Saturday, December 4, 2010

Arsenic - any one?

Element number 33 of the periodic table jumped into prominence this week with the discovery of arsenic based life form on earth. It seems the bacteria GFAJ-1 uses arsenic instead of phosphorus (which all known life forms use) for its DNA backbone.
Arsenic, famous as the poison of choice in Agatha Christie’s Miss Marple stories as well as being allegedly used by the English to finish off Napoleon Bonaparte, works well as a poison due to its similarity with Phosphorous - our cells easily accept it and try to use it in lieu of Phosphorous.

Discovered in Mono Lake, California by geomicrobiologist Felissa Wolfe-Simon, GFAJ-1 does not naturally prefer arsenic. But when grown in culture and given an arsenic rich diet, devoid of any phosphorus, instead of dying of like other organisms this particular bacteria, GFAJ-1 used arsenic in place of phosphorus in DNA and other molecules inside the cell.

How is this discovery so significant? It is a very momentous discovery for two reasons - (1) It implies that life can be very different from what we think - especially as we search for extraterrestrial life. It is not a coincidence that the announcement of this discovery was made by NASA as one of relevance to astrobiology (2) It might also support the theory of the origin of life in hydrothermal vents down under the oceans (a concept well explained by Nick Lane in his book ‘Life Ascending’).

Till now, the biochemistry of life has been dominated by the Big Six - Oxygen, Hydrogen, Carbon, Nitrogen, Sulphur and Phosphorous - the critical elements for life to exist. Well, now here is new biological paradigm - and let us see what new science this will give us.