1
|
Klein JA, Predeus AV, Greissl AR, Clark-Herrera MM, Cruz E, Cundiff JA, Haeberle AL, Howell M, Lele A, Robinson DJ, Westerman TL, Wrande M, Wright SJ, Green NM, Vallance BA, McClelland M, Mejia A, Goodman AG, Elfenbein JR, Knodler LA. Pathogenic diversification of the gut commensal Providencia alcalifaciens via acquisition of a second type III secretion system. Infect Immun 2024:e0031424. [PMID: 39254346 DOI: 10.1128/iai.00314-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2024] [Accepted: 08/13/2024] [Indexed: 09/11/2024] Open
Abstract
Providencia alcalifaciens is a Gram-negative bacterium found in various water and land environments and organisms, including insects and mammals. Some P. alcalifaciens strains encode gene homologs of virulence factors found in pathogenic Enterobacterales members, such as Salmonella enterica serovar Typhimurium and Shigella flexneri. Whether these genes are pathogenic determinants in P. alcalifaciens is not known. In this study, we investigated P. alcalifaciens-host interactions at the cellular level, focusing on the role of two type III secretion systems (T3SS) belonging to the Inv-Mxi/Spa family. T3SS1b is widespread in Providencia spp. and encoded on the chromosome. A large plasmid that is present in a subset of P. alcalifaciens strains, primarily isolated from diarrheal patients, encodes for T3SS1a. We show that P. alcalifaciens 205/92 is internalized into eukaryotic cells, lyses its internalization vacuole, and proliferates in the cytosol. This triggers caspase-4-dependent inflammasome responses in gut epithelial cells. The requirement for the T3SS1a in entry, vacuole lysis, and cytosolic proliferation is host cell type-specific, playing a more prominent role in intestinal epithelial cells than in macrophages or insect cells. In a bovine ligated intestinal loop model, P. alcalifaciens colonizes the intestinal mucosa and induces mild epithelial damage with negligible fluid accumulation in a T3SS1a- and T3SS1b-independent manner. However, T3SS1b was required for the rapid killing of Drosophila melanogaster. We propose that the acquisition of two T3SS has allowed P. alcalifaciens to diversify its host range, from a highly virulent pathogen of insects to an opportunistic gastrointestinal pathogen of animals.
Collapse
Affiliation(s)
- Jessica A Klein
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | | | - Aimee R Greissl
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Mattie M Clark-Herrera
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Eddy Cruz
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jennifer A Cundiff
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Amanda L Haeberle
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Maya Howell
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Aaditi Lele
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Donna J Robinson
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Trina L Westerman
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA
| | - Marie Wrande
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Sarah J Wright
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Nicole M Green
- Public Health Laboratory, Los Angeles County Department of Public Health, Downey, California, USA
| | - Bruce A Vallance
- Division of Gastroenterology, Hepatology and Nutrition, BC Children's Hospital and the University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael McClelland
- Department of Microbiology and Molecular Genetics, University of California, Irvine, California, USA
| | - Andres Mejia
- Comparative Pathology Laboratory, Research Animal Resources and Compliance, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Alan G Goodman
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
- School of Molecular Biosciences, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Johanna R Elfenbein
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA
| | - Leigh A Knodler
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
- Department of Microbiology and Molecular Genetics, Robert Larner College of Medicine at The University of Vermont, Burlington, Vermont, USA
| |
Collapse
|
2
|
Biswas P, Khan A, Mallick AI. Targeted Bioimaging of Microencapsulated Recombinant LAB Vector Expressing Fluorescent Reporter Protein: A Non-invasive Approach for Microbial Tracking. ACS Biomater Sci Eng 2024; 10:5210-5225. [PMID: 39087888 DOI: 10.1021/acsbiomaterials.4c00597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2024]
Abstract
Lactococcus lactis (L. lactis), the first genetically modified Generally Recognized As Safe (GRAS) category Lactic Acid producing Bacteria (LAB), is best known for its generalized health-promoting benefits and ability to express heterologous proteins. However, achieving the optimal probiotic effects requires a selective approach that would allow us to study in vivo microbial biodistribution, fate, and immunological consequences. Although the chemical conjugation of fluorophores and chromophores represent the standard procedure to tag microbial cells for various downstream applications, it requires a high-throughput synthesis scheme, which is often time-consuming and expensive. On the contrary, the genetic manipulation of LAB vector, either chromosomally or extra-chromosomally, to express bioluminescent or fluorescent reporter proteins has greatly enhanced our ability to monitor bacterial transit through a complex gut environment. However, with faster passage and quick washing out from the gut due to rhythmic contractions of the digestive tract, real-time tracking of LAB vectors, particularly non-commensal ones, remains problematic. To get a deeper insight into the biodistribution of non-commensal probiotic bacteria in vivo, we bioengineered L. lactis to express fluorescence reporter proteins, mCherry (bright red monomeric fluorescent protein) and mEGFP (monomeric enhanced green fluorescent protein), followed by microencapsulation with a mucoadhesive and biodegradable polymer, chitosan. We show that coating of recombinant Lactococcus lactis (rL. lactis) with chitosan polymer, cross-linked with tripolyphosphate (TPP), retains their ability to express the reporter proteins stably without altering the specificity and sensitivity of fluorescence detection in vitro and in vivo. Further, we provide evidence of enhanced intragastric stability by chitosan-TPP (CS) coating of rL. lactis cells, allowing us to study the spatiotemporal distribution for an extended time in the gut of two unrelated hosts, avian and murine. The present scheme involving genetic modification and chitosan encapsulation of non-commensal LAB vector demonstrates great promise as a non-invasive and intensive tool for active live tracking of gut microbes.
