Many techniques can be employed in order to understand how viruses enter, replicate and assemble in cells. In 1939, Ellis and Delbruck developed a method to study a single round of virus multiplication using a one step growth curve. This method is possible due to the synchronization of replication of phage in the sample (Flint, 2002). .
A one step growth curve experiment begins when bacteriophage are infected with a very large number of phage particles. The large number of phage particles ensures all bacterium are rapidly infected. This high level of infection is called multiplicity of infection (MOI) and can be achieved with a phage to host ratio of 5 to 10 plaque-forming units (PFU) per cell (Flint, 2000). The phage/cell mixture is then diluted synchronizing the infection. As the infection of bacteriophage is synchronized, the interaction of virus with the cell population can be seen as a single interaction between phage and cell. In order to visualize the infection over time, samples of the phage/cell mixture are removed at intervals, plated and then quantified using the plaque assay (Madigan, 2000) .
It is possible to divide the multiplication cycle of viruses into five periods. The first period is the eclipse period. No phage particles can be detected during this period as the phage are being un-coated and phage DNA is being injected for replication (Flint, 2000). Following the eclipse period is the synthetic period. During the synthetic period intracellular phage, particles are being produced. As in the eclipse period, there are no phage particles released during the synthetic period. As the results of the first two periods are not apparent in the external environment they difficult to observe. Thus, the first two periods are combined in the third period called the latent period. The latent period is described as the time prior to the release of infections particles (Flint, 2000). The fourth period is the rise period and is detectable when progeny virus particles first appear.
