"It turned out the organism was able to tolerate these heavy metal concentrations (that are found in Mono Lake)," Pett-Ridge said. "Arsenic is right below phosphorous on the periodic table and it may have found a way to substitute arsenic for phosphorous in its biological makeup."
Cultures of the Mono Lake samples produced flourishing colonies of the bacterium cells, as expected, when fed a steady supply of phosphorus, along with other necessities. When researchers removed the phosphorus and replaced it with arsenic, however, the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new cells.
"The team hasn't yet established how the organism uses arsenic as a building block when it's a poison to most other life forms," Pett-Ridge said. "It could be an ancestral trait or a unique kind of metabolism. Or it could be that it lives in an environment where arsenic is very high and it found a niche to survive."
"This organisms' metabolic lifestyle suggests that life based on non-typical elements may be possible," Wolfe-Simon said. "This is important to scientists looking for clues to life on other planets."
NanoSIMS not only measures the elemental concentrations, but it also images them. It collects a picture of the image and identifies how much of a specific element is found in the sample. "We found that arsenic was higher in the cells than in the environment outside the cells," Pett-Ridge said.
"It's very difficult to make these measurements because the sample concentrations of arsenic are very low," she said. "But it's clear that the cells are incorporating arsenic into them. There are not a lot of organisms on the planet that can do this. "
The next step is to conduct protein biochemistry to find ou
|Contact: Anne Stark|
DOE/Lawrence Livermore National Laboratory