Contributions of a LysR Transcriptional Regulator to Listeria monocytogenes Virulence and Identification of Its Regulons

ABSTRACT The capacity of Listeria monocytogenes to adapt to environmental changes is facilitated by a large number of regulatory proteins encoded by its genome. Among these proteins are the uncharacterized LysR-type transcriptional regulators (LTTRs). LTTRs can work as positive and/or negative transcription regulators at both local and global genetic levels. Previously, our group determined by comparative genome analysis that one member of the LTTRs (NCBI accession no. WP_003734782) was present in pathogenic strains but absent from nonpathogenic strains. The goal of the present study was to assess the importance of this transcription factor in the virulence of L. monocytogenes strain F2365 and to identify its regulons. An L. monocytogenes strain lacking lysR (the F2365ΔlysR strain) displayed significant reductions in cell invasion of and adhesion to Caco-2 cells. In plaque assays, the deletion of lysR resulted in a 42.86% decrease in plaque number and a 13.48% decrease in average plaque size. Furthermore, the deletion of lysR also attenuated the virulence of L. monocytogenes in mice following oral and intraperitoneal inoculation. The analysis of transcriptomics revealed that the transcript levels of 139 genes were upregulated, while 113 genes were downregulated in the F2365ΔlysR strain compared to levels in the wild-type bacteria. lysR-repressed genes included ABC transporters, important for starch and sucrose metabolism as well as glycerolipid metabolism, flagellar assembly, quorum sensing, and glycolysis/gluconeogenesis. Conversely, lysR activated the expression of genes related to fructose and mannose metabolism, cationic antimicrobial peptide (CAMP) resistance, and beta-lactam resistance. These data suggested that lysR contributed to L. monocytogenes virulence by broad impact on multiple pathways of gene expression. IMPORTANCE Listeria monocytogenes is the causative agent of listeriosis, an infectious and fatal disease of animals and humans. In this study, we have shown that lysR contributes to Listeria pathogenesis and replication in cell lines. We also highlight the importance of lysR in regulating the transcription of genes involved in different pathways that might be essential for the growth and persistence of L. monocytogenes in the host or under nutrient limitation. Better understanding L. monocytogenes pathogenesis and the role of various virulence factors is necessary for further development of prevention and control strategies.

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Phenotypic stress response of Pseudomonas aeruginosa following culture in water microcosms

Journal of Water and Health ◽

10.2166/wh.2011.072 ◽

2012 ◽

Vol 10 (1) ◽

pp. 130-139 ◽

Cited By ~ 3

Author(s):

Jihane Cheriaa ◽

Mahmoud Rouabhia ◽

Makaoui Maatallah ◽

Amina Bakhrouf

Keyword(s):

Pseudomonas Aeruginosa ◽

Environmental Changes ◽

Starvation Period ◽

Wild Type ◽

Beta Lactam ◽

Antibiotic Resistant ◽

Aquatic Microcosms ◽

Beta Lactam Antibiotics ◽

In The Wild ◽

Human Infections

The purpose of the present study was to explore the potential behavioural changes of Pseudomonas aeruginosa following growth in different aquatic environmental conditions. To achieve this, P. aeruginosa was cultured in various water microcosms for 12 months under fixed (pH, nutrients and temperature) factors. P. aeruginosa responses to these conditions were investigated using colony morphotype, biochemical and enzymatic characterisation, pyocin typing, serotyping, sensitivity to different classes of antibiotics and molecular identification. Results show that starvation in water microcosms lead to unusual phenotypes. Of interest is that the pyocin changed from 24/n in the wild type to 83/a following culture in the water microcosms, and the serotype changed from O6 in the wild type to O1 in microcosm-cultured P. aeruginosa. Furthermore, the starvation period in various aquatic microcosms enhanced the resistance of P. aeruginosa against beta-lactam antibiotics. Compared to the other aquatic environments, the seawater microcosm produced the greatest amount of variations in P. aeruginosa. Overall, data demonstrated a high adaptability of P. aeruginosa to environmental changes. This may explain the unusual antibiotic-resistant phenotypes belonging to P. aeruginosa species, and their capacity for spreading that leads to human infections.

