Horizon, Host: Ted Simons

December 6, 2010


Host: Ted Simons

New Life on Earth


  • All known life on earth requires phosphorus as an essential nutrient. However, the discovery of a bacteria that uses the normally toxic element of arsenic instead of phosphorus is changing thoughts on what life on other planets might need to exist. A NASA-funded research team made the announcement about the new life on earth, and Arizona State University professors Paul Davies and Ariel Anbar co-authored the paper on the discovery. Both talk about their findings.
Guests:
  • Paul Davies - Arizona State University
  • Ariel Anbar - Arizona State University
Category: Science

View Transcript
Ted Simons:
A major announcement about life on earth was made last week by NASA and four ASU scientists. Researchers found a microbe that uses arsenic as a basic building block of life, something that would separate the organism from any form of life as we know it. I'll talk to two of the researchers about their findings, but first, here's an excerpt of a NASA press briefing that features the ASU scientist who led the project.
Felisa Wolfe-Simon: All life we know -- uses six elements in critical pieces we're familiar with, including DNA and RNA, and the information technology of the cell. The proteins and lipids, which separate you from everything else and by discovering, we've discovered in our organism, that can substitute one element for another. I'd like to introduce to you this bacterium. These are not little potatoes. They're microbes that scientists lovingly call little bugs and this is a bacterium though it looks ordinary, like a micrograph many of us may have seen, but it's doing something extraordinary. And we'll talk about that. But first, let's find out where this microbe is from. This is a map of Mono Lake, California. It's east of the Sierras, out of Yosemite national park. It's basic and got high levels of arsenic and teeming with life and this inhospitable environment teems with life and is a major stopping point for migratory birds. We took the mud of this lake, and we wanted to see if anything would grow if we took that mud and gave it a laboratory environment that was rich in everything else it needed. Sugar, vitamins, not that bad for us. And we added no phosphorus and high doses of arsenic. A double whammy. It was driven by my question: There a microbe on earth that can substitute arsenic for phosphorus in its basic molecular constituency? We found that it grew and thrived and that was amazing. Nothing should have grown. Put your plant in the dark. It doesn't grow. So something grew. Now we wanted to find out what was happening. So we measured the inside of the cells and measured the total arsenic concentration inside the cells. That was taking up this arsenic. That's unusual and found that the arsenic was associated specifically with a band of genomic DNA. Here we see the double helix of the DNA and I want to highlight the phosphate, the light orange balls, and it stitches together as we see the edges of the DNA. It holds together the DNA, the backbone. And what we think is happening, all the evidence we've collected suggests, is that instead of these, we'll see these orange, light orange bulbs disappear and represented by green bulb, the arsenic is substituting for phosphorus in the backbone of DNA. And what I've presented to you today is a microbe doing something different than life as we knew it. All life on earth required carbon, nitrogen, oxygen, hydrogen, phosphorus and sulfur. So I've shown here today that we discovered a microbe that can substitute arsenic for phosphorus and if there's a organism on earth doing something different, we've cracked open the door for what's possible for life elsewhere in the universe and that's profound.

Ted Simons:
Here now to discuss the discovery of the arsenic-based bacteria are ASU professors Paul Davies and Ariel Anbar, who coauthored the paper on the findings. Good to have you here. She was at ASU, but a lot of this work, most was done elsewhere.

Paul Davies :
When I came here, we began, the three of us, to develop the ideas for this arsenic life. Then she went to the U.S. geological survey, to work there, and going out into the field and looking for it. And in this case, the field is Mono lake.

Ted Simons:
Let's get in more layman's terms. That was a good description for scientists, but some are scratching their heads. What is she talking about?

Ariel Anbar:
Finding a microorganism that is able to substitute arsenic for phosphorus. Some are familiar with it. Arsenic is a poison; you know that, right? So they're chemically similar to each other. The reason arsenic is toxic, poisonous, it gets into your body, mimics phosphorus and gums up the machinery. She's found a microbe to replace phosphorus with arsenic.

Ted Simons:
Fully replace or adapt?

Paul Davies :
We don't know the detailed answers, how much is replaced, but clearly some of it has. When they're pulled out of the lake, the replacement hasn't happened. They have dual capabilities. They like phosphorus and arsenic as well and go with whatever you give them.

Ted Simons:
Again, this was mostly done, pulled out of the lake and then you do laboratory tests?

Paul Davies:
Right, the U.S. geological survey and carefully experimenting and it's a -- painstaking work, involving a lot of people.

Ariel Anbar:
She's working in the lab. And looking at how microorganisms can tolerate arsenic. The structural substitution, replacing phosphorus, it's a building block of biology, replacing phosphorus with arsenic. That's a novel thing.

Ted Simons:
Was it there all along? Did it evolve, do we know?

Ariel Anbar:
I think at this point, the jury is out. We don't really know. It's -- it certainly has the ability in the lab. We don't know if it's doing it in nature. It's logical it would. The reason Felicia went to this lake, because it was a logical place. All bets are off. It's a new story.

Ted Simons:
So we've got this microbe, and arsenic, obviously, bad for us?

Paul Davies:
Not recommended.

Ted Simons:
Good for it, though, the microbe. Do we know -- is phosphorus toxic to the microbe?

Paul Davies:
If we follow the arsenic, maybe go to place where there's more arsenic, we might find organisms for which phosphorus would be a poison.

Ariel Anbar:
But that's speculation.

