Sigma B Is a Stress-Induced Transcription Factor in Bacillus Subtilis

question 11

Multiple Choice

Sigma B is a stress-induced transcription factor in Bacillus subtilis. Bacteria producing a sigma B-YFP fusion protein were exposed to constant energy stress, and fluorescence pulses emitted by individual cells were detected by time-lapse microscopy. Could this result have been obtained using a sigma B-b-gal fusion protein?

• A) Yes. Hydrolysis of X-Gal by b-galactosidase produces a blue product detectable by eye.
• B) Yes. Hydrolysis of ONPG by b-galactosidase in liquid medium produces an orange compound measurable by spectrophotometry.
• C) Yes. It depends on how well the reporter gene is inserted into the vector with respect to the position of the ribosome-binding site.
• D) No. Whereas YFP fluorescence can be carefully observed and measured by time-lapse microscopy, b-gal activity is measured as an average of the population as a whole.
• E) No; the product would not be detectable by eye.

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