A novel stress response pathway mediates biofilm architecture in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a multidrug-resistant opportunistic pathogen, with chronic infections often associated with biofilm formation. Here, we investigate the previously uncharacterized gene PA3049, which is upregulated under biofilm conditions, to determine its role in infection, biofilm formation, and antimicrobial sensitivity. We show that the small uncharacterised protein PA3049, renamed as Biofilm architecture Regulator (BatR), promotes biofilm establishment and enhances biofilm survival in sub-inhibitory concentrations of antibiotics. Proteomic analysis revealed that BatR influences the R2/F2 pyocin cluster, which drives explosive cell lysis and extracellular DNA (eDNA) release during biofilm development. We further identify a specific interaction between BatR and PA0486 (SrkA), an uncharacterised Ser/Thr protein kinase. We show that SrkA controls biofilm and pyocyanin production, and lysis-mediated eDNA release through regulation of the R2/F2 pyocin cluster and activation of bacteriophage Pf4. Our findings support a model in which SrkA directly regulates key biofilm-associated phenotypes, while BatR acts as a modulatory partner that tunes SrkA activity under specific conditions. Finally, BatR function was tested in high-validity infection models, including the ex vivo pig lung model of cystic fibrosis infection and a synthetic chronic-wound model. In these models, BatR contributes to biofilm architecture and antibiotic resistance and modulates pyocyanin production. Our study implicates the BatR/SrkA system in the response of P. aeruginosa biofilms to antibiotic challenge in lung infections.