Wired News is reporting a new study published today in Science in which a bacterium that lives on arsenic has been discovered swimming around in Mono Lake in California. Wired reports:
Hours before their special news conference today, the cat is out of the bag: NASA has discovered a completely new life form that doesn't share the biological building blocks of anything currently living in planet Earth. This changes everything.
At their conference today, NASA scientist Felisa Wolfe Simon will announce that they have found a bacteria whose DNA is completely alien to what we know today. Instead of using phosphorus, the bacteria uses arsenic. All life on Earth is made of six components: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Every being, from the smallest amoeba to the largest whale, share the same life stream. Our DNA blocks are all the same.
Or as the Science press release more sedately explains:
Can you imagine eating toxic waste for breakfast? Researchers have discovered a bacterium that can live and grow entirely off arsenic, reports a new study. The findings point for the first time to a microorganism that is able to use a toxic chemical (rather than the usual phosphate) to sustain growth and life. Arsenic is normally highly toxic to living organisms because it disrupts metabolic pathways, but chemically it behaves in a similar way to phosphate. Scientists have previously found organisms that can chemically alter arsenic; and these organisms have been implicated in ground water poisoning events in Bangladesh and other places in Asia when people have shifted to using borehole or well water to avoid cholera. Now, Felisa Wolfe-Simon and colleagues have found a bacterium able to completely swap arsenic for phosphorus to the extent that it can even incorporate arsenic into its DNA. The salt-loving bacteria, a member Halomonadaceae family of proteobacteria, came from the toxic and briny Mono Lake in California. In the lab, the researchers grew the bacteria in Petri dishes in which phosphate salt was gradually replaced by arsenic, until the bacteria could grow without needing phosphate, an essential building block for various macromolecules present in all cells, including nucleic acids, lipids and proteins. Using radio-tracers, the team closely followed the path of arsenic in the bacteria; from the chemical's uptake to its incorporation into various cellular components. Arsenic had completely replaced phosphate in the molecules of the bacteria, right down its DNA.
Still I don't think that we phosphate-based lifeforms have anything to worry about since we totally dominate the biosphere. Nevertheless, I fear that had researchers actually made this critter, it would probably be banned [PDF].
Update: Just noticed Tim already posted on this.