scholarly journals Plant-associated Pseudomonas aeruginosa harbor multiple virulence traits essential for mammalian infection

2021 ◽  
Author(s):  
Sakthivel Ambreetha ◽  
Ponnusamy Marimuthu ◽  
Kalai Mathee ◽  
Dananjeyan Balachandar
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Health Hazard ◽  
Opportunistic Pathogen ◽  
Swarming Motility ◽  
Clinical Strains ◽  
C Elegans ◽  
Virulence Traits ◽  
Mammalian Infection

Pseudomonas aeruginosa is a leading opportunistic pathogen capable of causing fatal infections in immunocompromised individuals and patients with degenerative lung diseases. Agricultural soil and plants are the vast reservoirs of this dreaded pathogen. However, there have been limited attempts to analyze the pathogenicity of P. aeruginosa strains associated with edible vegetable plants. This study aims to elucidate the virulence attributes of P. aeruginosa strains isolated from the rhizosphere and endophytic niches of cucumber, tomato, eggplant, and chili collected from agricultural fields. Virulence of the agricultural strains was compared to three previously characterized clinical isolates. Our results showed that 50% of the plant-associated strains formed significant levels of biofilm and exhibited swarming motility. Nearly 80% of these strains produced considerable levels of rhamnolipid and exhibited at least one type of lytic activity (hemolysis, proteolysis, and lipolysis). Their virulence was also assessed based on their ability to suppress the growth of plant pathogens (Xanthomonas oryzae, Pythium aphanidermatum, Rhizoctonia solani, and Fusarium oxysporum) and kill a select nematode (Caenorhabditis elegans). The plant-associated strains showed significantly higher virulence against the bacterial phytopathogen whereas the clinical strains had significantly higher antagonism against the fungal pathogens. In C. elegans slow-killing assay, the clinical strains caused 50-100% death while a maximum of 40% mortality was induced by the agricultural strains. This study demonstrates that some of the P. aeruginosa strains associated with edible plants harbor multiple virulence traits. Upon infection of humans or animals, these strains may evolve to be more pathogenic and pose a significant health hazard.

scholarly journals PQS Produced by the Pseudomonas aeruginosa Stress Response Repels Swarms Away from Bacteriophage and Antibiotics

2019 ◽  
Vol 201 (23) ◽  
Author(s):  
Jean-Louis Bru ◽  
Brandon Rawson ◽  
Calvin Trinh ◽  
Katrine Whiteson ◽  
Nina Molin Høyland-Kroghsbo ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Stress Response ◽  
Antibiotic Treatment ◽  
Bacterial Pathogen ◽  
Warning Signal ◽  
Opportunistic Pathogen ◽  
Evolutionary Strategy ◽  
Swarming Motility ◽  
Content Type ◽  
Bacteriophage Infection

ABSTRACT We investigate the effect of bacteriophage infection and antibiotic treatment on the coordination of swarming, a collective form of flagellum- and pilus-mediated motility in bacteria. We show that phage infection of the opportunistic bacterial pathogen Pseudomonas aeruginosa abolishes swarming motility in the infected subpopulation and induces the release of the Pseudomonas quinolone signaling molecule PQS, which repulses uninfected subpopulations from approaching the infected area. These mechanisms have the overall effect of limiting the infection to a subpopulation, which promotes the survival of the overall population. Antibiotic treatment of P. aeruginosa elicits the same response, abolishing swarming motility and repulsing approaching swarms away from the antibiotic-treated area through a PQS-dependent mechanism. Swarms are entirely repelled from the zone of antibiotic-treated P. aeruginosa, consistent with a form of antibiotic evasion, and are not repelled by antibiotics alone. PQS has multiple functions, including serving as a quorum-sensing molecule, activating an oxidative stress response, and regulating the release of virulence and host-modifying factors. We show that PQS serves additionally as a stress warning signal that causes the greater population to physically avoid cell stress. The stress response at the collective level observed here in P. aeruginosa is consistent with a mechanism that promotes the survival of bacterial populations. IMPORTANCE We uncover a phage- and antibiotic-induced stress response in the clinically important opportunistic pathogen Pseudomonas aeruginosa. Phage-infected P. aeruginosa subpopulations are isolated from uninfected subpopulations by the production of a stress-induced signal. Activation of the stress response by antibiotics causes P. aeruginosa to physically be repelled from the area containing antibiotics altogether, consistent with a mechanism of antibiotic evasion. The stress response observed here could increase P. aeruginosa resilience against antibiotic treatment and phage therapy in health care settings, as well as provide a simple evolutionary strategy to avoid areas containing stress.

