COMMUNICATION BETWEEN VIRUSES GUIDES LYSIS-LYSOGENY DECISIONS

In every infection, temperate bacteriophages (phages) need to choose between the lytic and lysogenic life cycles. Whereas the lytic cycle involves phage replication and eventual host lysis, in the lysogenic cycle the phage integrates its DNA into the bacterial chromosome and remains latent. In the coliphage Lambda the lysis/lysogeny decision is known to be governed by a combination of the starvation status of the cell and the multiplicity of infection. However, for other phages the parameters governing this decision are unknown.

We discovered a family of phages that use a quorum-sensing-like communication system to guide the lysis/lysogeny decision. During infection, the phages produce a peptide autoinducer that is maturated outside of the cell and then internalized into the bacteria. This peptide is sensed by a phage-encoded receptor which, upon binding to the peptide, promotes the gene expression program that leads to lysogeny. Thus, after several successful cycles of lytic infection the concentration of the peptide in the medium elevates, leading the phage to switch into a lysogenic life cycle. We found that different phage species encode different communication peptides, leading to be phage specific activity. This discovery of communication between viruses shed new light on virus-host interactions.