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Mutation of the Transcriptional Regulator YtoI Rescues Listeria monocytogenes Mutants Deficient in the Essential Shared Metabolite 1,4-Dihydroxy-2-Naphthoate (DHNA)

Infection and Immunity ◽

10.1128/iai.00366-19 ◽

2019 ◽

Vol 88 (1) ◽

Author(s):

Grischa Y. Chen ◽

Cheng-Yen Kao ◽

Hans B. Smith ◽

Drew P. Rust ◽

Zachary M. Powers ◽

...

Keyword(s):

Listeria Monocytogenes ◽

Metabolic Regulation ◽

Critical Role ◽

Transcriptional Regulator ◽

Host Cells ◽

Missense Mutations ◽

Content Type ◽

Independent Functions ◽

In The Wild ◽

Suppressor Mutants

ABSTRACT Listeria monocytogenes, a Gram-positive, facultative intracellular pathogen, survives and replicates in the cytosol of host cells. Synthesis of 1,4-dihydroxy-2-naphthoate (DHNA), an intermediate of menaquinone biosynthesis, is essential for cytosolic survival of L. monocytogenes independent from its role in respiration. Here, we demonstrate that DHNA is essential for virulence in a murine model of listeriosis due to both respiration-dependent and -independent functions. In addition, DHNA can be both secreted and utilized as an extracellular shared metabolite to promote cytosolic survival inside host macrophages. To understand the role(s) of DHNA in L. monocytogenes intracellular survival and virulence, we isolated DHNA-deficient (ΔmenD strain) suppressor mutants that formed plaques in monolayers of fibroblasts. Five ΔmenD suppressor (mds) mutants additionally rescued at least 50% of the cytosolic survival defect of the parent ΔmenD mutant. Whole-genome sequencing revealed that four of the five suppressor mutants had independent missense mutations in a putative transcriptional regulator, ytoI (lmo1576). Clean deletion and complementation in trans confirmed that loss of ytoI could restore plaquing and cytosolic survival of DHNA-deficient L. monocytogenes. RNA-seq transcriptome analysis revealed five genes (lmo0944, lmo1575, lmo1577, lmo2005, and lmo2006) expressed at a higher level in the ΔytoI strain than in the wild-type strain, whereas two genes (lmo1917 and lmo2103) demonstrated lower expression in the ΔytoI mutant. Intriguingly, the majority of these genes are involved in controlling pyruvate flux. Metabolic analysis confirmed that acetoin, acetate, and lactate flux were altered in a ΔytoI mutant, suggesting a critical role for regulating these metabolic programs. In conclusion, we have demonstrated that, similar to findings in select other bacteria, DHNA can act as a shared resource, and it is essential for cytosolic survival and virulence of L. monocytogenes. Furthermore, we have identified a novel transcriptional regulator in L. monocytogenes and determined that its metabolic regulation is implicated in cytosolic survival of L. monocytogenes.

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Caulobacter crescentusAdapts to Phosphate Starvation by Synthesizing Anionic Glycoglycerolipids and a Novel Glycosphingolipid

mBio ◽

10.1128/mbio.00107-19 ◽

2019 ◽

Vol 10 (2) ◽

Cited By ~ 5

Author(s):

Gabriele Stankeviciute ◽

Ziqiang Guan ◽

Howard Goldfine ◽

Eric A. Klein

Keyword(s):

