Yes, there is indeed a lot of worry in the air, about the potential for escape of Genetically Modified organisms into the environment. Generally, this involves crop plants which have been modified to resist certain diseases, or to be immune to certain herbicides so that one can spray the crop and zap all weeds in one fell swoop.
But what if the GM organisms are bacteria? Why would one want to modify bacteria anyway? One reason might be to treat effluent and remove toxic chemicals, another might be to produce biofuels in an energy-efficient way. But it practice it would be as impossible to contain these bugs as to prevent all radioactive leakage from a damaged nuclear plant, but with the added prospect of the leakage being able to multiply.
So, at the Free University of Berlin, they have been making steps towards making ‘alien’ bacteria to whom the Earth at large would be, so to speak, ‘another planet’ on which they could not survive.
All organisms (on our planet anyway) contain the base Thymine in their DNA. Now in Berlin they have been taking a sample of Escherichia coli (which we all know and love), and subjecting it to increasing concentrations of normally toxic 5-Chlorouracil, whose molecule resembles that of Thymine except that the methyl group has been replaced by a chlorine atom.
After 1000 generations, they found that not only could the bacteria withstand 5-Chlorouracil, they had replaced the Thymine in their DNA with the new chemical and were no longer able to synthesize Thymine. As a result, they are totally dependent on the new chemical, and cannot survive in the outside world. Ideally, genetically engineered modifications of these bacteria should, therefore, be completely containable.
This reminds me of an Ariadne column in the New Scientist, where Daedalus proposed to combat increasing pesticide resistance by getting all pests hooked on their respective pesticides, so that one could halt any imminent outbreak by not spraying them.
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