Collapse
Affiliation(s)
- Prakash Biswas
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, Nadia, West Bengal 741246, India
| | - Afruja Khan
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, Nadia, West Bengal 741246, India
| | - Amirul Islam Mallick
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, Nadia, West Bengal 741246, India
| |
Collapse
|
3
|
Klein JA, Predeus AV, Greissl AR, Clark-Herrera MM, Cruz E, Cundiff JA, Haeberle AL, Howell M, Lele A, Robinson DJ, Westerman TL, Wrande M, Wright SJ, Green NM, Vallance BA, McClelland M, Mejia A, Goodman AG, Elfenbein JR, Knodler LA. Pathogenic diversification of the gut commensal Providencia alcalifaciens via acquisition of a second type III secretion system. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.07.595826. [PMID: 38895369 PMCID: PMC11185699 DOI: 10.1101/2024.06.07.595826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Providencia alcalifaciens is a Gram-negative bacterium found in a wide variety of water and land environments and organisms. It has been isolated as part of the gut microbiome of animals and insects, as well as from stool samples of patients with diarrhea. Specific P. alcalifaciens strains encode gene homologs of virulence factors found in other pathogenic members of the same Enterobacterales order, such as Salmonella enterica serovar Typhimurium and Shigella flexneri. Whether these genes are also pathogenic determinants in P. alcalifaciens is not known. Here we have used P. alcalifaciens 205/92, a clinical isolate, with in vitro and in vivo infection models to investigate P. alcalifaciens -host interactions at the cellular level. Our particular focus was the role of two type III secretion systems (T3SS) belonging to the Inv-Mxi/Spa family. T3SS 1b is widespread in Providencia spp. and encoded on the chromosome. T3SS 1a is encoded on a large plasmid that is present in a subset of P. alcalifaciens strains, which are primarily isolates from diarrheal patients. Using a combination of electron and fluorescence microscopy and gentamicin protection assays we show that P. alcalifaciens 205/92 is internalized into eukaryotic cells, rapidly lyses its internalization vacuole and proliferates in the cytosol. This triggers caspase-4 dependent inflammasome responses in gut epithelial cells. The requirement for the T3SS 1a in entry, vacuole lysis and cytosolic proliferation is host-cell type specific, playing a more prominent role in human intestinal epithelial cells as compared to macrophages. In a bovine ligated intestinal loop model, P. alcalifaciens colonizes the intestinal mucosa, inducing mild epithelial damage with negligible fluid accumulation. No overt role for T3SS 1a or T3SS 1b was seen in the calf infection model. However, T3SS 1b was required for the rapid killing of Drosophila melanogaster . We propose that the acquisition of two T3SS by horizontal gene transfer has allowed P. alcalifaciens to diversify its host range, from a highly virulent pathogen of insects to an opportunistic gastrointestinal pathogen of animals.
Collapse
|
4
|
Liang Z, Tong J, Wu X, Liu S, Wu J, Yu Y, Zhang L, Zhao C, Lu Q, Nie J, Huang W, Wang Y. Development of a SARS-CoV-2 neutralization assay based on a pseudotyped virus using a HIV system. MedComm (Beijing) 2024; 5:e517. [PMID: 38525106 PMCID: PMC10959455 DOI: 10.1002/mco2.517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 02/06/2024] [Accepted: 02/25/2024] [Indexed: 03/26/2024] Open
Abstract
Regarding the extensive global attention to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that constitutes an international public health emergency, pseudovirus neutralization assays have been widely applied due to their advantages of being able to be conducted in biosafety level 2 laboratories and having a high safety factor. In this study, by adding a blue fluorescent protein (AmCyan) gene to the HIV system pSG3-△env backbone plasmid HpaI and truncating the C-terminal 21 amino acids of the SARS-CoV-2 spike protein (S), high-titer SARS-CoV-2-Sdel21-AmCyan fluorescent pseudovirus was successfully packaged. The fluorescent pseudovirus was used to establish a neutralization assay in a 96-well plate using 293T cells stably transfected with the AF cells. Then, parameters such as the ratio of backbone and membrane plasmid, sensitive cells, inoculation of cells and virus, as well as incubation and detection time were optimized. The pseudovirus neutralization assay demonstrated high accuracy, sensitivity, repeatability, and a strong correlation with the luminescent pseudovirus neutralization assay. Additionally, we scaled up the neutralizing antibody determination method by increasing the plate size from 96 wells to 384 wells. We have established a robust fluorescent pseudotyped virus neutralization assay for SARS-CoV-2 using the HIV system, providing a foundation for serum neutralization antibody detection, monoclonal antibody screening, and vaccine development.
Collapse
Affiliation(s)
- Ziteng Liang
- Chinese Academy of Medical Sciences & Peking Union Medical CollegeDongcheng District, BeijingChina
- Division of HIV/AIDS and Sex‐transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), WHO Collaborating Center for Standardization and Evaluation of BiologicalsNHC Key Laboratory of Research on Quality and Standardization of Biotech Products and NMPA Key Laboratory for Quality Research and Evaluation of Biological ProductsBeijingChina
| | - Jincheng Tong
- Division of HIV/AIDS and Sex‐transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), WHO Collaborating Center for Standardization and Evaluation of BiologicalsNHC Key Laboratory of Research on Quality and Standardization of Biotech Products and NMPA Key Laboratory for Quality Research and Evaluation of Biological ProductsBeijingChina
| | - Xi Wu
- Division of HIV/AIDS and Sex‐transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), WHO Collaborating Center for Standardization and Evaluation of BiologicalsNHC Key Laboratory of Research on Quality and Standardization of Biotech Products and NMPA Key Laboratory for Quality Research and Evaluation of Biological ProductsBeijingChina
| | - Shuo Liu
- Changping LaboratoryChangping District, BeijingChina
| | - Jiajing Wu
- Beijing Yunling Biotechnology Co., Ltd.BeijingChina
| | - Yuanling Yu
- Changping LaboratoryChangping District, BeijingChina
| | - Li Zhang
- Division of HIV/AIDS and Sex‐transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), WHO Collaborating Center for Standardization and Evaluation of BiologicalsNHC Key Laboratory of Research on Quality and Standardization of Biotech Products and NMPA Key Laboratory for Quality Research and Evaluation of Biological ProductsBeijingChina
| | - Chenyan Zhao
- Division of HIV/AIDS and Sex‐transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), WHO Collaborating Center for Standardization and Evaluation of BiologicalsNHC Key Laboratory of Research on Quality and Standardization of Biotech Products and NMPA Key Laboratory for Quality Research and Evaluation of Biological ProductsBeijingChina
| | - Qiong Lu
- Division of HIV/AIDS and Sex‐transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), WHO Collaborating Center for Standardization and Evaluation of BiologicalsNHC Key Laboratory of Research on Quality and Standardization of Biotech Products and NMPA Key Laboratory for Quality Research and Evaluation of Biological ProductsBeijingChina
| | - Jianhui Nie
- Division of HIV/AIDS and Sex‐transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), WHO Collaborating Center for Standardization and Evaluation of BiologicalsNHC Key Laboratory of Research on Quality and Standardization of Biotech Products and NMPA Key Laboratory for Quality Research and Evaluation of Biological ProductsBeijingChina
