Arbitrium phages can manipulate each other's lysis/lysogeny decisions

# Arbitrium phages can manipulate each other's lysis/lysogeny decisions *Published: 2026 May 14* (2)Environment and Sustainability Institute, Penryn Campus, Penryn, Cornwall TR10 9FE, UK. (3)Department of Biosciences, Durham University, Stockton Road, Durham DH1 3LE, UK. (4)Strathclyde Institute of Pharmacy and Biomedical Sciences, 161 Cathedral Street, Glasgow G4 0RE, UK. (5)Department of Biosciences, Durham University, Stockton Road, Durham DH1 3LE, UK; New England Biolabs, 240 County Road, Ipswich, MA 01938, USA. (6)Department of Biosciences, University of Exeter, Streatham Campus, Exeter EX4 4QD, UK. Many viruses can switch between lytic replication and dormancy (or lysogeny). It was recently discovered that some viruses that infect bacteria (known as bacteriophage or phage) employ peptide-based ("arbitrium") communication systems to optimize their lysis/lysogeny switch; high peptide concentrations signal a lack of susceptible hosts and trigger lysogeny, while low peptide concentrations signal an abundance of uninfected hosts and prompt lysis. Here, we demonstrate that arbitrium phages belonging to different species and genera can influence each other's infection dynamics by secreting similar communication peptides, leading to early lysogenization of the signal-receiving phage and elevated fitness of the signal-emitting phage. Antagonistic coevolution between signal-emitting and signal-receiving phages to manipulate each other's infection behaviors may explain the rapid diversification of arbitrium systems and their frequent horizontal exchange to escape the noise of crosstalk. DOI: 10.1016/j.cell.2026.02.020