scholarly journals Rhizospheric and endophytic Pseudomonas aeruginosa in edible vegetable plants share molecular and metabolic traits with clinical isolates

2021 ◽  
Author(s):  
Sakthivel Ambreetha ◽  
Ponnusammy Marimuthu ◽  
Kalai Mathee ◽  
Dananjeyan Balachandar
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Opportunistic Pathogen ◽  
Clinical Isolates ◽  
Clinical Strains ◽  
Hospital Acquired Infections ◽  
Metabolic Traits ◽  
Potential Source ◽  
Salad Vegetables ◽  
Hospital Acquired ◽  
Indole 3 Acetic Acid

Pseudomonas aeruginosa, a leading opportunistic pathogen causing hospital-acquired infections is predominantly present in agricultural settings. There are minimal attempts to examine the molecular and functional attributes shared by agricultural and clinical strains of P. aeruginosa. This study aims to investigate the presence of P. aeruginosa in edible vegetable plants (including salad vegetables) and analyze the evolutionary and metabolic relatedness of the agricultural and clinical strains. Eighteen rhizospheric and endophytic P. aeruginosa strains were isolated from cucumber, tomato, eggplant, and chili directly from the farms. The identity of these strains was confirmed using biochemical, and molecular markers and their genetic and metabolic traits were compared with clinical isolates. DNA fingerprinting analyses and 16S rDNA-based phylogenetic tree revealed that the plant- and human-associated strains are evolutionarily related. Both agricultural and clinical isolates possessed plant-beneficial properties, including mineral solubilization (phosphorous, potassium, and zinc), ammonification, and the ability to release extracellular siderophore and indole-3 acetic acid. These findings suggest that rhizospheric and endophytic P. aeruginosa strains are genetically and functionally analogous to the clinical isolates. This study highlights the edible plants as a potential source for human and animal transmission of P. aeruginosa.

scholarly journals NtrBC Selectively Regulates Host-Pathogen Interactions, Virulence, and Ciprofloxacin Susceptibility of Pseudomonas aeruginosa

2021 ◽  
Vol 11 ◽  
Author(s):  
Morgan A. Alford ◽  
Beverlie Baquir ◽  
Andy An ◽  
Ka-Yee G. Choi ◽  
Robert E. W. Hancock
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Respiratory Tract ◽  
Transient State ◽  
Opportunistic Pathogen ◽  
Resistance Mechanisms ◽  
Upper Respiratory Tract ◽  
Intrinsic Resistance ◽  
Swarming Motility ◽  
Adaptive Resistance ◽  
Host Interactions

Pseudomonas aeruginosa is a metabolically versatile opportunistic pathogen capable of infecting distinct niches of the human body, including skin wounds and the lungs of cystic fibrosis patients. Eradication of P. aeruginosa infection is becoming increasingly difficult due to the numerous resistance mechanisms it employs. Adaptive resistance is characterized by a transient state of decreased susceptibility to antibiotic therapy that is distinct from acquired or intrinsic resistance, can be triggered by various environmental stimuli and reverted by removal of the stimulus. Further, adaptive resistance is intrinsically linked to lifestyles such as swarming motility and biofilm formation, both of which are important in infections and lead to multi-drug adaptive resistance. Here, we demonstrated that NtrBC, the master of nitrogen control, had a selective role in host colonization and a substantial role in determining intrinsic resistance to ciprofloxacin. P. aeruginosa mutant strains (ΔntrB, ΔntrC and ΔntrBC) colonized the skin but not the respiratory tract of mice as well as WT and, unlike WT, could be reduced or eradicated from the skin by ciprofloxacin. We hypothesized that nutrient availability contributed to these phenomena and found that susceptibility to ciprofloxacin was impacted by nitrogen source in laboratory media. P. aeruginosa ΔntrB, ΔntrC and ΔntrBC also exhibited distinct host interactions, including modestly increased cytotoxicity toward human bronchial epithelial cells, reduced virulence factor production and 10-fold increased uptake by macrophages. These data might explain why NtrBC mutants were less adept at colonizing the upper respiratory tract of mice. Thus, NtrBC represents a link between nitrogen metabolism, adaptation and virulence of the pathogen P. aeruginosa, and could represent a target for eradication of recalcitrant infections in situ.

