Light‐Induced Proteomic Changes in <i>Pseudomonas aeruginosa</i> Biofilms

Pseudomonas aeruginosa is highly adaptable to environmental cues, including light. While specific light-responsive mechanisms have been studied in P. aeruginosa, the effects of light on biofilm proteomes remain unclear. Here, we employed quantitative proteomics to examine responses to white and red light in P. aeruginosa PA14 wild-type and bacteriophytochrome BphP null (ΔbphP) biofilms. Biofilms were cultivated under dark, white, and red light conditions. Peptides were analyzed using an Orbitrap Exploris 240 mass spectrometer. Across five experimental groups (n = 3), 3,875 proteins were identified and quantified with >99.9% data completeness and CV <15%. Of these, 862 proteins were differentially expressed (>1.5-fold, FDR 5%) in response to light. Red light induced the upregulation of proteins involved in osmotic stress response and carbohydrate metabolism in wild-type biofilms. Catalase KatE was upregulated >20-fold, while catalase KatA was suppressed, indicating a differential oxidative stress response. These patterns were reversed in a ΔbphP mutant, suggesting BphP-dependent regulation. Light exposure also reduced expression of the virulence factors elastase (LasB) and protease LasA (LasA). Several targets of the AlgB/RpoN network, including the anti-sigma factor MucA, showed BphP-linked changes. These findings confirm the role of BphP as a key regulator of light-mediated proteomic adaptation in P. aeruginosa biofilms.