| | - Weijin Huang
- Division of HIV/AIDS and Sex‐transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), WHO Collaborating Center for Standardization and Evaluation of BiologicalsNHC Key Laboratory of Research on Quality and Standardization of Biotech Products and NMPA Key Laboratory for Quality Research and Evaluation of Biological ProductsBeijingChina
| | - Youchun Wang
- Chinese Academy of Medical Sciences & Peking Union Medical CollegeDongcheng District, BeijingChina
- Division of HIV/AIDS and Sex‐transmitted Virus Vaccines, Institute for Biological Product Control, National Institutes for Food and Drug Control (NIFDC), WHO Collaborating Center for Standardization and Evaluation of BiologicalsNHC Key Laboratory of Research on Quality and Standardization of Biotech Products and NMPA Key Laboratory for Quality Research and Evaluation of Biological ProductsBeijingChina
- Changping LaboratoryChangping District, BeijingChina
| |
Collapse
|
5
|
Wu Y, Zoller BGE, Kamal MAM, Hotop SK, Lehr CM, Brönstrup M, Dersch P, Empting M. Establishment of an In Bacterio Assay for the Assessment of Carbon Storage Regulator A (CsrA) Inhibitors. Chembiochem 2023; 24:e202300369. [PMID: 37435861 DOI: 10.1002/cbic.202300369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/12/2023] [Accepted: 07/12/2023] [Indexed: 07/13/2023]
Abstract
Polymicrobial infections involving various combinations of microorganisms, such as Escherichia, Pseudomonas, or Yersinia, can lead to acute and chronic diseases in for example the gastrointestinal and respiratory tracts. Our aim is to modulate microbial communities by targeting the posttranscriptional regulator system called carbon storage regulator A (CsrA) (or also repressor of secondary metabolites (RsmA)). In previous studies, we identified easily accessible CsrA binding scaffolds and macrocyclic CsrA binding peptides through biophysical screening and phage display technology. However, due to the lack of an appropriate in bacterio assay to evaluate the cellular effects of these inhibitor hits, the focus of the present study is to establish an in bacterio assay capable of probing and quantifying the impact on CsrA-regulated cellular mechanisms. We have successfully developed an assay based on a luciferase reporter gene assay, which in combination with a qPCR expression gene assay, allows for the monitoring of expression levels of different downstream targets of CsrA. The chaperone protein CesT was used as a suitable positive control for the assay, and in time-dependent experiments, we observed a CesT-mediated increase in bioluminescence over time. By this means, the cellular on-target effects of non-bactericidal/non-bacteriostatic virulence modulating compounds targeting CsrA/RsmA can be evaluated.
Collapse
Affiliation(s)
- Yingwen Wu
- Department of Antiviral & Antivirulence Drugs (AVID), Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Saarland University, 66123, Saarbrücken, Germany
- Cluster of Excellence RESIST (EXC 2155), Hanover Medical School, Carl-Neuberg-Straße 1, 30625, Hanover, Germany
| | - Ben G E Zoller
- Department of Antiviral & Antivirulence Drugs (AVID), Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Saarland University, 66123, Saarbrücken, Germany
| | - Mohamed Ashraf Mostafa Kamal
- Department of Drug Delivery (DDEL), Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Saarland University, 66123, Saarbrücken, Germany
- Department of Pharmacy, Saarland University, 66123, Saarbrücken, Germany
| | - Sven-Kevin Hotop
- Department of Chemical Biology, Helmholtz Centre for Infection Research, German Center for Infection Research (DZIF), 38124, Braunschweig, Germany
| | - Claus-Michael Lehr
- Department of Drug Delivery (DDEL), Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Saarland University, 66123, Saarbrücken, Germany
- Department of Pharmacy, Saarland University, 66123, Saarbrücken, Germany
| | - Mark Brönstrup
- Department of Chemical Biology, Helmholtz Centre for Infection Research, German Center for Infection Research (DZIF), 38124, Braunschweig, Germany
| | - Petra Dersch
- Institute of Infectiology, Center for Molecular Biology of Inflammation (ZMBE), University of Münster, 48149, Münster, Germany
| | - Martin Empting
- Department of Antiviral & Antivirulence Drugs (AVID), Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Saarland University, 66123, Saarbrücken, Germany
- Department of Pharmacy, Saarland University, 66123, Saarbrücken, Germany
- Cluster of Excellence RESIST (EXC 2155), Hanover Medical School, Carl-Neuberg-Straße 1, 30625, Hanover, Germany
| |
Collapse
|
6
|
Ovchinnikova OG, Treat LP, Teelucksingh T, Clarke BR, Miner TA, Whitfield C, Walker KA, Miller VL. Hypermucoviscosity Regulator RmpD Interacts with Wzc and Controls Capsular Polysaccharide Chain Length. mBio 2023; 14:e0080023. [PMID: 37140436 PMCID: PMC10294653 DOI: 10.1128/mbio.00800-23] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 04/04/2023] [Indexed: 05/05/2023] Open
Abstract
Klebsiella pneumoniae is a leading cause of nosocomial infections, including pneumonia, bacteremia, and urinary tract infections. Treatment options are increasingly restricted by the high prevalence of resistance to frontline antibiotics, including carbapenems, and the recently identified plasmid-conferred colistin resistance. The classical pathotype (cKp) is responsible for most of the nosocomial infections observed globally, and these isolates are often multidrug resistant. The hypervirulent pathotype (hvKp) is a primary pathogen capable of causing community-acquired infections in immunocompetent hosts. The hypermucoviscosity (HMV) phenotype is strongly associated with the increased virulence of hvKp isolates. Recent studies demonstrated that HMV requires capsule (CPS) synthesis and the small protein RmpD but is not dependent on the increased amount of capsule associated with hvKp. Here, we identified the structure of the capsular and extracellular polysaccharide isolated from hvKp strain KPPR1S (serotype K2) with and without RmpD. We found that the polymer repeat unit structure is the same in both strains and that it is identical to the K2 capsule. However, the chain length of CPS produced by strains expressing rmpD demonstrates more uniform length. This property was reconstituted in CPS from Escherichia coli isolates that possess the same CPS biosynthesis pathway as K. pneumoniae but naturally lack rmpD. Furthermore, we demonstrate that RmpD binds Wzc, a conserved capsule biosynthesis protein required for CPS polymerization and export. Based on these observations, we present a model for how the interaction of RmpD with Wzc could impact CPS chain length and HMV. IMPORTANCE Infections caused by Klebsiella pneumoniae continue to be a global public health threat; the treatment of these infections is complicated by the high frequency of multidrug resistance. K. pneumoniae produces a polysaccharide capsule required for virulence. Hypervirulent isolates also have a hypermucoviscous (HMV) phenotype that increases virulence, and we recently demonstrated that a horizontally acquired gene, rmpD, is required for HMV and hypervirulence but that the identity of the polymeric product(s) in HMV isolates is uncertain. Here, we demonstrate that RmpD regulates capsule chain length and interacts with Wzc, a part of the capsule polymerization and export machinery shared by many pathogens. We further show that RmpD confers HMV and regulates capsule chain length in a heterologous host (E. coli). As Wzc is a conserved protein found in many pathogens, it is possible that RmpD-mediated HMV and increased virulence may not be restricted to K. pneumoniae.