An experimentally evolved variant of RsmA confirms its central role in the control of Pseudomonas aeruginosa social motility

2020 ◽  
Author(s):  
Sophie Robitaille ◽  
Yossef López de los Santos ◽  
Marie-Christine Groleau ◽  
Fabrice Jean-Pierre ◽  
Nicolas Doucet ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Experimental Evolution ◽  
Opportunistic Pathogen ◽  
Environmental Cues ◽  
Nucleotide Substitutions ◽  
Swarming Motility ◽  
Single Nucleotide ◽  
Component Systems ◽  
Two Component Systems

AbstractBacteria can colonize a variety of different environments by modulating their gene regulation using two-component systems. The versatile opportunistic pathogen Pseudomonas aeruginosa has been studied for its capacity to adapt to a broad range of environmental conditions. The Gac/Rsm pathway is composed of the sensor kinase GacS, that detects environmental cues, and the response regulator GacA, that modulates the expression of a specific genes. This system, through the sRNA repressors RsmY and RsmZ, negatively controls the activity of the protein RsmA, which is centrally involved in the transition from chronic to acute infections by post-transcriptionally regulating several virulence functions. RsmA positively regulates swarming motility, a social surface behaviour. Through a poorly defined mechanism, RsmA is also indirectly regulated by HptB, and a ΔhptB mutant exhibits a severe swarming defect. Since a ΔhptB mutant retains all the known functions required for that type of motility, we used an experimental evolution approach to identify elements responsible for its swarming defect. After a few passages under swarming conditions, the defect of the ΔhptB mutant was rescued by the emergence of spontaneous single nucleotide substitutions in the gacA and rsmA genes. Since GacA indirectly represses RsmA activity, it was coherent that an inactivating mutation in gacA would compensate the ΔhptB swarming defect. However, the effect of the mutation in rsmA was unexpected since RsmA promotes swarming; indeed, using expression reporters, we found that the mutation that does not abolish its activity. Instead, using electrophoretic mobility shift assays and molecular simulations, we show that this variant of RsmA is actually less amenable to titration by its cognate repressor RsmY, supporting the other phenotypes observed for this mutant. These results confirm the central role of RsmA as a regulator of swarming motility in P. aeruginosa and identify residues crucial for RsmA function in social motility.Author summaryBacteria need to readily adapt to their environment. Two-component systems (TCS) allow such adaption by triggering bacterial regulation changes through the detection of environmental cues. The opportunistic pathogen Pseudomonas aeruginosa possesses more than 60 TCS in its genome. The Gac/Rsm is a TCS extensively studied for its implication in virulence regulation. This system regulates the transition between chronic and acute bacterial infection behaviours. To acquire a better understanding of this regulation, we performed a directed experimental evolution on a swarming-deficient mutant in a poorly understood regulatory component of the Gac/Rsm pathway. We observed single nucleotide substitutions that allowed restoration of a swarming phenotype similar to the wild-type behaviour. More specifically, mutations were found in the gacA and rsmA genes. Interestingly, the observed mutation in rsmA does not result in loss of function of the protein but rather alters its susceptibility to repression by its cognate interfering sRNA. Since modification in the RNA sequence of RsmA results in the rescue of swarming motility, we confirm the central role of this posttranscriptional repressor in this social lifestyle.

scholarly journals Peptide 1018 inhibits swarming and influences Anr-regulated gene expression downstream of the stringent stress response in Pseudomonas aeruginosa

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250977
Author(s):  
Lauren V. Wilkinson ◽  
Morgan A. Alford ◽  
Shannon R. Coleman ◽  
Bing C. Wu ◽  
Amy H. Y. Lee ◽  
...  
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Stress Response ◽  
Opportunistic Pathogen ◽  
Transcriptional Analysis ◽  
Insertion Mutant ◽  
Swarming Motility ◽  
Innate Defense ◽  
Expression Of Genes ◽  
Regulated Gene Expression