Cell Body ◽

Environmental Changes ◽

Caulobacter Crescentus ◽

Phosphate Starvation ◽

Phosphate Limitation ◽

Phage Resistance ◽

Cationic Antimicrobial Peptide ◽

Content Type ◽

Outer Membranes ◽

Lipid Species

ABSTRACTCaulobacter crescentusadapts to phosphate starvation by elongating its cell body and a polar stalk structure. The stalk is an extension of the Gram-negative envelope containing inner and outer membranes as well as a peptidoglycan cell wall. Cellular elongation requires a 6- to 7-fold increase in membrane synthesis, yet phosphate limitation would preclude the incorporation of additional phospholipids. In the place of phospholipids,C. crescentuscan synthesize several glycolipid species, including a novel glycosphingolipid (GSL-2). While glycosphingolipids are ubiquitous in eukaryotes, the presence of GSL-2 inC. crescentusis surprising since GSLs had previously been found only inSphingomonasspecies, in which they play a role in outer membrane integrity. In this paper, we identify three proteins required for GSL-2 synthesis: CcbF catalyzes the first step in ceramide synthesis, while Sgt1 and Sgt2 sequentially glycosylate ceramides to produce GSL-2. Unlike inSphingomonas, GSLs are nonessential inC. crescentus; however, the presence of ceramides does contribute to phage resistance and susceptibility to the cationic antimicrobial peptide polymyxin B. The identification of a novel lipid species specifically produced upon phosphate starvation suggests that bacteria may be able to synthesize a wider variety of lipids in response to stresses than previously observed. Uncovering these lipids and their functional relevance will provide greater insight into microbial physiology and environmental adaptation.IMPORTANCEBacteria adapt to environmental changes in a variety of ways, including altering their cell shape.Caulobacter crescentusadapts to phosphate starvation by elongating its cell body and a polar stalk structure containing both inner and outer membranes. While we generally think of cellular membranes being composed largely of phospholipids, cellular elongation occurs when environmental phosphate, and therefore phospholipid synthesis, is limited. In order to adapt to these environmental constraints,C. crescentussynthesizes several glycolipid species, including a novel glycosphingolipid. This finding is significant because glycosphingolipids, while ubiquitous in eukaryotes, are extremely rare in bacteria. In this paper, we identify three proteins required for GSL-2 synthesis and demonstrate that they contribute to phage resistance. These findings suggest that bacteria may synthesize a wider variety of lipids in response to stresses than previously observed.

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Occurrence, Persistence, and Contamination Routes ofListeria monocytogenesGenotypes on Three Finnish Dairy Cattle Farms: a Longitudinal Study

Applied and Environmental Microbiology ◽

10.1128/aem.02000-17 ◽

2017 ◽

Vol 84 (4) ◽

Cited By ~ 8

Author(s):

Hanna Castro ◽

Anniina Jaakkonen ◽

Marjaana Hakkinen ◽

Hannu Korkeala ◽

Miia Lindström

Keyword(s):

Longitudinal Study ◽

Listeria Monocytogenes ◽

Dairy Cattle ◽

Control Strategies ◽

Dairy Farms ◽

Bulk Tank Milk ◽

Content Type ◽

Bulk Tank ◽

Contamination Routes ◽

Cattle Farms

ABSTRACTThe molecular epidemiology ofListeria monocytogeneswas investigated in a longitudinal study of three Finnish dairy farms during 2013 to 2016. A total of 186 bulk tank milk (BTM), 224 milk filter sock (MFS), and 1,702 barn environment samples were analyzed, and isolates ofL. monocytogeneswere genotyped using pulsed-field gel electrophoresis.L. monocytogenesoccurred throughout the year in all sample types, and the prevalence in MFS increased significantly during the indoor season.L. monocytogeneswas more prevalent in MFS (29%) than in BTM (13%) samples. However, the prevalence ofL. monocytogenesvaried more between farms in samples of MFS (13 to 48%) than in BTM (10 to 16%). For each farm, theL. monocytogenesgenotypes detected were classified by persistence (defined as persistent if isolated from ≥3 samples during ≥6 months) and predominance (defined as predominant if >5% prevalence on at least one farm visit). The prevalence of sporadic genotypes was 4 to 5% on all three farms. In contrast, the prevalence of persistent predominant genotypes varied between farms by 4% to 16%. The highest prevalence of persistent predominant genotypes was observed on the farm with the poorest production hygiene. Persistent predominant genotypes were most prevalent on feeding surfaces, water troughs, and floors. Genotypes isolated from the milking system or from cow udders had a greater relative risk of occurring in BTM and MFS than genotypes that only occurred elsewhere in the farm, supporting the hypothesis thatL. monocytogenes is transmitted to milk from contamination on the udder surface or in the milking equipment.IMPORTANCEListeria monocytogenesis a ubiquitous environmental bacterium and the causative agent of a serious foodborne illness, listeriosis. Dairy products are common vehicles of listeriosis, and dairy cattle farms harborL. monocytogenesgenotypes associated with human listeriosis outbreaks. Indeed, dairy cattle farms act as a reservoir ofL. monocytogenes, and the organism is frequently detected in bulk tank milk (BTM) and in the feces of clinically healthy cows. The ecology ofL. monocytogenesin the farm environment is complex and poorly understood. Isolates of the sameL. monocytogenesgenotype can occur in the farm for years, but the factors contributing to the persistence of genotypes on dairy farms are unknown. Knowledge of the persistence patterns and contamination routes ofL. monocytogeneson dairy farms can improve management of the contamination pressure in the farm environment and aid in the development of focused control strategies to reduce BTM contamination.

