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Isidro-Coxca MI, Ortiz-Jiménez S, Puente JL. Type 1 fimbria and P pili: regulatory mechanisms of the prototypical members of the chaperone-usher fimbrial family. Arch Microbiol 2024; 206:373. [PMID: 39127787 PMCID: PMC11316696 DOI: 10.1007/s00203-024-04092-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2024] [Revised: 07/18/2024] [Accepted: 07/27/2024] [Indexed: 08/12/2024]
Abstract
Adherence to both cellular and abiotic surfaces is a crucial step in the interaction of bacterial pathogens and commensals with their hosts. Bacterial surface structures known as fimbriae or pili play a fundamental role in the early colonization stages by providing specificity or tropism. Among the various fimbrial families, the chaperone-usher family has been extensively studied due to its ubiquity, diversity, and abundance. This family is named after the components that facilitate their biogenesis. Type 1 fimbria and P pilus, two chaperone-usher fimbriae associated with urinary tract infections, have been thoroughly investigated and serve as prototypes that have laid the foundations for understanding the biogenesis of this fimbrial family. Additionally, the study of the mechanisms regulating their expression has also been a subject of great interest, revealing that the regulation of the expression of the genes encoding these structures is a complex and diverse process, involving both common global regulators and those specific to each operon.
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Affiliation(s)
- María I Isidro-Coxca
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Mor, 62210, Mexico.
| | - Stephanie Ortiz-Jiménez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Mor, 62210, Mexico
| | - José L Puente
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Mor, 62210, Mexico.
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2
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Chen J, Dai W, Cui S, Lei W, Dai D. Screening of antigenic epitopes related to the adhesion of the avian Escherichia coli Type 1 Fimbrial Agglutinin Domain. BMC Vet Res 2023; 19:187. [PMID: 37789311 PMCID: PMC10546689 DOI: 10.1186/s12917-023-03742-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 09/15/2023] [Indexed: 10/05/2023] Open
Abstract
BACKGROUND Avian Escherichia coli (E.coli) type 1 fimbriae adhere to avian tracheal epithelial cells through the FimH protein. However, the adhesion-related antigen is still unknown. The purpose of this study was to analyze the antigenicity of the type 1 fimbrial FimH protein of wild-type avian E. coli, screen antigen epitopes, and prepare monoclonal antibodies (mAbs) that can block the adhesion of avian E. coli. RESULTS In this study, the nucleic acid homologies of MG2 (O11), TS12 (O18), and YR5 (O78) with K12 were 97.7%, 99.6%, and 97.7%, respectively, and the amino acid sequence similarity reached 98.7%, 99.3%, and 98.0%, respectively. The epitopes and hydrophilicities of the FimH proteins of these three strains were similar. The more obvious lectin domain epitopes were located at FimH protein positions 111-124 and 154-162. The mAbs 7C2 and 7D8 against these two epitopes were prepared. An adhesion inhibition test showed that 7C2 and 7D8 blocked bacterial adhesion to avian tracheal epithelial cells. The mAb 7C2 against the 111-124 epitope inhibited O78 strain adhesion by 93%, and the mAb 7D8 against the 154-162 epitope inhibited O78 strain adhesion by 49%, indicating that these two epitopes are closely related to the adhesion of type 1 fimbriae. However, only the 111-124 epitope-recognizing mAb 7C2 inhibited bacterial agglutination of erythrocytes, indicating that host cell receptor binding and erythrocyte agglutination are not mediated by the same spatial locations within the FimH protein. CONCLUSIONS The results demonstrate that the mAbs 7C2 and 7D8 against FimH protein positions 111-124 and 154-162 could inhibit the adhesion of E.coli to the chicken trachea.
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Affiliation(s)
- Junhong Chen
- School of Animal Science and Food Engineering, Jinling Institute of Technology, Nanjing, 210038, China
| | - Wei Dai
- School of Animal Science and Food Engineering, Jinling Institute of Technology, Nanjing, 210038, China
| | - Shengling Cui
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Weiqiang Lei
- School of Animal Science and Food Engineering, Jinling Institute of Technology, Nanjing, 210038, China
| | - Dingzhen Dai
- School of Animal Science and Food Engineering, Jinling Institute of Technology, Nanjing, 210038, China.
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Himpsl SD, Shea AE, Zora J, Stocki JA, Foreman D, Alteri CJ, Mobley HLT. The oxidative fumarase FumC is a key contributor for E. coli fitness under iron-limitation and during UTI. PLoS Pathog 2020; 16:e1008382. [PMID: 32106241 PMCID: PMC7064253 DOI: 10.1371/journal.ppat.1008382] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 03/10/2020] [Accepted: 02/05/2020] [Indexed: 01/17/2023] Open
Abstract
The energy required for a bacterium to grow and colonize the host is generated by metabolic and respiratory functions of the cell. Proton motive force, produced by these processes, drives cellular mechanisms including redox balance, membrane potential, motility, acid resistance, and the import and export of substrates. Previously, disruption of succinate dehydrogenase (sdhB) and fumarate reductase (frdA) within the oxidative and reductive tricarboxylic acid (TCA) pathways in uropathogenic E. coli (UPEC) CFT073 indicated that the oxidative, but not the reductive TCA pathway, is required for fitness in the urinary tract. Those findings led to the hypothesis that fumA and fumC encoding fumarase enzymes of the oxidative TCA cycle would be required for UPEC colonization, while fumB of the reductive TCA pathway would be dispensable. However, only UPEC strains lacking fumC had a fitness defect during experimental urinary tract infection (UTI). To further characterize the role of respiration in UPEC during UTI, additional mutants disrupting both the oxidative and reductive TCA pathways were constructed. We found that knock-out of frdA in the sdhB mutant strain background ameliorated the fitness defect observed in the bladder and kidneys for the sdhB mutant strain and results in a fitness advantage in the bladder during experimental UTI. The fitness defect was restored in the sdhBfrdA double mutant by complementation with frdABCD. Taken together, we demonstrate that it is not the oxidative or reductive pathway that is important for UPEC fitness per se, but rather only the oxidative TCA enzyme FumC. This fumarase lacks an iron-sulfur cluster and is required for UPEC fitness during UTI, most likely acting as a counter measure against exogenous stressors, especially in the iron-limited bladder niche.
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Affiliation(s)
- Stephanie D. Himpsl
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Allyson E. Shea
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Jonathan Zora
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Jolie A. Stocki
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Dannielle Foreman
- Department of Natural Sciences, University of Michigan Dearborn, Dearborn, Michigan, United States of America
| | - Christopher J. Alteri
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- Department of Natural Sciences, University of Michigan Dearborn, Dearborn, Michigan, United States of America
- * E-mail:
| | - Harry L. T. Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
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Flexible Metabolism and Suppression of Latent Enzymes Are Important for Escherichia coli Adaptation to Diverse Environments within the Host. J Bacteriol 2019; 201:JB.00181-19. [PMID: 31160397 DOI: 10.1128/jb.00181-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 05/27/2019] [Indexed: 12/13/2022] Open
Abstract
Bacterial metabolism is necessary for adaptation to the host microenvironment. Flexible metabolic pathways allow uropathogenic Escherichia coli (UPEC) to harmlessly reside in the human intestinal tract and cause disease upon extraintestinal colonization. E. coli intestinal colonization requires carbohydrates as a carbon source, while UPEC extraintestinal colonization requires gluconeogenesis and the tricarboxylic acid cycle. UPEC containing disruptions in two irreversible glycolytic steps involving 6-carbon (6-phosphofructokinase; pfkA) and 3-carbon (pyruvate kinase; pykA) substrates have no fitness defect during urinary tract infection (UTI); however, both reactions are catalyzed by isozymes: 6-phosphofructokinases Pfk1 and Pfk2, encoded by pfkA and pfkB, and pyruvate kinases Pyk II and Pyk I, encoded by pykA and pykF UPEC strains lacking one or both phosphofructokinase-encoding genes (pfkB and pfkA pfkB) and strains lacking one or both pyruvate kinase genes (pykF and pykA pykF) were investigated to determine their regulatory roles in carbon flow during glycolysis by examining their fitness during UTI and in vitro growth requirements. Loss of a single phosphofructokinase-encoding gene has no effect on fitness, while the pfkA pfkB double mutant outcompeted the parental strain in the bladder. A defect in bladder and kidney colonization was observed with loss of pykF, while loss of pykA resulted in a fitness advantage. The pykA pykF mutant was indistinguishable from wild-type in vivo, suggesting that the presence of Pyk II rather than the loss of Pyk I itself is responsible for the fitness defect in the pykF mutant. These findings suggest that E. coli suppresses latent enzymes to survive in the host urinary tract.IMPORTANCE Urinary tract infections are the most frequently diagnosed urologic disease, with uropathogenic Escherichia coli (UPEC) infections placing a significant financial burden on the health care system by generating more than two billion dollars in annual costs. This, in combination with steadily increasing antibiotic resistances to present day treatments, necessitates the discovery of new antimicrobial agents to combat these infections. By broadening our scope beyond the study of virulence properties and investigating bacterial physiology and metabolism, we gain a better understanding of how pathogens use nutrients and compete within host microenvironments, enabling us to cultivate new therapeutics to exploit and target pathogen growth requirements in a specific host environment.
