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Transcriptomic analysis reveals a global alkyl-quinolone-independent regulatory role for PqsE in facilitating the environmental adaptation of Pseudomonas aeruginosa to plant and animal hosts.

Rampioni G, Pustelny C, Fletcher MP, Wright VJ, Bruce M, Rumbaugh KP, Heeb S, Cámara M, Williams P - Environ. Microbiol. (2010)

Bottom Line: To gain insights into the relationship between the AQ stimulon, the PqsE stimulon and the regulatory function of PqsE, we constructed a pqsE inducible mutant (pqsEind) and compared the transcriptomes of the induced and uninduced states with a pqsA mutant.Furthermore, pqsE was required for swarming motility and virulence in plant and animal infection models in the absence of AQs, while mature biofilm development required both pqsA and pqsE.Taken together these data reveal that PqsE is a key regulator within the QS circuitry facilitating the environmental adaptation of P. aeruginosa.

View Article: PubMed Central - PubMed

Affiliation: School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University Park, University of Nottingham, Nottingham NG7 2RD, UK.

ABSTRACT
The quorum sensing (QS) system of Pseudomonas aeruginosa constitutes a sophisticated genome-wide gene regulatory network employing both N-acylhomoserine lactone and 2-alkyl-4-quinolone (AQ) signal molecules. AQ signalling utilizes 2-heptyl-3-hydroxy-4-quinolone (PQS) and its immediate precursor, 2-heptyl-4-quinolone (HHQ). AQ biosynthesis requires the first four genes of the pqsABCDE operon and while the biochemical function of pqsE is not known, it is required for the production of secondary metabolites such as pyocyanin. To gain insights into the relationship between the AQ stimulon, the PqsE stimulon and the regulatory function of PqsE, we constructed a pqsE inducible mutant (pqsEind) and compared the transcriptomes of the induced and uninduced states with a pqsA mutant. Of 158 genes exhibiting altered expression in the pqsA mutant, 51% were also affected in the pqsE mutant. Following induction of pqsE, 237 genes were differentially expressed compared with the wild-type strain. In the pqsEind strain, pqsA was highly expressed but following induction both pqsA expression and AQ biosynthesis were repressed, revealing a negative autoregulatory role for PqsE. Furthermore, pqsE was required for swarming motility and virulence in plant and animal infection models in the absence of AQs, while mature biofilm development required both pqsA and pqsE. Taken together these data reveal that PqsE is a key regulator within the QS circuitry facilitating the environmental adaptation of P. aeruginosa.

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Simplified schematic representation of the AQ-dependent QS in P. aeruginosa (modified from Diggle et al., 2007). HHQ, the immediate precursor of PQS, drives the expression of the pqsABCDE operon via PqsR(MvfR) and is also converted to PQS by the action of the monooxygenase, PqsH. PQS also drives pqsABCDE expression via PqsR. PqsE positively regulates biofilm, swarming virulence and secondary metabolite gene expression but negatively regulates pqsABCDE expression. PQS also binds ferric iron which results in the induction of high affinity siderophore iron transport genes. AHL and AQ-dependent QS are linked because LasR/3-oxo-C12-HSL is required for maximal expression of pqsH and pqsR whereas pqsR and pqsABCDE are repressed by RhlR/C4-HSL.
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fig04: Simplified schematic representation of the AQ-dependent QS in P. aeruginosa (modified from Diggle et al., 2007). HHQ, the immediate precursor of PQS, drives the expression of the pqsABCDE operon via PqsR(MvfR) and is also converted to PQS by the action of the monooxygenase, PqsH. PQS also drives pqsABCDE expression via PqsR. PqsE positively regulates biofilm, swarming virulence and secondary metabolite gene expression but negatively regulates pqsABCDE expression. PQS also binds ferric iron which results in the induction of high affinity siderophore iron transport genes. AHL and AQ-dependent QS are linked because LasR/3-oxo-C12-HSL is required for maximal expression of pqsH and pqsR whereas pqsR and pqsABCDE are repressed by RhlR/C4-HSL.

