Colonies of the bacterium Serratia marcescens are red when incubated at 22°C but white when incubated at 37°C. This is an example of
A) antigenic variation.
B) genotypic change.
C) phenotypic change.
D) mutation.
E) selective media.

Question

Colonies of the bacterium Serratia marcescens are red when incubated at 22°C but white when incubated at 37°C. This is an example of 
A) antigenic variation.
B) genotypic change.
C) phenotypic change.
D) mutation.
E) selective media.

Quizplus · Accepted Answer

The change in color of Serratia marcescens colonies is a phenotypic change, meaning the expression of a certain gene or genes is influenced by environmental factors like temperature. This does not necessarily imply a change in the genetic sequence or genotype of the bacteria.

Colonies of the Bacterium Serratia Marcescens Are Red When Incubated at 22°C