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Comprehensive Identification of Fim-Mediated Inversions in Uropathogenic Escherichia coli with Structural Variation Detection Using Relative Entropy. mSphere 2019; 4:4/2/e00693-18. [PMID: 30971446 PMCID: PMC6458436 DOI: 10.1128/msphere.00693-18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UTI is a common ailment that affects more than half of all women during their lifetime. The leading cause of UTIs is UPEC, which relies on type 1 pili to colonize and persist within the bladder during infection. The regulation of type 1 pili is remarkable for an epigenetic mechanism in which a section of DNA containing a promoter is inverted. The inversion mechanism relies on what are thought to be dedicated recombinase genes; however, the full repertoire for these recombinases is not known. We show here that there are no additional targets beyond those already identified for the recombinases in the entire genome of two UPEC strains, arguing that type 1 pilus expression itself is the driving evolutionary force for the presence of these recombinase genes. This further suggests that targeting the type 1 pilus is a rational alternative nonantibiotic strategy for the treatment of UTI. Most urinary tract infections (UTIs) are caused by uropathogenic Escherichia coli (UPEC), which depends on an extracellular organelle (type 1 pili) for adherence to bladder cells during infection. Type 1 pilus expression is partially regulated by inversion of a piece of DNA referred to as fimS, which contains the promoter for the fim operon encoding type 1 pili. fimS inversion is regulated by up to five recombinases collectively known as Fim recombinases. These Fim recombinases are currently known to regulate two other switches: the ipuS and hyxS switches. A long-standing question has been whether the Fim recombinases regulate the inversion of other switches, perhaps to coordinate expression for adhesion or virulence. We answered this question using whole-genome sequencing with a newly developed algorithm (structural variation detection using relative entropy [SVRE]) for calling structural variations using paired-end short-read sequencing. SVRE identified all of the previously known switches, refining the specificity of which recombinases act at which switches. Strikingly, we found no new inversions that were mediated by the Fim recombinases. We conclude that the Fim recombinases are each highly specific for a small number of switches. We hypothesize that the unlinked Fim recombinases have been recruited to regulate fimS, and fimS only, as a secondary locus; this further implies that regulation of type 1 pilus expression (and its role in gastrointestinal and/or genitourinary colonization) is important enough, on its own, to influence the evolution and maintenance of multiple additional genes within the accessory genome of E. coli. IMPORTANCE UTI is a common ailment that affects more than half of all women during their lifetime. The leading cause of UTIs is UPEC, which relies on type 1 pili to colonize and persist within the bladder during infection. The regulation of type 1 pili is remarkable for an epigenetic mechanism in which a section of DNA containing a promoter is inverted. The inversion mechanism relies on what are thought to be dedicated recombinase genes; however, the full repertoire for these recombinases is not known. We show here that there are no additional targets beyond those already identified for the recombinases in the entire genome of two UPEC strains, arguing that type 1 pilus expression itself is the driving evolutionary force for the presence of these recombinase genes. This further suggests that targeting the type 1 pilus is a rational alternative nonantibiotic strategy for the treatment of UTI.
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Temporal Regulation of fim Genes in Uropathogenic Escherichia coli during Infection of the Murine Urinary Tract. J Pathog 2017; 2017:8694356. [PMID: 29445547 PMCID: PMC5763102 DOI: 10.1155/2017/8694356] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 11/28/2017] [Accepted: 12/07/2017] [Indexed: 11/17/2022] Open
Abstract
Uropathogenic Escherichia coli (UPEC) adhere to cells in the human urinary tract via type 1 pili that undergo phase variation where a 314-bp fimS DNA element flips between Phase-ON and Phase-OFF orientations through two site-specific recombinases, FimB and FimE. Three fim-lux operon transcriptional fusions were created and moved into the clinical UPEC isolate NU149 to determine their temporal regulation in UPEC growing in the urinary tract. Within murine urinary tracts, the UPEC strains demonstrated elevated transcription of fimA and fimB early in the infection, but lower transcription by the fifth day in murine kidneys. In contrast, fimE transcription was much lower than either fimA or fimB early, increased markedly at 24 h after inoculation, and then dropped five days after inoculation. Positioning of fimS was primarily in the Phase-ON position over the time span in UPEC infected bladders, whereas in UPEC infected murine kidneys the Phase-OFF orientation was favored by the fifth day after inoculation. Hemagglutination titers with guinea pig erythrocytes remained constant in UPEC growing in infected murine bladders but fell substantially in UPEC infected kidneys over time. Our results show temporal in vivo regulation of fim gene expression in different environmental niches when UPEC infects the murine urinary tract.
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Abstract
Escherichia coli is the most common Gram-negative bacillary organism causing meningitis, and E. coli meningitis continues to be an important cause of mortality and morbidity throughout the world. Our incomplete knowledge of its pathogenesis contributes to such mortality and morbidity. Recent reports of E. coli strains producing CTX-M-type or TEM-type extended-spectrum β-lactamases create a challenge. Studies using in vitro and in vivo models of the blood-brain barrier have shown that E. coli meningitis follows a high degree of bacteremia and invasion of the blood-brain barrier. E. coli invasion of the blood-brain barrier, the essential step in the development of E. coli meningitis, requires specific microbial and host factors as well as microbe- and host-specific signaling molecules. Blockade of such microbial and host factors contributing to E. coli invasion of the blood-brain barrier is shown to be efficient in preventing E. coli penetration into the brain. The basis for requiring a high degree of bacteremia for E. coli penetration of the blood-brain barrier, however, remains unclear. Continued investigation on the microbial and host factors contributing to a high degree of bacteremia and E. coli invasion of the blood-brain barrier is likely to identify new targets for prevention and therapy of E. coli meningitis.
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Harbaugh SV, Goodson MS, Dillon K, Zabarnick S, Kelley-Loughnane N. Riboswitch-Based Reversible Dual Color Sensor. ACS Synth Biol 2017; 6:766-781. [PMID: 28121427 DOI: 10.1021/acssynbio.6b00199] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Riboswitches are RNA-based "sensors" that utilize chemically induced structural changes in the 5'-untranslated region of mRNA to regulate expression of downstream genes. Coupling a specific riboswitch with a reporter gene system translates chemical detection by the cell into a quantifiable reporter protein signal. For the majority of reporter gene systems, the readout signal is only expressed in the presence of the target analyte. This makes it difficult to determine the viability and localization of the uninduced biosensor when it is used for "real-word" applications. To address this problem, we developed a dual-color reporter comprising elements of the E. coli fimbriae phase variation system: recombinase FimE controlled by a synthetic riboswitch and an invertible DNA segment (fimS) containing a constitutively active promoter placed between two fluorescent protein genes. Without an analyte, the fluorescent reporter constitutively expressed green fluorescent protein (GFPa1). Addition of the analyte initiated translation of fimE causing unidirectional inversion of the fimS segment and constitutive expression of red fluorescent protein (mKate2). Thus, the sensor is always fluorescent, but its color is determined by detection of a specific analyte. We demonstrate that the recombinase-based dual-color reporter can be successfully applied to monitor the activation of a theophylline synthetic riboswitch that was used as our model system. To show the feasibility of the FimE recombinase-based system to serve as a reporter for monitoring activation of multiple synthetic riboswitches and, therefore, expand the applicability of the system, we tested a number of previously developed synthetic riboswitches responsive to different analytes. We show that the dual-color reporter system can be successfully used to monitor activation of M6 and M6″ riboswitches responsive to ammeline and pyrimido[4,5-d]pyrimidine-2,4-diamine, respectively, and a 2,4,6-trinitrotoluene-responsive riboswitch developed in this study. We also demonstrate that the system can be reversed by HbiF recombinase-mediated fimS inversion to the initial state of the fluorescent reporter, creating a resettable and reusable cell-based sensor.
