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Heavy Metal Bioremediation

tobacco.jpgBioremediation is the process of using living organisms -- typically plants or microbes -- to remove toxic material from the environment. Previous examples we've noted include seaweed cleaning up DDT, bacteria removing uranium from groundwater around weapons production sites, and tumbleweeds removing uranium from the soil. In most cases, the bioremediation takes advantage of a natural process within the selected organism.

Most, but not all: SciDev.net reports on work being done at the Peking University's College of Life in Beijing to bioengineer tobacco to bioremediate heavy metals from the soil, and algae to remove metals from water. This doesn't use a natural feature of the organisms, however. Instead, it uses a rat gene involved in the creation of a protein in rat livers that binds with toxic metals:

The genetically modified (GM) tobacco produces the protein in its roots and can absorb several hundred times more heavy metal ions from soil than normal tobacco, says Ru. The plants can then be burnt and the heavy metals safely removed from the ash. [...]
A different method was used with the GM algae. Ru's team pasted the algae to a nylon membrane, which was then lowered into polluted water. After absorbing the heavy metals, the algae-covered membranes were taken out of the water and the heavy metals were extracted from them in the safety of a laboratory.

Heavy metals in soil and water are serious health problems in China and elsewhere in the industrializing developing world. Novel approaches that can be employed without great expense are definitely welcome.

But safety remains an issue. The engineered tobacco doesn't live long enough to reproduce, so there's currently little risk of the biotech plant escaping into the wild. Nonetheless, it's frustrating to read that that researchers have "not yet considered" the safety aspects of their work.

Concepts like "zero waste" and "sustainable design" work best when integrated into the product development process. This allows the designers to consider at each step of the process whether the choices made could have an unintended result, rather than having to go back afterwards to clean up problems. Similarly, consideration of the ecosystem interactions coming from biotech research are best done during the engineering research, not as an afterthought. Perhaps what we need is the articulation of a "precautionary process" model for biotech research.

Comments (3)

Daniel Haran:

Most exotic species will die in their new ecosystem- probably more than 97-98%. A few will barely hang on and a critical few can have devastating impact: Caulerpa Taxifolia and Zebra mussels being two well-known examples.

It is next to impossible to know in advance which organisms will thrive. Caulerpa Taxifolia (link) would not have seemed like a likely candidate- it had evolved in tropical waters, much warmer than the Mediterranean Sea. When I studied this 10 years ago, I was shocked to find out that exotic species are the second leading cause of biodiversity loss- after habitat loss.

It's unlikely that engineered algae will take out a keystone species or spread far and wide. But unlike the tobacco example you mentionned, there isn't an "undo" button. Exotic species are inherently unpredictable, and that probably applies to "engineered" exotics too.

Until a scientist can make a good case that there's no chance of "genetic pollution", they haven't done their homework. I realize some scientists will see this as reactionary and anti-progress. There certainly will be interesting avenues that I wouldn't want to pursue because the risk, no matter how low, would likely result in catastrophe.


My old advisor does research in phytoremediation w/o gene modified plants. Plain old lettuce and canola seed plants. Just wanted to give her a shout out for people who are interested.


Ben Hunt:

Genetic pollution is probably preferable to heavy metal pollution. Biodiversity loss is probably fine if it will result in the construction of actual ecosystems where there were none. And that is in the worst case scenario. Heavy metal pollution destroys 99.9% of the microbial diversity in a cubic gram of soil.

These are the elements of expedience that these scientists have decided upon. I do not know of any science that is done only with complete purity of intention.


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