43) Methylobacterium extorquens is an example of a methylotroph, a microbe that

Question

43) Methylobacterium extorquens is an example of a methylotroph, a microbe that grows on single carbon compounds as methanol. As part of their metabolism, they convert methanol to formaldehyde, a toxic chemical that is preser their cytoplasm as part of their regular growth. You are trying to identify genes involved in protecting cells from (damage) caused by the presence of formaldehyde. You take two samples of cells from an actively growing culture (logarithmic phase) in a chemostat, place each sample in a flask, and then expose one culture to formaldehyde. After an hour, you extract mRNA from each culture and reverse transcribe the mRNA to cDNA. For the experimental cells (formaldehyde added), you incorporate nucleotides that are labeled with a red fluorescent dye, and for the control cells (no formaldehyde added), you incorporate nucleotides that are labeled with a green fluorescent dye. You then hybridize both sets of DNA to a microarray containing nucleotide sequences representing every gene in the genome of M. extorquens. You then analyze the microarray and obtain ratios of expression of red to green Consider the following expression ratios: unknown gene A: 35.6 unknown gene B: 0.998 unknown gene C: 0.02 a. Which of these genes would you predict is involved in protecting M. extorquens from formaldehyde stress? b. Consider the other two genes that you did not predict are involved in protection from formaldehyde exposure Suggest a role for each (i.e, what might each of these genes be involved in?) and how would you explain their expression ratios?

Explanation / Answer

43a. ANS: According to the above given results an unknown gene was significantly involved in the protection of M.extorquens from formaldehyde stress. It is mainly happen because during this the ration of red to green that is experimental cells with formaldehye to that of controls without formaldehyde.

43b. ANS: In this the other gene should be involvd and participate in another cellular processes other that cell division, protection from formaldehyde.

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