scholarly journals The Pseudomonas aeruginosa Sensor Kinase KinB Negatively Controls Alginate Production through AlgW-Dependent MucA Proteolysis

2009 ◽  
Vol 191 (7) ◽  
pp. 2285-2295 ◽  
Author(s):  
F. Heath Damron ◽  
Dongru Qiu ◽  
Hongwei D. Yu
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Response Regulator ◽  
Negative Regulator ◽  
Loss Of Function ◽  
Cystic Fibrosis Mutation ◽  
Strain Pao1 ◽  
Alginate Production ◽  
Mucoid Conversion ◽  
Σ Factor ◽  
Lung Infections

ABSTRACT Mucoidy, or overproduction of the exopolysaccharide known as alginate, in Pseudomonas aeruginosa is a poor prognosticator for lung infections in cystic fibrosis. Mutation of the anti-σ factor MucA is a well-accepted mechanism for mucoid conversion. However, certain clinical mucoid strains of P. aeruginosa have a wild-type (wt) mucA. Here, we describe a loss-of-function mutation in kinB that causes overproduction of alginate in the wt mucA strain PAO1. KinB is the cognate histidine kinase for the transcriptional activator AlgB. Increased alginate production due to inactivation of kinB was correlated with high expression at the alginate-related promoters P algU and P algD . Deletion of alternative σ factor RpoN (σ54) or the response regulator AlgB in kinB mutants decreased alginate production to wt nonmucoid levels. Mucoidy was restored in the kinB algB double mutant by expression of wt AlgB or phosphorylation-defective AlgB.D59N, indicating that phosphorylation of AlgB was not required for alginate overproduction when kinB was inactivated. The inactivation of the DegS-like protease AlgW in the kinB mutant caused loss of alginate production and an accumulation of the hemagglutinin (HA)-tagged MucA. Furthermore, we observed that the kinB mutation increased the rate of HA-MucA degradation. Our results also indicate that AlgW-mediated MucA degradation required algB and rpoN in the kinB mutant. Collectively, these studies indicate that KinB is a negative regulator of alginate production in wt mucA strain PAO1.

scholarly journals Targeted Chemoenzymatic Synthesis of Sugar Nucleotide Probes Reveal an Inhibitor of the GDP-D-Mannose Dehydrogenase from Pseudomonas Aeruginosa

2020 ◽  
Author(s):  
Laura Beswick ◽  
Eleni Dimitriou ◽  
Sanaz Ahmadipour ◽  
Ayesha Zafar ◽  
Martin Rejzek ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Autosomal Recessive ◽  
Genetic Disorder ◽  
Loss Of Function ◽  
Bacterial Strains ◽  
Sugar Nucleotide ◽  
Guanosine Diphosphate ◽  
Mannuronic Acid ◽  
Mucoid Conversion ◽  
Lung Infections

<p>Sufferers of the autosomal recessive genetic disorder cystic fibrosis are at extremely high risk for contracting chronic lung infections. Over their lifetime one bacterial strain in particular, <i>Pseudomonas aeruginosa</i>, becomes the dominant pathogen. Bacterial strains incur loss-of-function mutations in the mucA gene that lead to a phenomenon known as mucoid conversion, resulting in copious secretion of alginate, a carbohydrate exopolysaccharide. Strategies that can stop the production of alginate in mucoid <i>Pseudomonas aeruginosa </i>infections are therefore of paramount importance. To aid in this we developed a series of sugar nucleotide chemical tools to probe an enzyme critical to alginate biosynthesis, guanosine diphosphate mannose dehydrogenase (GMD). This enzyme catalyses the irreversible formation of the alginate sugar nucleotide building block, guanosine diphosphate mannuronic acid. Using a chemoenzymatic strategy we accessed a series of modified sugar nucleotides, identifying a C6-amide derivative of the native substrate as a micromolar inhibitor of GMD.<b> </b>This discovery will provide a framework for wider inhibition strategies against GMD to be developed.<b></b></p>

scholarly journals Targeted Chemoenzymatic Synthesis of Sugar Nucleotide Probes Reveal an Inhibitor of the GDP-D-Mannose Dehydrogenase from Pseudomonas Aeruginosa

