A research lab is using DNA microarrays to examine gene expression in Salmonella enterica during stress. It was noted that when exposed to nutrient limitations, 20 new genes were expressed (as compared to normal laboratory growth conditions); when exposed to oxidative stress, 24 new genes were expressed; and when exposed to low pH, 15 new genes were expressed. The lab then subjected the bacteria to growth in macrophage phagolysosomes, which mimicked the previous three conditions, and noted 59 new genes being expressed. Which of the following would best explain this result? A. The experiment is probably wrong and should be repeated since the number should be lower than 59 because it is likely that some of the stress-induced genes would overlap, so the total number would be lower than adding up the results for the three individual changes in gene expression.
B. The results are probably wrong, and the experiment should be repeated since there would likely be even more stress-induced gene expression due to not only the three stressors that were encountered individually but also due to any additional stress not yet accounted for due to being in the phagolysosome.
C. This is expected since all three stresses are encountered and the effect would be additive, so the 59 genes would be the same as the 20 genes for low-nutrient stress, the 24 genes for oxidative stress, and the 15 genes for low pH stress.
D. The results are probably wrong, and the experiment should be repeated since there should be less binding on the DNA microarrays due to the low pH conditions.
E. The result is most likely a coincidence since some of the genes for the different stressors would overlap, some genes wouldn't be expressed under the combined conditions, and some new genes would likely be expressed due to the unrecognized stress of growing in the phagolysosome.