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Affiliation(s)
- Svetlana V. Harbaugh
- 711th
Human Performance Wing, Airman Systems Directorate, Air Force Research
Laboratory, Wright-Patterson Air Force Base, Wright-Patterson AFB, Ohio 45433, United States
- The Henry M. Jackson Foundation, 6720A Rockledge Drive, Bethesda, Maryland 20817, United States
| | - Michael S. Goodson
- 711th
Human Performance Wing, Airman Systems Directorate, Air Force Research
Laboratory, Wright-Patterson Air Force Base, Wright-Patterson AFB, Ohio 45433, United States
- UES, Inc., 4401 Dayton-Xenia
Road, Dayton, Ohio 45432, United States
| | - Kateri Dillon
- 711th
Human Performance Wing, Airman Systems Directorate, Air Force Research
Laboratory, Wright-Patterson Air Force Base, Wright-Patterson AFB, Ohio 45433, United States
| | - Sarah Zabarnick
- 711th
Human Performance Wing, Airman Systems Directorate, Air Force Research
Laboratory, Wright-Patterson Air Force Base, Wright-Patterson AFB, Ohio 45433, United States
| | - Nancy Kelley-Loughnane
- 711th
Human Performance Wing, Airman Systems Directorate, Air Force Research
Laboratory, Wright-Patterson Air Force Base, Wright-Patterson AFB, Ohio 45433, United States
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9
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The UbiI (VisC) Aerobic Ubiquinone Synthase Is Required for Expression of Type 1 Pili, Biofilm Formation, and Pathogenesis in Uropathogenic Escherichia coli. J Bacteriol 2016; 198:2662-72. [PMID: 27161114 DOI: 10.1128/jb.00030-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 05/04/2016] [Indexed: 01/03/2023] Open
Abstract
UNLABELLED Uropathogenic Escherichia coli (UPEC), which causes the majority of urinary tract infections (UTI), uses pilus-mediated adherence to initiate biofilm formation in the urinary tract. Oxygen gradients within E. coli biofilms regulate expression and localization of adhesive type 1 pili. A transposon mutant screen for strains defective in biofilm formation identified the ubiI (formerly visC) aerobic ubiquinone synthase gene as critical for UPEC biofilm formation. In this study, we characterized a nonpolar ubiI deletion mutant and compared its behavior to that of wild-type bacteria grown under aerobic and anoxic conditions. Consistent with its function as an aerobic ubiquinone-8 synthase, deletion of ubiI in UPEC resulted in reduced membrane potential, diminished motility, and reduced expression of chaperone-usher pathway pili. Loss of aerobic respiration was previously shown to negatively impact expression of type 1 pili. To determine whether this reduction in type 1 pili was due to an energy deficit, wild-type UPEC and the ubiI mutant were compared for energy-dependent phenotypes under anoxic conditions, in which quinone synthesis is undertaken by anaerobic quinone synthases. Under anoxic conditions, the two strains exhibited wild-type levels of motility but produced diminished numbers of type 1 pili, suggesting that the reduction of type 1 pilus expression in the absence of oxygen is not due to a cellular energy deficit. Acute- and chronic-infection studies in a mouse model of UTI revealed a significant virulence deficit in the ubiI mutant, indicating that UPEC encounters enough oxygen in the bladder to induce aerobic ubiquinone synthesis during infection. IMPORTANCE The majority of urinary tract infections are caused by uropathogenic E. coli, a bacterium that can respire in the presence and absence of oxygen. The bladder environment is hypoxic, with oxygen concentrations ranging from 4% to 7%, compared to 21% atmospheric oxygen. This work provides evidence that aerobic ubiquinone synthesis must be engaged during bladder infection, indicating that UPEC bacteria sense and use oxygen as a terminal electron acceptor in the bladder and that this ability drives infection potential despite the fact that UPEC is a facultative anaerobe.
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Sarkar S, Roberts LW, Phan MD, Tan L, Lo AW, Peters KM, Paterson DL, Upton M, Ulett GC, Beatson SA, Totsika M, Schembri MA. Comprehensive analysis of type 1 fimbriae regulation in fimB-null strains from the multidrug resistant Escherichia coli ST131 clone. Mol Microbiol 2016; 101:1069-87. [PMID: 27309594 DOI: 10.1111/mmi.13442] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2016] [Indexed: 12/17/2022]
Abstract
Uropathogenic Escherichia coli (UPEC) of sequence type 131 (ST131) are a pandemic multidrug resistant clone associated with urinary tract and bloodstream infections. Type 1 fimbriae, a major UPEC virulence factor, are essential for ST131 bladder colonization. The globally dominant sub-lineage of ST131 strains, clade C/H30-R, possess an ISEc55 insertion in the fimB gene that controls phase-variable type 1 fimbriae expression via the invertible fimS promoter. We report that inactivation of fimB in these strains causes altered regulation of type 1 fimbriae expression. Using a novel read-mapping approach based on Illumina sequencing, we demonstrate that 'off' to 'on' fimS inversion is reduced in these strains and controlled by recombinases encoded by the fimE and fimX genes. Unlike typical UPEC strains, the nucleoid-associated H-NS protein does not strongly repress fimE transcription in clade C ST131 strains. Using a genetic screen to identify novel regulators of fimE and fimX in the clade C ST131 strain EC958, we defined a new role for the guaB gene in the regulation of type 1 fimbriae and in colonisation of the mouse bladder. Our results provide a comprehensive analysis of type 1 fimbriae regulation in ST131, and highlight important differences in its control compared to non-ST131 UPEC.
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Affiliation(s)
- Sohinee Sarkar
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, 4059, Australia
| | - Leah W Roberts
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Minh-Duy Phan
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Lendl Tan
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Alvin W Lo
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Kate M Peters
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - David L Paterson
- Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Royal Brisbane and Women's Hospital, University of Queensland Centre for Clinical Research, Brisbane, Queensland, 4029, Australia
| | - Mathew Upton
- Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, PL4 8AA, UK
| | - Glen C Ulett
- School of Medical Science, Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, 4222, Australia
| | - Scott A Beatson
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.
| | - Makrina Totsika
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, 4059, Australia.
| | - Mark A Schembri
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.
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Zhang H, Susanto TT, Wan Y, Chen SL. Comprehensive mutagenesis of the fimS promoter regulatory switch reveals novel regulation of type 1 pili in uropathogenic Escherichia coli. Proc Natl Acad Sci U S A 2016; 113:4182-7. [PMID: 27035967 PMCID: PMC4839427 DOI: 10.1073/pnas.1522958113] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Type 1 pili (T1P) are major virulence factors for uropathogenic Escherichia coli (UPEC), which cause both acute and recurrent urinary tract infections. T1P expression therefore is of direct relevance for disease. T1P are phase variable (both piliated and nonpiliated bacteria exist in a clonal population) and are controlled by an invertible DNA switch (fimS), which contains the promoter for the fim operon encoding T1P. Inversion of fimS is stochastic but may be biased by environmental conditions and other signals that ultimately converge at fimS itself. Previous studies of fimS sequences important for T1P phase variation have focused on laboratory-adapted E coli strains and have been limited in the number of mutations or by alteration of the fimS genomic context. We surmounted these limitations by using saturating genomic mutagenesis of fimS coupled with accurate sequencing to detect both mutations and phase status simultaneously. In addition to the sequences known to be important for biasing fimS inversion, our method also identifies a previously unknown pair of 5' UTR inverted repeats that act by altering the relative fimA levels to control phase variation. Thus we have uncovered an additional layer of T1P regulation potentially impacting virulence and the coordinate expression of multiple pilus systems.
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Affiliation(s)
- Huibin Zhang
- Infectious Diseases Group, Genome Institute of Singapore, Singapore 138672
| | - Teodorus T Susanto
- Stem Cell and Development, Genome Institute of Singapore, Singapore 138672
| | - Yue Wan
- Stem Cell and Development, Genome Institute of Singapore, Singapore 138672
| | - Swaine L Chen
- Infectious Diseases Group, Genome Institute of Singapore, Singapore 138672; Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119074
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12
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Fernandez-Rodriguez J, Yang L, Gorochowski TE, Gordon DB, Voigt CA. Memory and Combinatorial Logic Based on DNA Inversions: Dynamics and Evolutionary Stability. ACS Synth Biol 2015; 4:1361-72. [PMID: 26548807 DOI: 10.1021/acssynbio.5b00170] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Genetic memory can be implemented using enzymes that catalyze DNA inversions, where each orientation corresponds to a "bit". Here, we use two DNA invertases (FimE and HbiF) that reorient DNA irreversibly between two states with opposite directionality. First, we construct memory that is set by FimE and reset by HbiF. Next, we build a NOT gate where the input promoter drives FimE and in the absence of signal the reverse state is maintained by the constitutive expression of HbiF. The gate requires ∼3 h to turn on and off. The evolutionary stabilities of these circuits are measured by passaging cells while cycling function. The memory switch is stable over 400 h (17 days, 14 state changes); however, the gate breaks after 54 h (>2 days) due to continuous invertase expression. Genome sequencing reveals that the circuit remains intact, but the host strain evolves to reduce invertase expression. This work highlights the need to evaluate the evolutionary robustness and failure modes of circuit designs, especially as more complex multigate circuits are implemented.
