Creatures with synthetic proteins may explain what extraterrestrial life looks like
By: Andrew Pollack, New York Times
Scientists are currently taking the first steps towards creating alternative life forms. These creatures will use a different genetic code than that present in all living creatures on Earth today.
These creatures - initially they will be bacteria - will have new chemical units in their DNA and their proteins will consist of synthetic building blocks. Scientists hope to be able to try and understand, through these creatures, what extraterrestrial life might look like. They also hope to use them to produce new medical or electronic materials, which cannot be produced with the help of living organisms.
The limits of the new field of research are very far from the limits of genetic engineering carried out today. In genetic engineering, the order of DNA or protein compounds is changed to create new combinations, or DNA is transferred from one organism to another.
Adding completely new elements to DNA and proteins is actually rewriting the genetic code, which is the language in which life is written. Therefore, it is likely that the study will raise new ethical and safety questions.
However, there is still enough time before we have to face these questions: five to ten years will pass before it is possible to use the results of the research on a daily basis. According to researchers who have begun to conduct such experiments, the research, at least at this stage, should not raise concerns. If organisms with unnatural DNA managed to break free from a laboratory, they would die outside in no time.
Despite the great diversity of life on Earth, the genetic code of all creatures - from yeast and bacteria to humans - is written in four chemical DNA units, marked with the letters A, T, G and C. Different combinations of three letters - the so-called Codons - specify how to make different amino acids.
The amino acids combine into a chain like beads and form proteins that perform all the tasks of the cell. All living things use the same 20 amino acids. The genetic code is like a language containing four letters and twenty words. Despite this meager vocabulary, these words can be used to create the vast variety of sentences and paragraphs that characterize life.
But what if it would be possible to create more genetic letters and words? This, scientists say, will allow organisms to be even more diverse, just as some languages have sounds and concepts that don't exist in another.
Dr. David Tyrrell from the California Institute of Technology, caused bacteria to produce a protein with the characteristics of Teflon by replacing one of the bacteria's twenty natural amino acids with one unnatural amino acid. He did this without changing the bacteria's DNA. According to him, such a protein may one day be used to build artificial blood vessels.
Scientists say that creatures with a different genetic code may be considered alien life forms. Indeed, one of the goals of the research is to check what types of life might exist outside the Earth. "We think that there is no reason why life on Earth consists of these four DNA letters," says Dr. Steven Benner, a chemist from the University of Florida, "I would not be surprised if it turns out that life on Mars is made of different letters."
Dr. Brenner reported this month at the conference that he was able to use artificial DNA to create a protein with an unnatural amino acid, but only in laboratory flasks. According to him, it is extremely difficult to reproduce artificial DNA in a laboratory. When artificial DNA is inserted into living organisms, the process always results in their death.
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