1
|
Gong X, Teng Y, Zhang J, Gan Q, Song M, Alaraj A, Kner P, Yan Y. Architecting a Transcriptional Repressor-based Genetic Inverter for Tryptophan Derived Pathway Regulation in Escherichia coli. Metab Eng 2024:S1096-7176(24)00123-X. [PMID: 39293710 DOI: 10.1016/j.ymben.2024.09.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2024] [Accepted: 09/15/2024] [Indexed: 09/20/2024]
Abstract
Efficient microbial cell factories require intricate and precise metabolic regulations for optimized production, which can be significantly aided by implementing regulatory genetic circuits with versatile functions. However, constructing functionally diverse genetic circuits in host strains is challenging. Especially, functional diversification based on transcriptional repressors has been rarely explored due to the difficulty in inverting their repression properties. To address this, we proposed a design logic to create transcriptional repressor-based genetic inverters for functional enrichment. As proof of concept, a tryptophan-inducible genetic inverter was constructed by integrating two sets of transcriptional repressors, PtrpO1-TrpR1 and PtetO1-TetR. In this genetic inverter, the repression of TetR towards PtetO1 could be alleviated by the tryptophan-TrpR1 complex in the presence of tryptophan, leading to the activated output. Subsequently, we optimized the dynamic performance of the inverter and constructed tryptophan-triggered dynamic activation systems. Further coupling of the original repression function of PtrpO1-TrpR1 with inverter variants realized the tryptophan-triggered bifunctional regulation system. Finally, the dynamic regulation systems enabled tryptophan production monitoring. These systems also remarkably increased the titers of the tryptophan derivatives tryptamine and violacein by 2.0-fold and 7.4-fold, respectively. The successful design and application of the genetic inverter enhanced the applicability of transcriptional repressors.
Collapse
Affiliation(s)
- Xinyu Gong
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Yuxi Teng
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Jianli Zhang
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Qi Gan
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Ming Song
- School of Electrical and Computer Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Ameen Alaraj
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Peter Kner
- School of Electrical and Computer Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Yajun Yan
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA 30602, USA.
| |
Collapse
|
2
|
Schulte M, Grotheer L, Hensel M. Bright individuals: Applications of fluorescent protein-based reporter systems in single-cell cellular microbiology. Mol Microbiol 2024; 121:605-617. [PMID: 38234267 DOI: 10.1111/mmi.15227] [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: 07/18/2023] [Revised: 12/30/2023] [Accepted: 01/02/2024] [Indexed: 01/19/2024]
Abstract
Activation and function of virulence functions of bacterial pathogens are highly dynamic in time and space, and can show considerable heterogeneity between individual cells in pathogen populations. To investigate the complex events in host-pathogen interactions, single cell analyses are required. Fluorescent proteins (FPs) are excellent tools to follow the fate of individual bacterial cells during infection, and can also be deployed to use the pathogen as a sensor for its specific environment in host cells or host organisms. This Resources describes design and applications of dual fluorescence reporters (DFR) in cellular microbiology. DFR feature constitutively expressed FPs for detection of bacterial cells, and FPs expressed by an environmentally regulated promoter for interrogation of niche-specific cues or nutritional parameters. Variations of the basic design allow the generation of DFR that can be used to analyze, on single cell level, bacterial proliferation during infection, subcellular localization of intracellular bacteria, stress response, or persister state. We describe basic considerations for DFR design and review recent applications of DFR in cellular microbiology.
Collapse
Affiliation(s)
- Marc Schulte
- Abt. Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
- CellNanOs-Center of Cellular Nanoanalytics Osnabrück, Universität Osnabrück, Osnabrück, Germany
| | - Luisa Grotheer
- Abt. Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
| | - Michael Hensel
- Abt. Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
- CellNanOs-Center of Cellular Nanoanalytics Osnabrück, Universität Osnabrück, Osnabrück, Germany
| |
Collapse
|
3
|
Abstract
The ability to manipulate the bacterial genome is an obligatory premise for the study of gene function and regulation in bacterial cells. The λ red recombineering technique allows modification of chromosomal sequences with base-pair precision without the need of intermediate molecular cloning steps. Initially conceived to construct insertion mutants, the technique lends itself to a wide variety of applications including the creation of point mutants, seamless deletions, reporter, and epitope tag fusions and chromosomal rearrangements. Here, we introduce some of the most common implementations of the method.
Collapse
Affiliation(s)
- Nara Figueroa-Bossi
- Université Paris-Saclay, CEA, CNRS, Institut de Biologie Intégrative de la Cellule (I2BC), 91190 Gif-sur-Yvette, France
| | - Roberto Balbontín
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41080 Sevilla, Spain
| | - Lionello Bossi
- Université Paris-Saclay, CEA, CNRS, Institut de Biologie Intégrative de la Cellule (I2BC), 91190 Gif-sur-Yvette, France
| |
Collapse
|
4
|
Wang J, Teng Y, Gong X, Zhang J, Wu Y, Lou L, Li M, Xie ZR, Yan Y. Exploring and engineering PAM-diverse Streptococci Cas9 for PAM-directed bifunctional and titratable gene control in bacteria. Metab Eng 2023; 75:68-77. [PMID: 36404524 PMCID: PMC10947553 DOI: 10.1016/j.ymben.2022.10.005] [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: 05/02/2022] [Revised: 10/05/2022] [Accepted: 10/23/2022] [Indexed: 11/18/2022]
Abstract
The RNA-guided Cas9s serve as powerful tools for programmable gene editing and regulation; their targeting scopes and efficacies, however, are always constrained by the PAM sequence stringency. Most Streptococci Cas9s, including the prototype SpCas9 from S. pyogenes, specifically recognize a canonical NGG PAM via a conserved RxR PAM-binding motif within the PAM-interaction (PI) domain. Here, SpCas9-based mining unveils three distinct and rarely presented PAM-binding motifs (QxxxR, QxQ and RxQ) among Streptococci Cas9 orthologs. With the catalytically-dead QxxxR-containing SedCas9 from S. equinus, we dissect its NAG PAM specificity and elucidate its underlying recognition mechanism via computational prediction and mutagenesis analysis. Replacing the SedCas9 PI domain with alternate PAM-binding motifs rewires its PAM specificity to NGG or NAA. Moreover, a semi-rational design with minimal mutation creates a SedCas9-NQ variant showing robust activity towards expanded NNG and NAA PAMs, based upon which we engineered a compact ω-SedCas9-NQ transcriptional regulator for PAM-directed bifunctional and titratable gene control. The ω-SedCas9-NQ mediated metabolic reprogramming of endogenous genes in Escherichia coli affords a 2.6-fold increase of 4-hydroxycoumarin production. This work reveals new Cas9 scaffolds with distinct PAM-binding motifs for PAM relaxation and creates a new PAM-diverse Cas9 variant for versatile gene control in bacteria.
Collapse
Affiliation(s)
- Jian Wang
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA, 30602, USA
| | - Yuxi Teng
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA, 30602, USA
| | - Xinyu Gong
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA, 30602, USA
| | - Jianli Zhang
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA, 30602, USA
| | - Yifei Wu
- School of Electrical and Computer Engineering, College of Engineering, The University of Georgia, Athens, GA, 30602, USA
| | - Lei Lou
- School of Electrical and Computer Engineering, College of Engineering, The University of Georgia, Athens, GA, 30602, USA
| | - Michelle Li
- North Oconee High School, Bogart, GA, 30622, USA
| | - Zhong-Ru Xie
- School of Electrical and Computer Engineering, College of Engineering, The University of Georgia, Athens, GA, 30602, USA
| | - Yajun Yan
- School of Chemical, Materials and Biomedical Engineering, College of Engineering, The University of Georgia, Athens, GA, 30602, USA.
| |
Collapse
|
5
|
Owen SV, Wenner N, Dulberger CL, Rodwell EV, Bowers-Barnard A, Quinones-Olvera N, Rigden DJ, Rubin EJ, Garner EC, Baym M, Hinton JCD. Prophages encode phage-defense systems with cognate self-immunity. Cell Host Microbe 2021; 29:1620-1633.e8. [PMID: 34597593 PMCID: PMC8585504 DOI: 10.1016/j.chom.2021.09.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 02/23/2021] [Accepted: 09/03/2021] [Indexed: 12/18/2022]
Abstract
Temperate phages are pervasive in bacterial genomes, existing as vertically inherited islands termed prophages. Prophages are vulnerable to predation of their host bacterium by exogenous phages. Here, we identify BstA, a family of prophage-encoded phage-defense proteins in diverse Gram-negative bacteria. BstA localizes to sites of exogenous phage DNA replication and mediates abortive infection, suppressing the competing phage epidemic. During lytic replication, the BstA-encoding prophage is not itself inhibited by BstA due to self-immunity conferred by the anti-BstA (aba) element, a short stretch of DNA within the bstA locus. Inhibition of phage replication by distinct BstA proteins from Salmonella, Klebsiella, and Escherichia prophages is generally interchangeable, but each possesses a cognate aba element. The specificity of the aba element ensures that immunity is exclusive to the replicating prophage, preventing exploitation by variant BstA-encoding phages. The BstA protein allows prophages to defend host cells against exogenous phage attack without sacrificing the ability to replicate lytically. BstA is an abortive infection protein found in prophages of Gram-negative bacteria aba, a short DNA sequence within the bstA locus, acts as a self-immunity element aba gives BstA-encoding prophages immunity to BstA-driven abortive infection Variant BstA proteins have distinct and cognate aba elements
Collapse
Affiliation(s)
- Siân V Owen
- Department of Biomedical Informatics and Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA, USA.
| | - Nicolas Wenner
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK; Biozentrum, University of Basel, Basel, Switzerland
| | - Charles L Dulberger
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, USA; Department of Molecular and Cellular Biology, Harvard University, Boston, MA, USA
| | - Ella V Rodwell
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Arthur Bowers-Barnard
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Natalia Quinones-Olvera
- Department of Biomedical Informatics and Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Daniel J Rigden
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, UK
| | - Eric J Rubin
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Ethan C Garner
- Department of Molecular and Cellular Biology, Harvard University, Boston, MA, USA
| | - Michael Baym
- Department of Biomedical Informatics and Laboratory of Systems Pharmacology, Harvard Medical School, Boston, MA, USA.
| | - Jay C D Hinton
- Institute of Infection, Veterinary & Ecological Sciences, University of Liverpool, Liverpool, UK.
| |
Collapse
|
6
|
Koeppel MB, Glaser J, Baumgartner T, Spriewald S, Gerlach RG, von Armansperg B, Leong JM, Stecher B. Scalable Reporter Assays to Analyze the Regulation of stx2 Expression in Shiga Toxin-Producing Enteropathogens. Toxins (Basel) 2021; 13:toxins13080534. [PMID: 34437405 PMCID: PMC8402550 DOI: 10.3390/toxins13080534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 07/27/2021] [Accepted: 07/28/2021] [Indexed: 12/02/2022] Open
Abstract
Stx2 is the major virulence factor of EHEC and is associated with an increased risk for HUS in infected patients. The conditions influencing its expression in the intestinal tract are largely unknown. For optimal management and treatment of infected patients, the identification of environmental conditions modulating Stx2 levels in the human gut is of central importance. In this study, we established a set of chromosomal stx2 reporter assays. One system is based on superfolder GFP (sfGFP) using a T7 polymerase/T7 promoter-based amplification loop. This reporter can be used to analyze stx2 expression at the single-cell level using FACSs and fluorescence microscopy. The other system is based on the cytosolic release of the Gaussia princeps luciferase (gluc). This latter reporter proves to be a highly sensitive and scalable reporter assay that can be used to quantify reporter protein in the culture supernatant. We envision that this new set of reporter tools will be highly useful to comprehensively analyze the influence of environmental and host factors, including drugs, small metabolites and the microbiota, on Stx2 release and thereby serve the identification of risk factors and new therapies in Stx-mediated pathologies.
