Preliminary Thoughts on the “Arsenic-Based Life” Paper
This is indeed an interesting paper. I have some questions about it; maybe I am misreading things. Pardon the terseness. I’ll update this post later this weekend.
1. What was the source of the arsenate used in the growth media?
I can’t find the vendor/product information in the paper or the SI. I am inclined to agree with Steve Benner and his suspicion that there may be sufficient phosphate in the “–P” media to support growth. Life has a nice ability to concentrate/pick out what it needs.
2. How could you think that arsenic is in the backbone of the DNA?
This paper shows that arsenic(V) esters hydrolyze in water in seconds. The authors hypothesize that the bacterium has mechanisms for coping with this, but how does that explain the fact that they see a nice, clean gel (with a single band) of the isolated DNA? Shouldn’t that band streak like the Dickens?
3. “Arsenic possesses a similar atomic radius [to phosphorus]“?
Is 15 picometers (P: 100 pm, As: 115 pm) really that similar? That seems like miles to me (on the atomic scale). It is bound to have profound implications for bond strength and molecular structure.
4. Title: “Using Arsenic” [vs. "Tolerating Arsenic"]
I am not convinced the data presented support the conclusion that these organisms are “using” arsenic. It will definitely be interesting to see if future work can isolate and characterize biomolecules from this organism that include covalent bonds to As. Regardless, this paper is interesting because it presents an organism that is very tolerant of arsenic.