Evolution mystery: Spider venom and bacteria share same toxin

[Mr. McD]

It's a case of evolutionary detective work. Biology researchers at Lewis & Clark College and the University of Arizona have found evidence for an ancient transfer of a toxin between ancestors of two very dissimilar organisms--spiders and a bacterium. But the mystery remains as how the toxin passed between the two organisms. Their research is published this month in the journal Bioinformatics, 22(3): 264-268, in an article titled "Lateral gene transfer of a dermonecrotic toxin between spiders and bacteria."

http://www.eurekalert.org/pub_releases/2006-02/lcc-ems020106.php

[benburch]

1. Interesting!

Possibly the genes passed through the mediation of a virus?

[xchrom]

2. wow

nature throws a curve ball -- how did that happen?

[rox63]

3. I know someone who nearly died from a brown recluse spider bite

If she had been a few more hours getting to the hospital, she would have lost her arm. Another day or so, and she might have died. As it was, they had to remove a big piece of dead flesh from her arm, which left her with a nasty-looking depression in her upper arm. Better that than dying, though. Her case was complicated by having a compromised immune system, because she has lupus.

[NNadir]

9. I had one of those, but it seems not to have been as serious.

I got it on my hand. I was in a surprising amount of pain for a few days, tremendous swelling, and the wound did look quite nasty. Everything healed fine though. I was lucky.

I was out chopping wood when I got it.

[Odin2005]

4. Lateral gene transfer is quite common.

Bacteria exchange genes all the time. It is rarer between bacteria and eukaryotes but it's still widespread.

[Mr. McD]

6. Only one successfully transferred gene per two thousand centuries

could furnish more than the estimated 300 genes separating humans from mice

[NickB79]

10. But, but, but, gene transfer is unnatural!

At least, when humans do it in labs :sarcasm:

[TechBear_Seattle]

5. Why a transfer and not parallel evolution?

If memory serves, all animal life shares some 75% of the same genes; is it so far fetched that two organisms, out of millions, would independently evolve the same mutation in what is probably the same gene?

[rman]

7. or why not the same evolutionary origin?

didn't pretty much all species evolve from bacteria?

So species share genes,
ie (as far as i know) there's only one gene that causes cell devision, and it shared across all species.

[NNadir]

8. One could argue the question either way.

I have no idea what the size of the protein is or other facts about the homology, which of course has some bearing on the question of whether or not it is probable that the origins are the same or different.

However, one of the arguments for so called "intelligent" design - yes a ridiculous argument - is that a shark, a whale, and a submarine all have the same basic structure: They are all long generally tapered cylinders, and therefore a shark and a whale must have been "designed," because submarines are designed. This ignores the fact that there is really only a few solutions to the problem of having the right hydrodynamics to minimize energy expenditure when moving under water. A shark, a whale and a submarine are all locally maximized combinatorial solutions to the problem of hydrodynamics, but there is no requirement that this maximum be reached by the same path. Sharks and fish are not very closely related; whales, of course, are descendants of land based animals. Neither animal is related to a submarine.

So it could be with a peptide or protein. There may be pathways to evolving a protein structure that has diverged considerably and then converged - for different purposes - on the same "solution."

This is not to say that the homology arose in this way, only to say that it is possible.

[drm604]

11. What about a symbiosis?

Could the spider have these or related bacteria living in it's venom organ and producing the toxin for it? If that's not the case now, maybe it was the case at one time and the spider has since taken over the job from the bacteria, possibly by physically incorporating the gene. I'm not a biologist so please be kind if this is a really stupid idea. :)

[Nikia]

13. Chlorophyll in plants may have evolved that way

The plant cell took in bacteria to make food for it through photosynthesis.

[Evoman]

12. Convergent evolution?

Its interesting, thats for sure.

[Dead_Parrot]

14. Maybe the bacteria was bitten by a radioactive spider...

...whilst working in the lab one night. :)

I'd probably come down on the side of convergent evolution. I can't see the coding genes for the entire toxin being passed over intact (although it is possible): For my money, it's more likley the toxin developed seperatly. There are, after all, only so many chemical combinations that can be easily made and have the desired effect.

(Disclaimer: I'm probably totally wrong. Fascinating stuff, though.)