A phage communication peptide alters Bacillus subtilis colony development and promotes sporulation
Temperate Bacillus phages use arbitrium peptides to coordinate lysis–lysogeny decisions, but whether the mature communication peptide can be sensed directly by Bacillus subtilis and affect its physiology and behavior is unknown. Here we show that the φ3T arbitrium peptide SAIRGA elicits a sequence- and stereochemistry-dependent response in Bacillus subtilis that is strongly expressed in surface-grown colony biofilms but is not accompanied by comparable changes in planktonic growth or static-liquid pellicle morphology. The response persists in the absence of AimR, the canonical arbitrium receptor. Within colonies, SAIRGA alters spatial PtapA activity and increases heat-resistant spore formation without increasing total viable cell yield. Untargeted metabolomics reveals broad dose-dependent remodeling that tracks peptide activity, while program-level proteomics independently converges on late-sporulation and mature-spore- associated states. This study highlights how a phage-derived peptide may act as a signal, enabling the host to pivot toward a survival-focused developmental state.