientific blather that is David Kirby. Trying to decide which is stupider, AoA or ENV, is rather like deciding whether it would be better to die of cancer or Lou Gehrig’s disease. Both can be horrible ways to go, but in the end you’re still dead, just as in the end your brain risks being rendered dead by reading either website.

Still, I’ve been blogging a lot about antivaccinationists lately, mostly because a lot has been happening, while I haven’t hit on another of my major areas of blogging interest in a while, namely evolution. So, it was with some trepidation that I visited for the first time in a long time that propaganda organ for “intelligent design” (ID) creationism, a variety of creationism that’s too disingenuous and cowardly in nature to show its true colors. However silly young earth creationists can be, at least they come right out and say that they think God did it all. Unlike ID creationists, creationists of the young earth variety don’t hide their true agenda couched in terms of saying some “designer” (who, they solemnly assure you, really and truly doesn’t have to be God but oddly enough seems to resemble strongly the Christian God) did it all.

One thing that ID creationists really, really hate is bacterial resistance to antibiotics, because that is one area of evolutionary biology where evolution and selection can be observed directly and that also has a great deal of relevance to human health and disease, thus demolishing the claims of certain ID creationists that the dreaded “Darwinism” has no relevance to medicine. Sometimes this leads the merry band of creationists at the Discovery Institute to make incredibly ridiculous (and even dangerous) recommendations about treating bacterial infections. Particularly difficult for them to understand is that the existence of multidrug resistance, be it in cancer or bacteria, is not evidence against “Darwinism.”

They’re at it again (or maybe I should say that Jonathan Wells is at it again), abusing a new scientific article in a vain attempt to show that it supports ID rather than “Darwinism.” The article is entitled The Irrelevance of Darwinian Evolution to Bacterial Resistance, which is launched in response to a recent article by Maurice et al1 about the mechanism of multidrug resistance in bacteria. As unbelievable as it sounds, I think that Wells is trying to out-stupid David Kirby, and that is simply begging for a dose of –well, you know what kind of insolence.

It’s fairly obvious right from the start that Wells didn’t read the actual article itself but rather skimmed the press release about it looking for statements to inflame him, which is not too difficult. (Apparently, all you have to do is to say that evolution is the driving force behind the emergence of antibiotic resistance to get him all riled, and he doesn’t disappoint:

Frédéric Dardel and his colleagues crystallized two forms of the antibiotic-modifying enzyme acetyltransferase and showed that it has a flexible active site that can evolve to enable bacteria to break down various antibiotics and render them useless. The research may aid in the design of new antibiotics to deal with this form of resistance, which is becoming a serious medical problem.

This is very good news! Unfortunately, Darwinists will probably claim — as they have done many times in the past — that their theory was indispensable to the achievement.

Yet Darwinian evolution had nothing to do with it.

As usual, so confident, so self-righteous, and so just plain wrong. Before I subject my remaining neurons to more of Well’s blather, let’s live up to the icon at the beginning of this post and actually blog about the peer-reviewed research in this article. Let’s, unlike Wells, actually read and discuss the actual peer-reviewed article itself, rather than the press release. I know, I know, it’s a radical concept, particularly to the merry band of antiscientific and anti-intellectuals at the Discovery Institute. But bear with me people. It’s what real scientists in the real world (as opposed to fake scientists in the fake world of the Discovery Institute) do.

As I’ve explained before, the ability to evolve multidrug resistance is a huge problem, be it by cancer cells or bacteria. In the case of cancer, the culprit is usually one or both of two molecular “pumps” on the cell surface with broad specificity that are able to actively expel a wide variety of chemotherapy drugs from the cell. The two pumps commonly found to confer chemoresistance in cancer are P-glycoprotein and the so-called multidrug resistance−associated protein (MRP), and mutations in these transporters can allow cancer cells to become resistant to multiple chemotherapeutic agents at once, no need for simultaneous mutations in three or more genes, as is sometimes claimed to be necessary by ID advocates, an argument similar to that used by Michael Behe in his most recent book. In the case of bacteria, enzymatic modification of the antibiotic to a form that can no longer bind to its cellular target is a more common mechanism of inactivation. Aminoglycosides (such as gentamycin) and fluoroquinolones (such as ciprofloxacin) are broad spectrum antibiotics. One of the most common mechanisms for the inactivation of aminoglycosides is the addition of an acetyl chemical group to a specific nitrogen, a process known as N-acetylation, a process mediated by an enzyme known as the aminoglycoside 6′-N-acetyl transferase (AAC(6′)). Two functional classes of this enzyme are known, AAC(6′)-I and AAC(6′)-II, each with differen substrate specificity. Now, isoforms of the AAC(6′)-Ib subclass have evolved to be able to modify some fluoroquinolones.

