Poison-Based Bacteria Redefines Life As We Know It

Arsenic is an element that is deadly to most living creatures, but bacteria living in California's Lake Mono thrive on it. Today NASA explains how those poison-eating organisms are changing the way we search for extraterrestrial life.

News of an arsenic-eating bacteria residing in alkaline Lake Mono first came two years ago. As reported by the BBC, researchers discovered a bacterium that utilizes arsenic in photosynthesis instead of water to transform carbon dioxide into food.

So what is different about NASA's new finding?

Dr. Felisa Wolfe-Simon of the US Geological Survey in Menlo Park says that the microbe, known as GFAJ-1, isn't simply substituting arsenic for water. It's substituting arsenic for phosphorus, one of the fundamental building blocks of life.

"We know that some microbes can breathe arsenic, but what we've found is a microbe doing something new — building parts of itself out of arsenic," said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence at the US Geological Survey in Menlo Park, California, and the research team's lead scientist. "If something here on Earth can do something so unexpected, what else can life do that we haven't seen yet?"

During the press conference, Wolfe-Simon explained that the reason arsenic is so toxic to normal life, is that it's so close to phosphorus our bodies can't tell them apart.

"Nothing should have grown," she said of the environment of Lake Mono. Yet it did. "It has solved the challenge of being alive in a very different way than we knew of."

The arsenic is associated specifically with a band of genomic DNA. It's inside the cell. It's part of the microbe, taking the place of phosphorus.

Arizona State University's Dr James Elser explained that the existence of an organism that does without phosphorus, has far-reaching possibilities. "It's very exciting to think about the possibilities of a clever organism that's evolved beyond using phosphorus," said Elser after explaining how vital the element is to life on Earth. He marveled over the possible uses for such an organism, including water treatment, bio-energy production, and even recovering phosphorus used in other processes.

Dr Steven Benner of the Foundation for Applied Molecular Evolution put things in layman's terms. Using a steel chain to represent a phosphorus bio-polymer, he likened arsenic to a tinfoil link. When a link is broken it searches for a replacement, and the chain could be confused by the similar structure of arsenic. He called the element a demon wolf, tricking organisms into taking it it.

"Remember, the weakness of the link is a weakness measured at room temperature... in water," Benner said. There are places in our own solar system, like Saturn's moon Rhea, for instance, where the conditions are very different, and that weakness might not be a weakness there.

NASA astrobiologist Dr Pamela Conrad spoke next. She develops habitability metrics for alien worlds, and she's delighted by the discovery, as it will make her change the way she defines those metrics. "The implication is that we still don't know everything there is to know about what might make a habitable environment on another planet. We have to increasingly broaden our perspective." Conrad said that while arsenic might not be a essential element life, it is a tolerable one, and that opens up the potential for other tolerable elements.

Dr Felisa Wolfe-Simon closed the conference by saying this wasn't about arsenic and wasn't about Mono Lake. "It's about thinking about life in a planetary concept and asking questions - simple questions, with a simple experimental design."


    That's so exciting. If their are other building blocks to life than unihabitable planets might actually by habitably to lifeforms that work differently to us.

    Sure it's interesting... in an boring kind of way.
    It's all cellular, show me something multicellular... something with a conciousness, that can use tools.

    Also, if this is from California... why is it NASA doing the selling?

      It has implications for astrobiology, presumably. Substituting arsenic for phosphorous makes it that bit more likely that life can form in weird conditions in space...

        But we already knew that extraterrestial life was going to be radically different to us...

          True. I guess this is just evidence that it's possible here on Earth as well.

          Did we? Its good to know you can see the future! What else do we know about these aliens?

          Thinking something is probable is not knowing until you see proof. Now we have proof. Its a stepping stone.

          As far as I know, most of the search for extra-terrestrial life has been based on the "6 building blocks". Namely we've been looking for earth-like planets that orbit a certain distance from the sun to receive a certain temperature range.

          This changes everything the scientists have been looking out for and considerably broadens the search criteria.

          PS. This is the active search for ET life, not the passive search for 'intelligent' ET where we wait out with our lil' radio dishes for them to contact us.

    So until this discovery, they've been basin ideas of alien life on the way life on our planet works?

    I've always thought that it would be obvious that alien life forms work much differently to ours - i mean, we evolved the way we have because of our atmosphere, there's nothing stating that life could evolve in other atmospheres (or lack thereof)

      It was more a case of cautious optimism. For the longest time, we could only assume based on what we've seen on our own planet (sample size of one), we had no idea if life was possible in any other environment, with different building blocks. Of course there was some theories about silicon-based life etc, but we still had no idea.

      This news is a huge deal because it proves that life doesn't have to conform to that of our higher-order species, even on Earth. It now opens the dictionary on what the definition of "life supporting planets" would be.

      But it was more of a symbolic discovery than anything.

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