New forms of life on Earth

It turns out phosphorus isn’t a necessary part of our DNA say American scientists who discovered a bacterium which can thrive in a toxic arsenic environment

The bacteria – known as strain GFAJ-1 – swaps phosphorous for arsenic in their DNA and cell membranes, and add a new dimension to what biologists consider the necessary elements for life. The bacteria is well known, but no one knew it was capable of using arsenic.

“What we’ve found is a microbe doing something new – building parts of itself out of arsenic,” said Felisa Wolfe-Simon, a NASA astrobiology fellow, “There’s an organism doing something different. We’ve cracked open the door to what’s possible for life elsewhere in the universe. And that’s profound.”

In order to show the bacteria thrived in toxic conditions, Wolfe-Simon took sediment from the Mono Lake in eastern California and put it in an environment where there is lots of arsenic and very little phosphorous. She did this several times, so only organisms happy in that environment survived.

“So the big question we all wanted to know was where has the arsenic gone? Is the arsenic really in their innards?” said Paul Davies, “Eventually, bit by bit the evidence accumulated that indeed the arsenic was in the DNA, the proteins, the lipid membranes and the metabolites, so it was everywhere where it is important.”

Scientists have known for some time that some microbes can use arsenic for energy, and the trio first began discussing the idea that ‘weird life’ – different life forms that don’t play by our biological rules – could exist on Earth.

“This is going to open up a whole new line of inquiry. First of all this can’t be the only arsenic organism on the planet, there is going to be a lot more, so this is a whole new domain of microbiology that it represents,” said Davies, “Who knows what else is out there is we take a harder look?”