Serratia marcescens bacteria has a gene that regulates red pigment production by cells. A student inoculates two nutrient agar plates of Serratia and incubates one at 250C and the other at 370C. Following incubation, the student observes that colonies on the 250C plate are red while those on the 370C plate are nonpigmented. Which of the following statements is a logical conclusion based on these results?
A. Low temperatures cause repression of certain housekeeping genes.
B. Serratia cells undergo a genotypic change that is proportional to changes in temperature.
C. This is an example of constitutive gene expression.
D. Serratia genes for pigment production are induced at certain temperatures.

Serratia genes for pigment production are induced at certain temperatures

Explanation:

The red pigment production is dependents on temperature.

Some bacteria are thermophile doing very well in extreme temperature while some are very sensitive to temperature changes.

The red pigment production is regulated by certain gene in the bacteria but can only be activated at certain temperature. 25°C was suitable for the red pigmentation that is why the plate color changed this indicate the sensitivity of the pigment production to temperature changes.

Conclusion - To get the best of serratia it is best to keep them at a temperature lower than the normal room temperature for the gene to be activated and full express itself.

is this a psat question, if so do not cheat try your best.