2020 ◽  
Author(s):  
Laura Beswick ◽  
Eleni Dimitriou ◽  
Sanaz Ahmadipour ◽  
Ayesha Zafar ◽  
Martin Rejzek ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Autosomal Recessive ◽  
Genetic Disorder ◽  
Loss Of Function ◽  
Bacterial Strains ◽  
Sugar Nucleotide ◽  
Guanosine Diphosphate ◽  
Mannuronic Acid ◽  
Mucoid Conversion ◽  
Lung Infections

<p>Sufferers of the autosomal recessive genetic disorder cystic fibrosis are at extremely high risk for contracting chronic lung infections. Over their lifetime one bacterial strain in particular, <i>Pseudomonas aeruginosa</i>, becomes the dominant pathogen. Bacterial strains incur loss-of-function mutations in the mucA gene that lead to a phenomenon known as mucoid conversion, resulting in copious secretion of alginate, a carbohydrate exopolysaccharide. Strategies that can stop the production of alginate in mucoid <i>Pseudomonas aeruginosa </i>infections are therefore of paramount importance. To aid in this we developed a series of sugar nucleotide chemical tools to probe an enzyme critical to alginate biosynthesis, guanosine diphosphate mannose dehydrogenase (GMD). This enzyme catalyses the irreversible formation of the alginate sugar nucleotide building block, guanosine diphosphate mannuronic acid. Using a chemoenzymatic strategy we accessed a series of modified sugar nucleotides, identifying a C6-amide derivative of the native substrate as a micromolar inhibitor of GMD.<b> </b>This discovery will provide a framework for wider inhibition strategies against GMD to be developed.<b></b></p>

scholarly journals Proteome Analysis of the Effect of Mucoid Conversion on Global Protein Expression in Pseudomonas aeruginosa Strain PAO1 Shows Induction of the Disulfide Bond Isomerase, DsbA

2000 ◽  
Vol 182 (24) ◽  
pp. 6999-7006 ◽  
Author(s):  
Sonal Malhotra ◽  
Laura A. Silo-Suh ◽  
Kalai Mathee ◽  
Dennis E. Ohman
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Disulfide Bond ◽  
Proteome Analysis ◽  
Gene Products ◽  
Extracellular Proteases ◽  
Strain Pao1 ◽  
Alginate Production ◽  
Mucoid Conversion ◽  
Disulfide Bond Isomerase ◽  
Alginate Biosynthesis

ABSTRACT Pseudomonas aeruginosa strains that cause chronic pulmonary infections in cystic fibrosis patients typically undergo mucoid conversion. The mucoid phenotype indicates alginate overproduction and is often due to defects in MucA, an antisigma factor that controls the activity of sigma-22 (AlgT [also called AlgU]), which is required for the activation of genes for alginate biosynthesis. In this study we hypothesized that mucoid conversion may be part of a larger response that activates genes other than those for alginate synthesis. To address this, a two-dimensional (2-D) gel analysis was employed to compare total proteins in strain PAO1 to those of its mucA22 derivative, PDO300, in order to identify protein levels enhanced by mucoid conversion. Six proteins that were clearly more abundant in the mucoid strain were observed. The amino termini of such proteins were determined and used to identify the gene products in the genomic database. Proteins involved in alginate biosynthesis were expected among these, and two (AlgA and AlgD) were identified. This result verified that the 2-D gel approach could identify gene products under sigma-22 control and upregulated bymucA mutation. Two other protein spots were also clearly upregulated in the mucA22 background, and these were identified as porin F (an outer membrane protein) and a homologue of DsbA (a disulfide bond isomerase). Single-copy gene fusions were constructed to test whether these proteins were enhanced in the mucoid strain due to increased transcription. The oprF-lacZ fusion showed little difference in levels of expression in the two strains. However, the dsbA-lacZ fusion showed two- to threefold higher expression in PDO300 than in PAO1, suggesting that its promoter was upregulated by the deregulation of sigma-22 activity. AdsbA-null mutant was constructed in PAO1 and shown to have defects predicted for a cell with reduced disulfide bond isomerase activity, namely, reduction in periplasmic alkaline phosphatase activity, increased sensitivity to dithiothreitol, reduced type IV pilin-mediated twitching motility, and reduced accumulation of extracellular proteases, including elastase. Although efficient secretion of elastase in the dsbA mutant was still demonstrable, the elastase produced appeared to be unstable, possibly as a result of mispaired disulfide bonds. Disruption ofdsbA in the mucoid PDO300 background did not affect alginate production. Thus, even though dsbA is coregulated with mucoid conversion, it was not required for alginate production. This suggests that mucA mutation, which deregulates sigma-22, results in a global response that includes other factors in addition to increasing the production of alginate.