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Affiliation(s)
- Jesus Fernandez-Rodriguez
- Synthetic
Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Lei Yang
- Synthetic
Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Thomas E. Gorochowski
- Synthetic
Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - D. Benjamin Gordon
- Synthetic
Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Broad
Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Christopher A. Voigt
- Synthetic
Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Broad
Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
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13
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Abstract
ABSTRACT
Type 1 fimbriae of
E. coli
, a chaperon-usher bacterial adhesin, are synthesized by the majority of strains of the bacterium. Although frequently produced by commensal strains, the adhesin is nevertheless a virulence factor in Extraintestinal Pathogenic
E. coli
(ExPEC). The role of the adhesin in pathogenesis is best understood in Uropathogenic
E. coli
(UPEC). Host attachment and invasion by type 1 fimbriate bacteria activates inflammatory pathways, with TLR4 signaling playing a predominant role. In a mouse model of cystitis, type 1 fimbriation not only enhances UPEC adherence to the surface of superficial umbrella cells of the bladder urothelium, but is both necessary and sufficient for their invasion. Moreover the adhesin plays a role in the formation of transient intracellular bacterial communities (IBCs) within the cytoplasm of urothelial cells as part of UPEC cycles of invasion. The expression of type 1 fimbriation is controlled by phase variation at the transcriptional level, a mode of gene regulation in which bacteria switch reversibly between fimbriate and afimbriate phases. Phase variation has been widely considered to be a mechanism enabling immune evasion. Notwithstanding the apparently random nature of phase variation, switching of type 1 fimbrial expression is nevertheless controlled by a range of environmental signals that include the amino sugars sialic acid and N-acetylglucosamine (GlcNAc). Sialic acid plays a pivotal role in innate immunity, including signaling by the toll-like receptors. Here how sialic acid and GlcNAc control type 1 fimbriation is described and the potential significance of this regulatory response is discussed.
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14
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Yang L, Nielsen AAK, Fernandez-Rodriguez J, McClune CJ, Laub MT, Lu TK, Voigt CA. Permanent genetic memory with >1-byte capacity. Nat Methods 2014; 11:1261-6. [PMID: 25344638 PMCID: PMC4245323 DOI: 10.1038/nmeth.3147] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 09/23/2014] [Indexed: 12/20/2022]
Abstract
Genetic memory enables the recording of information in the DNA of living cells. Memory can record a transient environmental signal or cell state that is then recalled at a later time. Permanent memory is implemented using irreversible recombinases that invert the orientation of a unit of DNA, corresponding to the [0,1] state of a bit. To expand the memory capacity, we have applied bioinformatics to identify 34 phage integrases (and their cognate attB and attP recognition sites), from which we build 11 memory switches that are perfectly orthogonal to each other and the FimE and HbiF bacterial invertases. Using these switches, a memory array is constructed in Escherichia coli that can record 1.375 bytes of information. It is demonstrated that the recombinases can be layered and used to permanently record the transient state of a transcriptional logic gate.
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Affiliation(s)
- Lei Yang
- Synthetic Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Alec A K Nielsen
- Synthetic Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Jesus Fernandez-Rodriguez
- Synthetic Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Conor J McClune
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Timothy K Lu
- 1] Synthetic Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. [2] Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Christopher A Voigt
- Synthetic Biology Center, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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15
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Chen YW, Teng CH, Ho YH, Jessica Ho TY, Huang WC, Hashimoto M, Chiang IY, Chen CS. Identification of bacterial factors involved in type 1 fimbria expression using an Escherichia coli K12 proteome chip. Mol Cell Proteomics 2014; 13:1485-94. [PMID: 24692643 DOI: 10.1074/mcp.m113.035667] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type 1 fimbriae are filamentous structures on Escherichia coli. These structures are important adherence factors. Because binding to the host cells is the first step of infection, type 1 fimbria is an important virulence factor of pathogenic E. coli. Expression of type 1 fimbria is regulated by a phase variation in which each individual bacterium can alternate between fimbriated (phase-ON) and nonfimbriated (phase-OFF) states. The phase variation is regulated by the flipping of the 314-bp fimS fragment, which contains the promoter driving the expression of the genes required for the synthesis of type 1 fimbria. Thus, the bacterial proteins able to interact with fimS are likely to be involved in regulating the expression of type 1 fimbria. To identify novel type 1 fimbria-regulating factors, we used an E. coli K12 proteome chip to screen for the bacterial factors able to interact with a 602-bp DNA fragment containing fimS and its adjacent regions. The Spr protein was identified by the proteome chip-based screening and further confirmed to be able to interact with fimS by electrophoretic mobility shift assay. Deletion of spr in the neonatal meningitis E. coli strain RS218 significantly increased the ratio of the bacterial colonies that contained the type 1 fimbria phase-ON cells on agar plates. In addition, Spr interfered with the interactions of fimS with the site-specific recombinases, FimB and FimE, which are responsible for mediating the flipping of fimS. These results suggest that Spr is involved in the regulation of type 1 fimbria expression through direct interaction with the invertible element fimS. These findings facilitate our understanding of the regulation of type 1 fimbria.
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Affiliation(s)
- Yi-Wen Chen
- From the ‡Graduate Institute of Systems Biology and Bioinformatics, National Central University, Jhongli City, Taiwan
| | - Ching-Hao Teng
- §Institute of Molecular Medicine, National Cheng Kung University Medical College, Tainan City, Taiwan; ¶Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City, Taiwan; ‖Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan City, Taiwan
| | - Yu-Hsuan Ho
- From the ‡Graduate Institute of Systems Biology and Bioinformatics, National Central University, Jhongli City, Taiwan
| | - Tien Yu Jessica Ho
- From the ‡Graduate Institute of Systems Biology and Bioinformatics, National Central University, Jhongli City, Taiwan
| | - Wen-Chun Huang
- ¶Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City, Taiwan
| | - Masayuki Hashimoto
- §Institute of Molecular Medicine, National Cheng Kung University Medical College, Tainan City, Taiwan; ‖Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan City, Taiwan
| | - I-Yuan Chiang
- **Department of Nutrition and Health Sciences, Kainan University. No. 1, Kainan Road, Luzhu Township, Taoyuan Country, Taiwan
| | - Chien-Sheng Chen
- From the ‡Graduate Institute of Systems Biology and Bioinformatics, National Central University, Jhongli City, Taiwan;
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16
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Abstract
The phase variation (reversible on-off switching) of the type 1 fimbrial adhesin of Escherichia coli involves a DNA inversion catalyzed by FimB (switching in either direction) or FimE (on-to-off switching). Here, we demonstrate that RfaH activates expression of a FimB-LacZ protein fusion while having a modest inhibitory effect on a comparable fimB-lacZ operon construct and on a FimE-LacZ protein fusion, indicating that RfaH selectively controls fimB expression at the posttranscriptional level. Further work demonstrates that loss of RfaH enables small RNA (sRNA) MicA inhibition of fimB expression even in the absence of exogenous inducing stress. This effect is explained by induction of σ(E), and hence MicA, in the absence of RfaH. Additional work confirms that the procaine-dependent induction of micA requires OmpR, as reported previously (A. Coornaert et al., Mol. Microbiol. 76:467-479, 2010, doi:10.1111/j.1365-2958.2010.07115.x), but also demonstrates that RfaH inhibition of fimB transcription is enhanced by procaine independently of OmpR. While the effect of procaine on fimB transcription is shown to be independent of RcsB, it was found to require SlyA, another known regulator of fimB transcription. These results demonstrate a complex role for RfaH as a regulator of fimB expression.
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17
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FimY does not interfere with FimZ-FimW interaction during type 1 fimbria production by Salmonella enterica serovar Typhimurium. Infect Immun 2013; 81:4453-60. [PMID: 24042120 DOI: 10.1128/iai.00795-13] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The production of type 1 fimbriae in Salmonella enterica serovar Typhimurium is controlled, in part, by three proteins, FimZ, FimY, and FimW. Amino acid sequence analysis indicates that FimZ belongs to the family of bacterial response regulators of two-component systems. In these studies, we have demonstrated that introducing a mutation mimicking phosphorylation of FimZ is necessary for activation of its target gene, fimA. In addition, the interaction of FimZ with FimW, a repressor of fimA expression, occurs only when FimZ is phosphorylated. Consequently, the negative regulatory effect of FimW is most likely due to downmodulation of the active FimZ protein. FimY does not appear to function as a response regulator, and its activity can be lost by mimicking the phosphorylation of FimY. Overproduction of FimY cannot alleviate the nonfimbriate phenotype in a FimZ mutant, whereas high levels of FimZ can overcome the nonfimbriate phenotype of a FimY mutant. It appears that FimY acts upstream of FimZ to activate fimA expression.