Collapse
Affiliation(s)
- Martin B. Koeppel
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany; (J.G.); (T.B.); (S.S.); (B.v.A.)
- German Center for Infection Research (DZIF), Partner Site LMU Munich, 80336 Munich, Germany
- Correspondence: (M.B.K.); (B.S.)
| | - Jana Glaser
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany; (J.G.); (T.B.); (S.S.); (B.v.A.)
- German Center for Infection Research (DZIF), Partner Site LMU Munich, 80336 Munich, Germany
| | - Tobias Baumgartner
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany; (J.G.); (T.B.); (S.S.); (B.v.A.)
- German Center for Infection Research (DZIF), Partner Site LMU Munich, 80336 Munich, Germany
| | - Stefanie Spriewald
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany; (J.G.); (T.B.); (S.S.); (B.v.A.)
- German Center for Infection Research (DZIF), Partner Site LMU Munich, 80336 Munich, Germany
| | - Roman G. Gerlach
- Mikrobiologisches Institut-Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen and Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Wasserturmstraße 3/5, 91054 Erlangen, Germany;
| | - Benedikt von Armansperg
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany; (J.G.); (T.B.); (S.S.); (B.v.A.)
- German Center for Infection Research (DZIF), Partner Site LMU Munich, 80336 Munich, Germany
| | - John M. Leong
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Ave, Boston, MA 02111, USA;
| | - Bärbel Stecher
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336 Munich, Germany; (J.G.); (T.B.); (S.S.); (B.v.A.)
- German Center for Infection Research (DZIF), Partner Site LMU Munich, 80336 Munich, Germany
- Correspondence: (M.B.K.); (B.S.)
| |
Collapse
|
7
|
Fernández PA, Zabner M, Ortega J, Morgado C, Amaya F, Vera G, Rubilar C, Salas B, Cuevas V, Valenzuela C, Baisón-Olmo F, Álvarez SA, Santiviago CA. Novel Template Plasmids pCyaA'-Kan and pCyaA'-Cam for Generation of Unmarked Chromosomal cyaA' Translational Fusion to T3SS Effectors in Salmonella. Microorganisms 2021; 9:microorganisms9030475. [PMID: 33668764 PMCID: PMC7996335 DOI: 10.3390/microorganisms9030475] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Accepted: 02/15/2021] [Indexed: 11/25/2022] Open
Abstract
The type III secretion systems (T3SS) encoded in pathogenicity islands SPI-1 and SPI-2 are key virulence factors of Salmonella. These systems translocate proteins known as effectors into eukaryotic cells during infection. To characterize the functionality of T3SS effectors, gene fusions to the CyaA’ reporter of Bordetella pertussis are often used. CyaA’ is a calmodulin-dependent adenylate cyclase that is only active within eukaryotic cells. Thus, the translocation of an effector fused to CyaA’ can be evaluated by measuring cAMP levels in infected cells. Here, we report the construction of plasmids pCyaA’-Kan and pCyaA’-Cam, which contain the ORF encoding CyaA’ adjacent to a cassette that confers resistance to kanamycin or chloramphenicol, respectively, flanked by Flp recombinase target (FRT) sites. A PCR product from pCyaA’-Kan or pCyaA’-Cam containing these genetic elements can be introduced into the bacterial chromosome to generate gene fusions by homologous recombination using the Red recombination system from bacteriophage λ. Subsequently, the resistance cassette can be removed by recombination between the FRT sites using the Flp recombinase. As a proof of concept, the plasmids pCyaA’-Kan and pCyaA’-Cam were used to generate unmarked chromosomal fusions of 10 T3SS effectors to CyaA’ in S. Typhimurium. Each fusion protein was detected by Western blot using an anti-CyaA’ monoclonal antibody when the corresponding mutant strain was grown under conditions that induce the expression of the native gene. In addition, T3SS-1-dependent secretion of fusion protein SipA-CyaA’ during in vitro growth was verified by Western blot analysis of culture supernatants. Finally, efficient translocation of SipA-CyaA’ into HeLa cells was evidenced by increased intracellular cAMP levels at different times of infection. Therefore, the plasmids pCyaA’-Kan and pCyaA’-Cam can be used to generate unmarked chromosomal cyaA’ translational fusion to study regulated expression, secretion and translocation of Salmonella T3SS effectors into eukaryotic cells.
Collapse
Affiliation(s)
- Paulina A. Fernández
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Marcela Zabner
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Jaime Ortega
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Constanza Morgado
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Fernando Amaya
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Gabriel Vera
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Carolina Rubilar
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Beatriz Salas
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Víctor Cuevas
- Facultad de Medicina y Ciencia, Universidad San Sebastián, 92101 Santiago, Chile;
| | - Camila Valenzuela
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
- Dynamics of Host-Pathogen Interactions Unit, Institut Pasteur, 75015 Paris, France
| | - Fernando Baisón-Olmo
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Sergio A. Álvarez
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
| | - Carlos A. Santiviago
- Laboratorio de Microbiología, Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, 92101 Santiago, Chile; (P.A.F.); (M.Z.); (J.O.); (C.M.); (F.A.); (G.V.); (C.R.); (B.S.); (C.V.); (F.B.-O.); (S.A.Á.)
- Correspondence: ; Tel.: +56-2-2978-1681
| |
Collapse
|
8
|
Fels U, Gevaert K, Van Damme P. Bacterial Genetic Engineering by Means of Recombineering for Reverse Genetics. Front Microbiol 2020; 11:548410. [PMID: 33013782 PMCID: PMC7516269 DOI: 10.3389/fmicb.2020.548410] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 08/14/2020] [Indexed: 12/11/2022] Open
Abstract
Serving a robust platform for reverse genetics enabling the in vivo study of gene functions primarily in enterobacteriaceae, recombineering -or recombination-mediated genetic engineering-represents a powerful and relative straightforward genetic engineering tool. Catalyzed by components of bacteriophage-encoded homologous recombination systems and only requiring short ∼40–50 base homologies, the targeted and precise introduction of modifications (e.g., deletions, knockouts, insertions and point mutations) into the chromosome and other episomal replicons is empowered. Furthermore, by its ability to make use of both double- and single-stranded linear DNA editing substrates (e.g., PCR products or oligonucleotides, respectively), lengthy subcloning of specific DNA sequences is circumvented. Further, the more recent implementation of CRISPR-associated endonucleases has allowed for more efficient screening of successful recombinants by the selective purging of non-edited cells, as well as the creation of markerless and scarless mutants. In this review we discuss various recombineering strategies to promote different types of gene modifications, how they are best applied, and their possible pitfalls.
Collapse
Affiliation(s)
- Ursula Fels
- Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium.,VIB-UGent Center for Medical Biotechnology, Ghent, Belgium
| | - Kris Gevaert
- VIB-UGent Center for Medical Biotechnology, Ghent, Belgium.,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Petra Van Damme
- Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
| |
Collapse
|
9
|
Self-Labeling Enzyme Tags for Translocation Analyses of Salmonella Effector Proteins. Methods Mol Biol 2020. [PMID: 32894488 DOI: 10.1007/978-1-0716-0791-6_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Salmonella enterica is an invasive, facultative intracellular pathogen with a highly sophisticated intracellular lifestyle. Invasion and intracellular proliferation are dependent on the translocation of effector proteins by two distinct type III secretion systems (T3SS) into the host cell. To unravel host-pathogen interactions, dedicated imaging techniques visualizing Salmonella effector proteins during the infection are essential. Here we describe a new approach utilizing self-labeling enzyme (SLE) tags as a universal labeling tool for tracing effector proteins. This method is able to resolve the temporal and spatial dynamics of effector proteins in living cells. The method is applicable to conventional confocal fluorescence microscopy, but also to tracking and localization microscopy (TALM), and super-resolution microscopy (SRM) of single molecules, allowing the visualization of effector proteins beyond the optical diffraction limit.
Collapse
|
10
|
Transcription of the Subtilase Cytotoxin Gene subAB 1 in Shiga Toxin-Producing Escherichia coli Is Dependent on hfq and hns. Appl Environ Microbiol 2019; 85:AEM.01281-19. [PMID: 31375495 DOI: 10.1128/aem.01281-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 07/30/2019] [Indexed: 01/06/2023] Open
Abstract
Certain foodborne Shiga toxin-producing Escherichia coli (STEC) strains carry genes encoding the subtilase cytotoxin (SubAB). Although the mode of action of SubAB is under intensive investigation, information about the regulation of subAB gene expression is currently not available. In this study, we investigated the regulation of the chromosomal subAB 1 gene in laboratory E. coli strain DH5α and STEC O113:H21 strain TS18/08 using a luciferase reporter gene assay. Special emphasis was given to the role of the global regulatory protein genes hfq and hns in subAB 1 promoter activity. Subsequently, quantitative real-time PCR was performed to analyze the expression of Shiga toxin 2a (Stx2a), SubAB1, and cytolethal distending toxin V (Cdt-V) genes in STEC strain TS18/08 and its isogenic hfq and hns deletion mutants. The deletion of hfq led to a significant increase of up to 2-fold in subAB 1 expression, especially in the late growth phase, in both strains. However, deletion of hns showed different effects on the promoter activity during the early and late exponential growth phases in both strains. Furthermore, upregulation of stx 2a and cdt-V was demonstrated in hfq and hns deletion mutants in TS18/08. These data showed that the expression of subAB 1, stx 2a, and cdt-V is integrated in the regulatory network of global regulators Hfq and H-NS in Escherichia coli IMPORTANCE Shiga toxin-producing Escherichia coli (STEC) strains are responsible for outbreaks of foodborne diseases, such as hemorrhagic colitis and the hemolytic uremic syndrome. The pathogenicity of those strains can be attributed to, among other factors, the production of toxins. Recently, the subtilase cytotoxin was detected in locus of enterocyte effacement (LEE)-negative STEC, and it was confirmed that it contributes to the cytotoxicity of those STEC strains. Although the mode of action of SubAB1 is under intensive investigation, the regulation of gene expression is currently not known. The global regulatory proteins H-NS and Hfq have impact on many cellular processes and have been described to regulate virulence factors as well. Here, we investigate the role of hns and hfq in expression of subAB 1 as well as stx 2a and cdt-V in an E. coli laboratory strain as well as in wild-type STEC strain TS18/08.
