Abstract
Sulfane sulfur, such as inorganic and organic polysulfide (HSn− and RSn−, n > 2), is a common cellular component, produced either from hydrogen sulfide oxidation or cysteine metabolism. In Pseudomonas aeruginosa PAO1, LasR is a quorum sensing master regulator. After binding its autoinducer, LasR binds to its target DNA to activate the transcription of a suite of genes, including virulence factors. Herein, we report that the production of hydrogen sulfide and sulfane sulfur were positively correlated in P. aeruginosa PAO1, and sulfane sulfur was able to modify LasR, which generated Cys188 persulfide and trisulfide and produced a pentasulfur link between Cys201 and Cys203. The modifications did not affect LasR binding to its target DNA site, but made it several-fold more effective than unmodified LasR in activating transcription in both in vitro and in vivo assays. On the contrary, H2O2 inactivates LasR via producing a disulfide bond between Cys201 and Cys203. P. aeruginosa PAO1 had a high cellular sulfane sulfur and high LasR activity in the mid log phase and early stationary phase, but a low sulfane sulfur and low LasR activity in the declination phase. Thus, sulfane sulfur is a new signaling factor in the bacterium, adding another level of control over LasR-mediated quorum sensing and turning down the activity in old cells.
Highlights
Hydrogen sulfide (H2 S) has been proposed as a new gaseous signaling molecule, mediating various biological functions in mammals, including humans [1,2,3,4,5]
Sulfane sulfur is sensed by these transcription factors to turn on the transcription of sulfur-oxidizing genes, including pdo coding for persulfide dioxygenase (PDO)
We show that sulfide (H2 S, HS, and S2 – ) and sulfane sulfur participate in LasR regulation in P. aeruginosa PAO1
Summary
Hydrogen sulfide (H2 S) has been proposed as a new gaseous signaling molecule, mediating various biological functions in mammals, including humans [1,2,3,4,5]. A synthetic gene circuit that combines SQR and CstR allows the host Escherichia coli to oxidize self-produced H2 S to sulfane sulfur and sense the latter, resulting in gene regulation in a manner similar to quorum sensing (QS) [13]. For bacteria with sulfide:quinone oxidoreductases (SQR), such as P. aeruginosa PAO1, self-produced sulfide is oxidized back to sulfane sulfur [16]. The H2 S-oxidizing mutant did not show any apparent differences in growth from the wild type, but the H2 S-producing mutant displayed a clear reduction of several virulence factors that are activated by LasR. Cellular sulfane sulfur level became low, which was associated with significantly low LasR activity
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