Science Is Sexy: Why Do NASA’s New Arsenic Bacteria Matter?

By Jimmy Rogers (@me)
Contributing Writer, [GAS]

Did you hear the news?  We’ve discovered alien life! We didn’t even have to go to another planet to find it…it was right here in our own back yard!  Ok, sure, we’re blowing things a little out of proportion, but even Mulder and Scully would agree that these arsenic-eating bacteria are “aliens.”

Here are the facts:

Last Thursday, NASA’s Astrobiology Institute announced at a press conference that they had discovered a new form of life, different from all previously discovered life-forms in one key way: it can live without phosphorous.  It has long been thought that all life on Earth required at least Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorous, and Sulfur, or “CHONPS”, to survive.  In this case, the new organism has found a way to replace phosphorous with arsenic.

The project was spearheaded by Dr. Felisa Wolfe-Simon, a geomicrobiologist and NASA Astrobiology researcher, who collected samples of bacteria from California’s famous Mono Lake.  The lake has high levels of naturally-accumulating arsenic and Wolfe-Simon hypothesized that some of the bacteria might have found a way to use the arsenic in place of phosphorous (As sits right below P on the periodic table).  They grew their sample (currently named GFAJ-1) on growth media with progressively less and less phosphorous, supplementing it with increasing levels of arsenic.  The real surprise came when they lowered the phosphorous levels below those thought to be required for any living cell. The bacteria still grew!

For you adventurous readers, Wolfe-Simon and her team published their findings in Science.  Here is the article and a short article about their work.  Also, if you want to follow the 32 year old scientist, she’s on Twitter.

Sooo, What’s the Big Deal?

As a microbiology grad student, I just about fell over when I heard about this discovery.  Then I looked around me and noticed nobody else had the same reaction.  I think there are a lot of reasons that non-microbiologists have to get excited about the new find, but maybe those reasons require a little explaining…

First off, any major change in a “dogmatic” science principle makes waves.  People rely on such principles when making scientific assumptions.  If you discovered a new planet but determined it had little phosphorous, you might safely assume it had no chance of life.  This new bacteria suggests that at least in the case of phosphorous, arsenic might work as a stand-in.  Beyond that, if nature teaches us anything, it’s that it never does something only once or one way.  Alternatives might exist for some or all of the other “required” elements as well.  Even Star Trek has played around with Silicon-based life forms a bit (in lieu of Carbon).


A Scanning Electron Micrograph (SEM) of the cells with low P and high As. (Science)

The next cool thing is that these bacteria were discovered here on our own planet.  If they developed, albeit in a fairly strange circumstance, what else might be lurking under our feet or in the oceans?  We generally assume that the vast majority of organisms on Earth are undiscovered by Man, so maybe we’ve yet to find even more bizarre microbes!

Lastly, studying extremophiles like GFAJ-1 can really pay off.  Ever seen CSI?  Almost all of the genetics they do (or pretend to do) are based on Polymerase Chain Reaction, or PCR.  The polymerase part is an enzyme that replicates DNA and is very heat-stable.  They found that enzyme while studying bacteria in the sulfur springs at Yellowstone National Park.  The thermophilic bacteria there can survive in almost boiling water, which is why they need such a heat-stable polymerase for replication.  We simply found a very lucrative use for it!

Are These Really Aliens Then?

I think by most people’s definition, these arsenophilic bacteria are NOT true aliens.  They developed on this planet and have probably been living here longer than we have.

That being said, there are a number of organisms on Earth that are so bizarre they really seem like aliens.  In fact, when Scully, on The X-Files, was trying to prove that the organisms in her lab were extraterrestrial, she looked at their DNA.  What she found was DNA with similar but significantly different chemistry (in that case, new nucleotides).  Believe it or not, the GFAJ-1 bacteria have almost the same phenomenon.  Because arsenic replaces the phosphorous throughout the cell, even the DNA backbone is made of arsenate instead of phosphate.  The differences extend beyond DNA into familiar molecules like ATP, too.

While they’re not from outer space, based on The X-Files, Mulder and Scully would certainly give these bugs the alien stamp of approval!

One more note:

Before I wrap up, I just want to clarify something I’ve heard a lot from non-scientists in response to this story.

“This is really cool, but they made these bacteria in the lab.  It’d be much cooler if they found these things in the wild.”

While laboratory conditions are not perfect replicas of a microbe’s natural habitat, rest assured that the scientists involved did not “make these bacteria capable of using arsenic.”  That ability developed over hundreds, thousands, or maybe even millions of years.  All the scientists did was give the bacteria what they needed to strut their stuff, so to speak.

Very cool stuff – this is one excited microbiology grad student!  Let me know what you think in the comments below or on Twitter!

Other installments in the “Science is Sexy” series:

[Mulder and Scully Image via Fox]