Collapse
Affiliation(s)
- Olga G. Ovchinnikova
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Logan P. Treat
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - Tanisha Teelucksingh
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Bradley R. Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Taryn A. Miner
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - Chris Whitfield
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Kimberly A. Walker
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - Virginia L. Miller
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
- Department of Genetics, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| |
Collapse
|
7
|
Silva-Rohwer AR, Held K, Yakhnin H, Babitzke P, Vadyvaloo V. CsrA-Mediated Translational Activation of the hmsE mRNA Enhances HmsD-Dependent C-di-GMP-Enabled Biofilm Production in Yersinia pestis. J Bacteriol 2023; 205:e0010523. [PMID: 37191545 PMCID: PMC10294631 DOI: 10.1128/jb.00105-23] [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: 03/20/2023] [Accepted: 04/20/2023] [Indexed: 05/17/2023] Open
Abstract
The plague bacterium, Yersinia pestis, forms a biofilm-mediated blockage in the flea foregut that enhances its transmission by fleabite. Biofilm formation is positively controlled by cyclic di-GMP (c-di-GMP), which is synthesized by the diguanylate cyclases (DGC), HmsD and HmsT. While HmsD primarily promotes biofilm-mediated blockage of fleas, HmsT plays a more minor role in this process. HmsD is a component of the HmsCDE tripartite signaling system. HmsC and HmsE posttranslationally inhibit or activate HmsD, respectively. HmsT-dependent c-di-GMP levels and biofilm formation are positively regulated by the RNA-binding protein CsrA. In this study we determined whether CsrA positively regulates HmsD-dependent biofilm formation through interactions with the hmsE mRNA. Gel mobility shift assays determined that CsrA binds specifically to the hmsE transcript. RNase T1 footprint assays identified a single CsrA binding site and CsrA-induced structural changes in the hmsE leader region. Translational activation of the hmsE mRNA was confirmed in vivo using plasmid-encoded inducible translational fusion reporters and by HmsE protein expression studies. Furthermore, mutation of the CsrA binding site in the hmsE transcript significantly reduced HmsD-dependent biofilm formation. These results suggest that CsrA binding leads to structural changes in the hmsE mRNA that enhance its translation to enable increased HmsD-dependent biofilm formation. Given the requisite function of HmsD in biofilm-mediated flea blockage, this CsrA-dependent increase in HmsD activity underscores that complex and conditionally defined modulation of c-di-GMP synthesis within the flea gut is required for Y. pestis transmission. IMPORTANCE Mutations enhancing c-di-GMP biosynthesis drove the evolution of Y. pestis to flea-borne transmissibility. c-di-GMP-dependent biofilm-mediated blockage of the flea foregut enables regurgitative transmission of Y. pestis by fleabite. The Y. pestis diguanylate cyclases (DGC), HmsT and HmsD, which synthesize c-di-GMP, play significant roles in transmission. Several regulatory proteins involved in environmental sensing, as well as signal transduction and response regulation, tightly control DGC function. An example is CsrA, a global posttranscriptional regulator that modulates carbon metabolism and biofilm formation. CsrA integrates alternative carbon usage metabolism cues to activate c-di-GMP biosynthesis through HmsT. Here, we demonstrated that CsrA additionally activates hmsE translation to promote c-di-GMP biosynthesis through HmsD. This emphasizes that a highly evolved regulatory network controls c-di-GMP synthesis and Y. pestis transmission.