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18
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Bateman SL, Stapleton AE, Stamm WE, Hooton TM, Seed PC. The type 1 pili regulator gene fimX and pathogenicity island PAI-X as molecular markers of uropathogenic Escherichia coli. MICROBIOLOGY-SGM 2013; 159:1606-1617. [PMID: 23744903 DOI: 10.1099/mic.0.066472-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Uropathogenic Escherichia coli (UPEC) fall within a larger group of isolates producing extraintestinal disease. UPEC express type 1 pili as a critical virulence determinant mediating adherence to and invasion into urinary tract tissues. Type 1 pili expression is under regulation by a family of site-specific recombinases, including FimX, which is encoded from a genomic island called PAI-X for pathogenicity island of FimX. Using a new multiplex PCR, fimX and the additional PAI-X genes were found to be highly associated with UPEC (144/173 = 83.2 %), and more prevalent in UPEC of lower urinary tract origin (105/120 = 87.5 %) than upper urinary tract origin (39/53 = 74 %; P<0.05) or commensal isolates (28/78 = 36 %; P≤0.0001). The Fim-like recombinase gene fimX is the only family member that has a significant association with UPEC compared to commensal isolates. Our results indicate PAI-X genes, including the type 1 pili regulator gene fimX, are highly prevalent among UPEC isolates and have a strong positive correlation with genomic virulence factors, suggesting a potential role for PAI-X in the extraintestinal pathogenic E. coli lifestyle.
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Affiliation(s)
- Stacey L Bateman
- Center for Microbial Pathogenesis, Duke University School of Medicine, Durham, NC 27710, USA.,Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Ann E Stapleton
- Department of Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Walter E Stamm
- Deceased.,Department of Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Thomas M Hooton
- Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33146, USA
| | - Patrick C Seed
- Department of Pediatrics, Duke University School of Medicine, Durham, NC 27710, USA.,Center for Microbial Pathogenesis, Duke University School of Medicine, Durham, NC 27710, USA.,Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA
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19
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Prc contributes to Escherichia coli evasion of classical complement-mediated serum killing. Infect Immun 2012; 80:3399-409. [PMID: 22825444 DOI: 10.1128/iai.00321-12] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Escherichia coli is a common Gram-negative organism that causes bacteremia. Prc, a bacterial periplasmic protease, and its homologues are known to be involved in the pathogenesis of Gram-negative bacterial infections. The present study examined the role of Prc in E. coli bacteremia and characterized the ability of the prc mutant of the pathogenic E. coli strain RS218 to cause bacteremia and survive in human serum. The prc mutant of RS218 exhibited a decreased ability to cause a high level of bacteremia and was more sensitive to serum killing than strain RS218. This sensitivity was due to the mutant's decreased ability to avoid the activation of the antibody-dependent and -independent classical complement cascades as well as its decreased resistance to killing mediated by the membrane attack complex, the end product of complement system activation. The demonstration of Prc in the evasion of classical complement-mediated serum killing of pathogenic E. coli makes this factor a potential target for the development of therapeutic and preventive measures against E. coli bacteremia.
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20
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NlpI facilitates deposition of C4bp on Escherichia coli by blocking classical complement-mediated killing, which results in high-level bacteremia. Infect Immun 2012; 80:3669-78. [PMID: 22802341 DOI: 10.1128/iai.00320-12] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Neonatal meningitis Escherichia coli (NMEC) is the most common Gram-negative organism that is associated with neonatal meningitis, which usually develops as a result of hematogenous spread of the bacteria. There are two key pathogenesis processes for NMEC to penetrate into the brain, the essential step for the development of E. coli meningitis: a high-level bacteremia and traversal of the blood-brain barrier (BBB). Our previous study has shown that the bacterial outer membrane protein NlpI contributes to NMEC binding to and invasion of brain microvascular endothelial cells, the major component cells of the BBB, suggesting a role for NlpI in NMEC crossing of the BBB. In this study, we showed that NlpI is involved in inducing a high level of bacteremia. In addition, NlpI contributed to the recruitment of the complement regulator C4bp to the surface of NMEC to evade serum killing, which is mediated by the classical complement pathway. NlpI may be involved in the interaction between C4bp and OmpA, which is an outer membrane protein that directly interacts with C4bp on the bacterial surface. The involvement of NlpI in two key pathogenesis processes of NMEC meningitis may make this bacterial factor a potential target for prevention and therapy of E. coli meningitis.
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21
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Bateman SL, Seed PC. Epigenetic regulation of the nitrosative stress response and intracellular macrophage survival by extraintestinal pathogenic Escherichia coli. Mol Microbiol 2012; 83:908-25. [PMID: 22221182 DOI: 10.1111/j.1365-2958.2012.07977.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Extraintestinal pathogenic Escherichia coli (ExPEC) reside in the enteric tract as a commensal reservoir, but can transition to a pathogenic state by invading normally sterile niches, establishing infection and disseminating to invasive sites like the bloodstream. Macrophages are required for ExPEC dissemination, suggesting the pathogen has developed mechanisms to persist within professional phagocytes. Here, we report that FimX, an ExPEC-associated DNA invertase that regulates the major virulence factor type 1 pili (T1P), is also an epigenetic regulator of a LuxR-like response regulator HyxR. FimX regulated hyxR expression through bidirectional phase inversion of its promoter region at sites different from the type 1 pili promoter and independent of integration host factor (IHF). In vitro, transition from high to low HyxR expression produced enhanced tolerance of reactive nitrogen intermediates (RNIs), primarily through de-repression of hmpA, encoding a nitric oxide-detoxifying flavohaemoglobin. However, in the macrophage, HyxR produced large effects on intracellular survival in the presence and absence of RNI and independent of Hmp. Collectively, we have shown that the ability of ExPEC to survive in macrophages is contingent upon the proper transition from high to low HyxR expression through epigenetic regulatory control by FimX.
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Affiliation(s)
- Stacey L Bateman
- Department of Molecular Genetics and Microbiology Center for Microbial Pathogenesis Department of Pediatrics, Duke University School of Medicine, Durham, NC 27710, USA
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22
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Abstract
Uropathogenic Escherichia coli (UPEC) is the leading cause of urinary tract infections in women, causing significant morbidity and mortality in this population. Adherence to host epithelial cells is a pivotal step in the pathogenesis of UPEC. One of the most important virulence factors involved in mediating this attachment is the type 1 pilus (type 1 fimbria) encoded by a set of fim genes arranged in an operon. The expression of type 1 pili is controlled by a phenomenon known as phase variation, which reversibly switches between the expression of type 1 pili (Phase-ON) and loss of expression (Phase-OFF). Phase-ON cells have the promoter for the fimA structural gene on an invertible DNA element called fimS, which lines up to allow transcription, whereas transcription of the structural gene is silenced in Phase-OFF cells. The orientation of the fimS invertible element is controlled by two site-specific recombinases, FimB and FimE. Environmental conditions cause transcriptional and post-transcriptional changes in UPEC cells that affect the level of regulatory proteins, which in turn play vital roles in modulating this phase switching ability. The role of fim gene regulation in UPEC pathogenesis will be discussed.
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23
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Hcp family proteins secreted via the type VI secretion system coordinately regulate Escherichia coli K1 interaction with human brain microvascular endothelial cells. Infect Immun 2011; 80:1243-51. [PMID: 22184413 DOI: 10.1128/iai.05994-11] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Type VI secretion systems (T6SSs) are involved in the pathogenicity of several gram-negative bacteria. Based on sequence analysis, we found that a cluster of Escherichia coli virulence factors (EVF) encoding a putative T6SS exists in the genome of the meningitis-causing E. coli K1 strain RS218. The T6SS-associated deletion mutants exhibited significant defects in binding to and invasion of human brain microvascular endothelial cells (HBMEC) compared with the parent strain. Hcp family proteins (the hallmark of T6SS), including Hcp1 and Hcp2, were localized in the bacterial outer membrane, but the involvements of Hcp1 and Hcp2 have been shown to differ in E. coli-HBMEC interaction. The deletion mutant of hcp2 showed defects in the bacterial binding to and invasion of HBMEC, while Hcp1 was secreted in a T6SS-dependent manner and induced actin cytoskeleton rearrangement, apoptosis, and the release of interleukin-6 (IL-6) and IL-8 in HBMEC. These findings demonstrate that the T6SS is functional in E. coli K1, and two Hcp family proteins participate in different steps of E. coli interaction with HBMEC in a coordinate manner, e.g., binding to and invasion of HBMEC, the cytokine and chemokine release followed by cytoskeleton rearrangement, and apoptosis in HBMEC. This is the first demonstration of the role of T6SS in meningitis-causing E. coli K1, and T6SS-associated Hcp family proteins are likely to contribute to the pathogenesis of E. coli meningitis.
