Astrobiologists find alternate chemistry for life...on Earth, 12.02.10

Astrobiologists participating in a NASA funded study at Mono Lake in California have discovered that a strain of bacteria is capable of not only thriving on, but actually altering its genetic makeup to include arsenic. Arsenic is an element that is extremely poisonous to most forms of life on Earth, and chemically behaves in a similar manner to phosphorous, a crucial element to all cells’ “energy-carrying molecule,” and also in creating cell membranes. Arsenic, on the other hand, tends to disrupt metabolic pathways.


“The definition of life has just expanded,” said NASA’s associate administrator for the Science Mission Directorate, Ed Weiler. According to Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence in California, scientists were previously aware of some microbes that could breathe arsenic. Substituting arsenic into its genetic makeup, however, is something completely new and changes everything scientists thought they knew about DNA.


The star of the show is strain GFAJ-1, from the common family of bacteria Gammaproteobacteria. The bacteria was collected from mud samples in the lake and cultivated in laboratory tests. First the bacteria were fed using a mixture of elements that was low on phosphorous and high in arsenic. The mixture was changed to completely leave out the phosphorous and substitute even higher levels of arsenic, and the scientists discovered the bacteria actually began incorporating the arsenic into its DNA in place of the phosphorous. NASA said the results of the study were published in this week’s edition of Science Express.


The image on the left is of the GFAJ-1 grown first in the phosphorous mixture. The second image is of the bacteria once arsenic had been completely substituted into the slurry. Thronateeska Museum Guide and staff astronomer Jim Friese says “this expansion of the definition of life goes hand in hand with all the different and strange worlds we are finding out there [in space].” Scientists are now realizing that different chemistry really does not automatically mean there is no life there.

Image credit: NASA.

Image credit: NASA.

Credit: NASA.