NASA has made an announcement that it has discovered a new form of life. The irony is, contrary to some of the media hyperventilation in the run up to the announcement, the life NASA found is of this Earth — in California, in fact.
According to the NASA announcement:
“Researchers conducting tests in the harsh environment of Mono Lake in California have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes arsenic for phosphorus in its cell components.
“‘The definition of life has just expanded,’ said Ed Weiler, NASA’s associate administrator for the Science Mission Directorate at the agency’s Headquarters in Washington. ‘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.’
“This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth. The research is published in this week’s edition of Science Express.
“Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA, the structures that carry genetic instructions for life, and is considered an essential element for all living cells.
“Phosphorus is a central component of the energy-carrying molecule in all cells (adenosine triphosphate) and also the phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.”
In other words, to use the line from “Star Trek,” It’s life, but not as we know it.
The importance of the discovery of this new bacterium, strain GFAJ-1, which is part of the group of bacteria known as the Gammaproteobacteria, lies beyond just the new areas of microbiology research that have been opened up. It seems that GFAJ-1 can survive on both phosphorus and arsenic. The fact that a bacterium can substitute one of the basic building blocks of life for another element will certainly raise more questions than it answers.
DNA that uses arsenic instead of phosphorus should not exist. Such molecules should be so unstable that they would fall apart. Some have speculated that there may be a “shadow biosphere” of arsenic-based life hitherto undetected because scientists have not known what to look for.
The discovery proves in the real world a concept that has often been depicted in science fiction, that of life evolving with an alternate biochemistry. The importance of the discovery for NASA specifically is obvious. Hitherto, when space probes have searched for life beyond the Earth, say on Mars, it has searched for life with the common biochemistry that most life on Earth is known to have. The discovery of strain GFAJ-1 proves that the parameters of the search need to be expanded. Life can exist with alternate biochemistries, some in environments that would be hostile to the form of life most common on Earth.
Now the question arises, what other kinds of biochemistries are possible? Can such exist as life forms higher than bacteria? If so, then in what form would they take? No doubt purveyors of science fiction will begin to make speculations along those lines even as scientists begin to research into the possibilities. It promises to be exciting times for microbiologists for the foreseeable future.
Source: NASA-Funded Research Discovers Life Built With Toxic Chemical, NASA, December 2nd, 2010