The microbe in Mono Lake
GFAJ-1 can build DNA with arsenic rather than phosphorous. (Photo: www.edmonton.ctv.ca)
We are not alone. Felisa Wolfe-Simon from Arizona State University’s School of Earth and Space Exploration may not have found ALF or E.T., but believes a small, gnocchi-shaped microbe found in local Mono Lake waters is just as important. She announced her discovery on Thursday during a NASA press conference.
Bacterium GFAJ-1 was pulled from the bottom of Mono Lake and taken to Wolfe-Simon’s lab. The microbes were transported from the lake along with some mud and placed into artificial water that simulated the water of Mono. They were not given any phosphorous, an essential building block of life, but instead were doused with arsenic.
“Something grew where it should not have,” Wolfe-Simon explained during the press conference. “The fact that this microbe did something different than what we expected cracks open the door to life elsewhere.”
Why? According to Wolfe-Simon, the thought that an organism can survive without phosphorous opens the doors to exploration that life forms may be able to survive in completely different forms than were previously believed. Until now, it has been thought that every life form must contain phosphorous.
“We don’t know what makes a habitable environment on other planets,” said Pam Conrad, an astrobiologist for NASA. “Knowing that organisms can tolerate arsenic means that they might be able to tolerate other things as well. Things we may not have thought of yet.”
This is not the first time that scientists have had to rethink what life on other planets might mean. In 2004, a bacteria was discovered in the Southeastern Pacific Ocean that does not require either light or oxygen. This discovery led the way to a whole new line of research regarding life on other planets.
Wolfe-Simon’s recent discovery may once again require scientists to reinvent the wheel.
Back on Earth, Dr. James Elser, an expert in phosphorous and professor at ASU, participated in the press conference via phone and discussed the positive implications that could come about for Earthlings as well. Elser’s excitement was audible as he considered what clever organisms that have evolved away from phosphorous could mean for the world’s bioenergy problems.
Phosphorous is scarce, (according to Elser there are only a few countries where phosphorous mines are found), but it is used in large quantities for fertilizer. If there is an alternative to phosphorous, this could help solve bioenergy problems, because we would not have to rely on a finite resource, Elser said.
Many biofuel crops, for example, demand large amounts of phosphorous fertilizer.
Dr. Steven Benner, a chemist from the Foundation of Applied Molecular Evolution, also attended the press conference in order to, as he stated, “throw a wet blanket” on the whole discussion.
“Exceptional results require exceptional evidence,” Benner explained. He described arsenate (arsenic) in DNA as a “wolf in sheep’s clothing.”
“Arsenate in DNA is unstable. An organism wastes a lot of energy trying to put it into a DNA backbone only to have it break apart.”
Benner conceded that an organism could evolve to manage this weak link but did not seem convinced that’s what Wolfe-Simon’s bacteria was doing.
“The evidence that the molecule can’t exist is more overwhelming than the evidence that it can,” Benner said.
“It’s really not about arsenic or Mono Lake,” Wolfe-Simon replied. “It’s about asking questions about habitable life. We’ve shown a microbe that doesn’t need phosphorous when every living thing we’ve ever thought of needs phosphorous. So what other questions can we ask now?”
Wolfe-Simon clarified during a Q&A session that the microbes do have some phosphorous left in them but not enough to support the growth that was observed.
“We can think more broadly about environments that might be habitable,” Conrad added. “It will help us recognize life on other planets because when we find it, it’s not going to be a human being walking around. That would be too easy. We would hate to go somewhere and not see it.”
“In other words, it’s like the Horta from ‘The Devil in the Dark’ episode of ‘Star Trek,’” said Mary Voytek, director of NASA’s astrobiology program. “Maybe we can find E.T. now because we’ll know what we’re looking for.”
