If a single bacteriophage infects one E. coli cell present on a lawn of bacteria and, upon lysis, yields 200 viable viruses, how many phages will exist in a single plaque if three more lytic cycles occur? Dilution Factor Assay Results (a) 10⁴ All bacteria lysed (b) 10⁵ 14 plaques (c) 10⁶ 0 plaques

Key Concepts

Bacteriophage Life Cycle

The bacteriophage life cycle consists of attachment, penetration, biosynthesis, maturation, and lysis. In the lytic cycle, the phage infects a bacterial cell, replicates its genetic material, assembles new virions, and ultimately causes the cell to burst, releasing new phages. Understanding this cycle is crucial for predicting how many phages will be produced after multiple rounds of infection.

Plaque Formation

A plaque is a clear zone on a bacterial lawn where phages have lysed the bacteria. Each plaque originates from a single phage that infects a bacterium, leading to the death of that cell and its neighbors. The number of plaques can be used to estimate the concentration of phages in a sample, making it essential for quantifying viral populations in experiments.

Dilution Factor

The dilution factor is a measure of how much a sample has been diluted before analysis. In the context of bacteriophage assays, it helps determine the concentration of phages in the original sample based on the number of plaques observed at different dilutions. Understanding dilution factors is important for accurately interpreting experimental results and calculating the number of phages present in a given volume.