Wood (1974)

Poisonous chemicals are everywhere in our environment and are synthesized in a variety of ways. Mercury is one of the most well known toxic chemicals in our environment that can be traced back to both industrial production and natural production. In this review article we will analyze the various biological cycles mercury (and other toxic chemicals) take and how their presence impacts humans as well as other species.

While reading this article, here are a couple of questions to ask yourself:

-How does the volatility of elemental mercury affect the biological cycle for mercury toxins?

-Why does methylating a heavy metal result in a more toxic compound?

-Why is Dr Wood writing this review article?


7 Responses to “Wood (1974)”

  1. Adam Settimo Says:

    My questions have to do with controlled laboratory tailoring of microorganisms as a method of cleaning up heavy metal contamination from non natural processes. It is mentioned briefly and then not discussed further. I am just wondering if there is any expansion on this in some of the references. It says in the lab accelerated evolution, basically, can be used to tailor microorganisms to a specific contamination issue, what are the limitations of this process? Just how tailored can we make these microorganisms?

    Later it is said that it is not just the microorganism that must be present, but the conditions such as pH, temp, heavy metal availability, etc. must be correct; can these tailored microorganisms be fit to operate in higher lower pH or temp?

    Lastly, has any of the references looked into the potential harm of releasing this mass population of tailored microorganisms into the environment?

  2. Antony Says:

    I didn’t realize gold and silver are very toxic. Its a heavy metal so it makes sense. It is probably also only toxic in certain oxidation states. It was interesting to learn that the properties of transition metals can greatly vary from one oxidation state to the next. Like in the example they gave with cobalt.

    I have a question concerning the cycle of toxic metal. When authorities prevent you from fishing at certain places in certain time of the year because of “high levels mercury” is this because a certain species of mercury is more present than the next or do you think they are just concerned about all mercury?

    Lastly, when I worked with Dr. Ingram, we were extracting biosurfactant from bacteria for bioremediation of uranium contamination. Since there is a cycle that heavy metals go though can removing them altogether be bad? Can it throw off the natural balance?

  3. Daniel Says:

    It’s intriguing to see how many variable play into the movement of toxic compounds and their derivatives. And it’s kind of funny to see that sometimes certain bacteria can covert a toxic compound to something even worse.
    In the article, they state that if you can predict the environmental pathway of one compound, you could possibly use that same pathway for similar compounds (such as Hg to Pd). Has Wood done any future work on compounds of uranium? As it is also known to be environmentally toxic and is also naturally occurring and caused by anthropogenic sources. I’m curious to see if there are any bacteria that can convert uranium to other compounds.

  4. Daniel Begay Says:

    It’s interesting to see how many variables play into how toxic compound move around in the environment. Also that certain bacteria can sometimes convert these compounds to derivatives that are even more toxic.

    In the paper, it states that once you are able to understand the pathway for one type of toxic element/compound, there’s the possibility to use that same pathway on a similar element/compound (such as Hg to Pd or As to Se).

    Could this same process be used for radioactive elements/compounds that are toxic? After this paper, did Wood do any work with uranium, as it also occurs naturally and from anthropogenic sources? Is there any element/compound that has a similar pathway to uranium?

  5. Kevin Greenwood Says:

    Wood states that mercury is methylated via methylcorrinoids to the less volatile methylmercury. From there the methylmercury can be methylated again (though this is a very slow process) to the more volatile dimethylmercury, which ends up in the atmosphere. However he also states that methylmercury can be reduced back to elemental mercury.

    In this process, where does the equilibrium sit? I would expect that this process would bottleneck at methylmercury because of the low rate of conversion to dimethylmercury, but because rates aren’t given for the reverse process it is tough to tell. Also, it isn’t stated how fast dimethylmercury is photolyzed in the atmosphere. Which form of mercury predominates in the environment?

  6. Josh Ellsworth Says:

    My question is in regard to the Cobalt center in the methylcorrinoids. Why Cobalt and not Iron? The two species are essentially the same size at the 3+ oxidation state, so why use something that is going to be far less abundant than Iron? What about the d6 vs d5 electron configuration necessitates Cobalt?

  7. Porter Marsh Says:

    The paper went a different direction than I was expecting. On the first page Wood talks about creating mutated microorganisms in the lab that could be active in the dispersal and metabolism of persistent compounds. To me, that sentence and the implications of it were some the more interesting parts of the paper. When he says “an approach is possible in the laboratory” there’s no citation so I’m not sure exactly what literature he’s referring to but my question is about that possibility. In the past 40 or so years has there been much research on designing microorganisms to detoxify environments or even just solutions in a lab? Do you know if he had an example of a mutated microorganism being put to use in mind when he said this?

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