scholarly journals The histone-like protein AlgP regulon is distinct in mucoid and nonmucoid Pseudomonas aeruginosa and does not include alginate biosynthesis genes

Microbiology ◽  
2020 ◽  
Vol 166 (9) ◽  
pp. 861-866 ◽  
Author(s):  
Ashley R. Cross ◽  
Erika E. Csatary ◽  
Vishnu Raghuram ◽  
Frances L. Diggle ◽  
Marvin Whiteley ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Type Species ◽  
Bacterial Pathogen ◽  
Nitrous Oxide Reductase ◽  
Chronic Infections ◽  
Strain Pao1 ◽  
Content Type ◽  
Link Type ◽  
Alginate Production ◽  
Lung Infections

The opportunistic bacterial pathogen Pseudomonas aeruginosa causes acute and chronic infections that are notoriously difficult to treat. In people with cystic fibrosis, P. aeruginosa can cause lifelong lung infections, and isolation of mucoid P. aeruginosa , resulting from the overproduction of alginate, is associated with chronic infection. The histone-like protein AlgP has previously been implicated in the control of alginate gene expression in mucoid strains, but this regulation is unclear. To explore AlgP in further detail, we deleted algP in mucoid strains and demonstrated that the deletion of algP did not result in a nonmucoid phenotype or a decrease in alginate production. We showed that the algP promoter is expressed by both the nonmucoid strain PAO1 and the isogenic mucoid strain PDO300, suggesting that there may be genes that are differentially regulated between these strains. In support of this, using RNA sequencing, we identified a small AlgP regulon that has no significant overlap between PAO1 and PDO300 and established that alginate genes were not differentially regulated by the deletion of algP. Of note, we found that deleting algP in PAO1 increased expression of the nitric oxide operon norCBD and the nitrous oxide reductase genes nosRZ and subsequently promoted growth of PAO1 under anaerobic conditions. Altogether, we have defined a narrow regulon of genes controlled by AlgP and provided evidence that alginate production is not greatly affected by AlgP, countering the long-standing premise in the field.

Prc protease promotes mucoidy in mucA mutants of Pseudomonas aeruginosa

Microbiology ◽  
2005 ◽  
Vol 151 (7) ◽  
pp. 2251-2261 ◽  
Author(s):  
S. A. Reiling ◽  
J. A. Jansen ◽  
B. J. Henley ◽  
S. Singh ◽  
C. Chattin ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Gene Cluster ◽  
Sigma Factor ◽  
Respiratory Infections ◽  
Negative Regulator ◽  
Coding Region ◽  
Extreme Stress ◽  
Alginate Production ◽  
Stress Response System ◽  
Mutant Forms