Mentions: Pseudomonas aeruginosa employs a sophisticated multi-signal molecule QS system which operates to facilitate environmental adaptation at the population level (Fig. 4). To further refine our understanding of the individual contributions of key components of the AQ signalling pathway to P. aeruginosa physiology, we first determined the extent of the P. aeruginosa PAO1 pqsA stimulon, because this has not previously been reported. By profiling the transcripts present after maximal induction of the pqsABCDE operon, we observed that 158 genes were up- or down-regulated when the wild type was compared with the pqsA mutant strain (Table S1). However, only 18 and 21 of these genes were previously identified in transcriptome analyses of either (i) a P. aeruginosa PA14 pqsR (mvfR) mutant (Déziel et al., 2005) or (ii) P. aeruginosa PAO1 grown in the presence of exogenous PQS added at the point of inoculation (Bredenbruch et al., 2006) and compared with the corresponding wild-type strains. These variations are perhaps not particularly surprising given the differences in the strains and experimental conditions used. Although the pqsR mutant in common with the pqsA mutant is AQ-negative, it is not known whether PqsR directly drives the expression of target genes other than pqsA. Furthermore, the exogenous addition of PQS to the wild-type P. aeruginosa (which is already producing AQs in a population density dependent manner) is likely to advance and enhance PQS-dependent gene expression (Diggle et al., 2003), as well as inducing an oxidative/anti-oxidative stress response (Bredenbruch et al., 2006; Häussler and Becker, 2008). However, despite these differences, the recurrence of the same set of genes in at least two out of the three experiments, indicates that AQ-dependent QS plays a key role in regulating genes of known function including pqsABCDE, phnAB, phzABCDEFG, mexGHIompD, pchABCDEF, lecA, chiC and pvdH, as well as many others of unknown function.


Transcriptomic analysis reveals a global alkyl-quinolone-independent regulatory role for PqsE in facilitating the environmental adaptation of Pseudomonas aeruginosa to plant and animal hosts.

Rampioni G, Pustelny C, Fletcher MP, Wright VJ, Bruce M, Rumbaugh KP, Heeb S, Cámara M, Williams P - Environ. Microbiol. (2010)

Simplified schematic representation of the AQ-dependent QS in P. aeruginosa (modified from Diggle et al., 2007). HHQ, the immediate precursor of PQS, drives the expression of the pqsABCDE operon via PqsR(MvfR) and is also converted to PQS by the action of the monooxygenase, PqsH. PQS also drives pqsABCDE expression via PqsR. PqsE positively regulates biofilm, swarming virulence and secondary metabolite gene expression but negatively regulates pqsABCDE expression. PQS also binds ferric iron which results in the induction of high affinity siderophore iron transport genes. AHL and AQ-dependent QS are linked because LasR/3-oxo-C12-HSL is required for maximal expression of pqsH and pqsR whereas pqsR and pqsABCDE are repressed by RhlR/C4-HSL.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2901523&req=5

