Good Reader Questions on Arsenic Bacteria Story

This column on the “arsenic bacteria” controversy brought on some good questions. The following was the also posed by biologists when the announcement of the so-called arsenic bacteria came out:
 "What about the RNA?"

This is a great question. If these bugs were living with no phosphorus, they’d have to substitute in arsenic in the DNA and the RNA. So the researchers making the claim would have had to prove arsenic was in the RNA as well.


This question also brings out the difference between claims made by the paper and the press conference and press releases. In the scientific paper, the researchers were not clear how much arsenic actually got incorporated into the DNA.

The press materials implied there was no phosphorus at all in these bugs – they were the first known organisms to live without this essential element. At a NASA press conference the lead researcher also implied that all the phosphorus in the DNA was replaced by arsenic – how could it be otherwise if there was no phosphorus in the system?

An animated graphic used at the press conference showed phosphorus atoms represented by colored balls. All of them disappear from a DNA molecule, to be replaced by arsenic, represented by a different color. The graphic above is not the one used in the press conference, but it’s the same idea. 
The same reader asked if you’d have to call it something other than DNA:  “Not that I believe any of this but, if the "DNA" did not contain phosphorous it could not correctly be called deoxyribonucleic acid.”

I believe that would be the case, had there been any merit to the claim. Scientists have synthesized alternative nucleic acids – FNA, TNA, PNA, and the like.
As it turns out, it didn’t matter in the case of the arsenic bacteria. Biologists repeating the experiment found that no arsenic got into the DNA or the RNA.