A new life form discovered on Earth changes how they'll look for life on other planets

http://www.dispatch.com/live/content/local_news/stories/2010/12/03/arsenic-loving-life-here-may-affect-search-out-there.html

Friday, December 3, 2010 02:54 AM

By Spencer Hunt

THE COLUMBUS DISPATCH

Henry Bortman | New York Times

Felisa Wolfe-Simon, a NASA astrobiologist, found the microbe in the mud of Mono Lake, an alkaline- and arsenic-rich lake near Yosemite National Park.

NASA scientists announced yesterday that a new life form discovered on Earth changes how they'll look for life on other planets.
The potato-shape microbe found living in the mud of a poisonous California lake doesn't look special. But it can do something no other known organism can - thrive in arsenic and actually use the toxin in its DNA.
That something can live in such a poisonous place offers hope of finding life on planets that are unlike our own, the scientists said during a media briefing.
"We found that not only did this microbe cope and deal with the toxicity but that it grew and it thrived," said Felisa Wolfe-Simon, an astrobiologist who led the NASA research team that found and studied the microbe.
"I've always insisted in exceptions to the rule."
The rule, in this case, is that all life on Earth springs from six basic elemental building blocks: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. But tests showed the bacteria the team found - it was named GFAJ-1 - used arsenic as a replacement for phosphorus, something previously considered impossible.
Phosphorus, for example, is a key ingredient of energy-carrying molecules in all cells and helps form cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous because it disrupts those processes and cell structures.
Wolfe-Simon found the microbe in the mud at Mono Lake, an alkaline- and arsenic-rich lake near Yosemite National Park. Her research, published in the journal Science, involved taking bacteria-rich mud from that lake and looking for microbes.
They found GFAJ-1 and watched its behavior.
The findings are almost certain to be studied and challenged for years by microbiologists across the globe. Skeptics include Steven Brenner, a fellow at the Foundation for Applied Molecular Evolution in Gainesville, Fla.
"This is an exceptional result," said Brenner, who was invited by NASA to answer questions yesterday. "Chemists will require exceptional evidence to prove it."
Questions include whether arsenic completely or partially replaces phosphorus in the bacteria's DNA. Results show some phosphorus remains in the bacteria, but at levels Wolfe-Simon said are too small to make a difference.
"There is absolutely some phosphorus left in these cells, but it's not enough to support the growth that occurred," she said. "It's just flat-out too little."
Even skeptics say they are intrigued by the discovery.
"This organism has normal DNA, but it has the ability to incorporate arsenic at some level, which is amazing, really," said John Reeve, an Ohio State University microbiologist who studies "thermophiles" - organisms that live in inhospitable places, such as volcanic thermal vents in Yellowstone National Park and on ocean floors.
Reeve said that, until the 1980s, most people thought life couldn't exist in the vents' super-hot environment.
"Certainly you couldn't imagine something living in literally boiling temperatures," he said. "If you go to Yellowstone or these deep sea vents, there are organisms that virtually depend on this."
Even Brenner speculated that arsenic might be a better building block for life on other planets because it is more reactive than phosphorus.
He said life might prefer arsenic over phosphorus on Titan, a large moon of Saturn where the temperature dips to 290 degrees below zero.
The news follows a study announced this week that suggests there are 300 sextillion stars - three times as many as scientists previously calculated.
The more stars there are, the more planets there are. And that's more places for life to exist.