fig04: Simplified schematic representation of the AQ-dependent QS in P. aeruginosa (modified from Diggle et al., 2007). HHQ, the immediate precursor of PQS, drives the expression of the pqsABCDE operon via PqsR(MvfR) and is also converted to PQS by the action of the monooxygenase, PqsH. PQS also drives pqsABCDE expression via PqsR. PqsE positively regulates biofilm, swarming virulence and secondary metabolite gene expression but negatively regulates pqsABCDE expression. PQS also binds ferric iron which results in the induction of high affinity siderophore iron transport genes. AHL and AQ-dependent QS are linked because LasR/3-oxo-C12-HSL is required for maximal expression of pqsH and pqsR whereas pqsR and pqsABCDE are repressed by RhlR/C4-HSL.
Mentions: Pseudomonas aeruginosa employs a sophisticated multi-signal molecule QS system which operates to facilitate environmental adaptation at the population level (Fig. 4). To further refine our understanding of the individual contributions of key components of the AQ signalling pathway to P. aeruginosa physiology, we first determined the extent of the P. aeruginosa PAO1 pqsA stimulon, because this has not previously been reported. By profiling the transcripts present after maximal induction of the pqsABCDE operon, we observed that 158 genes were up- or down-regulated when the wild type was compared with the pqsA mutant strain (Table S1). However, only 18 and 21 of these genes were previously identified in transcriptome analyses of either (i) a P. aeruginosa PA14 pqsR (mvfR) mutant (Déziel et al., 2005) or (ii) P. aeruginosa PAO1 grown in the presence of exogenous PQS added at the point of inoculation (Bredenbruch et al., 2006) and compared with the corresponding wild-type strains. These variations are perhaps not particularly surprising given the differences in the strains and experimental conditions used. Although the pqsR mutant in common with the pqsA mutant is AQ-negative, it is not known whether PqsR directly drives the expression of target genes other than pqsA. Furthermore, the exogenous addition of PQS to the wild-type P. aeruginosa (which is already producing AQs in a population density dependent manner) is likely to advance and enhance PQS-dependent gene expression (Diggle et al., 2003), as well as inducing an oxidative/anti-oxidative stress response (Bredenbruch et al., 2006; Häussler and Becker, 2008). However, despite these differences, the recurrence of the same set of genes in at least two out of the three experiments, indicates that AQ-dependent QS plays a key role in regulating genes of known function including pqsABCDE, phnAB, phzABCDEFG, mexGHIompD, pchABCDEF, lecA, chiC and pvdH, as well as many others of unknown function.

Bottom Line: To gain insights into the relationship between the AQ stimulon, the PqsE stimulon and the regulatory function of PqsE, we constructed a pqsE inducible mutant (pqsEind) and compared the transcriptomes of the induced and uninduced states with a pqsA mutant.Furthermore, pqsE was required for swarming motility and virulence in plant and animal infection models in the absence of AQs, while mature biofilm development required both pqsA and pqsE.Taken together these data reveal that PqsE is a key regulator within the QS circuitry facilitating the environmental adaptation of P. aeruginosa.

View Article: PubMed Central - PubMed

Affiliation: School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University Park, University of Nottingham, Nottingham NG7 2RD, UK.

ABSTRACT
The quorum sensing (QS) system of Pseudomonas aeruginosa constitutes a sophisticated genome-wide gene regulatory network employing both N-acylhomoserine lactone and 2-alkyl-4-quinolone (AQ) signal molecules. AQ signalling utilizes 2-heptyl-3-hydroxy-4-quinolone (PQS) and its immediate precursor, 2-heptyl-4-quinolone (HHQ). AQ biosynthesis requires the first four genes of the pqsABCDE operon and while the biochemical function of pqsE is not known, it is required for the production of secondary metabolites such as pyocyanin. To gain insights into the relationship between the AQ stimulon, the PqsE stimulon and the regulatory function of PqsE, we constructed a pqsE inducible mutant (pqsEind) and compared the transcriptomes of the induced and uninduced states with a pqsA mutant. Of 158 genes exhibiting altered expression in the pqsA mutant, 51% were also affected in the pqsE mutant. Following induction of pqsE, 237 genes were differentially expressed compared with the wild-type strain. In the pqsEind strain, pqsA was highly expressed but following induction both pqsA expression and AQ biosynthesis were repressed, revealing a negative autoregulatory role for PqsE. Furthermore, pqsE was required for swarming motility and virulence in plant and animal infection models in the absence of AQs, while mature biofilm development required both pqsA and pqsE. Taken together these data reveal that PqsE is a key regulator within the QS circuitry facilitating the environmental adaptation of P. aeruginosa.

Show MeSH
Related in: MedlinePlus