 | |||
| "According to a new paper published in the journal Science, reporters are unable to thrive in an arsenic-rich environment." |
Towards the end of 2010, headlines all over the world reported an astonishing discovery: NASA scientists had discovered a bacterium that “not only metabolizes the normally toxic element (arsenic), but also seems to incorporate it into its DNA and other molecules in place of phosphorus”. This news sparked an ongoing controversy in the scientific community. The way this news was reported by the media insinuated that NASA scientists had found “alien life on [Earth].” What if the reports were true and accurate? How does it matter to science, and what does it tell us?
The answer to that lies in basic biochemistry. It has been known for years that all forms of life depend on basically six elements: carbon, oxygen, hydrogen, nitrogen, phosphorus and sulfur. These elements make up most of the macromolecules found in living cells. According to evolutionary biologists, the fact that DNA and RNA are the genetic materials for all life forms is proof of the fact that all life on Earth stems from the same source. In other words, it has been suggested that any living form that utilizes something other than these six elements to sustain life did not have the same evolutionary origin as everything on Earth did.
Through their experiments, Felisa Wolfe-Simon, along with other scientists, conducted experiments on a strain of GFAJ-1 bacteria, isolated from Mono Lake, California. They found bacteria that grow in an arsenic rich environment, and hypothesized that these bacteria use arsenic in their metabolic pathways. To test this hypothesis, they cultured some of these bacteria in an even more arsenic rich and phosphorus deficient environment than that of Mono Lake, hoping to find interesting results.
So what did really happen? It turns out that the researchers never did find bacteria that used arsenic in place of phosphorus in metabolic pathways under natural conditions. Instead, they cultured some, and forced the bacteria to grow in a medium which they weren't doing too well in (at least, not when compared to the one living in a phosphorus-rich environment).
Another problem with the specific research methods was the way the DNA was extracted by the authors. They used Phenol/Chloroform to separate out the soluble portions of the cell, including DNA and RNA. They then 'scanned' the contents using Inductively Coupled Plasma Mass Spectrometry (ICPMS), and noticed the presence of arsenic. The conclusion that can be drawn from this experiment is that some of the soluble cell contents (which may or may not include DNA/RNA) contain arsenic. In order to prove the presence of arsenic in the DNA, further purification of the DNA must be done.
Scientists all over the world has concluded that this research plan was not 'perfect'. However, despite the harsh reviews that the authors of this paper have received in the recent past, I do think that further research should be carried out in this field. I disagree with those that think that this paper should not have been published: there's a good reason researchers conduct literature reviews on experiments that they're trying to conduct. If anything, this paper serves as a good example of what to do differently in case the arsenic content in these bacteria is ever studied again (which I'm sure it will be, given the publicity that this project has gained).
Media Reports: http://www.sciencemag.org/content/330/6009/1302.full
Fun Facts about Arsenic: http://web.ebscohost.com/ehost/detail?hid=104&sid=e7ba62db-ca3b-44fb-96cc-0c542649476a%40sessionmgr114&vid=2&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=ulh&AN=9887515
No comments:
Post a Comment