# Bacteriophage Ecology Group

## Latent Period

*A measure of the duration of a phage infection, particularly a lytic infection.*

Latent periods begin with virion attachment, nucleic acid translocation into the bacterial cytoplasm, or with prophage induction. Latent periods then span the eclipse and post-eclipse or maturation periods and, for lytic phages, end with bacterial lysis. They typically are determined using single-step growth experiments though lysis profiles can also be employed.

Strictly, latent period can be used synonymously with constant period. For lytic cycles that begin with adsorption, the latent period basically can be described as overlapping the entirety of the infection. Also for lytic phages, but not for chronic infections, the latent period is equivalent to the duration of a productive infection.

This is the definition from Adams (1959), p. 440, "Elapsed time between infection or induction and lysis of cells in one-step growth. Latent periods of individual cells vary over a range called the rise period. When reported without qualification, latent period means minimum latent period." Latent period thus can mean constant period (= minimum latent period) or per-cell duration of infection as well as the halfway point during the rise period or indeed, though not typically invoked, the average per-cell lysis timing.

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