Mucoid strains of Pseudomonas aeruginosa that overproduce the exopolysaccharide alginate are a frequent cause of chronic respiratory infections in cystic fibrosis (CF) patients. The overproduction of alginate by these strains is often caused by mutations within mucA of the algU mucABCD gene cluster. This gene cluster encodes an extreme stress response system composed of the ECF alternative sigma factor AlgU, the anti-sigma factor MucA located in the inner membrane and the negative regulator MucB located in the periplasm. Most of the mutations in mucA found in mucoid strains cause a truncation of the C-terminal, periplasmic domain of MucA. The most significant effect of these mutations appears to be to reduce the levels of MucA. PA3257 (prc) was identified as a regulator of alginate production in P. aeruginosa through the isolation and study of mutations that partially suppressed the mucoid phenotype of a mucA22 strain. The suppressor of mucoidy (som) mutants isolated produced very little alginate when grown on LB medium, but were still mucoid when grown on Pseudomonas isolation agar. These som mutations and another previously isolated suppressor mutation were complemented by cosmids or plasmids carrying PA3257. PA3257 is predicted to encode a periplasmic protease similar to Prc or Tsp of Escherichia coli. Sequencing of prc from three strains with som suppressor mutations confirmed that each had a mutation within the prc coding region. The authors propose that Prc acts to degrade mutant forms of MucA. Additional evidence in support of this hypothesis is: (1) transcription from the AlgU-regulated algD reporter was reduced in som mutants; (2) inactivation of prc affected alginate production in mucoid strains with other mucA mutations found in CF isolates; (3) inactivation or overexpression of prc did not affect alginate production in strains with wild-type MucA.

scholarly journals The NtrC Family Regulator AlgB, Which Controls Alginate Biosynthesis in Mucoid Pseudomonas aeruginosa, Binds Directly to the algD Promoter

2007 ◽  
Vol 190 (2) ◽  
pp. 581-589 ◽  
Author(s):  
Andrew J. Leech ◽  
April Sprinkle ◽  
Lynn Wood ◽  
Daniel J. Wozniak ◽  
Dennis E. Ohman
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Response Regulator ◽  
Mobility Shift ◽  
Alginate Production ◽  
Mobility Shift Assay ◽  
Exponential Enrichment ◽  
Microarray Analyses ◽  
Phosphorylation Domain

ABSTRACT Alginate production in mucoid (MucA-defective) Pseudomonas aeruginosa is dependent upon several transcriptional regulators, including AlgB, a two-component response regulator belonging to the NtrC family. This role of AlgB was apparently independent of its sensor kinase, KinB, and even the N-terminal phosphorylation domain of AlgB was dispensable for alginate biosynthetic gene (i.e., algD operon) activation. However, it remained unclear whether AlgB stimulated algD transcription directly or indirectly. In this study, microarray analyses were used to examine a set of potential AlgB-dependent, KinB-independent genes in a PAO1 mucA background that overlapped with genes induced by d-cycloserine, which is known to activate algD expression. This set contained only the algD operon plus one other gene that was shown to be uninvolved in alginate production. This suggested that AlgB promotes alginate production by directly binding to the algD promoter (PalgD). Chromosome immunoprecipitation revealed that AlgB bound in vivo to PalgD but did not bind when AlgB had an R442E substitution that disrupted the DNA binding domain. AlgB also showed binding to PalgD fragments in an electrophoretic mobility shift assay at pH 4.5 but not at pH 8.0. A direct systematic evolution of ligands by exponential enrichment approach showed AlgB binding to a 50-bp fragment located at bp −224 to −274 relative to the start of PalgD transcription. Thus, AlgB belongs to a subclass of NtrC family proteins that can activate promoters which utilize a sigma factor other than σ54, in this case to stimulate transcription from the σ22-dependent PalgD promoter.

scholarly journals Potentiation of Aminoglycoside Lethality by C4-Dicarboxylates Requires RpoN in Antibiotic-Tolerant Pseudomonas aeruginosa

2019 ◽  
Vol 63 (10) ◽  
Author(s):  
Clayton W. Hall ◽  
Eszter Farkas ◽  
Li Zhang ◽  
Thien-Fah Mah
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Carbon Sources ◽  
Aminoglycoside Antibiotic ◽  
Loss Of Function ◽  
Mixed Genotype ◽  
Content Type ◽  
Promising Strategy ◽  
Transport Chain ◽  
Suitable Treatment ◽  
Lung Infections

