🔬 The Bacteriophage Rise

Bacteriophage Ecology Group News (BEG News) was published mostly quarterly as an online newsletter for a total of 24 issues, July 1999 through April 2005. As follows is a reprint of the editorial from Volume 10. The newsletter’s successors are the ongoing Phage.org website, phage-therapy.org, and the Bacteriophage Ecology Group Facebook page.

At the level of individual infections, our molecular understanding of phages integrates with our ecological understanding within a framework that I call phage organismal ecology. The details of the phage growth cycle impact on phage ecology and, ultimately, phage evolution. The relevant parameters include the latent period, the rise period, the burst size, adsorption kinetics, virion inactivation rates, and whether the phage displays a lytic, lysogenic, or chronic infection cycle.

The rise period is typically defined as that period of the one-step growth experiment during which extracellular phage titers increase from the burst of the first-infected bacterial cell to the burst of the last-infected cell. During the rise, phage progeny are being released from host cells, accumulating extracellularly until the last infected cell lyses.

The rise period has a duration equal to the standard deviation of the latent period. A short rise period means infected cells are all bursting at approximately the same time. A long rise period means greater variation in when individual infected cells burst.

From an ecological standpoint, a short rise period concentrates the release of phage progeny to a particular moment in time, making large numbers of free phage simultaneously available to adsorb to new host cells. A longer rise period spreads out progeny release, potentially allowing individual released progeny to infect new hosts before later-released progeny have even been released.

The rise period also impacts phage-mediated bacterial population dynamics. A shorter rise period means bursts more likely occur simultaneously, exposing bacteria to abrupt increases in phage densities. A longer rise period means a more gradual release of progeny phages and consequently more gradual phage-mediated bacterial mortality.

Thus the rise period is yet another aspect of the phage growth cycle with broader ecological and evolutionary implications.

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