Part of the latency-replication switch system which decides at the onset of infection whether to replicate and lyse the host or to lysogenize (latency) and keep the host viable. Peptide which is released by the infected host bacteria and acts as a communication agent that affects the latency versus replication (lysogeny-lysis) decision for any new infecting virus from the same specie. High concentration of arbitrium peptide results in increased lysogeny in the upcoming viruses. The arbitrium peptide is secreted by infected bacteria and, after several cycles of infection, accumulates in the extracellular medium. When a virus from the same specie subsequently infects an uninfected bacterium which has internalized the peptide via its OPP transporter, the peptide will binds to the viral AimR transcriptional regulator and prevents AimR transcriptional activation of the aimX locus. Inhibition of aimX transcription promotes lysogeny. Interacts with the viral AimR transcriptional regulator; this interaction changes the oligomeric state of AimR from an active dimer to an inactive monomer leading to lysogeny. Cleaved by host extracellular proteases, thereby releasing the mature arbitrium peptide.