ABSTRACT Antibiotic tolerance contributes to the inability of standard antimicrobial therapies to clear the chronic Pseudomonas aeruginosa lung infections that often afflict patients with cystic fibrosis (CF). Metabolic potentiation of bactericidal antibiotics with carbon sources has emerged as a promising strategy to resensitize tolerant bacteria to antibiotic killing. Fumarate (FUM), a C4-dicarboxylate, has been recently shown to resensitize tolerant P. aeruginosa to killing by tobramycin (TOB), an aminoglycoside antibiotic, when used in combination (TOB+FUM). Fumarate and other C4-dicarboxylates are taken up intracellularly by transporters regulated by the alternative sigma factor RpoN. Once in the cell, FUM is metabolized, leading to enhanced electron transport chain activity, regeneration of the proton motive force, and increased TOB uptake. In this work, we demonstrate that a ΔrpoN mutant displays impaired FUM uptake and, consequently, nonsusceptibility to TOB+FUM treatment. RpoN was also found to be essential for susceptibility to other aminoglycoside and C4-dicarboxylate combinations. Importantly, RpoN loss-of-function mutations have been documented to evolve in the CF lung, and these loss-of-function alleles can also result in TOB+FUM nonsusceptibility. In a mixed-genotype population of wild-type and ΔrpoN cells, TOB+FUM specifically killed cells with RpoN function and spared the cells that lacked RpoN function. Unlike C4-dicarboylates, both d-glucose and l-arginine were able to potentiate TOB killing of ΔrpoN stationary-phase cells. Our findings raise the question of whether TOB+FUM will be a suitable treatment option in the future for CF patients infected with P. aeruginosa isolates that lack RpoN function.

scholarly journals Frequency of quorum sensing mutations in Pseudomonas aeruginosa strains isolated from different environments

2021 ◽  
Author(s):  
Kathleen O’Connor ◽  
Conan Y. Zhao ◽  
Stephen P. Diggle
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Opportunistic Pathogen ◽  
Human Infection ◽  
Multiple Infection ◽  
Loss Of Function ◽  
Mutational Signatures ◽  
Amino Acid Length ◽  
Lung Infections

AbstractPseudomonas aeruginosa uses quorum sensing (QS) to coordinate the expression of multiple genes necessary for establishing and maintaining infection. lasR QS mutations have been shown to frequently arise in cystic fibrosis (CF) lung infections, however, there has been far less emphasis on determining whether QS system mutations arise across other environments. To test this, we utilized 852 publicly available sequenced P. aeruginosa genomes from the Pseudomonas International Consortium Database (IPCD) to study P. aeruginosa QS mutational signatures. We found that across all isolates, LasR is the most variable protein sequence compared to other QS proteins. In order to study isolates by source, we focused on a subset of 654 isolates collected from CF, wounds, and non-infection environmental isolates, where we could clearly identify their source. Using this sub-set analysis, we found that LasR mutations are not specific to CF lungs, but are common across all environments. We then used amino acid length as a proxy for observing loss of function in LasR proteins among the strains. We found that truncated LasR proteins are more abundant in P. aeruginosa strains isolated from human infection than the environment. Overall, our findings suggest that the evolution of lasR QS mutations in P. aeruginosa are common and not limited to infection environments.ImportancePseudomonas aeruginosa is an opportunistic pathogen which is often isolated from infection and environmental sources. P. aeruginosa uses quorum sensing (QS) to establish and adapt to infection environments. QS in P. aeruginosa is controlled by a complex hierarchical gene network in which the transcriptional regulator LasR has traditionally been thought to play a major controlling role. Despite this, lasR mutants are frequently isolated from chronic infection sites including the cystic fibrosis lung. Using an online P. aeruginosa strain database, we determined the frequency of mutation in key QS genes in multiple infection and non-infection environments and found that mutations and truncations in the lasR gene is more common than in other QS genes. Further, we found that lasR mutants are common in both infection and environmental strains. These findings further our understanding of QS in P. aeruginosa and have implications for the development of future therapies designed to inhibit QS.

scholarly journals Activation of the Pseudomonas aeruginosa AlgU Regulon through mucA Mutation Inhibits Cyclic AMP/Vfr Signaling

