Co-occurring divergent arbitrium receptors outside canonical prophage regions in bacterial genomes

Arbitrium signaling enables peptide-mediated communication among bacteriophages and regulates lysis-lysogeny decisions through diverse genetic architectures. Here, we identified two divergent AimR-like receptors in each of the alkaliphilic bacteria Alkalihalobacterium alkalinitrilicum DSM 22532 and Caldalkalibacillus mannanilyticus JCM 10596, with within-genome amino acid identities of 30.6% and 27.4%, respectively. All four receptors occurred outside predicted prophage regions, with distinct genomic neighborhoods and a putative aimP -like gene adjacent to one receptor. Despite substantial sequence divergence, structural comparisons revealed conservation within aligned regions of the AimR fold. Associations with mobile genetic elements suggest possible genomic mobility, although the evolutionary origins and functional roles of these receptors remain unresolved. These findings highlight the diversity of co-occurring AimR-like receptors in bacterial genomes.