Collapse
|
11
|
Self-Labeling Enzyme Tags for Analyses of Translocation of Type III Secretion System Effector Proteins. mBio 2019; 10:mBio.00769-19. [PMID: 31239375 PMCID: PMC6593401 DOI: 10.1128/mbio.00769-19] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Type III secretion systems (T3SS) are molecular machines in Gram-negative pathogens that translocate effector proteins with central roles in virulence. The analyses of the translocation, subcellular localization, and mode of action of T3SS effector proteins are of central importance for the understanding of host-pathogen interaction and pathogenesis of bacterial infections. The analysis of translocation requires dedicated techniques to address the temporal and spatial dynamics of translocation. Here we describe a novel approach to deploy self-labeling enzymes (SLE) as universal tags for localization and tracking of translocated effector proteins. Effector-SLE fusion proteins allow live-cell imaging of translocation by T3SS, superresolution microscopy, and single-molecule tracking of effector motility in living host cells. We describe the application of the approach to T3SS effector proteins for invasion and intracellular lifestyle of Salmonella enterica serovar Typhimurium and to a T3SS effector of Yersinia enterocolitica The novel approach enables analyses of the role of T3SS in host-pathogen interaction at the highest temporal and spatial resolution, toward understanding the molecular mechanisms of their effector proteins.IMPORTANCE Type III secretion systems mediate translocation of effector proteins into mammalian cells. These proteins interfere with host cell functions, being main virulence factors of Gram-negative pathogens. Analyses of the process of translocation, the subcellular distribution, and the dynamics of effector proteins in host cells have been hampered by the lack of suitable tags and detection systems. Here we describe the use of self-labeling enzyme tags for generation of fusions with effector proteins that are translocated and functional in host cell manipulation. Self-labeling reactions with cell-permeable ligand dyes are possible prior to or after translocation. We applied the new approach to superresolution microscopy for effector protein translocation. For the first time, we show the dynamic properties of effector proteins in living host cells after translocation by intracellular bacteria. The new approach of self-labeling enzyme tags fusions will enable analyses of type III secretion system effector proteins with new dimensions of temporal and spatial resolution.
Collapse
|
12
|
Schulte M, Sterzenbach T, Miskiewicz K, Elpers L, Hensel M, Hansmeier N. A versatile remote control system for functional expression of bacterial virulence genes based on the tetA promoter. Int J Med Microbiol 2019; 309:54-65. [DOI: 10.1016/j.ijmm.2018.11.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 10/21/2018] [Accepted: 11/14/2018] [Indexed: 11/16/2022] Open
|
13
|
Comparison of Salmonella enterica Serovars Typhi and Typhimurium Reveals Typhoidal Serovar-Specific Responses to Bile. Infect Immun 2018; 86:IAI.00490-17. [PMID: 29229736 PMCID: PMC5820949 DOI: 10.1128/iai.00490-17] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 12/06/2017] [Indexed: 01/19/2023] Open
Abstract
Salmonella enterica serovars Typhi and Typhimurium cause typhoid fever and gastroenteritis, respectively. A unique feature of typhoid infection is asymptomatic carriage within the gallbladder, which is linked with S. Typhi transmission. Despite this, S. Typhi responses to bile have been poorly studied. Transcriptome sequencing (RNA-Seq) of S. Typhi Ty2 and a clinical S. Typhi isolate belonging to the globally dominant H58 lineage (strain 129-0238), as well as S. Typhimurium 14028, revealed that 249, 389, and 453 genes, respectively, were differentially expressed in the presence of 3% bile compared to control cultures lacking bile. fad genes, the actP-acs operon, and putative sialic acid uptake and metabolism genes (t1787 to t1790) were upregulated in all strains following bile exposure, which may represent adaptation to the small intestine environment. Genes within the Salmonella pathogenicity island 1 (SPI-1), those encoding a type IIII secretion system (T3SS), and motility genes were significantly upregulated in both S. Typhi strains in bile but downregulated in S. Typhimurium. Western blots of the SPI-1 proteins SipC, SipD, SopB, and SopE validated the gene expression data. Consistent with this, bile significantly increased S. Typhi HeLa cell invasion, while S. Typhimurium invasion was significantly repressed. Protein stability assays demonstrated that in S. Typhi the half-life of HilD, the dominant regulator of SPI-1, is three times longer in the presence of bile; this increase in stability was independent of the acetyltransferase Pat. Overall, we found that S. Typhi exhibits a specific response to bile, especially with regard to virulence gene expression, which could impact pathogenesis and transmission.
Collapse
|
14
|
Wang J, Wu Y, Sun X, Yuan Q, Yan Y. De Novo Biosynthesis of Glutarate via α-Keto Acid Carbon Chain Extension and Decarboxylation Pathway in Escherichia coli. ACS Synth Biol 2017; 6:1922-1930. [PMID: 28618222 DOI: 10.1021/acssynbio.7b00136] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Microbial based bioplastics are promising alternatives to petroleum based synthetic plastics due to their renewability and economic feasibility. Glutarate is one of the most potential building blocks for bioplastics. The recent biosynthetic routes for glutarate were mostly based on the l-lysine degradation pathway from Pseudomonas putida that required lysine either by feeding or lysine overproduction via genetic manipulations. Herein, we established a novel glutarate biosynthetic pathway by incorporation of a "+1" carbon chain extension pathway from α-ketoglutarate (α-KG) in combination with α-keto acid decarboxylation pathway in Escherichia coli. Introduction of homocitrate synthase (HCS), homoaconitase (HA) and homoisocitrate dehydrogenase (HICDH) from Saccharomyces cerevisiae into E. coli enabled "+1" carbon extension from α-KG to α-ketoadipate (α-KA), which was subsequently converted into glutarate by a promiscuous α-keto acid decarboxylase (KivD) and a succinate semialdehyde dehydrogenase (GabD). The recombinant E. coli coexpressing all five genes produced 0.3 g/L glutarate from glucose. To further improve the titers, α-KG was rechanneled into carbon chain extension pathway via the clustered regularly interspersed palindromic repeats system mediated interference (CRISPRi) of essential genes sucA and sucB in tricarboxylic acid (TCA) cycle. The final strain could produce 0.42 g/L glutarate, which was increased by 40% compared with the parental strain.
Collapse
Affiliation(s)
- Jian Wang
- College
of Engineering, The University of Georgia, Athens, Georgia 30602, United States
| | - Yifei Wu
- State
Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
- Beijing
Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Xinxiao Sun
- State
Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
- Beijing
Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Qipeng Yuan
- State
Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
- Beijing
Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Yajun Yan
- College
of Engineering, The University of Georgia, Athens, Georgia 30602, United States
| |
Collapse
|
15
|
Fabiani FD, Renault TT, Peters B, Dietsche T, Gálvez EJC, Guse A, Freier K, Charpentier E, Strowig T, Franz-Wachtel M, Macek B, Wagner S, Hensel M, Erhardt M. A flagellum-specific chaperone facilitates assembly of the core type III export apparatus of the bacterial flagellum. PLoS Biol 2017; 15:e2002267. [PMID: 28771474 PMCID: PMC5542435 DOI: 10.1371/journal.pbio.2002267] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 06/30/2017] [Indexed: 11/21/2022] Open
Abstract
Many bacteria move using a complex, self-assembling nanomachine, the bacterial flagellum. Biosynthesis of the flagellum depends on a flagellar-specific type III secretion system (T3SS), a protein export machine homologous to the export machinery of the virulence-associated injectisome. Six cytoplasmic (FliH/I/J/G/M/N) and seven integral-membrane proteins (FlhA/B FliF/O/P/Q/R) form the flagellar basal body and are involved in the transport of flagellar building blocks across the inner membrane in a proton motive force-dependent manner. However, how the large, multi-component transmembrane export gate complex assembles in a coordinated manner remains enigmatic. Specific for most flagellar T3SSs is the presence of FliO, a small bitopic membrane protein with a large cytoplasmic domain. The function of FliO is unknown, but homologs of FliO are found in >80% of all flagellated bacteria. Here, we demonstrate that FliO protects FliP from proteolytic degradation and promotes the formation of a stable FliP–FliR complex required for the assembly of a functional core export apparatus. We further reveal the subcellular localization of FliO by super-resolution microscopy and show that FliO is not part of the assembled flagellar basal body. In summary, our results suggest that FliO functions as a novel, flagellar T3SS-specific chaperone, which facilitates quality control and productive assembly of the core T3SS export machinery. Many bacteria use the bacterial flagellum for directed movement in various environments. The assembly and function of the bacterial flagellum and the related virulence-associated injectisome relies on protein export via a conserved type III secretion system (T3SS). The multicomponent transmembrane core export apparatus of the flagellar T3SS consists of FlhA/B and FliP/Q/R and must assemble in a highly coordinated manner. In the present study, we determined the role of the transmembrane protein FliO in the maturation of the flagellar core protein export apparatus. We show that FliO functions as a flagellum-specific chaperone during the initial step of export apparatus assembly. FliO facilitates the efficient formation of a stable FliP–FliR core complex and is thus required for quality management and productive assembly of the flagellar export apparatus. Our results suggest a coordinated assembly process of the flagellar core export apparatus that nucleates with the FliO-dependent formation of a FliP–FliR complex. Subsequent incorporation of FliQ, FlhB, and FlhA leads to the assembly of a secretion-competent flagellar T3SS.
Collapse
Affiliation(s)
- Florian D. Fabiani
- Junior Research Group Infection Biology of Salmonella, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Thibaud T. Renault
- Junior Research Group Infection Biology of Salmonella, Helmholtz Centre for Infection Research, Braunschweig, Germany
- Max Planck Institute for Infection Biology, Berlin, Germany
| | - Britta Peters
- Abteilung Mikrobiologie, Fachbereich Biologie/Chemie, University of Osnabrück, Osnabrück, Germany
| | - Tobias Dietsche
- Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, University of Tübingen, Tübingen, Germany
| | - Eric J. C. Gálvez
- Junior Research Group Microbial Immune Regulation, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Alina Guse
- Junior Research Group Infection Biology of Salmonella, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Karen Freier
- Junior Research Group Infection Biology of Salmonella, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | | | - Till Strowig
- Junior Research Group Microbial Immune Regulation, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | | | - Boris Macek
- Proteome Center Tübingen, University of Tübingen, Tübingen, Germany
| | - Samuel Wagner
- Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Section of Cellular and Molecular Microbiology, University of Tübingen, Tübingen, Germany
- German Center for Infection Research (DZIF), Partner-site Tübingen, Tübingen, Germany
| | - Michael Hensel
- Abteilung Mikrobiologie, Fachbereich Biologie/Chemie, University of Osnabrück, Osnabrück, Germany
| | - Marc Erhardt
- Junior Research Group Infection Biology of Salmonella, Helmholtz Centre for Infection Research, Braunschweig, Germany
- * E-mail:
| |
Collapse
|
16
|
Structural and functional dissection reveals distinct roles of Ca2+-binding sites in the giant adhesin SiiE of Salmonella enterica. PLoS Pathog 2017; 13:e1006418. [PMID: 28558023 PMCID: PMC5466336 DOI: 10.1371/journal.ppat.1006418] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 06/09/2017] [Accepted: 05/18/2017] [Indexed: 11/20/2022] Open
Abstract
The giant non-fimbrial adhesin SiiE of Salmonella enterica mediates the first contact to the apical site of epithelial cells and enables subsequent invasion. SiiE is a 595 kDa protein composed of 53 repetitive bacterial immunoglobulin (BIg) domains and the only known substrate of the SPI4-encoded type 1 secretion system (T1SS). The crystal structure of BIg50-52 of SiiE revealed two distinct Ca2+-binding sites per BIg domain formed by conserved aspartate or glutamate residues. In a mutational analysis Ca2+-binding sites were disrupted by aspartate to serine exchange at various positions in the BIg domains of SiiE. Amounts of secreted SiiE diminish with a decreasing number of intact Ca2+-binding sites. BIg domains of SiiE contain distinct Ca2+-binding sites, with type I sites being similar to other T1SS-secreted proteins and type II sites newly identified in SiiE. We functionally and structurally dissected the roles of type I and type II Ca2+-binding sites in SiiE, as well as the importance of Ca2+-binding sites in various positions of SiiE. Type I Ca2+-binding sites were critical for efficient secretion of SiiE and a decreasing number of type I sites correlated with reduced secretion. Type II sites were less important for secretion, stability and surface expression of SiiE, however integrity of type II sites in the C-terminal portion was required for the function of SiiE in mediating adhesion and invasion. The interaction of Salmonella enterica with polarized epithelial cells depends on the function of SiiE, a 595 kDa adhesin containing 53 repeats of a bacterial immunoglobulin (BIg) domain. SiiE is secreted and surface-expressed by a cognate type I secretion system (T1SS). We found that BIg domains contain amino acid (aa) residues forming binding sites for Ca2+ ions. Two types of Ca2+-binding sites can be distinguished, termed type I and type II sites. We performed a structural and functional dissection of Ca2+-binding sites of SiiE. After mutation of aa residues forming type I and/or type II Ca2+-binding sites, we investigated the secretion, surface expression and function as adhesin for interaction with polarized epithelial cells of the SiiE variants. We found that Ca2+-binding sites are critical for supporting the secretion of SiiE. Integrity of type I sites in any position of SiiE is essential for efficient secretion and surface expression. In contrast integrity of type II sites is less important for secretion. However, loss of type II in the C-terminal, most distal portion of SiiE ablated SiiE-mediated adhesion, while loss of the type II sites in middle or N-terminal portions of SiiE had less or no effect on SiiE function. We propose a novel mechanism of Ca2+-dependent secretion and conformational fine tuning of SiiE as a large T1SS substrate with a central role in the interaction of S. enterica with host cells.
