Arsenic, a building block of life?

All life on Earth is made of six components: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. We assumed that was true, until today. In Mono Lake, about a year ago, researchers began testing a bacteria known as GFAJ-1. Today, their published study came out that this bacteria could survive using arsenic instead of phosphorus. There are many birds and other organisms that can “tolerate” arsenic, but this bacterium actively uses it in it’s cells.

Many of these bacteria are known to be able to tolerate high levels of arsenic, but GFAJ-1 can go a step further. When starved of phosphorus, it can instead incorporate arsenic into its DNA and continue growing. By introducing radioactive arsenic into the growth medium of some of the microbes, Wolfe-Simon learned that approximately one-tenth of the arsenic absorbed by the bacteria ended up in their nucleic acids. Within the DNA extracted from GFAJ-1 cells starved of phosphorus, arsenic bonded to oxygen and carbon in the same way phosphorus bonds to oxygen and carbon in normal DNA, and found that when cultured in arsenate solution it grew 60% as fast as it did in phosphate solution — not as well, but still robustly.

While some of the key properties of phosphate such as its thermodynamic instability as well as its kinetic stability make it advantageous for Earth’s biological life; Arsenic may be more thermodynamically realistic for life on other planets or moons such as Saturn’s moon Titan