The study in question, by Maurice et al, examined the X-ray crystallographic structure of narrow-spectrum and broad-spectrum variants of AAC(6′)-Ib; i.e. variants that can inactivate only specific aminoglycosides and variants that can inactivate aminoglycosides and fluoroquinolones. What is remarkable about what they found is that a mere two amino acid substitutions can induce a large structural change that allows the binding pocket of the enzyme to accommodate a wider variety of substrates, including some fluoroquinolones. In other words, single residue substitutions can have a huge effect on the function of the enzyme. In other words, teh enzyme has a great degree of plasticity upon which natural selection can work. Moreover, knowledge of the structure of this active site could guide the development of new drugs that could be used with fluoroquinolones or aminoglycosides to block the development of resistance. It’s a nice, elegant little solving of a structural problem that provides a useful new insight into the mechanism of bacterial resistance, concluding:

In addition to the ‘gaping’ ability of the active site, the specific scaffold of AAC(60)-Ib, in which recognition of the acetylatable substrate is mediated by the side chains of the exposed loops (as opposed to other AAC(60) enzymes), could provide the structural plasticity required for adaptation to new antibiotics. This could explain, in part, why this isoform has been selected under the pressure of antibiotic usage and is now widely distributed among pathogens. Conversely, such a broad distribution makes AAC(60)-Ib an attractive target for countering drug resistance. The reported structures could help in guiding the design of new aminoglycosides that avoid resistance. In addition, the observation that an original scaffold–piperazine ethane sulphonate–can mimic the transition state, could be an interesting lead for designing new inhibitors.

And John Wells has to fall all over himself to try to deny that it has anything to do with the hated “Darwinism”:

First, some bacteria happen to have a very complex enzyme (acetyltransferase), the origin of which Darwinism hasn’t really explained. Come to think of it, most cases of antibiotic resistance (including resistance to penicillin) involve complex enzymes, and the only “explanations” for them put forward by Darwinists are untestable just-so stories about imaginary mutations over unimaginable time scales.

As usual, ID advocates like Wells have a lot of nerve accusing anyone of untestable hypotheses and conclusions, given that ID is nothing but one big untestable hypothesis. In any case, the explanations for antibiotic resistance result from testable hypotheses, and evolutionary considerations have revealed more about the mechanisms of antibiotic resistance than any “God did it” (excuse me, I mean “the designer did it”) consideration of ID, particularly resistance to penicillins. Of course, Wells’ critique is so vacuously stupid that I suspect even he realizes it to some extent, which is perhaps why he falls back on favored evolution denialist canards such as this:

Second, the acetyltransferase story is about minor changes in an existing species of bacteria. But Darwin’s theory isn’t really about how existing species change over time. People had been observing those long before 1859, and most of the new insights we’ve gained since then have come from genetics, not Darwinism. Yet Mendel’s theory of genetics contradicted Darwin’s, and Darwinists rejected Mendelian genetics for half a century. And although an understanding of genetics is important when dealing with antibiotic resistance, Darwin’s theory of the origin of species by natural selection is not.

It’s amazing how ID creationists can’t seem to get past the 19th century when discussing science. Remember, the neo-Darwinian synthesis of the 1930s and 1940s successfully combined Darwin’s theory of evolution with population genetics and Mendelian genetics to form the basis of the theory of evolution as we know it today. Moreover, genetics and, more recently genomics, have only served to confirm the validity of the theory of evolution and strengthen its support. Really, ID creationists need to join the 21st century. But Wells’ first two objections pale in comparison as far as cranking the Stupid-O-Meter up to 11 goes compared to his third objection:

Third, Dardel and his colleagues made their discovery using protein crystallography. They were not guided by Darwinian evolutionary theory; in fact, they had no need of that hypothesis.

Wells needs to get a clue. X-ray crystallography is a technique that does not require evolutionary considerations. It’s a tool. However, it is in the the analysis of the data and the conclusions about how the alterations in one or two residues can alter the protein such that it has so much broader a specificity in the antibiotics that it can inactivate where evolutionary considerations are unavoidable. Evolution is the background against which this discovery was made; it allows investigators to predict and understand what mutations might result in a new, more resistant phenotype.

Having read this amazingly predictable and ignorant screed, I’m now reminded why ID creationists irritate me so. They are very much like antivaccinationists in that their beliefs are formed by ideology rather than science and thus cannot be swayed by science. Like antivaccinationists, they attack and downplay inconvenient (for them) science that shows them to be wrong, while twisting existing science into a pretzel in the process.

Maybe I should start perusing the HIV/AIDS denialist websites or the 9/11 “Truther” websites. If I’m going to hurt my brain cells, I should at least do it looking into areas that are will broaden my ability to handle pseudoscience and crankery.


1. Maurice, F., Broutin, I., Podglajen, I., Benas, P., Collatz, E., Dardel, F. (2008). Enzyme structural plasticity and the emergence of broad-spectrum antibiotic resistance. EMBO reports DOI: 10.1038/embor.2008.9

By Orac

Orac is the nom de blog of a humble surgeon/scientist who has an ego just big enough to delude himself that someone, somewhere might actually give a rodent's posterior about his copious verbal meanderings, but just barely small enough to admit to himself that few probably will. That surgeon is otherwise known as David Gorski.

That this particular surgeon has chosen his nom de blog based on a rather cranky and arrogant computer shaped like a clear box of blinking lights that he originally encountered when he became a fan of a 35 year old British SF television show whose special effects were renowned for their BBC/Doctor Who-style low budget look, but whose stories nonetheless resulted in some of the best, most innovative science fiction ever televised, should tell you nearly all that you need to know about Orac. (That, and the length of the preceding sentence.)

DISCLAIMER:: The various written meanderings here are the opinions of Orac and Orac alone, written on his own time. They should never be construed as representing the opinions of any other person or entity, especially Orac's cancer center, department of surgery, medical school, or university. Also note that Orac is nonpartisan; he is more than willing to criticize the statements of anyone, regardless of of political leanings, if that anyone advocates pseudoscience or quackery. Finally, medical commentary is not to be construed in any way as medical advice.

To contact Orac: [email protected]

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