Collapse
|
17
|
Barlag B, Beutel O, Janning D, Czarniak F, Richter CP, Kommnick C, Göser V, Kurre R, Fabiani F, Erhardt M, Piehler J, Hensel M. Single molecule super-resolution imaging of proteins in living Salmonella enterica using self-labelling enzymes. Sci Rep 2016; 6:31601. [PMID: 27534893 PMCID: PMC4989173 DOI: 10.1038/srep31601] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 07/20/2016] [Indexed: 12/23/2022] Open
Abstract
The investigation of the subcellular localization, dynamics and interaction of proteins and protein complexes in prokaryotes is complicated by the small size of the cells. Super-resolution microscopy (SRM) comprise various new techniques that allow light microscopy with a resolution that can be up to ten-fold higher than conventional light microscopy. Application of SRM techniques to living prokaryotes demands the introduction of suitable fluorescent probes, usually by fusion of proteins of interest to fluorescent proteins with properties compatible to SRM. Here we describe an approach that is based on the genetically encoded self-labelling enzymes HaloTag and SNAP-tag. Proteins of interest are fused to HaloTag or SNAP-tag and cell permeable substrates can be labelled with various SRM-compatible fluorochromes. Fusions of the enzyme tags to subunits of a type I secretion system (T1SS), a T3SS, the flagellar rotor and a transcription factor were generated and analysed in living Salmonella enterica. The new approach is versatile in tagging proteins of interest in bacterial cells and allows to determine the number, relative subcellular localization and dynamics of protein complexes in living cells.
Collapse
Affiliation(s)
- Britta Barlag
- Abt. Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
| | - Oliver Beutel
- Abt. Biophysik, Universität Osnabrück, Osnabrück, Germany
| | - Dennis Janning
- Abt. Neurobiologie, Universität Osnabrück, Osnabrück, Germany
| | | | | | - Carina Kommnick
- Abt. Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
| | - Vera Göser
- Abt. Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
| | - Rainer Kurre
- CALMOS, Universität Osnabrück, Osnabrück, Germany
| | - Florian Fabiani
- Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Marc Erhardt
- Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Jacob Piehler
- Abt. Biophysik, Universität Osnabrück, Osnabrück, Germany
| | - Michael Hensel
- Abt. Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
| |
Collapse
|
18
|
Koutsoumanis KP, Aspridou Z. Individual cell heterogeneity in Predictive Food Microbiology: Challenges in predicting a "noisy" world. Int J Food Microbiol 2016; 240:3-10. [PMID: 27412586 DOI: 10.1016/j.ijfoodmicro.2016.06.021] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 06/13/2016] [Accepted: 06/19/2016] [Indexed: 11/25/2022]
Abstract
Gene expression is a fundamentally noisy process giving rise to a significant cell to cell variability at the phenotype level. The phenotypic noise is manifested in a wide range of microbial traits. Heterogeneous behavior of individual cells is observed at the growth, survival and inactivation responses and should be taken into account in the context of Predictive Food Microbiology (PMF). Recent methodological advances can be employed for the study and modeling of single cell dynamics leading to a new generation of mechanistic models which can provide insight into the link between phenotype, gene-expression, protein and metabolic functional units at the single cell level. Such models however, need to deal with an enormous amount of interactions and processes that influence each other, forming an extremely complex system. In this review paper, we discuss the importance of noise and present the future challenges in predicting the "noisy" microbial responses in foods.
Collapse
Affiliation(s)
- Konstantinos P Koutsoumanis
- Laboratory of Food Microbiology and Hygiene, Department of Food Science and Technology, School of Agriculture, Forestry and Natural Environment, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
| | - Zafiro Aspridou
- Laboratory of Food Microbiology and Hygiene, Department of Food Science and Technology, School of Agriculture, Forestry and Natural Environment, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| |
Collapse
|
19
|
Møller TSB, Rau MH, Bonde CS, Sommer MOA, Guardabassi L, Olsen JE. Adaptive responses to cefotaxime treatment in ESBL-producingEscherichia coliand the possible use of significantly regulated pathways as novel secondary targets. J Antimicrob Chemother 2016; 71:2449-59. [DOI: 10.1093/jac/dkw198] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 04/26/2016] [Indexed: 12/12/2022] Open
|
20
|
Ren GX, Fan S, Guo XP, Chen S, Sun YC. Differential Regulation of c-di-GMP Metabolic Enzymes by Environmental Signals Modulates Biofilm Formation in Yersinia pestis. Front Microbiol 2016; 7:821. [PMID: 27375563 PMCID: PMC4891359 DOI: 10.3389/fmicb.2016.00821] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 05/16/2016] [Indexed: 11/13/2022] Open
Abstract
Cyclic diguanylate (c-di-GMP) is essential for Yersinia pestis biofilm formation, which is important for flea-borne blockage-dependent plague transmission. Two diguanylate cyclases (DGCs), HmsT and HmsD and one phosphodiesterase (PDE), HmsP are responsible for the synthesis and degradation of c-di-GMP in Y. pestis. Here, we systematically analyzed the effect of various environmental signals on regulation of the biofilm phenotype, the c-di-GMP levels, and expression of HmsT, HmsD, and HmsP in Y. pestis. Biofilm formation was higher in the presence of non-lethal high concentration of CaCl2, MgCl2, CuSO4, sucrose, sodium dodecyl sulfate, or dithiothreitol, and was lower in the presence of FeCl2 or NaCl. In addition, we found that HmsD plays a major role in biofilm formation in acidic or redox environments. These environmental signals differentially regulated expression of HmsT, HmsP and HmsD, resulting in changes in the intracellular levels of c-di-GMP in Y. pestis. Our results suggest that bacteria can sense various environmental signals, and differentially regulate activity of DGCs and PDEs to coordinately regulate and adapt metabolism of c-di-GMP and biofilm formation to changing environments.
Collapse
Affiliation(s)
- Gai-Xian Ren
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College Beijing, China
| | - Sai Fan
- Institute of Nutrition and Food Hygiene, Beijing Centre for Disease Control and Prevention Beijing, China
| | - Xiao-Peng Guo
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College Beijing, China
| | - Shiyun Chen
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences Wuhan, China
| | - Yi-Cheng Sun
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College Beijing, China
| |
Collapse
|
21
|
Abstract
The mutagenesis of enterobacterial genomes using phage λ Red recombinase functions is a rapid and versatile experimental tool. In addition to the rapid generation of deletions in the genome of Salmonella enterica, variations of the method allow site-directed mutagenesis, generation of reporter fusions, generation of chimeric genes, or transplantation of regulatory elements directly in the chromosome. We describe the application of these approaches with focus on practical aspects and critical steps.
Collapse
Affiliation(s)
- Frederik Czarniak
- Abteilung Mikrobiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, Barbarastr. 11, 49076, Osnabrück, Germany
| | | |
Collapse
|
22
|
Abstract
The bacteriophage λ Red homologous recombination system has been studied over the past 50 years as a model system to define the mechanistic details of how organisms exchange DNA segments that share extended regions of homology. The λ Red system proved useful as a system to study because recombinants could be easily generated by co-infection of genetically marked phages. What emerged from these studies was the recognition that replication of phage DNA was required for substantial Red-promoted recombination in vivo, and the critical role that double-stranded DNA ends play in allowing the Red proteins access to the phage DNA chromosomes. In the past 16 years, however, the λ Red recombination system has gained a new notoriety. When expressed independently of other λ functions, the Red system is able to promote recombination of linear DNA containing limited regions of homology (∼50 bp) with the Escherichia coli chromosome, a process known as recombineering. This review explains how the Red system works during a phage infection, and how it is utilized to make chromosomal modifications of E. coli with such efficiency that it changed the nature and number of genetic manipulations possible, leading to advances in bacterial genomics, metabolic engineering, and eukaryotic genetics.
Collapse
Affiliation(s)
- Kenan C Murphy
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01605
| |
Collapse
|
23
|
Song M, Kim JS, Liu L, Husain M, Vázquez-Torres A. Antioxidant Defense by Thioredoxin Can Occur Independently of Canonical Thiol-Disulfide Oxidoreductase Enzymatic Activity. Cell Rep 2016; 14:2901-11. [PMID: 26997275 DOI: 10.1016/j.celrep.2016.02.066] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 01/21/2016] [Accepted: 02/15/2016] [Indexed: 01/21/2023] Open
Abstract
The thiol-disulfide oxidoreductase CXXC catalytic domain of thioredoxin contributes to antioxidant defense in phylogenetically diverse organisms. We find that although the oxidoreductase activity of thioredoxin-1 protects Salmonella enterica serovar Typhimurium from hydrogen peroxide in vitro, it does not appear to contribute to Salmonella's antioxidant defenses in vivo. Nonetheless, thioredoxin-1 defends Salmonella from oxidative stress resulting from NADPH phagocyte oxidase macrophage expression during the innate immune response in mice. Thioredoxin-1 binds to the flexible linker, which connects the receiver and effector domains of SsrB, thereby keeping this response regulator in the soluble fraction. Thioredoxin-1, independently of thiol-disulfide exchange, activates intracellular SPI2 gene transcription required for Salmonella resistance to both reactive species generated by NADPH phagocyte oxidase and oxygen-independent lysosomal host defenses. These findings suggest that the horizontally acquired virulence determinant SsrB is regulated post-translationally by ancestrally present thioredoxin.
