A team of NASA-funded researchers discovered a micro-organism in the harsh environment of California’s Mono Lake able to thrive on arsenic, a startling finding that NASA said Dec. 2 will force scientists to rewrite biology textbooks and expand the scope of the search for life beyond Earth.

“The definition of life has just expanded,” NASA’s associate administrator for science, Edward Weiler, said during a press conference at the agency’s headquarters here to announce the findings. “As we pursue our efforts to seek signs of life in the solar system, we have to think more broadly, more diversely and consider life as we do not know it.”

The microbe researchers discovered at the bottom of Mono Lake uses highly toxic arsenic instead of phosphorous to build cells, something scientists previously believed impossible since all other known forms of life are composed of a combination of carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorous.

“We know that some microbes can breathe arsenic, but what we’ve found is a microbe doing something new — building parts of itself out of arsenic,” said Felisa Wolfe-Simon, a NASA astrobiology research fellow in residence at the U.S. Geological Survey in Menlo Park, Calif., and the research team’s lead scientist. The journal Science published the team’s finding Dec. 2 on its website.

Wolfe-Simon and her team successfully grew the newly discovered microbe, strain GFAJ-1, on a diet short on phosphorous but rich in arsenic. When researchers removed the phosphorous and replaced it with arsenic, the microbes continued to grow, NASA said in a press release. Subsequent analyses indicated that the microbes used the arsenic to produce the building blocks of new cells.

“Until now a life form using arsenic as a building block was only theoretical, but we now know such life exists in Mono Lake,” Carl Pilcher, director of the NASA Astrobiology Institute at the agency’s Ames Research Center in Mountain View, Calif., said in a statement.