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A Letter Added to the Organic Alphabet Soup

December 5, 2010

1991.  High school science class had us commit to memory the letters C, H, O and N.  These stand for Carbon, Hydrogen, Oxygen and Nitrogen.  The essential elements of organic life.

1996.  College chemistry class added S and P (sulfur and phosphorus) into the mix.  Professors call it the “big six.”  Easy to remember right?  A little bit of (Johnny) mnemonic if you happen to find yourself answering a quiz question on the topic.

C, H, O, N and a little bit of S and P.

2010.  December 2 is now an important date for our little mnemonic.  From this point onward, it now goes:

C, H, O, N and a little bit of S and P. Not much P around?  You can use As (Arsenic).

Uh oh.  Time to revise those biology textbooks.  Blame it on NASA –> NASA-Funded Research Discovers Life Built With Toxic Chemical

Better yet, blame it on the critter they found.  Meet strain GFAJ-1 of Halomonadaceae.

Critter Details:

  • GFAJ-1 is an extremophile.  In short, it’s a tough little bugger.
  • Found in Mono Lake, California.
  • Mono Lake is extremely salty and alkaline with a pH value of 10.  In comparison, household bleach has a pH of  around 11.
  • GFAJ-1 can substitute phosphorus with arsenic.  Essentially, it can utilize arsenic in its cellular structure.
  • It incorporates arsenic if phosphorus is in very limited quantities as found in experiments.
  • Arsenic is notoriously poisonous to multicellular organisms.

In short, it’s a bacteria that has the option of using a typically lethal element in order to survive.  Amazing right?  Maybe not to us non-scientific folks, but think about it this way.  Imagine meeting someone who does not need to eat but ingests sunlight and dangerous cosmic radiation instead.  A hundred geek cred points if you recognize the guy below:

Alas, I can only dish out silly analogies (please do chime in if you have a better analogy).  I leave it to the experts to provide clear and concise information on the discovery and its implications.

Alla Katsnelson writes in Nature News:

Many science-fiction writers have proposed life-forms that use alternate elemental building blocks, often silicon instead of carbon, but this marks the first known case in a real organism. Arsenic is positioned just below phosphorus in the periodic table, and the two elements can play a similar role in chemical reactions. For example, the arsenate ion, AsO43-, has the same tetrahedral structure and bonding sites as phosphate. It is so similar that it can get inside cells by hijacking phosphate’s transport mechanism, contributing to arsenic’s high toxicity to most organisms.

I’ve also found Ed Yong’s writeup on Discover Magazine to be the most casually informative.  His latest update in the article provides a little dose of skepticism from other experts.

On a less scientific note, it’s interesting that NASA encouraged some hype to build up prior to the announcement by embargoing details until the announcement itself.  Some blogs and online publications even cried Aliens! Not at all far-fetched considering the details of the announcement.  Even I was sucked into the hype machine by speculating that the Cassini probe has finally found life in one of Saturn’s moons.

I’m hoping that that NASA’s next announcement has less embargo and more aliens in it.


Updated: December 7, 2010

I mentioned briefly that Ed Yong’s article referred to some scientists casting doubt on this discovery.  Interesting news broke today on the same note.  A coworker sent me an article in Slate by Carl Zimmer which details criticisms on the find.  No mincing of words from the author of the counter-argument as she used the word “flim-flam” to refer to Wolf-Simon’s research. Needless to say, this is science at work where investigations inevitably follow a major find.

Arsenic isn’t exactly something you want to eat. It has a deserved reputation as a powerful poison. It has been used as a murder weapon and it contaminates the drinking water of millions of people. It’s about as antagonistic to life as a chemical can get. But in California’s Mono Lake, Felisa Wolfe-Simon has discovered bacteria that not only shrug off arsenic’s toxic effects, but positively thrive on it. They can even incorporate the poisonous element into their proteins and DNA, using it in place of phosphorus.
One Comment
  1. chongkee permalink

    nuclear man from superman 4

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