Abstract
Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen whose virulence is dependent on quorum sensing (QS). DksA1, an RNA polymerase-binding transcriptional regulator, plays a role in determining a number of phenotypes, including QS-mediated virulence. We therefore envisioned that DksA1 inhibitors may help to control P. aeruginosa infection. Here, we screened a library of 6970 chemical compounds and identified two compounds (henceforth termed Dkstatins) that specifically suppressed DksA1 activity. Treatment with these two compounds also substantially decreased the production of elastase and pyocyanin, dominant virulence determinants of P. aeruginosa, and protected murine hosts from lethal infection from a prototype strain of P. aeruginosa, PAO1. The Dkstatins also suppressed production of homoserine lactone (HSL)-based autoinducers that activate P. aeruginosa QS. The level of 3-oxo-C12-HSL produced by Dkstatin-treated wildtype PAO1 closely resembled that of the ΔdksA1 mutant. RNA-Seq analysis showed that transcription levels of QS- and virulence-associated genes were markedly reduced in Dkstatin-treated PAO1 cells, indicating that Dkstatin-mediated suppression occurs at the transcriptional level. Importantly, Dkstatins increased the antibiotic susceptibilities of PAO1, particularly to protein synthesis inhibitors, such as tobramycin and tetracycline. Co-immunoprecipitation assays demonstrated that these Dkstatins interfered with DksA1 binding to the β subunit of RNA polymerase, pointing to a potential mechanism of action. Collectively, our results illustrate that inhibition of P. aeruginosa QS may be achieved via DksA1 inhibitors and that Dkstatins may serve as potential lead compounds to control infection.
Highlights
Pseudomonas aeruginosa, an opportunistic human pathogen, has extensive metabolic capabilities of adapting to diverse environments including immunocompromised human hosts [1]
We examined whether the phenotype observed in Salmonella is detected in P. aeruginosa
Our goal was to isolate compounds that make PAO1 behave like the ΔdksA1 mutant
Summary
Pseudomonas aeruginosa, an opportunistic human pathogen, has extensive metabolic capabilities of adapting to diverse environments including immunocompromised human hosts [1]. P. aeruginosa harbors five genes in its genome encoding proteins belonging to the DksA superfamily, including two that are highly homologous to the typical DksA in E. coli [12, 19]. Of these two DksA homologs, named DksA1 and DksA2, DksA1 is structurally and functionally similar to E. coli DksA. DksA1 was identified to regulate a wide range of phenotypes including quorum sensing (QS)-related virulence, anaerobiosis, and motilities [13]. Based upon these findings, we hypothesized that DksA1 may be an efficient target for inhibiting P. aeruginosa infection
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