4.) Serratia marcescens bacteria has a gene that regulates red pigment productio

Question

4.) 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.

Serratia cells undergo a genotypic change that is proportional to changes in temperature.

This is an example of constitutive gene expression.

Serratia genes for pigment production are induced at certain temperatures.

Explanation / Answer

Serratia marcesens produces a red pigment called prodigiosin which is a secondary metabolite. The genes for pigment production are induced at certain temparature so they appear red at 270C but are nonpigmented at 370C. It is possible that pigment production ceases at this temparature due to mild stresses. Temparature may play a role in regulating expression of the pigment pathway and hence its production depends on certain optimal temparature.

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