Do you think humans and other animals will ever evolve toxic metal immunity?

[Norbert]

Sort of like plants and bacteria do in response to antibiotics and pesticides/herbicides. I know that's not a good comparison, but I can't think of any better one. I'm interested in whether vertebrates can evolve immunity to heavy metals. Humans have been mining, handling and poisoning themselves (and the biosphere) with lead since time immemorial. We are constantly in contact with this dangerous metal. It is being released by aging homes, in mines, in industrial settings, etc. Do you think it's possible for the vertebrate body to evolve mechanisms for dealing with lead and other heavy-metal toxins? Perhaps by putting them to use like other metals such as iron or zinc?

 

My apologies if this question seems silly, I am more of a math person.

Edited August 1, 2012 by Norbert

[Delta1212]

Heavy metals aren't killing off percentages of the population on par with what antibiotics do to bacteria. I don't really think there is enough of a selection pressure there to result in any significant evolutionary response.

[Norbert]

Heavy metals aren't killing off percentages of the population on par with what antibiotics do to bacteria. I don't really think there is enough of a selection pressure there to result in any significant evolutionary response.

 

So it does sound possible? Do you think the organism would develop more efficient ways to pull the lead from the blood and block it from depositing in tissue, or would it develop ways to actually put the lead to good use, like it does with iron and other metals?

Edited August 1, 2012 by Norbert

[CharonY]

The use of heavy metals such as iron, copper, manganese has a very long evolutionary history. Prokaryotes started using them and we just maintained it. Highly complex organisms usually have not the ability for radical changes, so utilizing the metals in novel ways is pretty much out of the question.

[akh]

So it does sound possible? Do you think the organism would develop more efficient ways to pull the lead from the blood and block it from depositing in tissue, or would it develop ways to actually put the lead to good use, like it does with iron and other metals?

 

Although they are considered less complex, bacteria are much more biochemically versatile than humans and animals. I doubt that humans or any animal has the biochemical capacity to evolve such abilities.

[CharonY]

In fact, over the course of evolution we lost quite a number of metabolic abilities that prokaryotes still have.

[Joatmon]

 

Worms have evolved to live on a diet which includes heavy metals.

 

"Newly evolved "superworms" that feast on toxic waste could help cleanse polluted industrial land, a new study says.

 

These hardcore heavy metal fans, unearthed at disused mining sites in England and Wales, devour lead, zinc, arsenic, and copper."

 

 

http://news.nationalgeographic.com/news/2008/10/081007-super-worms.html

[akh]

 

Worms have evolved to live on a diet which includes heavy metals.

 

"Newly evolved "superworms" that feast on toxic waste could help cleanse polluted industrial land, a new study says.

 

These hardcore heavy metal fans, unearthed at disused mining sites in England and Wales, devour lead, zinc, arsenic, and copper."

 

 

http://news.national...uper-worms.html

 

Very cool article. Thanks

 

But still, a worm is not a vertebrate. Fecundity, generation time, and constant selective pressures are huge factors.

 

I think the OP mixed two separate questions as one. Could they become immune? Could they evolve to utilize the metals? The worms have not utilized the metals. Utilizing the metal would require a new biochemical process. However, they have evolved a protein that encapsulates the toxic metal so it cannot do harm. Also, I would suspect, but I would have to dig deeper, that this is not a truly novel protein, but rather a modification of an existing protein.

 

Beautiful example of evolution in motion in any case.

Edited August 2, 2012 by akh

[CharonY]

The article is written rather badly. This may be the article that eventually came from that initial data. Note that all earthworms devour heavy metals. These are just more resilient, though I think they are still looking whether they use the same mechanisms (i.e. quantitative changes) or whether they may have developed novel strategies (bit less likely).

[Moontanman]

If the resistance to heavy metals is acquired by vertebrates i would suggest that cooperation with bacteria that detoxify heavy metals is far more likely.

 

Elephants is a good example of this, they eat things like grass, leaves, tree bark, small limbs and anything else vegetable they can ingest but they can't digest any of it, in fact with out their symbiotic bacteria that actually do the digesting they would starve no matter how much food they ate.

 

Due to the elephants slow reproductive rate i once saw an estimate we that it would take literally billions of generation of elephants have a decent chance evolving the ability to digest their food items. Symbiosis with bacteria is far quicker and cheaper from a genetic stand point.

 

Instead of evolving these traits complex animals use bacteria to do the work for them, termites are another example... with out their gut bacteria they could not eat wood...

[akh]

If the resistance to heavy metals is acquired by vertebrates i would suggest that cooperation with bacteria that detoxify heavy metals is far more likely.

 

Elephants is a good example of this, they eat things like grass, leaves, tree bark, small limbs and anything else vegetable they can ingest but they can't digest any of it, in fact with out their symbiotic bacteria that actually do the digesting they would starve no matter how much food they ate.

 

Due to the elephants slow reproductive rate i once saw an estimate we that it would take literally billions of generation of elephants have a decent chance evolving the ability to digest their food items. Symbiosis with bacteria is far quicker and cheaper from a genetic stand point.

 

Instead of evolving these traits complex animals use bacteria to do the work for them, termites are another example... with out their gut bacteria they could not eat wood...

 

 

I agree, it was actually my first reaction to the "worm" paper before a read it. I thought it was possible that a bacterial symbiot was responsible. Interesting line of thought though. What if we engineered yogurt cultures with probiotics which had the ability encapsulate toxins before they entered our systems?

 

I would prefer a clean environment, but...

 

 

[CharonY]

Well, metal reduction (often dissimilatory) is a common process with which bacteria can reduce metal toxicity, provided that the reduced metal is actually less toxic, of course. Some resident bacteria are at least theoretically able to do so. However, considering that in the gut other electron acceptors may be available. On the other hand, contaminated soil often contain these metal reducing bacteria, so the worm may just take them up, too. But then they would have to compete with the other gut bacteria, that may be outcompeting them.

However, the majority of the detoxification in earthworms and other invertebrates appears to involve the binding to proteins as e.g. via metallothioneins and they are quite likely to play a larger role for the overall adaptation.

Edited August 3, 2012 by CharonY