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Interactional mechanisms of Paenibacillus polymyxa SC2 and pepper (Capsicum annuum L.) suggested by transcriptomics

BMC Microbiology ◽

10.1186/s12866-021-02132-2 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Hu Liu ◽

Yufei Li ◽

Ke Ge ◽

Binghai Du ◽

Kai Liu ◽

...

Keyword(s):

Capsicum Annuum ◽

Biofilm Formation ◽

Rhizosphere Soil ◽

Paenibacillus Polymyxa ◽

Systemic Resistance ◽

Expression Of Genes ◽

Transcription Factor Genes ◽

Transcription Regulators ◽

Relationship Of ◽

Stimulation Of

Abstract Background Paenibacillus polymyxa SC2, a bacterium isolated from the rhizosphere soil of pepper (Capsicum annuum L.), promotes growth and biocontrol of pepper. However, the mechanisms of interaction between P. polymyxa SC2 and pepper have not yet been elucidated. This study aimed to investigate the interactional relationship of P. polymyxa SC2 and pepper using transcriptomics. Results P. polymyxa SC2 promotes growth of pepper stems and leaves in pot experiments in the greenhouse. Under interaction conditions, peppers stimulate the expression of genes related to quorum sensing, chemotaxis, and biofilm formation in P. polymyxa SC2. Peppers induced the expression of polymyxin and fusaricidin biosynthesis genes in P. polymyxa SC2, and these genes were up-regulated 2.93- to 6.13-fold and 2.77- to 7.88-fold, respectively. Under the stimulation of medium which has been used to culture pepper, the bacteriostatic diameter of P. polymyxa SC2 against Xanthomonas citri increased significantly. Concurrently, under the stimulation of P. polymyxa SC2, expression of transcription factor genes WRKY2 and WRKY40 in pepper was up-regulated 1.17-fold and 3.5-fold, respectively. Conclusions Through the interaction with pepper, the ability of P. polymyxa SC2 to inhibit pathogens was enhanced. P. polymyxa SC2 also induces systemic resistance in pepper by stimulating expression of corresponding transcription regulators. Furthermore, pepper has effects on chemotaxis and biofilm formation of P. polymyxa SC2. This study provides a basis for studying interactional mechanisms of P. polymyxa SC2 and pepper.

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WblAch, a Pivotal Activator of Natamycin Biosynthesis and Morphological Differentiation in Streptomyces chattanoogensis L10, Is Positively Regulated by AdpAch

Applied and Environmental Microbiology ◽

10.1128/aem.01849-14 ◽

2014 ◽

Vol 80 (22) ◽

pp. 6879-6887 ◽

Cited By ~ 22

Author(s):

Pin Yu ◽

Shui-Ping Liu ◽

Qing-Ting Bu ◽

Zhen-Xing Zhou ◽

Zhen-Hong Zhu ◽

...

Keyword(s):

Morphological Differentiation ◽

Binding Activity ◽

Transcriptional Analysis ◽

Antibiotic Biosynthesis ◽

Content Type ◽

Real Time Quantitative Pcr ◽

Dna Binding Activity ◽

In The Wild ◽

Natamycin Production ◽

Streptomyces Chattanoogensis

ABSTRACTDetailed mechanisms ofWhiB-like (Wbl) proteins involved in antibiotic biosynthesis and morphological differentiation are poorly understood. Here, we characterize the role of WblAch, aStreptomyces chattanoogensisL10 protein belonging to this superfamily. Based on DNA microarray data and verified by real-time quantitative PCR (qRT-PCR), the expression ofwblAchwas shown to be positively regulated by AdpAch. Gel retardation assays and DNase I footprinting experiments showed that AdpAchhas specific DNA-binding activity for the promoter region ofwblAch. Gene disruption and genetic complementation revealed that WblAchacts in a positive manner to regulate natamycin production. WhenwblAchwas overexpressed in the wild-type strain, the natamycin yield was increased by ∼30%. This provides a strategy to generate improved strains for natamycin production. Moreover, transcriptional analysis showed that the expression levels ofwhigenes (includingwhiA,whiB,whiH, andwhiI) were severely depressed in the ΔwblAchmutant, suggesting that WblAchplays a part in morphological differentiation by influencing the expression of thewhigenes.

