Phage with a Sixth Sense: Francis Santoriello Reveals How φVP882 Uses Quorum Signals and Surfaces to Decide Its Fate
- Ray Sullivan
- 20 hours ago
- 2 min read
At the 2025 Theobald Smith Society Spring Symposium, postdoctoral researcher Francis Santoriello of the Bassler Lab at Princeton University delivered a fascinating talk on how a bacterial virus (phage) uses host communication systems to determine whether to kill its host or lie dormant.
The focus was φVP882, a temperate phage that infects Vibrio parahaemolyticus. Like all temperate phages, φVP882 must decide whether to immediately lyse its host and release progeny or integrate into the host genome and enter a latent state (lysogeny). What makes φVP882 unique is that it has co-opted the host’s quorum sensing (QS) system to inform that decision.
In bacteria, QS enables population-wide coordination through signaling molecules called autoinducers. At high cell density, these molecules accumulate and activate group behaviors like biofilm formation. Santoriello showed that φVP882 listens in on these QS signals using its own receptor, VqmAφ, which detects a host-produced autoinducer (DPO). At high host density, VqmAφ triggers lysis—presumably to maximize phage transmission.
Santoriello asked a new question: does quorum sensing also control the initial decision between lysis and lysogeny? Using V. parahaemolyticus mutants locked in high or low cell density states, he discovered that lysogeny is favored at low density. In liquid cultures, this depends on Qrr sRNAs, small regulatory RNAs produced at low density that promote lysogeny independently of their known target, the QS master regulator OpaR.
However, when cells were infected on solid surfaces, the story changed. There, lysogeny depended not on Qrrs, but on the surface-sensing ScrABC system, which is repressed by OpaR. Without OpaR, ScrABC is expressed, lowering cyclic-di-GMP levels and promoting lysogeny. This link was confirmed by artificially tuning cyclic-di-GMP using unrelated enzymes: decreasing levels promoted lysogeny, increasing them blocked it.
In summary, φVP882 doesn’t just “eavesdrop” on host density. It also senses whether the host is on a surface or in liquid and tailors its lifecycle accordingly. Low cell density always favors lysogeny, but the mechanism—Qrr sRNAs or ScrABC—depends on the environment. At high density, lysis is triggered by VqmAφ and OpaR.
Santoriello’s work reveals a sophisticated integration of multiple sensory inputs by a virus, allowing it to finely tune its lifecycle for optimal transmission. It’s a powerful example of how deeply intertwined microbial communication and viral decision-making can be.
See Frank’s talk at: https://youtu.be/C9mJxVSD75M
Santoriello FJ, Bassler BL. The LuxO-OpaR quorum-sensing cascade differentially controls Vibriophage VP882 lysis-lysogeny decision making in liquid and on surfaces. PLoS Genet. 2024 Jul 30;20(7):e1011243. doi: 10.1371/journal.pgen.1011243. PMID: 39078816; PMCID: PMC11315295.