Monday, July 9, 2012

Redefining the Chemistry of Life? Followup

In January 2011, I wrote a blog post on a (media-hyped) discovery of a strain of bacteria that appeared to be using arsenic instead of phosphorus in its biochemistry. In the post, I argued that this organism does not at all "redefine the chemistry of life" or find "arsenic tasty," as the study and media commentary suggested. I concluded that (at best) this organism is a facultative arsenophile, which means it seems that it can use arsenic in its biochemistry when necessary but prefers phosphorus and needs it to thrive.

In the most recent issue of Science (the journal in which the original study was published), two more papers have been published by teams who did independent research on the bacteria in question (GFAJ-1), and their findings refute the contention that GFAJ-1 is using arsenic at all. One shows that there is no evidence for arsenates being incorporated into the bacteria's nucleic acids. The other argues that GFAJ-1 is really an arsenic-resistant bacteria (a possibility I noted in my original post) that still needs phosphates to survive and thrive.

If you want my take on the research, the original post I wrote on the topic is still relevant. My original conclusion, which appears to still be valid, was as follows:
It is not an organism that has a "redefining" biochemistry, it is not an "arsenic-base" organism, it does not find "arsenic tasty"; at best it an extremophile that can possibly make use of arsenic when it is the only thing available in the environment but its preference would be phosphate.
Before I wrap this post up, I want to comment on one more thing that I quoted from Dr. Rana above. It has been suggested that this type of organism could represent an alternate way that life could emerge. Sorry, but this kind of organism does not provide a different possible pathway for life to originate. The reason why Dr. Rana says that, and I agree, is because this type of organism not only has the biochemistry of normal bacteria but has extra mechanisms that allow it to live under the harsh condition of excess arsenic. In short, it is an organism that is significantly more complex than normal bacteria that is based on phosphates alone. Arsenate is unstable, so unless you already have in place mechanisms that could stabilize the arsenates, there is no way life could form with arsenates. Origin of life in an arsenate system (vs. a phosphate system) is a significantly more complex pathway and even more improbable than the existing, phosphate-based origin of life scenarios. The same is true for all extremophiles. In fact, there have been papers written by other biologists arguing this point.
So, after time for further research and peer-review, life is still CHNOPS-based (see the original post for explanation on that) and no other alternate pathway for the origins of life is evidenced by this study. Life is still as delicate and complicated as science has consistently shown and requires an Intelligent Designer for its existence.

By His Grace,

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