What job can a bug give? A controversy over the arsenic-guzzling bacterium cultured by NASA

The mysteries of life’s evolution on our planet drive us to explore the limits of biology. Life forms on Earth as we know are composed of six essential elements: carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus. However, a recently published research work funded by the National Aeronautics and Space Administration (NASA), USA, has almost shaken the fundamental knowledge about what is life made of on Earth. The research team led by NASA astrobiologist Felisa Wolfe-Simon described a microbe isolated from California’s Mono Lake that could sustain its growth by using toxic chemical arsenic (As) instead of phosphorus (P). This surprising discovery was published online by Science Express on December 2 last year (Wolfe-Simon et al., 2010, online). If the authors of the paper were right, we would have to expand our definition of life on this planet. The arsenic-bug they grew was dubbed GFAJ-1, which interestingly stands for “Give Felisa A Job.” Felisa Wolfe-Simon, an American biogeochemist and microbial geobiologist, is a member of the NASA Astrobiology Institute whose research focuses on evolutionary microbiology and exotic metabolic pathways. During the last two or three years, Wolfe-Simon and colleagues had proposed that arsenate ðAsO 3� 4 Þ could be able to substitute for phosphate ðPO 3� 4 Þ in various biochemical pathways. As belongs to the same group as P on the periodic table and shares some similar chemical properties with P. Located in California, United States, the arsenic-rich Mono Lake has a bizarre and extraterrestrial beauty that captured Wolfe-Simon’s interests, not only because of its scenery, but for the potential presence of shadowy biosphere containing exotic life forms. The researchers led by Wolfe-Simon used Mono Lake bottom sediments as inocula in an aerobic artificial medium