It’s life, Jim, but not as we know it

NASA is due to announce today that they have discovered a form of bacteria living in the arsenic-rich Mono Lake in California. This is slightly old news (e.g. from 2008) mind you.

The bacteria is incredibly novel though — it is apparently capable of thriving by metabolizing arsenate. This is completely unlike any other life form known on the planet. We don’t even yet know if we’re related, in fact. Turns out we’re distant cousins!

Duquesne-based scientist John F.Stolz figured out that the bacteria were able to do this because they contain certain enzymes, or proteins, that act like a key, allowing the chemical reaction to occur.

Bacteria that generate energy by metabolising (reducing) arsenate are already known. But Ronald Oremland and colleagues at the US Geological Survey in Menlo Park, California, were puzzled by the great range of arsenic-eating bacteria. If they evolved recently they must have passed the ability to metabolise arsenic to each other by lateral gene transfer, he says.

Alternatively, arsenic metabolism could have evolved much earlier, giving plenty of time for bacteria to diversify. The newly discovered bacteria from oxygen-free hot springs in Mono Lake, California, support this interpretation. It’s likely that the newly-discovered arsenite photosynthesis, which produces arsenates, opened up niches for these arsenate reducing microbes, the researchers suggest.

This form of life could have derived from a separate biogenesis event. It could have evolved at a very early stage in our planetary biology. Or it could have evolved relatively recently. Regardless of how these bacteria managed to come across this enzymatic ability to eat poison, it ultimately means we can greatly expand the window in which we should be searching for extraterrestrial life — because some life needs only arsenic and sunlight to thrive.

Original study here, though it’s behind a paywall.

Edit: Apparently the novelty is the point of the announcement, not so much the “newly discovered” part. Any evidence that this is a separate biogenesis event will impact heavily the search for extraterrestrial life, insofar as it would prove that abiogenesis can occur in a far vaster range of circumstances than the ones that occurred on our planet. According to the BBC:

Until now, the idea has been that life on Earth must be composed of at least the six elements carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus – no example had ever been found that violates this golden rule of biochemistry.

[…]

One idea to shore up these theories is to begin to look for examples of life here on Earth that break the “golden rules” of biochemistry – in effect, finding life that evolved separately from our own lineage.

John Elliott, a leader of the UK’s search for extraterrestrial intelligence, explained how such evidence on Earth could be suggestive about life elsewhere.

“If we can find a ‘second genesis’ on our planet, obviously separate from our own evolution, you could then extrapolate that life can generate multiple times – that it’s not a one-off phenomenon,” he told BBC News.

“And that’s incredible evidence for it happening on other planets.

Edit 2: These bacteria are not from a separate abiogenesis event, sadly. Doesn’t make them any less cool, though. Nor does it mean abiogenesis can’t happen in these circumstances, only that it didn’t happen in Mono Lake.

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It’s life, Jim, but not as we know it
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5 thoughts on “It’s life, Jim, but not as we know it

  1. 1

    Worth checking out Ed Yong’s Twitter feed for details on this. He’s had the embargoed paper for a bit, I think, so he’s got more information.

    So far: the bacteria are related to us. They thrive better using phosphorus than arsenic; they’ve simply evolved to the point where they can use the arsenic instead.

  2. 2

    Sigh. Updated WordPress, it undid my Reply hacks. Quote then delete the quote works fine though.

    Thanks, lady. Ed Yong’s excellent breakdown is here. The main thing that’s novel about them is that they use arsenic at all, since it’s not one of the golden six elements that generally comprise life. So they ARE related to us, though distantly. That’s not to say that life CAN’T begin in arsenic-rich environments, is the upshot. Just that it didn’t happen here.

    Kinda sad that it wasn’t another abiogenesis event (for obvious reasons).

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