Pseudomonas aeruginosa is a ubiquitous opportunistic pathogen that causes considerable human morbidity and mortality, particularly in nosocomial infections and individuals with cystic fibrosis. P. aeruginosa can adapt to surface growth by undergoing swarming motility, a rapid multicellular movement that occurs on viscous soft surfaces with amino acids as a nitrogen source. Here we tested the small synthetic host defense peptide, innate defense regulator 1018, and found that it inhibited swarming motility at concentrations as low as 0.75 μg/ml, well below the MIC for strain PA14 planktonic cells (64 μg/ml). A screen of the PA14 transposon insertion mutant library revealed 29 mutants that were more tolerant to peptide 1018 during swarming, five of which demonstrated significantly greater swarming than the WT in the presence of peptide. Transcriptional analysis (RNA-Seq) of cells that were inoculated on swarming plates containing 1.0 μg/ml peptide revealed differential expression of 1,190 genes compared to cells swarming on plates without peptide. Furthermore, 1018 treatment distinctly altered the gene expression profile of cells when compared to that untreated cells in the centre of the swarm colonies. Peptide-treated cells exhibited changes in the expression of genes implicated in the stringent stress response including those regulated by anr, which is involved in anaerobic adaptation, indicative of a mechanism by which 1018 might inhibit swarming motility. Overall, this study illustrates potential mechanisms by which peptide 1018 inhibits swarming surface motility, an important bacterial adaptation associated with antibiotic resistance, virulence, and dissemination of P. aeruginosa.

Pseudomonas aeruginosa in bottled drinking water in Sri Lanka: a potential health hazard

2014 ◽  
Vol 14 (6) ◽  
pp. 1045-1050
Author(s):  
A. T. Herath ◽  
C. L. Abayasekara ◽  
Rohana Chandrajith ◽  
N. K. B. Adikaram
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Drinking Water ◽  
Sri Lanka ◽  
Dna Sequencing ◽  
Membrane Filtration ◽  
Health Hazard ◽  
Opportunistic Pathogen ◽  
Bottled Water ◽  
Potential Health ◽  
Bottled Drinking Water

Pseudomonas aeruginosa, a food- and water-borne opportunistic pathogen, constitutes a health risk mostly to immunocompromised patients, and also affects the taste, odour and turbidity of potable water. In order to detect P. aeruginosa in bottled water in Sri Lanka, 36 bottled water brands were collected randomly from retail and supermarkets island wide. P. aeruginosa was detected by the membrane filtration technique, using cetrimide agar supplemented with nalidixic acid. The isolates were subjected to confirmatory tests, viz: ISO 16266:2006 methods and growth at 4 and 42°C, and API 20NE followed by DNA sequencing. Presumptive isolates of P. aeruginosa were observed on cetrimide agar in 50% of brands. Among these isolates, ISO procedures confirmed 58% as P. aeruginosa. Thirty-nine randomly selected isolates were identified as P. aeruginosa by the API 20NE, three of which were further confirmed by DNA sequencing. The presence of P. aeruginosa in bottled water raises health concerns since P. aeruginosa is an indicator of inferior water quality. Therefore, strict regulations and regular monitoring of bottling plants are recommended in order to supply safe and acceptable bottled drinking water to the Sri Lankan market.

scholarly journals Coordination of Swarming Motility, Biosurfactant Synthesis, and Biofilm Matrix Exopolysaccharide Production in Pseudomonas aeruginosa

2014 ◽  
Vol 80 (21) ◽  
pp. 6724-6732 ◽  
Author(s):  
Shiwei Wang ◽  
Shan Yu ◽  
Zhenyin Zhang ◽  
Qing Wei ◽  
Lu Yan ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Opportunistic Pathogen ◽  
Bacterial Survival ◽  
Swarming Motility ◽  
Content Type ◽  
Exopolysaccharide Production ◽  
Complex Process ◽  
Exopolysaccharide Biosynthesis ◽  
Biofilm Matrix