Collapse
Affiliation(s)
- Miryoung Song
- Department of Immunology and Microbiology, University of Colorado School of Medicine, 12800 East 19(th) Avenue, Aurora, CO 80045, USA
| | - Ju-Sim Kim
- Department of Immunology and Microbiology, University of Colorado School of Medicine, 12800 East 19(th) Avenue, Aurora, CO 80045, USA
| | - Lin Liu
- Department of Immunology and Microbiology, University of Colorado School of Medicine, 12800 East 19(th) Avenue, Aurora, CO 80045, USA
| | - Maroof Husain
- Department of Immunology and Microbiology, University of Colorado School of Medicine, 12800 East 19(th) Avenue, Aurora, CO 80045, USA; Division of Molecular and Translational Biomedicine, Department of Anesthesiology and Perioperative Medicine, University of Alabama, Birmingham, 619 South 19(th) Street, Birmingham, AL 35249-6810, USA
| | - Andrés Vázquez-Torres
- Department of Immunology and Microbiology, University of Colorado School of Medicine, 12800 East 19(th) Avenue, Aurora, CO 80045, USA; Veterans Affairs Eastern Colorado Health Care System, 1055 Clermont Street, Denver, CO 80220, USA.
| |
Collapse
|
24
|
Møller TSB, Overgaard M, Nielsen SS, Bortolaia V, Sommer MOA, Guardabassi L, Olsen JE. Relation between tetR and tetA expression in tetracycline resistant Escherichia coli. BMC Microbiol 2016; 16:39. [PMID: 26969122 PMCID: PMC4788846 DOI: 10.1186/s12866-016-0649-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 02/29/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Tetracyclines are among the most used antibiotics in livestock worldwide. Resistance is widely disseminated in Escherichia coli, where it is generally mediated by tetracycline efflux pumps, such as TetA. Expression of tetracycline efflux pumps is tightly controlled by the repressor TetR, which has been shown to be tetracycline-responsive at sub-MIC tetracycline concentrations. The objective of this study was to investigate the effects of increasing tetracycline concentrations on the growth of TetA-producing E. coli, and to determine how expression of tetA and tetR related to each other in different growth phases in the presence of tetracycline. RESULTS A tetracycline resistant E. coli strain containing tetA and tetR on the chromosome was constructed and cultured in the presence of increasing concentrations of tetracycline. Expression of tetR and tetA was measured at four time points in different growth phases by quantitative real-time PCR. The TetA-producing E. coli exhibited prolonged lag phase with increasing concentrations of tetracycline, while expression of tetA and tetR increased and decreased, respectively, with increasing tetracycline concentration. The levels of tetA and tetR mRNA varied depending on growth phase, resulting in a gradual decrease of the tetA/tetR ratio from approximately 4 in the lag phase to approximately 2 in the stationary phase. CONCLUSION This study shows that the expression of tetR and tetA is tetracycline concentration- and growth phase-dependent, contributing to improved understanding of the relationships between E. coli growth, tetracycline exposure and expression of tetracycline resistance.
Collapse
Affiliation(s)
- Thea S B Møller
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, C, Denmark
| | - Martin Overgaard
- Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense, Denmark.,Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Søren S Nielsen
- Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, C, Denmark
| | - Valeria Bortolaia
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, C, Denmark
| | - Morten O A Sommer
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark.,Novo Nordisk Foundation Centre for Biosustainability, Technical University of Denmark, Hørsholm, Denmark
| | - Luca Guardabassi
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, C, Denmark
| | - John E Olsen
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, C, Denmark.
| |
Collapse
|
25
|
Nedialkova LP, Sidstedt M, Koeppel MB, Spriewald S, Ring D, Gerlach RG, Bossi L, Stecher B. Temperate phages promote colicin-dependent fitness of Salmonella enterica serovar Typhimurium. Environ Microbiol 2015; 18:1591-603. [PMID: 26439675 DOI: 10.1111/1462-2920.13077] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/25/2015] [Accepted: 09/28/2015] [Indexed: 12/12/2022]
Abstract
Bacteria employ bacteriocins for interference competition in microbial ecosystems. Colicin Ib (ColIb), a pore-forming bacteriocin, confers a significant fitness benefit to Salmonella enterica serovar Typhimurium (S. Tm) in competition against commensal Escherichia coli in the gut. ColIb is released from S. Tm into the environment, where it kills susceptible competitors. However, colicin-specific release proteins, as they are known for other colicins, have not been identified in case of ColIb. Thus, its release mechanism has remained unclear. In the current study, we have established a new link between ColIb release and lysis activity of temperate, lambdoid phages. By the use of phage-cured S. Tm mutant strains, we show that the presence of temperate phages and their lysis genes is necessary and sufficient for release of active ColIb into the culture supernatant. Furthermore, phage-mediated lysis significantly enhanced S. Tm fitness in competition against a ColIb-susceptible competitor. Finally, transduction with the lambdoid phage 933W rescued the defect of E. coli strain MG1655 with respect to ColIb release. In conclusion, ColIb is released from bacteria in the course of phage lysis. Our data reveal a new mechanism for colicin release and point out a novel function of temperate phages in enhancing colicin-dependent bacterial fitness.
Collapse
Affiliation(s)
- Lubov P Nedialkova
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336, Munich, Germany
| | - Maja Sidstedt
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336, Munich, Germany
| | - Martin B Koeppel
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336, Munich, Germany.,German Center for Infection Research (DZIF), partner site LMU Munich, Munich, Germany
| | - Stefanie Spriewald
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336, Munich, Germany
| | - Diana Ring
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336, Munich, Germany.,German Center for Infection Research (DZIF), partner site LMU Munich, Munich, Germany
| | - Roman G Gerlach
- Wernigerode Branch, Robert Koch Institute, Project Group 5, Burgstr. 37, 38855, Wernigerode, Germany
| | - Lionello Bossi
- CNRS, Centre de Genetique Moleculaire, Gif-sur-Yvette Cedex, 91198, France
| | - Bärbel Stecher
- Max-von-Pettenkofer Institute, LMU Munich, Pettenkoferstr. 9a, 80336, Munich, Germany.,German Center for Infection Research (DZIF), partner site LMU Munich, Munich, Germany
| |
Collapse
|
26
|
Hicks KG, Delbecq SP, Sancho-Vaello E, Blanc MP, Dove KK, Prost LR, Daley ME, Zeth K, Klevit RE, Miller SI. Acidic pH and divalent cation sensing by PhoQ are dispensable for systemic salmonellae virulence. eLife 2015; 4:e06792. [PMID: 26002083 PMCID: PMC4473727 DOI: 10.7554/elife.06792] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Accepted: 05/22/2015] [Indexed: 12/30/2022] Open
Abstract
Salmonella PhoQ is a histidine kinase with a periplasmic sensor domain (PD) that promotes virulence by detecting the macrophage phagosome. PhoQ activity is repressed by divalent cations and induced in environments of acidic pH, limited divalent cations, and cationic antimicrobial peptides (CAMP). Previously, it was unclear which signals are sensed by salmonellae to promote PhoQ-mediated virulence. We defined conformational changes produced in the PhoQ PD on exposure to acidic pH that indicate structural flexibility is induced in α-helices 4 and 5, suggesting this region contributes to pH sensing. Therefore, we engineered a disulfide bond between W104C and A128C in the PhoQ PD that restrains conformational flexibility in α-helices 4 and 5. PhoQW104C-A128C is responsive to CAMP, but is inhibited for activation by acidic pH and divalent cation limitation. phoQW104C-A128CSalmonella enterica Typhimurium is virulent in mice, indicating that acidic pH and divalent cation sensing by PhoQ are dispensable for virulence. DOI:http://dx.doi.org/10.7554/eLife.06792.001 Salmonella bacteria cause illnesses in humans, such as food poisoning and typhoid fever. In response to a Salmonella infection, immune cells known as macrophages detect and engulf the bacteria. The conditions inside the macrophage (which include an acidic pH and high levels of antimicrobial molecules) can destroy some bacteria. However, Salmonella bacteria (which are also called salmonellae) can sense and counteract these hostile conditions; this allows them to remodel their surface to survive and reproduce inside macrophages and continue to cause disease. A protein known as PhoQ, which is found on the surface of Salmonella bacteria, is a sensor that detects when the bacterium is inside a macrophage and so needs to boost its defenses. The PhoQ sensor is able to respond to acidity, the absence of divalent cations—such as magnesium and calcium ions—and certain antimicrobial peptide molecules. These conditions and components are used inside macrophages to try and kill the bacteria, but it was not known which of these signals PhoQ actually senses during an infection. Hicks et al. established how the sensor region of PhoQ changes when it is exposed to acid. This knowledge enabled variants of this protein to be constructed that do not respond when exposed to acidic conditions or low levels of divalent cations. Salmonellae that have these modified PhoQ sensors were still able to infect macrophages and cause disease in mice. These findings suggest that antimicrobial peptide sensing alone is sufficient to trigger the bacteria's defenses inside host organisms. Understanding how salmonellae detect antimicrobial factors could help with the development of new treatments for the diseases caused by these bacteria. Furthermore, the new tools developed by Hicks et al. could be applied to other systems to characterize how bacteria interact with their host environment during infection. DOI:http://dx.doi.org/10.7554/eLife.06792.002
Collapse
Affiliation(s)
- Kevin G Hicks
- Department of Microbiology, University of Washington Medical School, Seattle, United States
| | - Scott P Delbecq
- Department of Biochemistry, University of Washington Medical School, Seattle, United States
| | - Enea Sancho-Vaello
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad del País Vasco/Euskal Herriko Unibertsitatea (CSIC,UPV/EHU), Leioa, Bizkaia, Spain
| | - Marie-Pierre Blanc
- Department of Microbiology, University of Washington Medical School, Seattle, United States
| | - Katja K Dove
- Department of Biochemistry, University of Washington Medical School, Seattle, United States
| | - Lynne R Prost
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
| | - Margaret E Daley
- Department of Chemistry and Biochemistry, University of San Diego, San Diego, United States
| | - Kornelius Zeth
- Department of Biochemistry and Molecular Biology, University of Basque Country, Leioa, Spain
| | - Rachel E Klevit
- Department of Biochemistry, University of Washington Medical School, Seattle, United States
| | - Samuel I Miller
- Department of Microbiology, University of Washington Medical School, Seattle, United States
| |
Collapse
|
27
|
Virulence Gene Regulation by L-Arabinose in Salmonella enterica. Genetics 2015; 200:807-19. [PMID: 25991823 DOI: 10.1534/genetics.115.178103] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 05/14/2015] [Indexed: 01/06/2023] Open
Abstract
Invasion of the intestinal epithelium is a critical step in Salmonella enterica infection and requires functions encoded in the gene cluster known as Salmonella Pathogenicity Island 1 (SPI-1). Expression of SPI-1 genes is repressed by L-arabinose, and not by other pentoses. Transport of L-arabinose is necessary to repress SPI-1; however, repression is independent of L-arabinose metabolism and of the L-arabinose-responsive regulator AraC. SPI-1 repression by L-arabinose is exerted at a single target, HilD, and the mechanism appears to be post-translational. As a consequence of SPI-1 repression, l-arabinose reduces translocation of SPI-1 effectors to epithelial cells and decreases Salmonella invasion in vitro. These observations reveal a hitherto unknown role of L-arabinose in gene expression control and raise the possibility that Salmonella may use L-arabinose as an environmental signal.
