Identification of a novel RhlI/R-PrrH-LasI/Phzc/PhzD signalling cascade and its implication in P. aeruginosa virulence

Abstract

Small regulatory RNAs (sRNAs) act as key regulators in many bacterial signalling cascades. However, in P. aeruginosa, the sRNAs involved in quorum sensing (QS) regulation and their function are still largely unknown. Here, we explored how the prrH locus sRNA influences P. aeruginosa virulence in the context of the QS regulatory network. First, gain- and loss-of-function studies showed that PrrH affects pyocyanin, elastase and rhamnolipid production; biofilm formation; and swimming and swarming motility and impaired the viability of P. aeruginosa in human whole blood. Next, our investigation disclosed that LasI and PhzC/D were directly repressed by PrrH. In addition, RhlI, the key member of the rhl QS system, diminished the expression of PrrH and enhanced the expression of downstream genes. Bioinformatics analysis found two binding sites of RhlR, the transcription factor of the rhl system, on the promoter region of prrH. Further β-galactosidase reporter and qPCR assays confirmed that PrrH was transcriptionally repressed by RhlR. Collectively, our data identified a novel RhlI/R-PrrH-LasI/PhzC/PhzD regulatory circuitry that may contribute to P. aeruginosa pathogenesis. Our findings indicate that PrrH is a quorum regulatory RNA (Qrr) in P. aeruginosa and provide new insight into PrrH’s function.

The Small RNA AmiL Regulates Quorum Sensing-Mediated Virulence in Pseudomonas aeruginosa PAO1

“…Upon binding with 3-oxo-C12-HSL and C4-HSL, the receptor proteins LasR and RhlR get activated and quickly activate the las and rhl systems. We thus investigated the influence of 3-oxo-C12-HSL and C4-HSL treatments on AmiL expression, with concentrations ranging from 5 to 40 μM according to reported studies that have demonstrated they can activate the las and rhl systems ( 25 , 43 – 45 ). Our data showed that even a high concentration of 3-oxo-C12-HSL had little influence on AmiL expression, whereas C4-HSL treatment dramatically inhibited its expression in a dose-dependent manner ( Fig.…”

“…The EV pROp200, a Gm-resistant overexpression plasmid that can replicate stably in P. aeruginosa under the strong promoter P tac , was saved in our lab. This plasmid was used by Lu et al in our previous study to construct lasR or rhlR gene-overexpressing strains, named LasR + and RhlR + , respectively ( 25 ). These two strains were used in this study.…”

“…Subsequently, ReaL is also shown to base-pair with rpoS mRNA to negatively control RpoS synthesis, which is involved in the regulation of QS ( 24 ). A previous study in our lab found sRNA PrrH directly represses LasI and its expression is negatively regulated by the rhl system, and thus involves in the regulation of virulence factors, biofilm, and motility ( 25 ). In addition, sRNA PhrS and PrrF modulate the pqs system by regulating PqsR and AntR, respectively ( 26 , 27 ).…”

YbeY Controls the Type III and Type VI Secretion Systems and Biofilm Formation through RetS in Pseudomonas aeruginosa

“…For example, crcZ, which is related to carbon metabolism, is upregulated in the exponential phase but downregulated in the stationary phase, indicating that YbeY is involved in the growth phase-dependent metabolism regulation. The production of sRNA P27, PrrH, and NrsZ, involved in quorum sensing, was altered by the ybeY mutation (49)(50)(51). The RpoS-dependent sRNA RgsA, which regulates Fis and AcpP, is downregulated, which might be due to the defective expression of rpoS in the ybeY mutant (52).…”

Non-antibiotic methods against Pseudomonas aeruginosa include QS inhibitors: a narrative review

“…Non-antibiotic methods against Pseudomonas aeruginosa include QS inhibitors: a narrative review AR mechanism of PA AR mechanism of PA is complex, and several factors are involved (9)(10)(11)(12): First, changes in cell membrane permeability: (I) high expression efflux pumps on the cell membrane of PA that transport drugs to the outside of cells; (II) the loss or low expression of membrane poreforming proteins: the main drug-resistant mechanism of carbapenems is the loss or decrease of outer membrane pore-forming protein OprD2. Second, the production of inactivated enzymes or modified enzymes on PA, such lactamase and aminoglycosidase.…”