Investigating the role of a putative antiviral defense system in intercellularly regulated immunity in communities of P. aeruginosa

Abstract

The coevolution of bacteria and bacteriophages has given rise to an incredible diversity of strategies for antiviral defense. Interestingly, many of these immune systems are shared not only across species but between prokaryotic and eukaryotic organisms, with several conserved modules shared between the two domains of life. However, one component of eukaryotic immunity has not yet been identified in bacteria: an intercellular communication system that regulates antiviral systems in response to infection. Parallels in antiviral strategies between bacteria and eukaryotes at the molecular level hint at a conservation of tactics at the multicellular level, specifically the presence of a medium through which bacteria communicate the presence of infection and coordinate antiphage resistance. Recent results have demonstrated that a small molecule released during cell lysis upregulates bacteriophage resistance in previously uninfected populations of P. aeruginosa, providing a mechanism for coordinating collective immunity in bacterial populations. The system activated by this signal appears to have broad regulatory power, spanning previously characterized antiviral defense systems and putative novel defense systems. Here we identify a candidate gene for intercellularly regulated antiviral defense, and investigate its role in responding to the signal present in cell lysate. We find that this gene is not necessary for the strengthened immune response to infection, but that WT strains for this gene outcompete a knockout strain in mixed culture, especially with the addition of cell lysate extract.