Chlorine is bad for you. Don’t eat it. Don’t drink it (i.e., don’t drink bleach). If you happen to see a cloud of yellow-green gas floating nearby, walk away and don’t breathe it. But new research may show that some organisms can thrive in a chlorine-rich environment. They might even come to depend on this deadly poison for survival.
Science fiction often speculates about alternative biochemistries, most notably silicon based life. Up until recently, we’ve only been able to study carbon based life, where carbon is used as the primary building block for organic molecules. Since silicon is similar to carbon, Sci-Fi says it might be possible for some alien creature to substitute silicon for carbon.
In December of last year, NASA scientists announced the discovery of bacteria which could replace their phosphorus with arsenic. This research is still in dispute (sometimes the arguments get a little personal), but it seems researchers generally agree arsenic based life could exist somewhere, if not on Earth. (See my previous posts on arsenic eating bacteria, “Eat Your Arsenic” and “Don’t Eat That Arsenic!”)
Now researchers in Germany claim they’ve engineered new E. coli bacteria which substitute a chlorine compound for part of the bacteria’s DNA. As far as I can tell, this discovery is not in dispute… yet. But again, it shows that real scientists believe an alternative biochemistry is possible.
Please note that while people use terms like arsenic based and chlorine based life, these examples are still carbon based. Carbon can do things that no other element can, not even silicon. It can form strong, lightweight chains of atoms, which are extremely useful for making things like DNA (see “Carbon vs. Silicon” for more). Swapping silicon for carbon makes those chains fall apart. If a silicon based life form exists, like the one pictured below, its biochemistry has to be completely different from ours and not just a one-for-one substitution.
As astronomers discover more and more planets outside our solar system, those alternative biochemistries become very important. When they examine these planets, looking for telltale clues of oxygen-nitrogen atmospheres and other signs of life-as-we-know-it, they also have to remain open to the possibility of life-as-we-don’t-know-it. Maybe even the highly unlikely silicon based life of science fiction.
P.S.: No word yet on any Sci-Fi thrillers where bleach-immune E. coli escape from the lab to wreak havoc of innocent humans’ digestive systems.