A plaque assay studies viruses through what measurement?

• A. The number of bacterial colonies that grow on a plate
• B. The number of bacterial colonies that are lysed upon infection of a bacteriophage
• C. Comparison between the number and size of bacterial colonies
• D. Rate of Infection

Answer: (B)

Verified step by step guidance

1. Understand that a plaque assay is a method used to measure the number of virus particles present in a sample by observing the effect of the virus on host cells, typically bacteria.
2. Recognize that in a plaque assay, bacteriophages (viruses that infect bacteria) are mixed with a bacterial culture and then spread on an agar plate.
3. Identify that as the bacteriophages infect and lyse the bacterial cells, clear zones called plaques form on the agar plate where the bacteria have been destroyed.
4. Note that each plaque corresponds to a single virus particle that initiated the infection, allowing for the quantification of virus particles in the original sample.
5. Conclude that the measurement in a plaque assay is the number of bacterial colonies that are lysed upon infection by a bacteriophage, which is indicated by the number of plaques formed on the plate.