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Secretion of Anti-Plasmodium Effector Proteins from a Natural Pantoea agglomerans Isolate by Using PelB and HlyA Secretion Signals

Applied and Environmental Microbiology ◽

10.1128/aem.00514-11 ◽

2011 ◽

Vol 77 (13) ◽

pp. 4669-4675 ◽

Cited By ~ 43

Author(s):

Dawn C. Bisi ◽

David J. Lampe

Keyword(s):

Control Strategies ◽

Pectate Lyase ◽

Erwinia Carotovora ◽

Individual Characteristics ◽

Pantoea Agglomerans ◽

Effector Proteins ◽

World Health ◽

Content Type ◽

E Coli ◽

The Individual

ABSTRACTThe insect-vectored disease malaria is a major world health problem. New control strategies are needed to supplement the current use of insecticides and medications. A genetic approach can be used to inhibit development of malaria parasites (Plasmodiumspp.) in the mosquito host. We hypothesized thatPantoea agglomerans, a bacterial symbiont ofAnophelesmosquitoes, could be engineered to express and secrete anti-Plasmodiumeffector proteins, a strategy termed paratransgenesis. To this end, plasmids that include thepelBorhlyAsecretion signals from the genes of related species (pectate lyase fromErwinia carotovoraand hemolysin A fromEscherichia coli, respectively) were created and tested for their efficacy in secreting known anti-Plasmodiumeffector proteins (SM1, anti-Pbs21, and PLA2) inP. agglomeransandE. coli.P. agglomeranssuccessfully secreted HlyA fusions of anti-Pbs21 and PLA2, and these strains are under evaluation for anti-Plasmodiumactivity in infected mosquitoes. Varied expression and/or secretion of the effector proteins was observed, suggesting that the individual characteristics of a particular effector may require empirical testing of several secretion signals. Importantly, those strains that secreted efficiently grew as well as wild-type strains under laboratory conditions and, thus, may be expected to be competitive with the native microbiota in the environment of the mosquito midgut.

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The impact of executives’ perceptions of environmental threats and organizational slack on innovation strategies

Nankai Business Review International ◽

10.1108/nbri-11-2015-0029 ◽

2016 ◽

Vol 7 (2) ◽

pp. 216-230 ◽

Cited By ~ 4

Author(s):

Chengyuan Wang ◽

Biao Luo ◽

Yong Liu ◽

Zhengyun Wei

Keyword(s):

Cognitive Theory ◽

Environmental Changes ◽

Ordinary Least Squares ◽

Organizational Slack ◽

Least Squares Regression ◽

Content Type ◽

Environmental Threats ◽

Innovation Strategies ◽

The Impact ◽

The Relationship

Purpose The paper aims to study the relationship between executives’ perceptions of environmental threats and innovation strategies and investigate the moderating effect of contextual factor (i.e. organizational slack) on such relations. It proposes a dualistic relationship between executives’ perceptions of environmental threats and innovation strategies, in which different perceptions of environmental threats will lead to corresponding innovation strategies, and dyadic organizational slack can promote such processes. Design/methodology/approach The paper is based on a survey with 163 valid questionnaires, which were all completed by executives. Hierarchical ordinary least-squares regression analysis is used to test the hypotheses proposed in this paper. Findings The paper provides empirical insights about that executives tend to choose exploratory innovation when they perceive environmental changes as likely loss threats, yet adopt exploitative innovation when perceiving control-reducing threats. Furthermore, unabsorbed slack (e.g. financial redundancy) positively moderates both relationships, while absorbed slack (e.g. operational redundancy) merely positively influences the relationship between the perception of control-reducing threats and exploitative innovation. Originality/value The paper bridges the gap between organizational innovation and cognitive theory by proposing a dualistic relationship between executives’ perceptions of environmental threats and innovation strategies. The paper further enriches innovation studies by jointly considering both subjective and objective influence factors of innovation and argues that organizational slack can moderate such dualistic relationship.

