What is the purpose of performing a plaque assay?

The purpose of performing a plaque assay is to quantify virus particles based on their ability to infect and lyse bacterial cells. This technique allows researchers to determine the concentration of viral particles in a sample by mixing a diluted viral suspension with a culture of susceptible bacteria. When the virus infects the bacteria, it replicates and ultimately causes the cells to lyse, releasing new viral particles. The areas where bacterial lysis occurs form clear zones called plaques. By counting these plaques and knowing the dilution factor, one can calculate the number of infectious virus particles present in the original sample, usually expressed as plaque-forming units per milliliter (PFU/mL). This method is particularly important in virology for studying phages and other viruses that infect bacteria.

Other options such as determining microbial species diversity, identifying antibiotic susceptibility, or measuring microbial metabolic rates focus on different aspects of microbiology and do not relate to the specific quantification of viruses through their lytic activity.