The Arsenic Monsters!!!

Journal: Science Express
Date: December 2, 2010
Length: 5 pages
Title of Article: A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus
Summary By: Anastasia

Article Summary:
All living things are mostly composed of 6 major elements: carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorous. No organisms have been found that don't follow this rule - until now, that is. NASA scientists have recently discovered a bacterium that can replace the phosphorous in its cell body with arsenic, an element that, while similar to phosphorous in structure, is nevertheless toxic to most living things. The environment where these little arsenic monsters live (Mono Lake, CA) has little phosphorous, but a very high concentration of arsenic. The bacteria have taken advantage of this by evolving the ability to incorporate arsenic into those structures in their cells that would normally require phosphorous. This by itself is not surprising; around 20 other types of bacteria can do this. What makes these bacteria from the Halomonadaceae family special is the fact that they can live entirely on arsenic, without using phosphorous at all. It is the only known organism that can do this.

Scientists discovered this organism's special secret by isolating it from the mud on the lake's bottom and growing it in a petri dish. Gradually, they gave the bacterial less and less phosphorous and more and more arsenic, until, eventually, there was no phosphorous in the dish at all. They were surprised to find that the bacteria were still able to thrive in these circumstances.

Conclusion:
This discovery is important not only in a biological sense, but also in the context of space science. Many planets have different ratios of elements than we do here on earth. Previously, those planets that did not contain large amounts of the 6 elements vital for Earth life were dismissed as unsuitable for any life forms. However, these arsenic-munching bacteria prove that it is possible for organisms to do without at least one of these 6 elements, raising new possibilities and hopes in the search for extraterrestrial life.