Collapse
|
28
|
Kjeldsen TSB, Sommer MOA, Olsen JE. Extended spectrum β-lactamase-producing Escherichia coli forms filaments as an initial response to cefotaxime treatment. BMC Microbiol 2015; 15:63. [PMID: 25888392 PMCID: PMC4367913 DOI: 10.1186/s12866-015-0399-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 02/24/2015] [Indexed: 11/10/2022] Open
Abstract
Background β-lactams target the peptidoglycan layer in the bacterial cell wall and most β-lactam antibiotics cause filamentation in susceptible Gram-negative bacteria at low concentrations. The objective was to determine the initial morphological response of cephalosporin resistant CTX-M-1-producing E. coli to cefotaxime and to determine whether the response depended on the growth phase of the bacterium and the concentration of antibiotic. Results Two antibiotic resistant strains carrying blaCTX-M-1 on the chromosome and on an IncI1 plasmid and three sensitive strains were used in this study. The resistant strains displayed elongated cells when exposed to cefotaxime at sub-inhibitory as well as therapeutic concentrations (1 to 512 mg/L of cefotaxime) in both lag and early exponential phase, suggesting that the elongation was an initial response mechanism to the antibiotic. Normal sized cells were the dominant cell type in exponential and stationary growth phase. No elongated cells were seen in cultures without cefotaxime. In cultures with high concentrations of cefotaxime (128–512 mg/L), no growth other than initial filamentation was observed, but spheroplats appeared after 14–17 hours in cultures of the resistant strains. Filaments were also observed in sensitive control strains with sub-inhibitory concentrations of cefotaxime. Conclusions We showed that E. coli resistant to β-lactams by an extended-spectrum β-lactamase, blaCTX-M-1, produced filaments when exposed to cefotaxime. The filament formation was restricted to early growth phases and the time the cells grew as filaments was antibiotic concentration dependent. This indicates that antibiotic resistant E. coli undergo the same morphological changes as sensitive bacteria in the presence of β-lactam antibiotic. It was showed that the filament formation was an initial response to the antibiotics.
Collapse
Affiliation(s)
- Thea S B Kjeldsen
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, 1870, Frederiksberg C, Denmark.
| | - Morten O A Sommer
- Department of Systems Biology, Technical University of Denmark, 2800, Lyngby, Denmark. .,Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2970, Hørsholm, Denmark.
| | - John E Olsen
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, 1870, Frederiksberg C, Denmark.
| |
Collapse
|
29
|
Patterns of expression and translocation of the ubiquitin ligase SlrP in Salmonella enterica serovar Typhimurium. J Bacteriol 2014; 196:3912-22. [PMID: 25182488 DOI: 10.1128/jb.02158-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
SlrP is an E3 ubiquitin ligase that can be translocated into eukaryotic host cells by the two type III secretion systems that are expressed by Salmonella enterica serovar Typhimurium and are encoded in Salmonella pathogenicity islands 1 (SPI1) and 2 (SPI2). Expression of slrP and translocation of its product were examined using lac, 3×FLAG, and cyaA' translational fusions. Although slrP was expressed in different media, optimal expression was found under conditions that imitate the intravacuolar environment and promote synthesis of the SPI2-encoded type III secretion system. Translocation into mammalian cells took place through the SPI1- or the SPI2-encoded type III secretion system, depending on specific host cell type and timing. A search for genetic factors involved in controlling the expression of slrP unveiled LeuO, Lon, and the two-component system PhoQ/PhoP as novel regulators of slrP. Our experiments suggest that LeuO and Lon act through HilD under SPI1-inducing conditions, whereas PhoP directly interacts with the slrP promoter to activate transcription under SPI2 inducing conditions.
Collapse
|
30
|
Kjeldsen TSB, Overgaard M, Nielsen SS, Bortolaia V, Jelsbak L, Sommer M, Guardabassi L, Olsen JE. CTX-M-1 β-lactamase expression in Escherichia coli is dependent on cefotaxime concentration, growth phase and gene location. J Antimicrob Chemother 2014; 70:62-70. [DOI: 10.1093/jac/dku332] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
31
|
Inflammation fuels colicin Ib-dependent competition of Salmonella serovar Typhimurium and E. coli in enterobacterial blooms. PLoS Pathog 2014; 10:e1003844. [PMID: 24391500 PMCID: PMC3879352 DOI: 10.1371/journal.ppat.1003844] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 11/06/2013] [Indexed: 01/09/2023] Open
Abstract
The host's immune system plays a key role in modulating growth of pathogens and the intestinal microbiota in the gut. In particular, inflammatory bowel disorders and pathogen infections induce shifts of the resident commensal microbiota which can result in overgrowth of Enterobacteriaceae (“inflammation-inflicted blooms”). Here, we investigated competition of the human pathogenic Salmonella enterica serovar Typhimurium strain SL1344 (S. Tm) and commensal E. coli in inflammation-inflicted blooms. S. Tm produces colicin Ib (ColIb), which is a narrow-spectrum protein toxin active against related Enterobacteriaceae. Production of ColIb conferred a competitive advantage to S. Tm over sensitive E. coli strains in the inflamed gut. In contrast, an avirulent S. Tm mutant strain defective in triggering gut inflammation did not benefit from ColIb. Expression of ColIb (cib) is regulated by iron limitation and the SOS response. CirA, the cognate outer membrane receptor of ColIb on colicin-sensitive E. coli, is induced upon iron limitation. We demonstrate that growth in inflammation-induced blooms favours expression of both S. Tm ColIb and the receptor CirA, thereby fuelling ColIb dependent competition of S. Tm and commensal E. coli in the gut. In conclusion, this study uncovers a so-far unappreciated role of inflammation-inflicted blooms as an environment favouring ColIb-dependent competition of pathogenic and commensal representatives of the Enterobacteriaceae family. Colicins are bacterial protein toxins which show potent activity against sensitive strains in vitro. Ecological models suggest that colicins play a major role in modulating dynamics of bacterial populations in the gut. However, previous studies could not readily confirm these predictions by respective in vivo experiments. In animal models, colicin-producing strains only show a minor or even absent fitness benefit over sensitive competitors. Here, we propose that the gut environment plays a crucial role in generating conditions for bacterial competition by colicin Ib (ColIb). Gut inflammation favours overgrowth of Enterobacteriaceae (“inflammation-inflicted Enterobacterial blooms”). We show that a pathogenic Salmonella Typhimurium (S. Tm) strain benefits from ColIb production in competition against commensal E. coli upon growth in inflammation-inflicted blooms. In the absence of gut inflammation, ColIb production did not confer a competitive advantage to S. Tm. In the inflamed gut, the genes for ColIb production in S. Tm and its corresponding ColIb-surface receptor CirA in E. coli were markedly induced, as compared to the non-inflamed gut. Therefore, environmental conditions in inflammation-inflicted blooms favour colicin-dependent competition of Enterobacteriaceae by triggering ColIb production and susceptibility at the same time. Our findings reveal a role of colicins as important bacterial fitness factors in inflammation-induced blooms.
Collapse
|
32
|
Grin I, Hartmann MD, Sauer G, Hernandez Alvarez B, Schütz M, Wagner S, Madlung J, Macek B, Felipe-Lopez A, Hensel M, Lupas A, Linke D. A trimeric lipoprotein assists in trimeric autotransporter biogenesis in enterobacteria. J Biol Chem 2013; 289:7388-98. [PMID: 24369174 PMCID: PMC3953254 DOI: 10.1074/jbc.m113.513275] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Trimeric autotransporter adhesins (TAAs) are important virulence factors of many Gram-negative bacterial pathogens. TAAs form fibrous, adhesive structures on the bacterial cell surface. Their N-terminal extracellular domains are exported through a C-terminal membrane pore; the insertion of the pore domain into the bacterial outer membrane follows the rules of β-barrel transmembrane protein biogenesis and is dependent on the essential Bam complex. We have recently described the full fiber structure of SadA, a TAA of unknown function in Salmonella and other enterobacteria. In this work, we describe the structure and function of SadB, a small inner membrane lipoprotein. The sadB gene is located in an operon with sadA; orthologous operons are only found in enterobacteria, whereas other TAAs are not typically associated with lipoproteins. Strikingly, SadB is also a trimer, and its co-expression with SadA has a direct influence on SadA structural integrity. This is the first report of a specific export factor of a TAA, suggesting that at least in some cases TAA autotransport is assisted by additional periplasmic proteins.
Collapse
Affiliation(s)
- Iwan Grin
- From the Max Planck Institut für Entwicklungsbiologie, 72076 Tübingen
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Wille T, Wagner C, Mittelstädt W, Blank K, Sommer E, Malengo G, Döhler D, Lange A, Sourjik V, Hensel M, Gerlach RG. SiiA and SiiB are novel type I secretion system subunits controlling SPI4-mediated adhesion ofSalmonella enterica. Cell Microbiol 2013; 16:161-78. [DOI: 10.1111/cmi.12222] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 09/25/2013] [Accepted: 09/27/2013] [Indexed: 12/28/2022]
Affiliation(s)
- Thorsten Wille
- Nachwuchsgruppe 3; RKI Bereich Wernigerode; Wernigerode Germany
| | - Carolin Wagner
- Mikrobiologisches Institut; Universitätsklinikum Erlangen; Erlangen Germany
- Abt. Mikrobiologie; Universität Osnabrück; Osnabrück Germany
| | | | - Kathrin Blank
- Nachwuchsgruppe 3; RKI Bereich Wernigerode; Wernigerode Germany
| | - Erik Sommer
- Zentrum für Molekulare Biologie der Universität Heidelberg; DKFZ-ZMBH-Alliance; Heidelberg Germany
| | - Gabriele Malengo
- Zentrum für Molekulare Biologie der Universität Heidelberg; DKFZ-ZMBH-Alliance; Heidelberg Germany
| | - Daniela Döhler
- Mikrobiologisches Institut; Universitätsklinikum Erlangen; Erlangen Germany
| | - Anna Lange
- Nachwuchsgruppe 3; RKI Bereich Wernigerode; Wernigerode Germany
| | - Viktor Sourjik
- Zentrum für Molekulare Biologie der Universität Heidelberg; DKFZ-ZMBH-Alliance; Heidelberg Germany
| | - Michael Hensel
- Abt. Mikrobiologie; Universität Osnabrück; Osnabrück Germany
| | | |
Collapse
|
34
|
The type VI secretion system encoded in Salmonella pathogenicity island 19 is required for Salmonella enterica serotype Gallinarum survival within infected macrophages. Infect Immun 2013; 81:1207-20. [PMID: 23357385 DOI: 10.1128/iai.01165-12] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Salmonella enterica serotype Gallinarum is the causative agent of fowl typhoid, a disease characterized by high morbidity and mortality that causes major economic losses in poultry production. We have reported that S. Gallinarum harbors a type VI secretion system (T6SS) encoded in Salmonella pathogenicity island 19 (SPI-19) that is required for efficient colonization of chicks. In the present study, we aimed to characterize the SPI-19 T6SS functionality and to investigate the mechanisms behind the phenotypes previously observed in vivo. Expression analyses revealed that SPI-19 T6SS core components are expressed and produced under in vitro bacterial growth conditions. However, secretion of the structural/secreted components Hcp1, Hcp2, and VgrG to the culture medium could not be determined, suggesting that additional signals are required for T6SS-dependent secretion of these proteins. In vitro bacterial competition assays failed to demonstrate a role for SPI-19 T6SS in interbacterial killing. In contrast, cell culture experiments with murine and avian macrophages (RAW264.7 and HD11, respectively) revealed production of a green fluorescent protein-tagged version of VgrG soon after Salmonella uptake. Furthermore, infection of RAW264.7 and HD11 macrophages with deletion mutants of SPI-19 or strains with genes encoding specific T6SS core components (clpV and vgrG) revealed that SPI-19 T6SS contributes to S. Gallinarum survival within macrophages at 20 h postuptake. SPI-19 T6SS function was not linked to Salmonella-induced cytotoxicity or cell death of infected macrophages, as has been described for other T6SS. Our data indicate that SPI-19 T6SS corresponds to a novel tool used by Salmonella to survive within host cells.
