Bacterial viruses manipulate infection decisions among themselves

Bacteriophages (phages) that infect bacteria use chemical signals to influence the behavior of other viruses in the same environment. A recent study shows an interaction between distinct communication systems. The result alters decisions between lysis and lysogeny. The mechanism favors emitting bacteriophages and imposes costs on receptors.

Researchers analyzed bacteriophages with an arbitrium system, based on signaling peptides. These compounds indicate host availability. Low concentrations stimulate lysis, while high concentrations lead to lysogeny. The study demonstrated frequent exposure to non-cognate signals produced by other phages present in the same host or environment.

Common coexistence

Data indicate the common coexistence of multiple prophages in bacterial genomes. Approximately 35% of the genomes evaluated carry two arbitrium systems. Some cases present up to eight. This overlap creates a favorable environment for signal interference.

Experiments with synthetic peptides confirmed cross-response. The Phi3T model bacteriophage reacted not only to its SAIRGA signal, but also to four other similar peptides. This interaction reduced virulence and increased the frequency of lysogeny. The effect occurred through direct binding to the AimR receptor.

Tests with different phages revealed a broad pattern of crosstalk. Some systems responded to multiple signals. Others showed high specificity. Interactions occurred bidirectionally or unilaterally. In certain cases, one phage influences another without reciprocity.

Ecological impact

Tests with conditioned media showed a direct ecological impact. Signals produced by a bacteriophage altered subsequent infections. Receptor phages began to adopt lysogeny earlier. Simultaneous co-infections confirmed the pattern. The presence of an emitting phage increased the lysogeny rate of another in the same culture.

Experiments with lysogens indicated an additional effect. A resident prophage produced signals capable of influencing invading phages. The result increased the formation of polylysogens. This process reduces the risk of lysis of the host cell.

Structural analysis explained part of the specificity. Interactions between peptides and receptors depend on fine-tuning in molecular structure. Small differences in amino acids alter affinity. This allows for the recognition of similar signals. It also limits interaction with divergent peptides.

Competitive Landscape

The results indicate a competitive scenario among viruses. Emitter bacteriophages can manipulate rivals. They induce early lysogeny in competitors. This reduces the replication of these viruses. At the same time, it preserves the host for the emitter.

The study suggests evolutionary pressure on arbitrary systems. Interference between signals can create disadvantages. This favors the evolution of new signal-receptor pairs. Horizontal gene exchange contributes to the observed diversity.

Further information at doi.org/10.1016/j.cell.2026.02.020