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In VivoStudies Suggest that Induction of VanS-Dependent Vancomycin Resistance Requires Binding of the Drug to d-Ala-d-Ala Termini in the Peptidoglycan Cell Wall

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00523-13 ◽

2013 ◽

Vol 57 (9) ◽

pp. 4470-4480 ◽

Cited By ~ 29

Author(s):

Min Jung Kwun ◽

Gabriela Novotna ◽

Andrew R. Hesketh ◽

Lionel Hill ◽

Hee-Jeon Hong

Keyword(s):

Cell Wall ◽

Transcriptional Activation ◽

Streptomyces Coelicolor ◽

Constitutive Expression ◽

Transcriptional Response ◽

Vancomycin Resistance ◽

Content Type ◽

Expression Of Genes ◽

Peptidoglycan Cell Wall

ABSTRACTVanRS two-component regulatory systems are key elements required for the transcriptional activation of inducible vancomycin resistance genes in bacteria, but the precise nature of the ligand signal that activates these systems has remained undefined. Using the resistance system inStreptomyces coelicoloras a model, we have undertaken a series ofin vivostudies which indicate that the VanS sensor kinase in VanB-type resistance systems is activated by vancomycin in complex with thed-alanyl-d-alanine (d-Ala-d-Ala) termini of cell wall peptidoglycan (PG) precursors. Complementation of an essentiald-Ala-d-Ala ligase activity by constitutive expression ofvanAencoding a bifunctionald-Ala-d-Ala andd-alanyl-d-lactate (d-Ala-d-Lac) ligase activity allowed construction of strains that synthesized variable amounts of PG precursors containingd-Ala-d-Ala. Assays quantifying the expression of genes under VanRS control showed that the response to vancomycin in these strains correlated with the abundance ofd-Ala-d-Ala-containing PG precursors; strains producing a lower proportion of PG precursors terminating ind-Ala-d-Ala consistently exhibited a lower response to vancomycin. Pretreatment of wild-type cells with vancomycin or teicoplanin to saturate and mask thed-Ala-d-Ala binding sites in nascent PG also blocked the transcriptional response to subsequent vancomycin exposure, and desleucyl vancomycin, a vancomycin analogue incapable of interacting withd-Ala-d-Ala residues, failed to inducevangene expression. Activation of resistance by a vancomycin–d-Ala-d-Ala PG complex predicts a limit to the proportion of PG that can be derived from precursors terminating ind-Ala-d-Lac, a restriction also enforced by the bifunctional activity of the VanA ligase.

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New Aspects of RpoE in Uropathogenic Proteus mirabilis

Infection and Immunity ◽

10.1128/iai.02232-14 ◽

2014 ◽

Vol 83 (3) ◽

pp. 966-977 ◽

Cited By ~ 10

Author(s):

Ming-Che Liu ◽

Kuan-Ting Kuo ◽

Hsiung-Fei Chien ◽

Yi-Lin Tsai ◽

Shwu-Jen Liaw

Keyword(s):

Urinary Tract ◽

Virulence Factors ◽

Stress Responses ◽

Proteus Mirabilis ◽

Immune Cell ◽

Polymyxin B ◽

Urothelial Cells ◽

Cationic Antimicrobial Peptide ◽

Content Type ◽

Tract Infections

Proteus mirabilisis a common human pathogen causing recurrent or persistent urinary tract infections (UTIs). The underlying mechanisms forP. mirabilisto establish UTIs are not fully elucidated. In this study, we showed that loss of the sigma factor E (RpoE), mediating extracytoplasmic stress responses, decreased fimbria expression, survival in macrophages, cell invasion, and colonization in mice but increased the interleukin-8 (IL-8) expression of urothelial cells and swarming motility. This is the first study to demonstrate that RpoE modulated expression of MR/P fimbriae by regulatingmrpI, a gene encoding a recombinase controlling the orientation of MR/P fimbria promoter. By real-time reverse transcription-PCR, we found that the IL-8 mRNA amount of urothelial cells was induced significantly by lipopolysaccharides extracted fromrpoEmutant but not from the wild type. These RpoE-associated virulence factors should be coordinately expressed to enhance the fitness ofP. mirabilisin the host, including the avoidance of immune attacks. Accordingly,rpoEmutant-infected mice displayed more immune cell infiltration in bladders and kidneys during early stages of infection, and therpoEmutant had a dramatically impaired ability of colonization. Moreover, it is noteworthy that urea (the major component in urine) and polymyxin B (a cationic antimicrobial peptide) can induce expression ofrpoEby the reporter assay, suggesting that RpoE might be activated in the urinary tract. Altogether, our results indicate that RpoE is important in sensing environmental cues of the urinary tract and subsequently triggering the expression of virulence factors, which are associated with the fitness ofP. mirabilis, to build up a UTI.

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