Atypical BlaIR Two-Component System in Pseudomonas aeruginosa Regulates Virulence but not β-Lactam Resistance

With the rise of antimicrobial resistance, anti-virulence therapeutics are a viable alternative to circumvent resistance pressures. Hypothetical genes and proteins are an under-studied source of potential virulence factor targets. We performed bioinformatic analyses to identify conserved hypothetical genes enriched in pathogenic Pseudomonas aeruginosa but not in non-pathogenic strains. This analysis identified an atypical BlaIR system, which we named pvmSR, that regulated P. aeruginosa virulence in a Caenorhabditis elegans infection model. This is in contrast with the typical BlaIR system from Staphylococcus aureus, which regulates resistance to {beta}-lac-tam antibiotics. The{Delta} pvmSR mutant showed reduced virulence in a C. elegans slow-killing assay. To understand how PvmSR regulated virulence in vivo, we performed dual RNA-seq to analyze transcriptomic changes in both C. elegans and P. aeruginosa. We found that C. elegans responded to P. aeruginosa {Delta}pvmSR infection by decreasing expression of lysosome and phagocytosis pathways. In P. aeruginosa {Delta}pvmSR, we observed decreased gene expression of several known virulence factors including the hydrogen cyanide synthase, hcnC, and heparinase, hepP. Additionally, we observed dysregulation in genes important for quorum sensing and biofilm formation. Collectively, our findings indicated that PvmSR contributed to virulence regulation and may serve as a potential anti-virulence target.