Collapse
Affiliation(s)
- Amelia R. Silva-Rohwer
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
| | - Kiara Held
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
| | - Helen Yakhnin
- Department of Biochemistry and Molecular Biology, Center for RNA Molecular Biology, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Paul Babitzke
- Department of Biochemistry and Molecular Biology, Center for RNA Molecular Biology, Pennsylvania State University, University Park, Pennsylvania, USA
| | - Viveka Vadyvaloo
- Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA
| |
Collapse
|
8
|
Simulated Colonic Fluid Replicates the In Vivo Growth Capabilities of Citrobacter rodentium cpxRA Mutants and Uncovers Additive Effects of Cpx-Regulated Genes on Fitness. Infect Immun 2022; 90:e0031422. [PMID: 36000875 PMCID: PMC9476912 DOI: 10.1128/iai.00314-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Citrobacter rodentium is an attaching and effacing (A/E) pathogen used to model enteropathogenic and enterohemorrhagic Escherichia coli infections in mice. During colonization, C. rodentium must adapt to stresses in the gastrointestinal tract, such as antimicrobial peptides, pH changes, and bile salts. The Cpx envelope stress response (ESR) is a two-component system used by some bacteria to remediate stress by modulating gene expression, and it is necessary for C. rodentium pathogenesis in mice. Here, we utilized simulated colonic fluid (SCF) to mimic the gastrointestinal environment, which we show strongly induces the Cpx ESR and highlights a fitness defect specific to the ΔcpxRA mutant. While investigating genes in the Cpx regulon that may contribute to C. rodentium pathogenesis, we found that the absence of the Cpx ESR resulted in higher expression of the locus of enterocyte effacement (LEE) master regulator, ler, and that the genes yebE, ygiB, bssR, and htpX relied on CpxRA for proper expression. We then determined that CpxRA and select gene mutants were essential for proper growth in SCF when in the presence of extraneous stressors and in competition. Although none of the Cpx-regulated gene mutants exhibited marked virulence phenotypes in vivo, the ΔcpxRA mutant had reduced colonization and attenuated virulence, as previously determined, which replicated the in vitro growth phenotypes specific to SCF. Overall, these results indicate that the ΔcpxRA virulence defect is not due to any single Cpx regulon gene examined. Instead, attenuation may be the result of defective growth in the colonic environment resulting from the collective impact of multiple Cpx-regulated genes.
Collapse
|
9
|
Identification of Translocation Inhibitors Targeting the Type III Secretion System of Enteropathogenic Escherichia coli. Antimicrob Agents Chemother 2021; 65:e0095821. [PMID: 34543097 DOI: 10.1128/aac.00958-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infections with enteropathogenic Escherichia coli (EPEC) cause severe diarrhea in children. The noninvasive bacteria adhere to enterocytes of the small intestine and use a type III secretion system (T3SS) to inject effector proteins into host cells to modify and exploit cellular processes in favor of bacterial survival and replication. Several studies have shown that the T3SSs of bacterial pathogens are essential for virulence. Furthermore, the loss of T3SS-mediated effector translocation results in increased immune recognition and clearance of the bacteria. The T3SS is, therefore, considered a promising target for antivirulence strategies and novel therapeutics development. Here, we report the results of a high-throughput screening assay based on the translocation of the EPEC effector protein Tir (translocated intimin receptor). Using this assay, we screened more than 13,000 small molecular compounds of six different compound libraries and identified three substances which showed a significant dose-dependent effect on translocation without adverse effects on bacterial or eukaryotic cell viability. In addition, these substances reduced bacterial binding to host cells, effector-dependent cell detachment, and abolished attaching and effacing lesion formation without affecting the expression of components of the T3SS or associated effector proteins. Moreover, no effects of the inhibitors on bacterial motility or Shiga-toxin expression were observed. In summary, we have identified three new compounds that strongly inhibit T3SS-mediated translocation of effectors into mammalian cells, which could be valuable as lead substances for treating EPEC and enterohemorrhagic E. coli infections.
Collapse
|
10
|
Mikaty G, Coullon H, Fiette L, Pizarro-Cerdá J, Carniel E. The invasive pathogen Yersinia pestis disrupts host blood vasculature to spread and provoke hemorrhages. PLoS Negl Trop Dis 2021; 15:e0009832. [PMID: 34610007 PMCID: PMC8519436 DOI: 10.1371/journal.pntd.0009832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 10/15/2021] [Accepted: 09/22/2021] [Indexed: 11/29/2022] Open
Abstract
Yersinia pestis is a powerful pathogen with a rare invasive capacity. After a flea bite, the plague bacillus can reach the bloodstream in a matter of days giving way to invade the whole organism reaching all organs and provoking disseminated hemorrhages. However, the mechanisms used by this bacterium to cross and disrupt the endothelial vascular barrier remain poorly understood. In this study, an innovative model of in vivo infection was used to focus on the interaction between Y. pestis and its host vascular system. In the draining lymph nodes and in secondary organs, bacteria provoked the porosity and disruption of blood vessels. An in vitro model of endothelial barrier showed a role in this phenotype for the pYV/pCD1 plasmid that carries a Type Three Secretion System. This work supports that the pYV/pCD1 plasmid is responsible for the powerful tissue invasiveness capacity of the plague bacillus and the hemorrhagic features of plague. The plague bacillus, Yersinia pestis, is a powerful pathogen with a rare invasive capacity and is among the few bacteria capable to provoke disseminated hemorrhages. However, the mechanisms used by this bacterium to cross and disrupt the endothelial vascular barrier remain poorly understood. Recent technical progress in microscopy, associated with the use of original fluorescent mutant in mice, allowed us to develop an innovative model of infection in vivo. This model permitted to look directly into the interaction between Y. pestis and its host vascular system, in 3D reconstructed tissues without physical alteration. We were able to observe the degradation of blood vessels in the draining lymph nodes and to visualize the spreading of the bacteria into secondary organs directly through the vascular barrier. Classical in vitro experiments validated the in vivo observation and demonstrated the role of some of the bacterial components in this phenotype. This work shows an unprecedented visualization of the pathogenesis of Y. pestis and decipher part of the powerful invasiveness capacity of the plague bacillus and the hemorrhagic features of plague.
