The LuxO-OpaR quorum-sensing cascade differentially controls Vibriophage VP882 lysis-lysogeny decision making in liquid and on surfaces

Abstract

Quorum sensing (QS) is a process of cell-to-cell communication that bacteria use to synchronize collective behaviors. QS relies on the production, release, and group-wide detection of extracellular signaling molecules called autoinducers (AIs). Vibrios use two QS systems: the LuxO-OpaR circuit and the VqmA-VqmR circuit. Both QS circuits control group behaviors including biofilm formation and surface motility. The Vibrio parahaemolyticus temperate phage ϕVP882 encodes a VqmA homolog (called VqmAϕ). When VqmAϕ is produced by ϕVP882 lysogens, it binds to the host-produced AI called DPO and launches the ϕVP882 lytic cascade. This activity times induction of lysis with high host cell density and presumably promotes maximal phage transmission to new cells. Here, we explore whether, in addition to induction from lysogeny, QS controls the initial establishment of lysogeny by ϕVP882 in naïve host cells. Using mutagenesis, phage infection assays, and phenotypic analyses, we show that ϕVP882 connects its initial lysis-lysogeny decision to both host cell density and whether the host resides in liquid or on a surface. Only host cells in the low-density QS state undergo lysogenic conversion. The QS regulator LuxO~P promotes ϕVP882 lysogenic conversion of low cell density planktonic host cells. By contrast, the ScrABC surface-sensing system regulates lysogenic conversion of low cell density surface-associated host cells. ScrABC controls the abundance of the second messenger molecule cyclic diguanylate, which in turn, modulates motility. The scrABC operon is only expressed when its QS repressor, OpaR, is absent. Thus, at low cell density, QS-dependent derepression of scrABC drives lysogenic conversion in surface-associated host cells. These results demonstrate that ϕVP882 integrates cues from multiple sensory pathways into its lifestyle decision making upon infection of a new host cell.