ABSTRACTBiofilm formation is a complex process in which many factors are involved. Bacterial swarming motility and exopolysaccharides both contribute to biofilm formation, yet it is unclear how bacteria coordinate swarming motility and exopolysaccharide production. Psl and Pel are two key biofilm matrix exopolysaccharides inPseudomonas aeruginosa. This opportunistic pathogen has three types of motility, swimming, twitching, and swarming. In this study, we found that elevated Psl and/or Pel production reduced the swarming motility ofP. aeruginosabut had little effect on swimming and twitching. The reduction was due to decreased rhamnolipid production with no relation to the transcription ofrhlAB, two key genes involved in the biosynthesis of rhamnolipids. Rhamnolipid-negativerhlRandrhlABmutants synthesized more Psl, whereas exopolysaccharide-deficient strains exhibited a hyperswarming phenotype. These results suggest that competition for common sugar precursors catalyzed by AlgC could be a tactic forP. aeruginosato balance the synthesis of exopolysaccharides and rhamnolipids and to control bacterial motility and biofilm formation inversely because the biosynthesis of rhamnolipids, Psl, and Pel requires AlgC to provide the sugar precursors and an additionalalgCgene enhances the biosynthesis of Psl and rhamnolipids. In addition, our data indicate that the increase in RhlI/RhlR expression attenuated Psl production. This implied that the quorum-sensing signals could regulate exopolysaccharide biosynthesis indirectly in bacterial communities. In summary, this study represents a mechanism that bacteria utilize to coordinate swarming motility, biosurfactant synthesis, and biofilm matrix exopolysaccharide production, which is critical for biofilm formation and bacterial survival in the environment.

scholarly journals Clustered Regularly Interspaced Short Palindromic Repeat-Dependent, Biofilm-Specific Death of Pseudomonas aeruginosa Mediated by Increased Expression of Phage-Related Genes

mBio ◽  
2015 ◽  
Vol 6 (3) ◽  
Author(s):  
Gary E. Heussler ◽  
Kyle C. Cady ◽  
Katja Koeppen ◽  
Sabin Bhuju ◽  
Bruce A. Stanton ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Adaptive Immune System ◽  
Opportunistic Pathogen ◽  
Swarming Motility ◽  
Content Type ◽  
Minimal Impact ◽  
Crispr System ◽  
Alternative Function

ABSTRACTTheclusteredregularlyinterspacedshortpalindromicrepeat (CRISPR)/CRISPR-associated (CRISPR/Cas) system is an adaptive immune system present in many archaea and bacteria. CRISPR/Cas systems are incredibly diverse, and there is increasing evidence of CRISPR/Cas systems playing a role in cellular functions distinct from phage immunity. Previously, our laboratory reported one such alternate function in which the type 1-F CRISPR/Cas system of the opportunistic pathogenPseudomonas aeruginosastrain UCBPP-PA14 (abbreviated asP. aeruginosaPA14) inhibits both biofilm formation and swarming motility when the bacterium is lysogenized by the bacteriophage DMS3. In this study, we demonstrated that the presence of just the DMS3 protospacer and the protospacer-adjacent motif (PAM) on theP. aeruginosagenome is necessary and sufficient for this CRISPR-dependent loss of these group behaviors, with no requirement of additional DMS3 sequences. We also demonstrated that the interaction of the CRISPR system with the DMS3 protospacer induces expression of SOS-regulated phage-related genes, including the well-characterized pyocin operon, through the activity of the nuclease Cas3 and subsequent RecA activation. Furthermore, our data suggest that expression of the phage-related genes results in bacterial cell death on a surface due to the inability of the CRISPR-engaged strain to downregulate phage-related gene expression, while these phage-related genes have minimal impact on growth and viability under planktonic conditions. Deletion of the phage-related genes restores biofilm formation and swarming motility while still maintaining a functional CRISPR/Cas system, demonstrating that the loss of these group behaviors is an indirect effect of CRISPR self-targeting.IMPORTANCEThe various CRISPR/Cas systems found in both archaea and bacteria are incredibly diverse, and advances in understanding the complex mechanisms of these varied systems has not only increased our knowledge of host-virus interplay but has also led to a major advancement in genetic engineering. Recently, increasing evidence suggested that bacteria can co-opt the CRISPR system for functions besides adaptive immunity to phage infection. This study examined one such alternative function, and this report describes the mechanism of type 1-F CRISPR-dependent loss of the biofilm and swarming in the medically relevant opportunistic pathogenPseudomonas aeruginosa. Since both biofilm formation and swarming motility are important in the virulence ofP. aeruginosa, a full understanding of how the CRISPR system can regulate such group behaviors is fundamental to developing new therapeutics.