Collapse
Affiliation(s)
- Guillain Mikaty
- Institut Pasteur, Yersinia Research Unit, Paris, France
- * E-mail:
| | | | - Laurence Fiette
- Institut Pasteur, Unité d’histopathologie humaine et modèles animaux, Paris, France
| | | | | |
Collapse
|
11
|
CsrA Enhances Cyclic-di-GMP Biosynthesis and Yersinia pestis Biofilm Blockage of the Flea Foregut by Alleviating Hfq-Dependent Repression of the hmsT mRNA. mBio 2021; 12:e0135821. [PMID: 34340543 PMCID: PMC8406273 DOI: 10.1128/mbio.01358-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Plague-causing Yersinia pestis is transmitted through regurgitation when it forms a biofilm-mediated blockage in the foregut of its flea vector. This biofilm is composed of an extracellular polysaccharide substance (EPS) produced when cyclic-di-GMP (c-di-GMP) levels are elevated. The Y. pestis diguanylate cyclase enzymes HmsD and HmsT synthesize c-di-GMP. HmsD is required for biofilm blockage formation but contributes minimally to in vitro biofilms. HmsT, however, is necessary for in vitro biofilms and contributes to intermediate rates of biofilm blockage. C-di-GMP synthesis is regulated at the transcriptional and posttranscriptional levels. In this, the global RNA chaperone, Hfq, posttranscriptionally represses hmsT mRNA translation. How c-di-GMP levels and biofilm blockage formation is modulated by nutritional stimuli encountered in the flea gut is unknown. Here, the RNA-binding regulator protein CsrA, which controls c-di-GMP-mediated biofilm formation and central carbon metabolism responses in many Gammaproteobacteria, was assessed for its role in Y. pestis biofilm formation. We determined that CsrA was required for markedly greater c-di-GMP and EPS levels when Y. pestis was cultivated on alternative sugars implicated in flea biofilm blockage metabolism. Our assays, composed of mobility shifts, quantification of mRNA translation, stability, and abundance, and epistasis analyses of a csrA hfq double mutant strain substantiated that CsrA represses hfq mRNA translation, thereby alleviating Hfq-dependent repression of hmsT mRNA translation. Additionally, a csrA mutant exhibited intermediately reduced biofilm blockage rates, resembling an hmsT mutant. Hence, we reveal CsrA-mediated control of c-di-GMP synthesis in Y. pestis as a tiered, posttranscriptional regulatory process that enhances biofilm blockage-mediated transmission from fleas.
Collapse
|
12
|
Zou L, Zhang C, Li Y, Yang X, Wang Y, Yan Y, Yang R, Huang M, Haq F, Yang C, Chen G. An improved, versatile and efficient modular plasmid assembly system for expression analyses of genes in Xanthomonas oryzae. MOLECULAR PLANT PATHOLOGY 2021; 22:480-492. [PMID: 33486879 PMCID: PMC7938625 DOI: 10.1111/mpp.13033] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 12/02/2020] [Accepted: 12/10/2020] [Indexed: 06/12/2023]
Abstract
Xanthomonas oryzae pathovars oryzae (Xoo) and oryzicola (Xoc) infect rice, causing bacterial blight and bacterial leaf streak, respectively, which are two economically important bacterial diseases in paddy fields. The interactions of Xoo and Xoc with rice can be used as models for studying fundamental aspects of bacterial pathogenesis and host tissue specificity. However, an improved vector system for gene expression analysis is desired for Xoo and Xoc because some broad host range vectors that can replicate stably in X. oryzae pathovars are low-copy number plasmids. To overcome this limitation, we developed a modular plasmid assembly system to transfer the functional DNA modules from the entry vectors into the pHM1-derived backbone vectors on a high-copy number basis. We demonstrated the feasibility of our vector system for protein detection, and quantification of virulence gene expression under laboratory conditions and in association with host rice and nonhost tobacco cells. This system also allows execution of a mutant complementation equivalent to the single-copy chromosomal integration system and tracing of pathogens in rice leaf. Based on this assembly system, we constructed a series of protein expression and promoter-probe vectors suitable for classical double restriction enzyme cloning. These vector systems enable cloning of all genes or promoters of interest from Xoo and Xoc strains. Our modular assembly system represents a versatile and highly efficient toolkit for gene expression analysis that will accelerate studies on interactions of X. oryzae with rice.
Collapse
Affiliation(s)
- Lifang Zou
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
- Key Laboratory of Urban Agriculture by Ministry of Agriculture of ChinaShanghai Jiao Tong UniversityShanghaiChina
- State Key Laboratory of Microbial MetabolismSchool of Life Sciences & BiotechnologyShanghai Jiao Tong UniversityShanghaiChina
| | - Cuiping Zhang
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
| | - Yilang Li
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
| | - Xiaofei Yang
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
| | - Yanyan Wang
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
| | - Yichao Yan
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
| | - Ruihuan Yang
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
| | - Mengsang Huang
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
| | - Fazal Haq
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
| | - Ching‐Hong Yang
- Department of Biological SciencesUniversity of WisconsinMilwaukeeWisconsinUSA
| | - Gongyou Chen
- School of Agriculture and BiologyShanghai Jiao Tong UniversityShanghaiChina
- Key Laboratory of Urban Agriculture by Ministry of Agriculture of ChinaShanghai Jiao Tong UniversityShanghaiChina
- State Key Laboratory of Microbial MetabolismSchool of Life Sciences & BiotechnologyShanghai Jiao Tong UniversityShanghaiChina
| |
Collapse
|
13
|
Derbise A, Echenique-Rivera H, Garcia-Lopez M, Beau R, Mattei M, Varet H, Dersch P, Pizarro-Cerdá J. Bread Feeding Is a Robust and More Physiological Enteropathogen Administration Method Compared to Oral Gavage. Infect Immun 2020; 88:e00810-19. [PMID: 32014893 PMCID: PMC7093149 DOI: 10.1128/iai.00810-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 01/22/2020] [Indexed: 12/25/2022] Open
Abstract
Oral administration is a preferred model for studying infection by bacterial enteropathogens such as Yersinia spp. In the mouse model, the most frequent method for oral infection consists of oral gavage with a feeding needle directly introduced in the animal stomach via the esophagus. In this study, we compared needle gavage to bread feeding as an alternative mode of bacterial administration. Using bioluminescence-expressing strains of Yersinia pseudotuberculosis and Yersinia enterocolitica, we detected very early upon needle gavage a bioluminescent signal in the neck area together with a signal in the abdominal region, highlighting the presence of two independent sites of bacterial colonization and multiplication. Bacteria were often detected in the esophagus and trachea, as well as in the lymph nodes draining the salivary glands, suggesting that lesions made during needle introduction into the animal oral cavity lead to rapid bacterial draining to proximal lymph nodes. We then tested an alternative mode of bacterial administration using pieces of bread containing bacteria. Upon bread feeding infection, mice exhibited a stronger bioluminescent signal in the abdominal region than with needle gavage, and no signal was detected in the neck area. Moreover, Y. pseudotuberculosis incorporated in the bread is less susceptible to the acidic environment of the stomach and is therefore more efficient in causing intestinal infections. Based on our observations, bread feeding constitutes a natural and more efficient administration method which does not require specialized skills, is less traumatic for the animal, and results in diseases that more closely mimic foodborne intestinal infection.
