Many temperate Bacillus phages utilize the arbitrium signaling system to control lysis/lysogeny decisions. While the function of the arbitrium signal AimP and its receptor AimR are well known, it is unclear how they control lysis in most arbitrium systems. Here, we show that a large majority of arbitrium systems are embedded in an extended module with three additional components; A small antirepressor protein (AimX), the phage repressor (AimC) and an adjacent cro-like protein (AimL). AimR-depend