Ted Simons:
Sure.

Paul Davies:
This one can work with both.

Ariel Anbar:
And, in fact, it prefers phosphorus.

Paul Davies:
Yes, yes.

Ariel Anbar:
But it can grow on arsenic, is what the laboratory experiments indicate.

Ted Simons:
We've got the phosphorus and arsenic. Got that figured out. I think. What does that say about life on earth, life as we know it?

Ariel Anbar:
What it says is that the building blocks of life are more flexible. There are six elements -- carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus and -- and here is an organism can replace one of those, and it's a big deal.

Ted Simons:
Replace in part, in full? How much do we replace?

Paul Davies:
We don't know at this stage, but there's another lesson that comes out of this -- remarkable organisms can hide under our noses. There's nothing that distinguishes this bug from anything else. If she had not done these experiments, nobody probably would have noticed. When you look at its genome, it doesn't look exceptional. The real point, you can't tell by looking what makes a microbe tick. So there's potential for all sorts of surprises in store.

Ted Simons:
Well, could one of those surprises -- and in reading on this, I saw this more than once -- the possibility of a shadow biosphere. First, what does that mean?


Ariel Anbar:
It's an idea that Paul is articulate in advancing. That there could be a -- hypothetically and this is just a small step in that direction. But the idea that you could have a biosphere, organisms that we see and recognize, but don't realize they have very different metabolisms.

Paul Davies:
I'll tell you the background how I got into it. We were interested in whether there's life elsewhere in the universe. When I was a lad, nobody believed there was anything beyond the earth. And now it's fashionable to say the earth is teeming with life. And one way of testing that, no planet is more earthlike than earth. So if life pops up in earthlike conditions, maybe there isn't just one form of life. Maybe more than one. The question is how do we find this so-called shadow biosphere. Is it a form of life that might look the same but different biochemically? We have a strategy for going to look for such a thing. This particular microbe is not the shadow biosphere. When you sequence its genome, it can be positioned on the same tree of life as you and me.

Ted Simons:
It's not completely alien?

Paul Davies:
No, it's not. But you can't tell by looking and maybe out there in mono lake or somewhere --

Ted Simons:
Is that a capital M?

Ariel Anbar:
It's a capital M and motivates good research and this project would not have happened if not for that idea. There's a tension between evidence and rigor and bold ideas and how do you balance that and it takes all sorts of ideas to push the field forward.

Ted Simons:
Correct me if I'm wrong, the implication here is that it's possible that life could have evolved from, as you mentioned, a 2.0, a different set of -- well, am I getting close there?

Ariel Anbar:
This relates to the search for earth beyond earth.

Paul Davies:
Exactly.

Ariel Anbar:
So -- so -- where it comes from, if the universe is teeming with life, many organisms out there, that means it's not hard for life to originate and you go down the path that Paul suggested.

Paul Davies:
If two forms of life right here on earth, it's conceivable that the other earthlike planets are going -- twice on one planet and none on the rest doesn't seem right.

Ariel Anbar:
This makes it a bit more likely -- it's a little bit smaller than it was a week ago.

Paul Davies:
Encourage people to look.

Ted Simons:
Sure. And speaking of encouraging people to look, have we been looking in the wrong ways for life on other project planets? Extraterrestrial life?

Ariel Anbar:
I direct a project at ASU, the school of space exploration, and the theme of our program and the project fits right into it, is follow the elements, so NASA had an idea of following the water to look for life and there's lots of water out there. Water is not a good enough guide. You only get one shot at Mars every so often and the philosophy is let's think about what life needs to survive and after water, you need the six building blocks that I mentioned. Our philosophy is let's think where they're in abundance. And now what Felicia's studies suggest, we need to think harder which elements to follow. Get us out of the box.

Ted Simons:
Is it also going to change the way microbiology is taught, learned? Thought about?

Ariel Anbar:
In some respects. Depends on how far this goes.

Paul Davies:
Yes, yes, when you find something really weird, there's -- one, it's a quirky little incidental embellishment on the body of knowledge and strikes something fundamental. Whether we have to rethink the whole microbiology of the planet. It would be exciting if it was the latter.

Ted Simons:
We've got the dreamer and the skeptic and the media. Are you surprised at the response of this thing? Everyone talking about ASU and space exploration and maybe a new form of life on earth. Surprise you a little bit?

Paul Davies:
No, I've been through a number of these sort of media flaps over the years. And I've seen them come and go, and we're pleased, of course, at the huge amount of interest. Maybe not surprised.

Ted Simons:
What about the response? What have you seen? Has any surprised you?

Ariel Anbar:
I don't know if I was surprised. I was dismayed by the rumors that build up. NASA announced a press conference and in the days between, people's imaginations ran away with them. There was going to be life on Titan announced and great ideas. But that wasn't the case.

Ted Simons:
People got overboard and we had to reel them back in.

Ariel Anbar:
Right.

Ted Simons: Let's go overboard more. Could this be dangerous? Are we talking Andromeda strain?

Paul Davies:
No, it's been sitting in Mono lake without anyone having ill effects but it could have therapeutic effects. It could be the complete opposite of dangerous. Groundwater contamination with arsenic is a real problem. And one way of tackling it is using -- and also a possible cancer therapy, and I'm looking forward to studying the cancer implications of this new organism.

Ted Simons:
Thank you for joining us. We appreciate it.

Ariel Anbar & Paul Davies:
Thank you.


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