Collapse
Affiliation(s)
- Anne Derbise
- Yersinia Research Unit, Institut Pasteur, Paris, France
| | | | | | - Rémi Beau
- Yersinia Research Unit, Institut Pasteur, Paris, France
| | - Myriam Mattei
- Animalerie Centrale, Centre de Ressources et Recherches Animales, Institut Pasteur, Paris, France
| | - Hugo Varet
- Bioinformatics and Biostatistics Hub, Département Biologie Computationnelle, Institut Pasteur, USR 3756 CNRS, Paris, France
| | - Petra Dersch
- Institute of Infectiology, Center for Molecular Biology of Inflammation, University of Münster, Münster, Germany
| | | |
Collapse
|
14
|
Exploring resveratrol dimers as virulence blocking agents - Attenuation of type III secretion in Yersinia pseudotuberculosis and Pseudomonas aeruginosa. Sci Rep 2020; 10:2103. [PMID: 32034212 PMCID: PMC7005745 DOI: 10.1038/s41598-020-58872-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 01/20/2020] [Indexed: 12/25/2022] Open
Abstract
Bacterial infections continue to threaten humankind and the rapid spread of antibiotic resistant bacteria is alarming. Current antibiotics target essential bacterial processes and thereby apply a strong selective pressure on pathogenic and non-pathogenic bacteria alike. One alternative strategy is to block bacterial virulence systems that are essential for the ability to cause disease but not for general bacterial viability. We have previously show that the plant natural product (-)-hopeaphenol blocks the type III secretion system (T3SS) in the Gram-negative pathogens Yersinia pseudotuberculosis and Pseudomonas aeruginosa. (-)-Hopeaphenol is a resveratrol tetramer and in the present study we explore various resveratrol dimers, including partial structures of (-)-hopeaphenol, as T3SS inhibitors. To allow rapid and efficient assessment of T3SS inhibition in P. aeruginosa, we developed a new screening method by using a green fluorescent protein reporter under the control of the ExoS promoter. Using a panel of assays we showed that compounds with a benzofuran core structure i.e. viniferifuran, dehydroampelopsin B, anigopreissin A, dehydro-δ-viniferin and resveratrol-piceatannol hybrid displayed significant to moderate activities towards the T3SS in Y. pseudotuberculosis and P. aeruginosa.
Collapse
|
15
|
Hui CY, Guo Y, Liu L, Zheng HQ, Gao CX, Zhang W. Construction of a RFP-lacZα bicistronic reporter system and its application in lead biosensing. PLoS One 2020; 15:e0228456. [PMID: 31999769 PMCID: PMC6991944 DOI: 10.1371/journal.pone.0228456] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 01/15/2020] [Indexed: 01/12/2023] Open
Abstract
The combination of a fluorescent reporter and enzymatic reporter provides a flexible and versatile way for the study of diverse biological processes, such as the detection of transcription and translation. Thus, there is an urgent need to develop this novel bifunctional reporter system. This study reports the design, construction, and validation of a new dicistronic mCherry-lacZα reporter system by artificial lac operon and pbr operon models in lacZM15-producing E. coli. It allows two reporter genes to be co-transcribed into a dicistronic mRNA strand, followed by coupled expression of mCherry and lacZα. In artificial lac operons, expression of the downstream lacZα was demonstrated to be positively related to expression of the upstream ORF. In artificial pbr operons, compared with the insertion of downstream full-length lacZ, the insertion of downstream lacZα exerted a slight effect on the response from the upstream mCherry. Furthermore, the downstream lacZα reporter showed stronger response to Pb(II) than the downstream full-length lacZ. Importantly, the response sensitivity of downstream lacZα was still higher than that of upstream mCherry in a dual RFP-lacZα reporter construct. The highly efficient expression profile of the reporter lacZα peptide makes it a preferred downstream reporter in polycistronic constructs. This novel bifunctional reporter system offers a robust tool for biological studies.
Collapse
Affiliation(s)
- Chang-ye Hui
- Department of Pathology & Toxicology, Shenzhen Prevention and Treatment Center for Occupational Diseases, Shenzhen, China
| | - Yan Guo
- Department of Science & Education, Shenzhen Prevention and Treatment Center for Occupational Diseases, Shenzhen, China
| | - Lisa Liu
- Institute of Translational Medicine, Shenzhen Second People’s Hospital, Shenzhen, China
| | - Hao-qu Zheng
- Department of Science & Education, Shenzhen Prevention and Treatment Center for Occupational Diseases, Shenzhen, China
| | - Chao-xian Gao
- Department of Pathology & Toxicology, Shenzhen Prevention and Treatment Center for Occupational Diseases, Shenzhen, China
| | - Wen Zhang
- Department of Pathology & Toxicology, Shenzhen Prevention and Treatment Center for Occupational Diseases, Shenzhen, China
| |
Collapse
|
16
|
Twittenhoff C, Heroven AK, Mühlen S, Dersch P, Narberhaus F. An RNA thermometer dictates production of a secreted bacterial toxin. PLoS Pathog 2020; 16:e1008184. [PMID: 31951643 PMCID: PMC6992388 DOI: 10.1371/journal.ppat.1008184] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 01/30/2020] [Accepted: 11/01/2019] [Indexed: 02/06/2023] Open
Abstract
Frequent transitions of bacterial pathogens between their warm-blooded host and external reservoirs are accompanied by abrupt temperature shifts. A temperature of 37°C serves as reliable signal for ingestion by a mammalian host, which induces a major reprogramming of bacterial gene expression and metabolism. Enteric Yersiniae are Gram-negative pathogens accountable for self-limiting gastrointestinal infections. Among the temperature-regulated virulence genes of Yersinia pseudotuberculosis is cnfY coding for the cytotoxic necrotizing factor (CNFY), a multifunctional secreted toxin that modulates the host’s innate immune system and contributes to the decision between acute infection and persistence. We report that the major determinant of temperature-regulated cnfY expression is a thermo-labile RNA structure in the 5’-untranslated region (5’-UTR). Various translational gene fusions demonstrated that this region faithfully regulates translation initiation regardless of the transcription start site, promoter or reporter strain. RNA structure probing revealed a labile stem-loop structure, in which the ribosome binding site is partially occluded at 25°C but liberated at 37°C. Consistent with translational control in bacteria, toeprinting (primer extension inhibition) experiments in vitro showed increased ribosome