Okay, you’ve probably heard the buzz about the “arsenic organism” supposedly discovered in Mono Lake, and how NASA’s 2pm press conference today will reveal more. I’ll be honest, I wasn’t that excited about it – extremophile bacteria metabolize some freaky stuff, and it seemed pretty clear the announcement wasn’t about extraterrestrial life. But Gizmodo is now claiming the critter has arsenic based DNA.

Did April Fools Day relocate to December? I’ll believe this story when I hear it from the researcher herself, but that would be SO COOL. I’m getting my wide-eyed-awestruck-biologist hat out of mothballs, and putting it next to my laptop, just in case.

Update: so it looks like I don’t need my awestruck hat. The bacteria appear to use arsenic as a building block of DNA when forced to – that is, when they are exposed to an arsenic-rich, phosphorus-depleted lab environment. But it’s not an obligate process. We have no evidence the DNA normally has an arsenic backbone. The bacteria thus don’t appear to be an arsenic-based lifeform in the sense that the Gizmodo article suggested.

Instead, they’re proof of the amazing flexibility of organisms to accommodate different building blocks of life, which is also cool. It suggests we should broaden our expectations for the biochemical needs of extraterrestrial life. That’s why NASA is involved. But the discovery certainly doesn’t mean we’ve proved extraterrestrial arsenic-based life exists, nor even that arsenic-based life exists on earth, outside the lab.

If you’d like to know more, read Ed Yong’s take; he pretty much nails it. Cool, but not awestruck-hat cool.

Incidentally, the CJR suggests NASA and AAAS handled this badly, as a matter of science communications. Hyping up a discovery with an exobiology spin that’s a bit of a stretch, then gagging the professional journalists with an embargo so they can’t debunk runaway rumors, and finally disappointing the public with a story that – however cool to biologists – is not what they expected. . . that seems like a series of questionable choices to me. I’m just sayin’.