Collapse
|
35
|
Georgi C, Buerger J, Hillen W, Berens C. Promoter strength driving TetR determines the regulatory properties of Tet-controlled expression systems. PLoS One 2012; 7:e41620. [PMID: 22848546 PMCID: PMC3407185 DOI: 10.1371/journal.pone.0041620] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 06/22/2012] [Indexed: 12/15/2022] Open
Abstract
Bacteria frequently rely on transcription repressors and activators to alter gene expression patterns in response to changes in the surrounding environment. Tet repressor (TetR) is a paradigm transcription factor that senses the environmental state by binding small molecule effectors, the tetracyclines. However, recently isolated peptides that act as inducers of TetR after having been fused to the C-terminus of a carrier protein, suggest that TetR can also regulate gene expression in a signal-transduction pathway. For this shift in regulatory mechanism to be successful, induction of TetR must be sensitive enough to respond to an inducing protein expressed at its endogenous level. To determine this regulatory parameter, a synthetic Tet-regulated system was introduced into the human pathogen Salmonella enterica serovar Typhimurium and tested for inducibility by a peptide. Reporter gene expression was detected if the peptide-containing carrier protein Thioredoxin 1 was strongly overproduced, but not if it was expressed at a level similar to the physiological level of Thioredoxin 1. This was attributed to high steady-state amounts of TetR which was expressed by the promoter of the chloramphenicol acetyl transferase gene (P(cat)). Reducing P(cat) strength either by directed or by random mutagenesis of its -10 element concomitantly reduced the intracellular amounts of TetR. Sensitive and quantitative induction of TetR by an inducing peptide, when it was fused to Thioredoxin 1 at its native locus in the genome, was only obtained with weak P(cat) promoter variants containing GC-rich -10 elements. A second important observation was that reducing the TetR steady-state level did not impair repression. This permits flexible adjustment of an inducible system's sensitivity simply by altering the expression level of the transcription factor. These two new layers of expression control will improve the quality and, thus, the applicability of the Tet and other regulatory systems.
Collapse
Affiliation(s)
- Christiane Georgi
- Lehrstuhl für Mikrobiologie, Department Biologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Julia Buerger
- Lehrstuhl für Mikrobiologie, Department Biologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Wolfgang Hillen
- Lehrstuhl für Mikrobiologie, Department Biologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Christian Berens
- Lehrstuhl für Mikrobiologie, Department Biologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| |
Collapse
|
36
|
The Yersinia pestis Rcs phosphorelay inhibits biofilm formation by repressing transcription of the diguanylate cyclase gene hmsT. J Bacteriol 2012; 194:2020-6. [PMID: 22328676 DOI: 10.1128/jb.06243-11] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Yersinia pestis, which causes bubonic plague, forms biofilms in fleas, its insect vectors, as a means to enhance transmission. Biofilm development is positively regulated by hmsT, encoding a diguanylate cyclase that synthesizes the bacterial second messenger cyclic-di-GMP. Biofilm development is negatively regulated by the Rcs phosphorelay signal transduction system. In this study, we show that Rcs-negative regulation is accomplished by repressing transcription of hmsT.
Collapse
|
37
|
Gaussia princeps luciferase as a reporter for transcriptional activity, protein secretion, and protein-protein interactions in Salmonella enterica serovar typhimurium. Appl Environ Microbiol 2011; 78:250-7. [PMID: 22020521 DOI: 10.1128/aem.06670-11] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gaussia princeps luciferase (Gluc) is widely used as a reporter in eukaryotes, but data about its applicability in bacteria are very limited. Here we show that a codon-optimized Gluc gene can be efficiently expressed in Salmonella enterica serovar Typhimurium. To test different Gluc variants as transcriptional reporters, we used the siiA promoter of Salmonella pathogenicity island 4 (SPI-4) driving expression of either an episomal or a chromosomally integrated Gluc gene. Most reliable results were obtained from lysates of single-copy Gluc reporter strains. Given the small size, high activity, and cofactor independence of Gluc, it might be especially suited to monitor secretion of bacterial proteins. We demonstrate its usefulness by luminescence detection of fusion proteins of Gluc and C-terminal portions of the SPI-4-encoded, type I-secreted adhesin SiiE in supernatants. The SiiE C-terminal moiety including immunoglobulin (Ig) domain 53 is essential and sufficient for mediating type I-dependent secretion of Gluc. In eukaryotes, protein-protein interaction studies based on split-Gluc protein complementation assays (PCA) could be established. We adapted these methods for use in Salmonella, demonstrating the interaction between the SPI-1-encoded effector SipA and its cognate secretion chaperone InvB. In conclusion, the versatile Gluc can be used to address a variety of biological questions, thus representing a valuable addition to the toolbox of modern molecular biology and microbiology.
Collapse
|
38
|
Wagner C, Polke M, Gerlach RG, Linke D, Stierhof YD, Schwarz H, Hensel M. Functional dissection of SiiE, a giant non-fimbrial adhesin of Salmonella enterica. Cell Microbiol 2011; 13:1286-301. [PMID: 21729227 DOI: 10.1111/j.1462-5822.2011.01621.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Salmonella enterica deploys the giant non-fimbrial adhesin SiiE to adhere to the apical side of polarized epithelial cells. The establishment of close contact is a prerequisite for subsequent invasion mediated by translocation of effector proteins of the Salmonella Pathogenicity Island 1 (SPI1)-encoded type III secretion system (T3SS). Although SiiE is secreted into the culture medium, the adhesin is retained on the bacterial envelope in the phase of highest bacterial invasiveness. To dissect the structural requirements for secretion, retention and adhesive properties, comprehensive deletional and functional analyses of various domains of SiiE were performed. We observed that β-sheet and coiled-coil domains in the N-terminal moiety of SiiE are required for the control of SiiE retention on the surface and co-ordinated release. These results indicate a novel molecular mechanism for the control of surface display of a T1SS-secreted adhesin that acts cooperatively with the SPI1-T3SS.
Collapse
Affiliation(s)
- Carolin Wagner
- Abteilung Mikrobiologie, Universität Osnabrück, Osnabrück, Germany
| | | | | | | | | | | | | |
Collapse
|
39
|
Porcheron G, Kut E, Canepa S, Maurel MC, Schouler C. Regulation of fructooligosaccharide metabolism in an extra-intestinal pathogenic Escherichia coli strain. Mol Microbiol 2011; 81:717-33. [PMID: 21692876 DOI: 10.1111/j.1365-2958.2011.07725.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A gene cluster involved in the metabolism of prebiotic short-chain fructooligosaccharides (scFOS) has recently been identified in the extra-intestinal avian pathogenic Escherichia coli strain BEN2908. This gene cluster, called the fos locus, plays a major role in the initiation stage of chicken intestinal colonization. This locus is composed of six genes organized as an operon encoding a sugar transporter and enzymes involved in scFOS metabolism, and of a divergently transcribed gene encoding a transcriptional regulator, FosR, belonging to the LacI/GalR family. To decipher the regulation of scFOS metabolism, we monitored the fos operon promoter activity using a luciferase reporter gene assay. We demonstrated that the expression of fos genes is repressed by FosR, controlled by catabolite repression and induced in the presence of scFOS. Using electrophoretic mobility shift assays and surface plasmon resonance experiments, we showed that FosR binds to two operator sequences of the fos operon promoter region. This binding to DNA was inhibited in the presence of scFOS, especially by GF2. We then propose a model of scFOS metabolism regulation in a pathogenic bacterium, which will help to identify the environmental conditions required for fos gene expression and to understand the role of this locus in intestinal colonization.
Collapse
Affiliation(s)
- Gaëlle Porcheron
- INRA, UR1282 Infectiologie Animale et Santé Publique, F-37380 Nouzilly, France
| | | | | | | | | |
Collapse
|
40
|
McCarthy Y, Yang L, Twomey KB, Sass A, Tolker-Nielsen T, Mahenthiralingam E, Dow JM, Ryan RP. A sensor kinase recognizing the cell-cell signal BDSF (cis-2-dodecenoic acid) regulates virulence in Burkholderia cenocepacia. Mol Microbiol 2011; 77:1220-36. [PMID: 20624216 DOI: 10.1111/j.1365-2958.2010.07285.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Burkholderia cenocepacia is an opportunistic human pathogen that uses cis-2-dodecenoic acid (BDSF) as a quorum-sensing signal to control expression of virulence factors. BDSF is a signal molecule of the diffusible signal factor (DSF) family that was first described in the plant pathogen Xanthomonas campestris. The mechanism of perception of this signal and the range of functions regulated in B. cenocepacia are, however, unknown. A screen for transposon mutants unable to respond to exogenous signal identified BCAM0227 as a potential BDSF sensor. BCAM0227 is a histidine sensor kinase with an input domain unrelated to that of RpfC, the DSF sensor found in xanthomonads. Transcriptome profiling established the scope of the BDSF regulon and demonstrated that the sensor controls expression of a subset of these genes. A chimeric sensor kinase in which the input domain of BCAM0227 replaced the input domain of RpfC was active in BDSF signal perception when expressed in X. campestris. Mutation of BCAM0227 gave rise to reduced cytotoxicity to Chinese hamster ovary cells and reduced virulence to Wax moth larvae and in the agar-bead mouse model of pulmonary infection. The findings identify BCAM0227 as a novel BDSF sensor and a potential target for interference in virulence-related signalling in B. cenocepacia.
Collapse
Affiliation(s)
- Yvonne McCarthy
- BIOMERIT Research Centre, Department of Microbiology, Biosciences Institute, University College Cork, Cork, Ireland
| | | | | | | | | | | | | | | |
Collapse
|
41
|
Blank K, Hensel M, Gerlach RG. Rapid and highly efficient method for scarless mutagenesis within the Salmonella enterica chromosome. PLoS One 2011; 6:e15763. [PMID: 21264289 PMCID: PMC3021506 DOI: 10.1371/journal.pone.0015763] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Accepted: 12/02/2010] [Indexed: 11/19/2022] Open
Abstract
Direct manipulation of bacterial chromosomes by recombination-based techniques has become increasingly important for both cognitive and applied research. Here we demonstrate, for the first time, the combination of the Red recombinase system with I-SceI endonuclease-based selection of successful recombinants after electroporation with short synthetic olignucleotides. We show the generation of scarless gene knockouts as well as site-directed mutagenesis using the Salmonella virulence-associated two component signaling system PhoPQ. The presented approach is very versatile for generating in-frame deletions, point mutations or insertions within bacterial chromosomes.
Collapse
Affiliation(s)
- Kathrin Blank
- Junior Research Group 3, Robert Koch Institute, Wernigerode Branch, Wernigerode, Germany
| | - Michael Hensel
- Division of Microbiology, School of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany
| | - Roman G. Gerlach
- Junior Research Group 3, Robert Koch Institute, Wernigerode Branch, Wernigerode, Germany
- * E-mail:
| |
Collapse
|
42
|
Regulation of nleA in Shiga toxin-producing Escherichia coli O84:H4 strain 4795/97. J Bacteriol 2010; 193:832-41. [PMID: 21131485 DOI: 10.1128/jb.00582-10] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many Shiga toxin-producing Escherichia coli (STEC) strains express a type III secretion system (TTSS) encoded by the locus of enterocyte effacement (LEE). Using the TTSS, STEC is able to inject effector proteins directly into eukaryotic host cells, where they cause characteristic attaching and effacing (A/E) lesions. In addition to the LEE-encoded effectors, a number of non-LEE-encoded effectors, located on phage-associated elements, have been described. One of them, the non-LEE-encoded effector A (NleA), is widely distributed among pathogenic E. coli. In this study, we investigated the influence of environmental conditions on the expression of the phage-encoded effector nleA gene (designated nleA(4795)) present in STEC O84:H4 strain 4795/97. We demonstrated that a particular NaCl concentration and starvation stress increase the activity of the nleA(4795) promoter. Moreover, several regulators that control nleA(4795) expression were identified. The involvement of the LEE regulators Ler, GrlA, and GrlR show that nleA(4795) is integrated in the LEE regulation circuit. Furthermore, the binding of Ler to sequences upstream of nleA(4795) underlined these findings.
