Phage-host interactions in soil

Abstract Phages are abundant and ubiquitous in nature, and are therefore important components of microbial communities. They can impact on host populations in several ways, including predation and alteration of host phenotype by genetic interactions. The dynamic survival of phage populations in soil requires infective interactions with host populations which must be undergoing growth. Hence survival is limited by the activity of soil bacteria, and phage populations must adopt strategies to overcome periods of inactivity. One of the most effective strategies is the lysogenic cycle of temperate phages. It is argued here that lysogeny in soil has a distinct advantage over virulence for phage and host survival, as opposed to aquatic ecosystems where virulence seems a more successful strategy for phage populations.