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24
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Totsika M, Beatson SA, Sarkar S, Phan MD, Petty NK, Bachmann N, Szubert M, Sidjabat HE, Paterson DL, Upton M, Schembri MA. Insights into a multidrug resistant Escherichia coli pathogen of the globally disseminated ST131 lineage: genome analysis and virulence mechanisms. PLoS One 2011; 6:e26578. [PMID: 22053197 PMCID: PMC3203889 DOI: 10.1371/journal.pone.0026578] [Citation(s) in RCA: 169] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Accepted: 09/29/2011] [Indexed: 11/18/2022] Open
Abstract
Escherichia coli strains causing urinary tract infection (UTI) are increasingly recognized as belonging to specific clones. E. coli clone O25b:H4-ST131 has recently emerged globally as a leading multi-drug resistant pathogen causing urinary tract and bloodstream infections in hospitals and the community. While most molecular studies to date examine the mechanisms conferring multi-drug resistance in E. coli ST131, relatively little is known about their virulence potential. Here we examined E. coli ST131 clinical isolates from two geographically diverse collections, one representing the major pathogenic lineages causing UTI across the United Kingdom and a second representing UTI isolates from patients presenting at two large hospitals in Australia. We determined a draft genome sequence for one representative isolate, E. coli EC958, which produced CTX-M-15 extended-spectrum β-lactamase, CMY-23 type AmpC cephalosporinase and was resistant to ciprofloxacin. Comparative genome analysis indicated that EC958 encodes virulence genes commonly associated with uropathogenic E. coli (UPEC). The genome sequence of EC958 revealed a transposon insertion in the fimB gene encoding the activator of type 1 fimbriae, an important UPEC bladder colonization factor. We identified the same fimB transposon insertion in 59% of the ST131 UK isolates, as well as 71% of ST131 isolates from Australia, suggesting this mutation is common among E. coli ST131 strains. Insertional inactivation of fimB resulted in a phenotype resembling a slower off-to-on switching for type 1 fimbriae. Type 1 fimbriae expression could still be induced in fimB-null isolates; this correlated strongly with adherence to and invasion of human bladder cells and bladder colonisation in a mouse UTI model. We conclude that E. coli ST131 is a geographically widespread, antibiotic resistant clone that has the capacity to produce numerous virulence factors associated with UTI.
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MESH Headings
- Animals
- Anti-Bacterial Agents/pharmacology
- Australia
- Base Sequence
- Colony Count, Microbial
- Disease Models, Animal
- Drug Resistance, Multiple, Bacterial/drug effects
- Drug Resistance, Multiple, Bacterial/genetics
- Escherichia coli/drug effects
- Escherichia coli/genetics
- Escherichia coli/isolation & purification
- Escherichia coli/pathogenicity
- Escherichia coli Infections/microbiology
- Fimbriae, Bacterial/drug effects
- Fimbriae, Bacterial/genetics
- Genes, Bacterial/genetics
- Genome, Bacterial/genetics
- Humans
- Internationality
- Mice
- Mutagenesis, Insertional/drug effects
- Mutagenesis, Insertional/genetics
- Mutation/genetics
- Operon/genetics
- Phylogeny
- Plasmids/genetics
- Sequence Analysis, DNA
- United Kingdom
- Urinary Bladder/drug effects
- Urinary Bladder/microbiology
- Urine/microbiology
- Virulence/drug effects
- Virulence/genetics
- Virulence Factors/genetics
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Affiliation(s)
- Makrina Totsika
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
| | - Scott A. Beatson
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
| | - Sohinee Sarkar
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
| | - Minh-Duy Phan
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
| | - Nicola K. Petty
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
| | - Nathan Bachmann
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
| | - Marek Szubert
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
| | - Hanna E. Sidjabat
- University of Queensland Centre for Clinical Research, Royal Brisbane and Women's Hospital, Brisbane, Australia
| | - David L. Paterson
- University of Queensland Centre for Clinical Research, Royal Brisbane and Women's Hospital, Brisbane, Australia
| | - Mathew Upton
- School of Translational Medicine, University of Manchester, Manchester, United Kingdom
- * E-mail: (MU); (MAS)
| | - Mark A. Schembri
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
- * E-mail: (MU); (MAS)
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25
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McVicker G, Sun L, Sohanpal BK, Gashi K, Williamson RA, Plumbridge J, Blomfield IC. SlyA protein activates fimB gene expression and type 1 fimbriation in Escherichia coli K-12. J Biol Chem 2011; 286:32026-35. [PMID: 21768111 PMCID: PMC3173223 DOI: 10.1074/jbc.m111.266619] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 07/13/2011] [Indexed: 01/23/2023] Open
Abstract
We have demonstrated that SlyA activates fimB expression and hence type 1 fimbriation, a virulence factor in Escherichia coli. SlyA is shown to bind to two operator sites (O(SA1) and O(SA2)), situated between 194 and 167 base pairs upstream of the fimB transcriptional start site. fimB expression is derepressed in an hns mutant and diminished by a slyA mutation in the presence of H-NS only. H-NS binds to multiple sites in the promoter region, including two sites (H-NS2 and H-NS3) that overlap O(SA1) and O(SA2), respectively. Mutations that disrupt either O(SA1) or O(SA2) eliminate or reduce the activating effect of SlyA but have different effects on the level of expression. We interpret these results as reflecting the relative competition between SlyA and H-NS binding. Moreover we show that SlyA is capable of displacing H-NS from its binding sites in vitro. We suggest SlyA binding prevents H-NS binding to H-NS2 and H-NS3 and the subsequent oligomerization of H-NS necessary for full inhibition of fimB expression. In addition, we show that SlyA activates fimB expression independently of two other known regulators of fimB expression, NanR and NagC. It is demonstrated that the rarely used UUG initiation codon limits slyA expression and that low SlyA levels limit fimB expression. Furthermore, Western blot analysis shows that cells grown in rich-defined medium contain ~1000 SlyA dimers per cell whereas those grown in minimal medium contain >20% more SlyA. This study extends our understanding of the role that SlyA plays in the host-bacterial relationship.
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Affiliation(s)
- Gareth McVicker
- From the School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom and
| | - Lei Sun
- From the School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom and
| | - Baljinder K. Sohanpal
- From the School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom and
| | - Krishna Gashi
- From the School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom and
| | - Richard A. Williamson
- From the School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom and
| | - Jacqueline Plumbridge
- the Institut de Biologie Physico-Chimique (Unité Propre de Recherche 9073, Centre National de la Recherche Scientifique), 13 Rue Pierre et Marrie Curie, 75005 Paris, France
| | - Ian C. Blomfield
- From the School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom and
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Dissemination and systemic colonization of uropathogenic Escherichia coli in a murine model of bacteremia. mBio 2010; 1. [PMID: 21116344 PMCID: PMC2993011 DOI: 10.1128/mbio.00262-10] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 10/27/2010] [Indexed: 01/19/2023] Open
Abstract
Infection with uropathogenic Escherichia coli (UPEC), the causative agent of most uncomplicated urinary tract infections, proceeds in an ascending manner and, if left untreated, may result in bacteremia and urosepsis. To examine the fate of UPEC after its entry into the bloodstream, we developed a murine model of sublethal bacteremia. CBA/J mice were inoculated intravenously with 1 × 106 CFU of pyelonephritis strain E. coli CFT073 carrying a bioluminescent reporter. Biophotonic imaging, used to monitor the infection over 48 h, demonstrated that the bacteria disseminated systemically and appeared to localize at discrete sites. UPEC was recovered from the spleen, liver, kidneys, lungs, heart, brain, and intestines as early as 20 min postinoculation, peaking at 24 h postinoculation. A nonpathogenic E. coli K-12 strain, however, disseminated at significantly lower levels (P < 0.01) and was cleared from the liver and cecum by 24 h postinoculation. Isogenic mutants lacking type 1 fimbriae, P fimbriae, capsule, TonB, the heme receptors Hma and ChuA, or particularly the sialic acid catabolism enzyme NanA were significantly outcompeted by wild-type CFT073 during bacteremia (P < 0.05), while flagellin and hemolysin mutants were not. E. coli is the primary cause of urinary tract infections. In severe cases of kidney infection, bacteria can enter the bloodstream and cause systemic disease. While the ability of E. coli to cause urinary tract infection has been extensively studied, the fate of these bacteria once they enter the bloodstream is largely unknown. Here we used an imaging technique to develop a mouse model of E. coli bloodstream infection and identify bacterial genes that are important for the bacteria to spread to and infect various organs. Understanding how urinary tract pathogens like E. coli cause disease after they enter the bloodstream may aid in the development of protective and therapeutic treatments.
