Interspecies Signaling through QscR, a Quorum Receptor of Pseudomonas aeruginosa

Abstract

The QS machinery of Pseudomonas aeruginosa, an opportunistic human pathogen, consists of three acyl-homoserine lactone (acyl-HSL) signaling systems, LasR-I, RhlR-I, and QscR. QscR, known as an orphan receptor and a repressor of other QS systems, operates its own regulon using N-3-oxododecanoyl HSL (3OC12), which is synthesized by LasI, as its signal. In this study, we addressed the role of QscR in interspecies communication. We found that QscR auto-activates its own transcription in the presence of 3OC12. In a single population of P. aeruginosa, where 3OC12 is the sole signal available for QscR, the QscR regulon is activated by 3OC12 produced by the LasI-R system. However, the broad signal specificity of QscR allowed it to respond to a non-P. aeruginosa signal, such as N-decanoyl HSL (C10) and N-3-hydroxydecanoyl HSL (3OHC10), which preferentially activated QscR to LasR. The signal extracts from Pseudomonas fluorescens and Burkholeria vietnamiensis also preferentially activated QscR. These non-P. aeruginosa signals activated QscR more strongly than 3OC12, the authentic P. aeruginosa signal. Since a variety of acyl-HSLs are produced in the multi-species habitat of nature, our study provides a clue for the particular situation that allows QscR to secede from the conventional QS cascade in mixed microbial community.

Anthranilate Deteriorates the Structure of Pseudomonas aeruginosa Biofilms and Antagonizes the Biofilm-Enhancing Indole Effect

“…For quantitative real-time PCR, 10 ng of cDNA and specific primers were mixed with 20 l of SYBR Premix Ex Taq (TaKaRa) and analyzed in thermal cycler real-time PCR system model TP8000 (TaKaRa, Japan). Genomic DNA was used as a standard for quantification, and nadB (PA0761) was used as an internal control, as described elsewhere (20).…”

“…Major AHLs of P. aeruginosa are N-3-oxododecanoyl-L-homoserine lactone (3OC 12 -HSL) and N-butyryl-L-homoserine lac-tone (C 4 -HSL), which are synthesized by LasI and RhlI, respectively, and bind to their cognate receptors, LasR (for 3OC 12 -HSL), QscR (for 3OC 12 -HSL), and RhlR (for C 4 -HSL), to regulate target genes (18)(19)(20). PQS, another important QS signal, also plays a significant role in the regulation of virulence genes and biofilm formation (21).…”

AntR-mediated bidirectional activation of antA and antR, anthranilate degradative genes in Pseudomonas aeruginosa

“…In bacteria, it has been reported that some transcriptions are bidirectionally regulated by transcription factors, such as LasR and QscR, quorum sensing regulators of Pseudomonas aeruginosa, which activate two divergent genes bidirectionally on a single binding site (Ha et al, 2012;Schuster et al, 2004). In this study, we report that AntR, a transcriptional activator involved in anthranilate metabolism regulates genes bidirectionally.…”

Biofilms: Maintenance, Development, and Disassembly of Bacterial Communities Are Determined by QS Cascades

“…QscR has broader signal specificity than LasR and can respond to some non-self-signals. Synthetic 3OHC10 activated QscR much more strongly than 3OC12 did (Ha et al 2012). The acyl side chain of C2 is ten-carbon as with that of C10-HSL, although it is a nonself-produced signal.…”