For the following article, \" A Bacterium That Can Grow by Using Arsenic Instead
ID: 141780 • Letter: F
Question
For the following article, "A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus Felisa Wolfe-Simon, et al. " http://science.sciencemag.org/content/332/6034/1163
Do not answer the following for the entire paper, it has to be specific for the following figure Thank you so much!!!
For the following figure explain the following in detail: Question/Hypothesis, Techniques Used, Controls, and Author’s Conclusions. What is the question/ hypothesis the author is trying to answer with the following figure. what techniques did they use to answer the question in the following figure, what are the controls they used in this figure, what are the author's conclusions answered in this figure. please explain in detail, thank you so much!
As-S As-Fe AS GFAJ-1 (data) Fit Fe 10um 4 -A(r +er) Fig. 3. X-ray analysis of GFAJ-1 +As-P described similarity of As coordinated like P in DNA. (A) EXAFS comparisons of the Fourier transformed data for As in model environments and GFAJ-1 (washed and fixed, collected on whole cells). Identification of each spectrum is indicated on the figure and from top to bottom are As-S, As-Fe, and GFAJ-1 data (collected on whole cells) and fit to the GFAJ-1 data (red line). (B) XRF maps indicated the correlation between As, iron (Fe) and zinc (Zn) and not with P with some variability but consistent with the trend that these elements are often found together (fig. S3, element correlation plots). The scale bar in the Zn quadrant of the maps is as designated and applies to all parts of the figure. Given the spatial resolution of these images, the structures identified as containing high As, Fe, and Zn are aggregates of cells. Ranges as indicated in the color bar run from cold to hot, in units of g cm-2, as follows: As, 0 to 1.6; P, 0 to 40; Fe, 0 to 32.1; and Zn, 0 to 2.8. Standards were used to calibrate signal and background (11)Explanation / Answer
Question: The authors wanted to determine the chemical environment of intracellular Arsenic in the bacterial strain GFAJ-1. They also intended to find out the oxidation state of As inside the bacterium.
Techniques used: For finding this they used the technique: Micro-x-ray absorption near edge spectroscopy (EXAFS). This technique measures X-ray absorption coefficient as a function of X-ray energy.
Controls: The controls used were bacteria grown on medium containing Arsenate, without any Phosphate ( +As/-P) and bacteria grown on medium with Phosphate and no arsenate ( -As/+P)
Conclusion: The figure shows EXAFs spectra for, As-S(Arsenic sulfur), As-Fe and GFAJ-1, which shows that As is not present in the form of As-S and As-Fe clusters rather it is present in the form of free AsO43– ions. This data showed that As was present in the cell is in the +5 oxidation state complexed with O and C. X-ray fluoroscence data showed high levels of As, alongwith high levels of iron and oxygen but low phosphorus in bacterial cells.