Collapse
|
43
|
Efficacy of intracellular activated promoters for generation of Salmonella-based vaccines. Infect Immun 2010; 78:4828-38. [PMID: 20732994 DOI: 10.1128/iai.00298-10] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Salmonella enterica is a versatile vaccine carrier for heterologous antigens. One strategy for vaccine antigen delivery is the use of live attenuated S. enterica strains that translocate heterologous antigens into antigen-presenting cells by means of type III secretion systems (T3SS). The feasibility of this approach has been demonstrated in various experimental vaccination studies. The efficacy of recombinant live vaccines is critically influenced by the optimal level of attenuation and many other factors. For the rational design of approaches involving translocation by T3SS, additional parameters are the level of expression of the heterologous antigens and the selection of carrier proteins for the delivery of antigens to desirable subcellular compartments of the target cell. We deployed the Salmonella pathogenicity island 2 (SPI2)-encoded T3SS for antigen delivery. The SPI2-T3SS and effector proteins are encoded by members of the large SsrAB regulon, including promoters with highly variable strength of expression. We investigated the effect of various in vivo-activated promoters of the SsrAB regulon on the efficacy of recombinant Salmonella vaccines. We observed that the use of promoters with higher strength results in greater synthesis of recombinant antigens and greater stimulation of T-cell responses in cell culture assays for the stimulation of T cells by the model antigen ovalbumin. In contrast, in vaccination experiments, promoters with a low level of expression resulted in the induction of higher amounts of T cells reactive to the model antigen listeriolysin. These results demonstrate that high-level expression of heterologous antigens does not necessarily result in optimal stimulation of immune responses.
Collapse
|
44
|
Hölzer SU, Hensel M. Functional dissection of translocon proteins of the Salmonella pathogenicity island 2-encoded type III secretion system. BMC Microbiol 2010; 10:104. [PMID: 20377892 PMCID: PMC2873485 DOI: 10.1186/1471-2180-10-104] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Accepted: 04/08/2010] [Indexed: 11/17/2022] Open
Abstract
Background Type III secretion systems (T3SS) are essential virulence factors of most Gram-negative bacterial pathogens. T3SS deliver effector proteins directly into the cytoplasm of eukaryotic target cells and for this function, the insertion of a subset of T3SS proteins into the target cell membrane is important. These proteins form hetero-oligomeric pores acting as translocon for the delivery of effector proteins. Salmonella enterica is a facultative intracellular pathogen that uses the Salmonella Pathogenicity Island 2 (SPI2)-encoded T3SS to manipulate host cells in order to survive and proliferate within the Salmonella-containing vacuole of host cells. Previous work showed that SPI2-encoded SseB, SseC and SseD act to form the translocon of the SPI2-T3SS. Results Here we investigated the structural requirements of SseB and SseD to form a functional translocon. Based on bioinformatic predictions, deletional analyses of SseB and SseD were performed and the effect on secretion by the T3SS, formation of a translocon, translocation of effector proteins and intracellular replication was investigated. Our data showed that both SseB and SseD are very sensitive towards alterations of the primary structure of the proteins. Although proteins encoded by mutant alleles were still secreted, we observed that all mutations resulted in a loss of function of the SPI2-T3SS. Conclusion These observations indicate that translocon proteins of the SPI2-T3SS are highly evolved towards the formation of multi-subunit complex in the host cell membrane. Structural alterations are not tolerated and abrogate translocon function.
Collapse
Affiliation(s)
- Stefanie U Hölzer
- Mikrobiologisches Institut, Universitätsklinikum Erlangen, Erlangen, Germany
| | | |
Collapse
|
45
|
Herrera CM, Hankins JV, Trent MS. Activation of PmrA inhibits LpxT-dependent phosphorylation of lipid A promoting resistance to antimicrobial peptides. Mol Microbiol 2010; 76:1444-60. [PMID: 20384697 PMCID: PMC2904496 DOI: 10.1111/j.1365-2958.2010.07150.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
During its transport to the bacterial surface, the phosphate groups of the lipid A anchor of Escherichia coli and Salmonella lipopolysaccharide are modified by membrane enzymes including ArnT, EptA and LpxT. ArnT and EptA catalyse the periplasmic addition of the positively charged substituents 4-amino-4-deoxy-L-arabinose and phosphoethanolamine respectively. These modifications are controlled by the PmrA transcriptional regulator and confer resistance to cationic antimicrobial peptides, including polymyxin. LpxT, however, catalyses the phosphorylation of lipid A at the 1-position forming 1-diphosphate lipid A increasing the negative charge of the bacterial surface. Here, we report that PmrA is involved in the regulation of LpxT. Interestingly, this regulation does not occur at the level of transcription, but rather following the assembly of LpxT into the inner membrane. PmrA-dependent inhibition of LpxT is required for phosphoethanolamine decoration of lipid A, which is shown here to be critical for E. coli to resist the bactericidal activity of polymyxin. Furthermore, although Salmonella lipid A is more prevalently modified with l-4-aminoarabinose, we demonstrate that loss of Salmonella lpxT greatly increases EptA modification. The current work is an example of the complexities associated with the structural remodelling of Gram-negative lipopolysaccharides promoting bacterial survival.
Collapse
Affiliation(s)
- Carmen M Herrera
- Section of Molecular Genetics and Microbiology, The University of Texas at Austin, Austin, TX 78712, USA
| | | | | |
Collapse
|
46
|
Abstract
Intracellular Salmonella enterica serovar Typhimurium deploys the Salmonella pathogenicity island 2 (SPI2)-encoded type III secretion system (T3SS) to modify host cell functions and accomplish intracellular replication. This virulence function is controlled by the two-component system SsrAB that regulates the expression of several operons in SPI2 and, in addition, a large number of genes for non-SPI2-encoded effector proteins. Here, we analyzed the relative expression levels of members of the SsrAB virulon. We used a novel reporter fusion strategy for single-copy chromosomal fusions, all done in an identical manner in order to enable direct quantitative comparison. We observed very high expression levels for sseJ and sifA; high expression levels for ssaG, steC, sseL, and sopD2; moderate expression levels for ssaB, sseA, sseG, sifB, pipB2, and sspH1; and low expression levels for sspH2, sseI, slrP, sseK1, sseK2, pipB, and gogB. The expression of the SsrAB virulon was highly dependent on the function of SsrB but also required EnvR/OmpZ. Deletion of PhoP, part of the global regulatory system PhoPQ, resulted in highly delayed expression of the SsrAB virulon under in vitro conditions; however, maximal expression was similar to that in a wild-type background. The expression levels of SsrAB-dependent genes in intracellular bacteria were in good agreement with in vitro analyses. We provide here a comprehensive and fully comparable analysis of the expression of genes in the SsrAB virulon. This information will be of interest for the selection of in vivo-activated promoters, for example, for rational design of recombinant vaccines.
Collapse
|
47
|
Effect of the O-antigen length of lipopolysaccharide on the functions of Type III secretion systems in Salmonella enterica. Infect Immun 2009; 77:5458-70. [PMID: 19797066 DOI: 10.1128/iai.00871-09] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The virulence of Salmonella enterica critically depends on the functions of two type III secretion systems (T3SS), with the Salmonella pathogenicity island 1 (SPI1)-encoded T3SS required for host cell invasion and the SPI2-T3SS enabling Salmonella to proliferate within host cells. A further T3SS is required for the assembly of the flagella. Most serovars of Salmonella also possess a lipopolysaccharide with a complex O-antigen (OAg) structure. The number of OAg units attached to the core polysaccharide varies between 16 and more than 100 repeats, with a trimodal distribution. This work investigated the correlation of the OAg length with the functions of the SPI1-T3SS and the SPI2-T3SS. We observed that the number of repeats of OAg units had no effect on bacterial motility. The interaction of Salmonella with epithelial cells was altered if the OAg structure was changed by mutations in regulators of OAg. Strains defective in synthesis of very long or long and very long OAg species showed increased translocation of a SPI1-T3SS effector protein and increased invasion. Invasion of a strain entirely lacking OAg was increased, but this mutant strain also showed increased adhesion. In contrast, translocation of a SPI2-T3SS effector protein and intracellular replication were not affected by modification of the OAg length. Mutant strains lacking the entire OAg or long and very long OAg were highly susceptible to complement killing. These observations indicate that the architecture of the outer membrane of Salmonella is balanced to permit sufficient T3SS function but also to confer optimal protection against antimicrobial defense mechanisms.
Collapse
|
48
|
Rapid oligonucleotide-based recombineering of the chromosome of Salmonella enterica. Appl Environ Microbiol 2009; 75:1575-80. [PMID: 19151186 DOI: 10.1128/aem.02509-08] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recombinant engineering using Red recombinase-based approaches offers efficient and rapid approaches to deletion and modification of genes. Here we describe a novel application of Red recombinant engineering that enables direct manipulation of chromosomal loci by electroporation with short synthetic DNA molecules. We demonstrate the use of this approach for the generation of scarless in-frame deletions in chromosomal genes of Salmonella enterica. Furthermore, we describe rapid site-directed mutagenesis within bacterial chromosomes without any requirement for cloning and mutating genes in vitro or for reintroducing mutant alleles into the chromosome. This approach can be expected to facilitate mutational analysis in S. enterica and in other bacterial species able to support Red-mediated recombination.
Collapse
|
49
|
Gerlach RG, Jäckel D, Geymeier N, Hensel M. Salmonella pathogenicity island 4-mediated adhesion is coregulated with invasion genes in Salmonella enterica. Infect Immun 2007; 75:4697-709. [PMID: 17635868 PMCID: PMC2044552 DOI: 10.1128/iai.00228-07] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Salmonella pathogenicity island 4 (SPI4) encodes a type I secretion system and the cognate substrate protein, SiiE. We have recently demonstrated that SiiE is a giant nonfimbrial adhesin involved in the adhesion of Salmonella enterica serovar Typhimurium to polarized epithelial cells. We also observed that under in vitro culture conditions, the synthesis and secretion of SiiE coincided with the activation of Salmonella invasion genes. These observations prompted us to investigate the regulation of SPI4 genes in detail. A novel approach for the generation of reporter gene fusions was employed to generate single-copy chromosomal fusions to various genes within SPI4, and the expression of these fusions was investigated. We analyzed the regulation of SPI4 genes and the roles of various regulatory systems for SPI4 expression. Our data show that the expression of SPI4 genes is coregulated with SPI1 invasion genes by the global regulator SirA. Expression of a SPI4 gene was also reduced in the absence of HilA, the central local regulator of SPI1 gene expression. Both SirA and HilA functions were required for the secretion of SiiE and the SPI4-mediated adhesion. Our data demonstrate that SPI4-mediated adhesion, as well as SPI1-mediated invasion, are tightly coregulated by the same regulatory circuits and induced under similar environmental conditions.
Collapse
Affiliation(s)
- Roman G Gerlach
- Institut für Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen, Wasserturmstr. 3-5, D-91054 Erlangen, Germany
| | | | | | | |
Collapse
|