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Katouli M. Population structure of gut Escherichia coli and its role in development of extra-intestinal infections. IRANIAN JOURNAL OF MICROBIOLOGY 2010; 2:59-72. [PMID: 22347551 PMCID: PMC3279776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Extra-intestinal pathogenic Escherichia coli (ExPEC) strains are divided into uropathogenic E. coli (UPEC), strains causing neonatal meningitis and septicaemic E. coli. The most common pathotype of ExPEC is found among patients with urinary tract infection (UTI), defined as UPEC. These bacteria are responsible for >90% of cases of UTI and are often found amongst the faecal flora of the same host. E.coli strains are classified into four phylogenetic groups, A, B1, B2, and D. Groups A and B1 are commensal strains and carry few virulence-associated genes (VGs) while pathogenic group B2 and D usually possess VGs which enhance colonic persistence and adhesion in the urinary tract (UT). The gastrointestinal (GI) tract is widely accepted as a reservoir for UPEC and is believed that healthy humans have a reservoir of UPEC strains, belonging to phylogenetic group B2, and to a lesser extent, group D. These strains have superior ability to survive and persist in the gut of humans and can spread to cause extra-intestinal infections. ExPEC trains possess a range of VGs which are involved in their pathogenesis. These include adhesins, toxins, iron-acquisition systems (e.g. siderophores), and capsules. Evolutionary influences on the acquisition and main role of VGs amongst E. coli are widely debated, with some research holding that the prevalence of strains with VGs increases the likelihood of infections, whereas others believe that VGs provide a selective advantage for infection of extra-intestinal sites. This review is intended to present our existing knowledge and gaps in this area.
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Affiliation(s)
- Mohammad Katouli
- Corresponding author: Dr. Mohammad Katouli Address: Faculty of Science, Health and Education, University of the Sunshine Coast, Maroochydore DC, 4556, Queensland, Australia. Tel: +61-754302845. Fax: +61-754302887. E-mail:
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NlpI contributes to Escherichia coli K1 strain RS218 interaction with human brain microvascular endothelial cells. Infect Immun 2010; 78:3090-6. [PMID: 20421385 DOI: 10.1128/iai.00034-10] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli K1 is the most common Gram-negative bacillary organism causing neonatal meningitis. E. coli K1 binding to and invasion of human brain microvascular endothelial cells (HBMECs) is a prerequisite for its traversal of the blood-brain barrier (BBB) and penetration into the brain. In the present study, we identified NlpI as a novel bacterial determinant contributing to E. coli K1 interaction with HBMECs. The deletion of nlpI did not affect the expression of the known bacterial determinants involved in E. coli K1-HBMEC interaction, such as type 1 fimbriae, flagella, and OmpA, and the contribution of NlpI to HBMECs binding and invasion was independent of those bacterial determinants. Previous reports have shown that the nlpI mutant of E. coli K-12 exhibits growth defect at 42 degrees C at low osmolarity, and its thermosensitive phenotype can be suppressed by a mutation on the spr gene. The nlpI mutant of strain RS218 exhibited similar thermosensitive phenotype, but additional spr mutation did not restore the ability of the nlpI mutant to interact with HBMECs. These findings suggest the decreased ability of the nlpI mutant to interact with HBMECs is not associated with the thermosensitive phenotype. NlpI was determined as an outer membrane-anchored protein in E. coli, and the nlpI mutant was defective in cytosolic phospholipase A(2)alpha (cPLA(2)alpha) phosphorylation compared to the parent strain. These findings illustrate the first demonstration of NlpI's contribution to E. coli K1 binding to and invasion of HBMECs, and its contribution is likely to involve cPLA(2)alpha.
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Identification of the site-specific DNA invertase responsible for the phase variation of SusC/SusD family outer membrane proteins in Bacteroides fragilis. J Bacteriol 2009; 191:6003-11. [PMID: 19648246 DOI: 10.1128/jb.00687-09] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The human gut microbe Bacteroides fragilis can alter the expression of its surface molecules, such as capsular polysaccharides and SusC/SusD family outer membrane proteins, through reversible DNA inversions. We demonstrate here that DNA inversions at 12 invertible regions, including three gene clusters for SusC/SusD family proteins, were controlled by a single tyrosine site-specific recombinase (Tsr0667) encoded by BF0667 in B. fragilis strain YCH46. Genetic disruption of BF0667 diminished or attenuated shufflon-type DNA inversions at all three susC/susD genes clusters, as well as simple DNA inversions at nine other loci, most of which colocalized with susC/susD family genes. The inverted repeat sequences found within the Tsr0667-regulated invertible regions shared the consensus motif sequence AGTYYYN(4)GDACT. Tsr0667 specifically mediated the DNA inversions of 10 of the 12 regions, even under an Escherichia coli background when the invertible regions were exposed to BF0667 in E. coli cells. Thus, Tsr0667 is an additional globally acting DNA invertase in B. fragilis, which probably involves the selective expression of SusC/SusD family outer membrane proteins.
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30
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Bayliss CD. Determinants of phase variation rate and the fitness implications of differing rates for bacterial pathogens and commensals. FEMS Microbiol Rev 2009; 33:504-20. [PMID: 19222587 DOI: 10.1111/j.1574-6976.2009.00162.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Phase variation (PV) of surface molecules and other phenotypes is a major adaptive strategy of pathogenic and commensal bacteria. Phase variants are produced at high frequencies and in a reversible manner by hypermutation or hypervariable methylation in specific regions of the genome. The major mechanisms of PV involve site-specific recombination, homologous recombination, simple sequence DNA repeat tracts or epigenetic modification by the dam methylase. PV rates of some of these mechanisms are subject to the influence of genome maintenance pathways such as DNA replication, recombination and repair while others are independent of these pathways. For each of these mechanisms, the rate of generation of phase variants is controlled by intrinsic and dispensable factors. These factors can impart environmental regulation on switching rates while many factors are subject to heterogeneity both within isolates of a species and between species. A major gap in our understanding is whether these environmental and epidemiological variations in PV rate have a major impact on fitness. Experimental approaches to studying the biological relevance of differing PV rates are being developed, and a recent intriguing finding is of a co-ordination of switching rates in the phase variable P-pili of uropathogenic bacteria.
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Knight SD, Bouckaert J. Structure, Function, and Assembly of Type 1 Fimbriae. GLYCOSCIENCE AND MICROBIAL ADHESION 2009; 288:67-107. [DOI: 10.1007/128_2008_13] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Oxygen-limiting conditions enrich for fimbriate cells of uropathogenic Proteus mirabilis and Escherichia coli. J Bacteriol 2008; 191:1382-92. [PMID: 19114498 DOI: 10.1128/jb.01550-08] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
MR/P fimbriae of uropathogenic Proteus mirabilis undergo invertible element-mediated phase variation whereby an individual bacterium switches between expressing fimbriae (phase ON) and not expressing fimbriae (phase OFF). Under different conditions, the percentage of fimbriate bacteria within a population varies and could be dictated by either selection (growth advantage of one phase) or signaling (preferentially converting one phase to the other in response to external signals). Expression of MR/P fimbriae increases in a cell-density dependent manner in vitro and in vivo. However, rather than the increased cell density itself, this increase in fimbrial expression is due to an enrichment of fimbriate bacteria under oxygen limitation resulting from increased cell density. Our data also indicate that the persistence of MR/P fimbriate bacteria under oxygen-limiting conditions is a result of both selection (of MR/P fimbrial phase variants) and signaling (via modulation of expression of the MrpI recombinase). Furthermore, the mrpJ transcriptional regulator encoded within the mrp operon contributes to phase switching. Type 1 fimbriae of Escherichia coli, which are likewise subject to phase variation via an invertible element, also increase in expression during reduced oxygenation. These findings provide evidence to support a mechanism for persistence of fimbriate bacteria under oxygen limitation, which is relevant to disease progression within the oxygen-restricted urinary tract.