2010 ◽  
Vol 192 (21) ◽  
pp. 5709-5717 ◽  
Author(s):  
Adriana K. Jones ◽  
Nanette B. Fulcher ◽  
Grant J. Balzer ◽  
Mark L. Urbanowski ◽  
Christopher L. Pritchett ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cyclic Amp ◽  
Virulence Factors ◽  
Sigma Factor ◽  
Respiratory Infections ◽  
Response Regulator ◽  
Selective Advantage ◽  
Virulence Determinants ◽  
Loss Of Function ◽  
Chronic Infections

ABSTRACT Pseudomonas aeruginosa is an opportunistic pathogen that causes acute, invasive infections in immunocompromised individuals and chronic, persistent respiratory infections in individuals with cystic fibrosis (CF). The differential progression of acute or chronic infections involves the production of distinct sets of virulence factors. P. aeruginosa strains isolated from patients with acute respiratory infection are generally nonencapsulated and express a variety of invasive virulence factors, including flagella, the type III secretion system (T3SS), type IV pili (TFP), and multiple secreted toxins and degradative enzymes. Strains isolated from chronically infected CF patients, however, typically lack expression of invasive virulence factors and have a mucoid phenotype due to the production of an alginate capsule. The mucoid phenotype results from loss-of-function mutations in mucA, which encodes an anti-sigma factor that normally prevents alginate synthesis. Here, we report that the cyclic AMP/Vfr-dependent signaling (CVS) pathway is defective in mucA mutants and that the defect occurs at the level of vfr expression. The CVS pathway regulates the expression of multiple invasive virulence factors, including T3SS, exotoxin A, protease IV, and TFP. We further demonstrate that mucA-dependent CVS inhibition involves the alternative sigma factor AlgU (AlgT) and the response regulator AlgR but does not depend on alginate production. Our findings show that a single naturally occurring mutation leads to inverse regulation of virulence factors involved in acute and persistent infections. These results suggest that mucoid conversion and inhibition of invasive virulence determinants may both confer a selective advantage to mucA mutant strains of P. aeruginosa in the CF lung.

scholarly journals Instantaneous Within-Patient Diversity of Pseudomonas aeruginosa Quorum-Sensing Populations from Cystic Fibrosis Lung Infections

2009 ◽  
Vol 77 (12) ◽  
pp. 5631-5639 ◽  
Author(s):  
Cara N. Wilder ◽  
Gopal Allada ◽  
Martin Schuster
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Opportunistic Pathogen ◽  
Homoserine Lactone ◽  
Loss Of Function ◽  
Selective Forces ◽  
Lung Infections

ABSTRACT In the opportunistic pathogen Pseudomonas aeruginosa, acyl-homoserine lactone (acyl-HSL) quorum sensing (QS) regulates biofilm formation and expression of many extracellular virulence factors. Curiously, QS-deficient variants, often carrying mutations in the central QS regulator LasR, are frequently isolated from infections, particularly from cystic fibrosis (CF) lung infections. Very little is known about the proportion and diversity of these QS variants in individual infections. Such information is desirable to better understand the selective forces that drive the evolution of QS phenotypes, including social cheating and innate (nonsocial) benefits. To obtain insight into the instantaneous within-patient diversity of QS, we assayed a panel of 135 concurrent P. aeruginosa isolates from eight different adult CF patients (9 to 20 isolates per patient) for various QS-controlled phenotypes. Most patients contained complex mixtures of QS-proficient and -deficient isolates. Among all patients, deficiency in individual phenotypes ranged from 0 to about 90%. Acyl-HSL, sequencing, and complementation analyses of variants with global loss-of-function phenotypes revealed dependency upon the central QS circuitry genes lasR, lasI, and rhlI. Deficient and proficient isolates were clonally related, implying evolution from a common ancestor in vivo. Our results show that the diversity of QS types is high within and among patients, suggesting diverse selection pressures in the CF lung. A single selective mechanism, be it of a social or nonsocial nature, is unlikely to account for such heterogeneity. The observed diversity also shows that conclusions about the properties of P. aeruginosa QS populations in individual CF infections cannot be drawn from the characterization of one or a few selected isolates.

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