I've been saying that researchers shouldn't invest the time and resources needed to test Wolfe-Simon et al's claims, because of the vanishingly small probability that they are correct. But I'm having second thoughts, because the most important claims can, I think, be very easily tested. So I've just sent an email off to GFAJ1samplerequest@gmail.com (thanks Dave Baltrus, @surt_lab, for tweeting this address), asking for information on how to obtain the bacterial strain GFAJ-1.
The main questions to answer are:
Q. 1. Is the approximately tenfold growth difference between +As/-P and -As/-P in Figure 1B due to the cells' use of As in place of P in DNA, RNA and other biomolecules?
Q. 2. Does DNA purified from cells grown with limiting P and abundant As contain significant amounts of covalently incorporated As?
Both of these questions can be answered by straightforward experiments. However a microbiologist like myself would need to work with someone (a chemist?) who could use a mass spec to assay As and P in the reagents, media and DNA. I'm assuming this is very straightforward, but perhaps readers can set me straight if I'm wrong.
I'll consider Q. 2 first because it initially seemed easiest.
1. Make culture media with 40 mM arsenate and varying levels of phosphate (at least 0, 3 and 1500 µM). The recipe for the base of 'AML60 salts' is available here; unfortunately this reference does not give the components of the 'trace metals stock' it uses, nor does the reference it cites. Don't worry about any phosphate contamination of the medium.
2. Inoculate the GFAJ-1 cells into the different media and culture them in screw-top vials at 28 °C in the dark. The Methods don't say anything about mixing, so probably stationary culture with occasional mixing is OK. I could turn down the temperature of one of my new/old incubators if we were to do this.
3. Monitor the culture growth by counting a defined volume of the cells under a microscope (a hemocytometer is useful for this). The cells will probably double every day or so.
4. Once the cells have stopped dividing, collect them by centrifugation and wash them several times with a simple solution such as PBS.
5. As a control for arsenic contamination, add to arsenic medium an equal number of E. coli cells that have been grown in medium without arsenic, and let them sit for a couple of hours. Then collect them and wash them along with the GFAJ-1 cells.
6. Mix the cells with 50 mM Tris 10 mM EDTA (no more than 10^9 cells per ml) and lyse them by adding SDS to 1%. Add RNase A (10 mM) and incubate at 37 °C for 20 minutes to degrade the RNA. Extract the lysed cells with twice with phenol and twice with phenol:chloroform.
7. To the aqueous phase add NaCl (150 mM) and ethanol to 70%. Collect the chromosomal DNA by spooling it onto the sealed tip of a glass Pasteur pipette. Wash the DNA by rinsing the tip with 70% ethanol, and let the DNA air-dry on the tip.
8. Dissolve the DNA in TE (10 mM tris 1 mM EDTA), aiming for a concentration of about 200 µg/ml, based on the number of cells you had in each prep.
Maybe have the chemist assay the spent media from the low-P cultures to see how the P concentration has changed.
Of course, for either experiment the most important practical question is 'Could these results be published?' I think they could. The best plan would be to have several independent labs do the same test and publish jointly - we'd have more impact and all get our names on a publication. On the other hand, we all have more important things to do...