AUTHOR=Kok Li-Ching , Tsai Chia-Chun , Liao Yu-Hsuan , Lo Yi-Ling , Cheng Nai-Wei , Lin Ching-Ting , Chang Hwan-You 

TITLE=Roles of transcriptional factor PsrA in the regulation of quorum sensing in Pseudomonas aeruginosa PAO1

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1424330

DOI=10.3389/fmicb.2024.1424330

ISSN=1664-302X

ABSTRACT=<p>The transcription factor PsrA regulates fatty acid metabolism, the type III secretion system, and quinolone signaling quorum sensing system in <italic>Pseudomonas aeruginosa</italic>. To explore additional roles of PsrA in <italic>P. aeruginosa</italic>, this study engineered a <italic>P. aeruginosa</italic> PAO1 strain to carry a recombinant plasmid with the <italic>psrA</italic> gene (pMMB<italic>psrA</italic>) and examined the impact of elevated <italic>psrA</italic> expression to the bacterium. Transcriptomic analysis revealed that PsrA significantly downregulated genes encoding the master quorum-sensing regulators, RhlR and LasR, and influenced many quorum-sensing-associated genes. The role of PsrA in quorum sensing was further corroborated by testing autoinducer synthesis in PAO1 [pMMB<italic>psrA</italic>] using two reporter bacteria strains <italic>Chromobacterium violaceum</italic> CV026 and <italic>Escherichia coli</italic> [pSB1075], which respond to short- and long-chain acyl homoserine lactones, respectively. Phenotypic comparisons of isogenic Δ<italic>psrA</italic>, Δ<italic>lasR</italic>, and Δ<italic>psrA</italic>Δ<italic>lasR</italic> mutants revealed that the reduced elastase, caseinase, and swarming activity in PAO1 [pMMB<italic>psrA</italic>] were likely mediated through LasR. Additionally, electrophoretic mobility shift assays demonstrated that recombinant PsrA could bind to the <italic>lasR</italic> promoter at a 5’-AAACGTTTGCTT-3′ sequence, which displays moderate similarity to the previously reported consensus PsrA binding motif. Furthermore, the PsrA effector molecule oleic acid inhibited PsrA binding to the <italic>lasR</italic> promoter and restored several quorum sensing-related phenotypes to wild-type levels. These findings suggest that PsrA regulates certain quorum-sensing phenotypes by negatively regulating <italic>lasR</italic> expression, with oleic acid acting as a crucial signaling molecule.</p>