NASA astrobiologists have discovered a microorganism in California that is doing something completely novel: substituting arsenic for phosphorus in its chemical makeup.
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. 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.It’s been known for a while that some microbes can metabolise arsenic, but what this organism is doing is building parts of itself out of arsenic, something no other known life forms can do. ”If something here on Earth can do something so unexpected,” asks Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow, “What else can life do that we haven’t seen yet?”
This will change the way astrobiologists look for life on other planets, including where they look (arsenic-rich atmospheres were previously considered off-limits) and what the definition of life really is (right now, we only know that life exists the way it does on Earth, so finding out that life can exist very differently and using different chemicals will expand what we think of when we think of “life”). This is the first alternative biology we’ve ever known to exist; previously, the idea of alternative biologies has been mere speculation, more common in the realms of pop-science and science fiction.
Source: NASA. Photo via Gizmodo. More info at NASA astrobiology.