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34
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Cortes MAM, Gibon J, Chanteloup NK, Moulin-Schouleur M, Gilot P, Germon P. Inactivation of ibeA and ibeT results in decreased expression of type 1 fimbriae in extraintestinal pathogenic Escherichia coli strain BEN2908. Infect Immun 2008; 76:4129-36. [PMID: 18591231 PMCID: PMC2519445 DOI: 10.1128/iai.00334-08] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Revised: 04/25/2008] [Accepted: 06/21/2008] [Indexed: 12/21/2022] Open
Abstract
IbeA in extraintestinal pathogenic Escherichia coli (ExPEC) strains was previously described for its role in invasion. Here we investigated the role of IbeA and IbeT, encoded by a gene located downstream of ibeA, in the adhesion of the avian ExPEC strain BEN2908 to human brain microvascular endothelial cells (HBMEC). The DeltaibeA mutant was less adhesive to HBMEC than the wild-type strain BEN2908 was. Because strain BEN2908 also expresses type 1 fimbriae, we measured the adhesion specifically due to IbeA by comparing the adhesive properties of a Deltafim derivative of strain BEN2908 to those of a double Deltafim DeltaibeA mutant. No differences were observed, indicating that the reduction of adhesion in BEN2908 DeltaibeA could be due to a decrease in type 1 fimbria expression. We indeed showed that the decreased adhesion of BEN2908 DeltaibeA was correlated with a decrease in type 1 fimbria expression. Accordingly, more bacteria had a fim promoter orientated in the off position in a culture of BEN2908 DeltaibeA than in a culture of BEN2908. Expression of fimB and fimE, two genes encoding recombinases participating in controlling the orientation of the fim promoter, was decreased in BEN2908 DeltaibeA. A reduction of type 1 fimbria expression due to a preferential orientation of the fim promoter in the off position was also seen in an ibeT mutant of strain BEN2908. We finally suggest a role for IbeA and IbeT in modulating the expression of type 1 fimbriae through an as yet unknown mechanism.
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Affiliation(s)
- Mélanie A M Cortes
- INRA, UR 1282 Infectiologie Animale et Santé Publique, Laboratoire de Pathogénie Bactérienne, Nouzilly, France
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35
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Dixon BP, Lu L, Chu A, Bissler JJ. RecQ and RecG helicases have distinct roles in maintaining the stability of polypurine.polypyrimidine sequences. Mutat Res 2008; 643:20-8. [PMID: 18582477 DOI: 10.1016/j.mrfmmm.2008.05.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 05/15/2008] [Accepted: 05/19/2008] [Indexed: 01/07/2023]
Abstract
DNA triplex structures can block the replication fork and result in double-stranded DNA breaks (DSBs). RecQ and RecG helicases may be important for replication of such sequences as RecQ resolves synthetic triplex DNA structures and RecG mediates replication restart by fork regression. Primer extension on an 88 bp triplex-forming polypurine.polypyrimidine (Pu.Py) tract from the PKD1 gene demonstrated that RecQ, but not RecG, facilitated primer extension by T7 DNA polymerase. A high-throughput, dual plasmid screening system using isogenic bacterial lines deficient in RecG, RecQ, or both, revealed that RecQ deficiency increased mutation to sequence flanking this 88 bp tract by eight to ten-fold. Although RecG facilitated small deletions in an 88 bp mirror repeat-containing sequence, it was absolutely required to maintain a 2.5 kb Pu.Py tract containing multiple mirror repeats. These results support a two-tiered model where RecQ facilitates fork progression through triplex-forming tracts and, failing processivity, RecG is critical for replication fork restart.
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Affiliation(s)
- Bradley P Dixon
- Division of Nephrology and Hypertension, Cincinnati Children's Hospital Medical Center, MLC 7022, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, United States
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Abstract
Escherichia coli is a predominant species among facultative anaerobic bacteria of the gastrointestinal tract. Both its frequent community lifestyle and the availability of a wide array of genetic tools contributed to establish E. coli as a relevant model organism for the study of surface colonization. Several key factors, including different extracellular appendages, are implicated in E. coli surface colonization and their expression and activity are finely regulated, both in space and time, to ensure productive events leading to mature biofilm formation. This chapter will present known molecular mechanisms underlying biofilm development in both commensal and pathogenic E. coli.
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Affiliation(s)
- C Beloin
- Groupe de Génétique des Biofilms, Institut Pasteur, CNRS URA 2172, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France
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The hek outer membrane protein of Escherichia coli strain RS218 binds to proteoglycan and utilizes a single extracellular loop for adherence, invasion, and autoaggregation. Infect Immun 2007; 76:1135-42. [PMID: 18160475 DOI: 10.1128/iai.01327-07] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Escherichia coli is the principal gram-negative causative agent of sepsis and meningitis in neonates. The pathogenesis of meningitis due to E. coli K1 involves mucosal colonization, transcytosis of epithelial cells, survival in the bloodstream, and eventually invasion of the meninges. The last two aspects have been well characterized at a molecular level. Less is known about the early stages of pathogenesis, i.e., adhesion to and invasion of epithelial cells. We have previously reported that the Hek protein causes autoaggregation and can mediate adherence to and invasion of epithelial cells. Here, we report that Hek-mediated adherence is dependent on binding to glycosoaminoglycan, in particular, heparin. The ability to hemagglutinate, autoaggregate, adhere, and invade is contingent on a putative 25-amino-acid loop that is exposed to the outside of the bacterial cells.
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Hannan TJ, Mysorekar IU, Chen SL, Walker JN, Jones JM, Pinkner JS, Hultgren SJ, Seed PC. LeuX tRNA-dependent and -independent mechanisms of Escherichia coli pathogenesis in acute cystitis. Mol Microbiol 2007; 67:116-28. [PMID: 18036139 DOI: 10.1111/j.1365-2958.2007.06025.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Uropathogenic Escherichia coli (UPEC) contain multiple horizontally acquired pathogenicity-associated islands (PAI) implicated in the pathogenesis of urinary tract infection. In a murine model of cystitis, type 1 pili-mediated bladder epithelial invasion and intracellular proliferation are key events associated with UPEC virulence. In this study, we examined the mechanisms by which a conserved PAI contributes to UPEC pathogenesis in acute cystitis. In the human UPEC strain UTI89, spontaneous excision of PAI II(UTI89) disrupts the adjacent leuX tRNA locus. Loss of wild-type leuX-encoded tRNA(5)(Leu) significantly delayed, but did not eliminate, FimB recombinase-mediated phase variation of type 1 pili. FimX, an additional FimB-like, leuX-independent recombinase, was also found to mediate type 1 pili phase variation. However, whereas FimX activity is relatively slow in vitro, it is rapid in vivo as a non-piliated strain lacking the other fim recombinases rapidly expressed type 1 pili upon experimental infection. Finally, we found that disruption of leuX, but not loss of PAI II(UTI89) genes, reduced bladder epithelial invasion and intracellular proliferation, independent of type 1 piliation. These findings indicate that the predominant mechanism for preservation of PAI II(UTI89) during the establishment of acute cystitis is maintenance of wild-type leuX, and not PAI II(UTI89) gene content.
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Affiliation(s)
- Thomas J Hannan
- Department of Molecular Microbiology and Microbial Pathogenesis, Washington University School of Medicine, St Louis, MO 63110, USA
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Abstract
Fimbria-mediated interaction with the host elicits both innate and adaptive immune responses, and thus their expression may not always be beneficial in vivo. Furthermore, the metabolic drain of producing fimbriae is significant. It is not surprising, therefore, to find that fimbrial production in Escherichia coli and Salmonella enterica is under extensive environmental regulation. In many instances, fimbrial expression is regulated by phase variation, in which individual cells are capable of switching between fimbriate and afimbriate states to produce a mixed population. Mechanisms of phase variation vary considerably between different fimbriae and involve both genetic and epigenetic processes. Notwithstanding this, fimbrial expression is also sometimes controlled at the posttranscriptional level. In this chapter, we review key features of the regulation of fimbrial gene expression in E. coli and Salmonella. The occurrence and distribution of fimbrial operons vary significantly among E. coli pathovars and even among the many Salmonella serovars. Therefore, general principles are presented on the basis of detailed discussion of paradigms that have been extensively studied, including Pap, type 1 fimbriae, and curli. The roles of operon specific regulators like FimB or CsgD and of global regulatory proteins like Lrp, CpxR, and the histone-like proteins H-NS and IHF are reviewed as are the roles of sRNAs and of signalling nucleotide cyclic-di-GMP. Individual examples are discussed in detail to illustrate how the regulatory factors cooperate to allow tight control of expression of single operons. Molecular networks that allow coordinated expression between multiple fimbrial operons and with flagella in a single isolate are also presented. This chapter illustrates how adhesin expression is controlled, and the model systems also illustrate general regulatory principles germane to our overall understanding of bacterial gene regulation.
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