scholarly journals Inverse Regulation of Biofilm Formation and Swarming Motility by Pseudomonas aeruginosa PA14

2007 ◽  
Vol 189 (9) ◽  
pp. 3603-3612 ◽  
Author(s):  
Nicky C. Caiazza ◽  
Judith H. Merritt ◽  
Kimberly M. Brothers ◽  
George A. O'Toole
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Opportunistic Pathogen ◽  
Wild Type ◽  
Regulatory Pathway ◽  
Early Step ◽  
Swarming Motility ◽  
Epistasis Analysis

ABSTRACT We previously reported that SadB, a protein of unknown function, is required for an early step in biofilm formation by the opportunistic pathogen Pseudomonas aeruginosa. Here we report that a mutation in sadB also results in increased swarming compared to the wild-type strain. Our data are consistent with a model in which SadB inversely regulates biofilm formation and swarming motility via its ability both to modulate flagellar reversals in a viscosity-dependent fashion and to influence the production of the Pel exopolysaccharide. We also show that SadB is required to properly modulate flagellar reversal rates via chemotaxis cluster IV (CheIV cluster). Mutational analyses of two components of the CheIV cluster, the methyl-accepting chemotaxis protein PilJ and the PilJ demethylase ChpB, support a model wherein this chemotaxis cluster participates in the inverse regulation of biofilm formation and swarming motility. Epistasis analysis indicates that SadB functions upstream of the CheIV cluster. We propose that P. aeruginosa utilizes a SadB-dependent, chemotaxis-like regulatory pathway to inversely regulate two key surface behaviors, biofilm formation and swarming motility.

scholarly journals σ Factor and Anti-σ Factor That Control Swarming Motility and Biofilm Formation in Pseudomonas aeruginosa

2015 ◽  
Vol 198 (5) ◽  
pp. 755-765 ◽  
Author(s):  
Bryan A. McGuffie ◽  
Isabelle Vallet-Gely ◽  
Simon L. Dove
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Cell Envelope ◽  
Opportunistic Pathogen ◽  
Chronic Infections ◽  
Swarming Motility ◽  
Content Type ◽  
Σ Factor ◽  
Stress Response System

ABSTRACTPseudomonas aeruginosais capable of causing a variety of acute and chronic infections. Here, we provide evidence thatsbrR(PA2895), a gene previously identified as required during chronicP. aeruginosarespiratory infection, encodes an anti-σ factor that inhibits the activity of its cognate extracytoplasmic-function σ factor, SbrI (PA2896). Bacterial two-hybrid analysis identified an N-terminal region of SbrR that interacts directly with SbrI and that was sufficient for inhibition of SbrI-dependent gene expression. We show that SbrI associates with RNA polymerasein vivoand identify the SbrIR regulon. In cells lacking SbrR, the SbrI-dependent expression ofmuiAwas found to inhibit swarming motility and promote biofilm formation. Our findings reveal SbrR and SbrI as a novel set of regulators of swarming motility and biofilm formation inP. aeruginosathat mediate their effects throughmuiA, a gene not previously known to influence surface-associated behaviors in this organism.IMPORTANCEThis study characterizes a σ factor/anti-σ factor system that reciprocally regulates the surface-associated behaviors of swarming motility and biofilm formation in the opportunistic pathogenPseudomonas aeruginosa. We present evidence that SbrR is an anti-σ factor specific for its cognate σ factor, SbrI, and identify the SbrIR regulon inP. aeruginosa. We find that cells lacking SbrR are severely defective in swarming motility and exhibit enhanced biofilm formation. Moreover, we identifymuiA(PA1494) as the SbrI-dependent gene responsible for mediating these effects. SbrIR have been implicated in virulence and in responding to antimicrobial and cell envelope stress. SbrIR may therefore represent a stress response system that influences the surface behaviors ofP. aeruginosaduring infection.

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