Researchers discovered that a new strain of bacteria that cause tuberculosis (M. tuberculosis) taken from a dead patient has a point mutation in the rpoB gene that codes for part of the RNA polymerase enzyme. This mutant form of RNA polymerase does not function as well as the more common form of RNA polymerase. A commonly used antibiotic called rifampin does not affect the mutant rpoB bacteria.
A researcher mixes M. tuberculosis with and without the rpoB mutation and adds the bacteria to cell cultures. Half the cell cultures contain only standard nutrients, while the other half of the cell cultures contain rifampin and the standard nutrients. After many cell generations, the researcher finds that ________.
A) very few M. tuberculosis in the standard nutrient cell cultures carry the rpoB gene mutation, but almost all of the M. tuberculosis in the cell cultures with rifampin carry the rpoB mutation
B) almost all M. tuberculosis in the standard nutrient cell cultures carry the rpoB gene mutation, but very few of the M. tuberculosis in the cell cultures with rifampin carry the rpoB mutation
C) very few M. tuberculosis in any of the cell cultures carry the rpoB gene mutation
D) almost all of the M. tuberculosis in both types of cell cultures carry the rpoB mutation
E) a mix of both M. tuberculosis strains thrive in the standard cell cultures, but no living bacteria can be found in the cell cultures that contain rifampin

Question

Quizplus · Accepted Answer

The presence of rifampin selects for the bacteria with the rpoB mutation because these bacteria are resistant to the antibiotic, allowing them to survive and reproduce. In the standard nutrient cultures without rifampin, the wild-type bacteria without the mutation are likely to outcompete the mutant bacteria since the mutation causes the RNA polymerase to function less effectively in the absence of antibiotic pressure.

Researchers Discovered That a New Strain of Bacteria That Cause