binding at elevated temperature. Point mutations locking the 5’-UTR in its 25°C structure impaired opening of the stem loop, ribosome access and translation initiation at 37°C. To assess the in vivo relevance of temperature control, we used a mouse infection model. Y. pseudotuberculosis strains carrying stabilized RNA thermometer variants upstream of cnfY were avirulent and attenuated in their ability to disseminate into mesenteric lymph nodes and spleen. We conclude with a model, in which the RNA thermometer acts as translational roadblock in a two-layered regulatory cascade that tightly controls provision of the CNFY toxin during acute infection. Similar RNA structures upstream of various cnfY homologs suggest that RNA thermosensors dictate the production of secreted toxins in a wide range of pathogens. Bacterial pathogens closely survey the ambient conditions and induce virulence genes only at appropriate conditions. Upon host contact, many pathogens secrete toxins in order to subvert host defense systems. We find that such a secreted toxin in enteropathogenic Yersinia pseudotuberculosis is produced only at host body temperature. This regulation depends on a temperature-responsive RNA structure, an RNA thermometer, in the 5’-untranslated region of the toxin mRNA, which prevents translation at low temperatures when the bacterium is outside the host. Preventing melting of the RNA structure at 37°C by nucleotide substitutions that stabilize base pairing resulted in avirulent Yersinia strains unable to infect mice. Given that similar RNA thermometer-like structures exist upstream of related toxin genes in various bacterial pathogens, we propose that RNA thermometer-mediated toxin production is an evolutionary conserved mechanism. Interfering with opening of such regulatory structures might thus be a promising strategy targeting a broad spectrum of bacterial pathogens.
Collapse
Affiliation(s)
| | - Ann Kathrin Heroven
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Sabrina Mühlen
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
- Institute of Infectiology, Center for Molecular Biology of Inflammation, University of Münster, Münster, Germany
| | - Petra Dersch
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
- Institute of Infectiology, Center for Molecular Biology of Inflammation, University of Münster, Münster, Germany
| | - Franz Narberhaus
- Microbial Biology, Ruhr University Bochum, Bochum, Germany
- * E-mail:
| |
Collapse
|
17
|
Temperature Control of psaA Expression by PsaE and PsaF in Yersinia pestis. J Bacteriol 2019; 201:JB.00217-19. [PMID: 31138630 PMCID: PMC6657601 DOI: 10.1128/jb.00217-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 05/22/2019] [Indexed: 12/19/2022] Open
Abstract
Y. pestis is a Gram-negative bacterial pathogen that causes bubonic plague. As a vector-borne pathogen, Y. pestis fluctuates between an arthropod vector (flea) and mammalian host. As such, Y. pestis must recognize environmental signals encountered within each host environment and respond by appropriately regulating gene expression. PsaA is a key Y. pestis mammalian virulence determinant that forms fimbriae. Our work provides evidence that Y. pestis utilizes multiple posttranscriptional mechanisms to regulate the levels of two PsaA regulatory proteins in response to both temperature and pH. This study offers insight into mechanisms that bacteria utilize to sense environmental cues and regulate the expression of determinants required for mammalian disease. PsaA, the subunit of the fimbria originally referred to as the “pH 6 antigen,” is required for full virulence of Yersinia pestis during bubonic plague. The expression of psaA is dependent upon specific environmental signals, and while the signals (high temperature and acidic pH) are defined, the mechanisms underlying this regulation remain unclear. In the closely related species Yersinia pseudotuberculosis, psaA transcription requires two regulatory genes, psaE and psaF, and it is speculated that posttranscriptional regulation of PsaE and/or PsaF contributes to the regulation of psaA transcription. Few studies have examined the regulation of psaA expression in Y. pestis, and prior to this work, the roles of psaE and psaF in Y. pestis had not been defined. The data presented here show that both psaE and psaF are required for psaA transcription in Y. pestis and that the impact of temperature and pH is mediated through discrete posttranscriptional effects on PsaE and PsaF. By generating antibodies that recognize endogenous PsaE and PsaF, we determined that the levels of both proteins are impacted by temperature and pH. High temperature is required for psaE and psaF translation via discrete mechanisms mediated by the mRNA 5′ untranslated region (UTR) upstream of each gene. Additionally, levels of PsaE and PsaF are impacted by pH. We show that PsaF enhances the stability of PsaE, and thus, both PsaE and PsaF are required for psaA transcription. Our data indicate that the environmental signals (temperature and pH) impact the expression of psaA by affecting the translation of psaE and psaF and the stability of PsaE and PsaF. IMPORTANCEY. pestis is a Gram-negative bacterial pathogen that causes bubonic plague. As a vector-borne pathogen, Y. pestis fluctuates between an arthropod vector (flea) and mammalian host. As such, Y. pestis must recognize environmental signals encountered within each host environment and respond by appropriately regulating gene expression. PsaA is a key Y. pestis mammalian virulence determinant that forms fimbriae. Our work provides evidence that Y. pestis utilizes multiple posttranscriptional mechanisms to regulate the levels of two PsaA regulatory proteins in response to both temperature and pH. This study offers insight into mechanisms that bacteria utilize to sense environmental cues and regulate the expression of determinants required for mammalian disease.
Collapse
|
18
|
Garay-Novillo JN, García-Morena D, Ruiz-Masó JÁ, Barra JL, Del Solar G. Combining Modules for Versatile and Optimal Labeling of Lactic Acid Bacteria: Two pMV158-Family Promiscuous Replicons, a Pneumococcal System for Constitutive or Inducible Gene Expression, and Two Fluorescent Proteins. Front Microbiol 2019; 10:1431. [PMID: 31297101 PMCID: PMC6607859 DOI: 10.3389/fmicb.2019.01431] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 06/06/2019] [Indexed: 11/24/2022] Open
Abstract
Labeling of bacterial cells with fluorescent proteins allows tracking the bacteria in competition and interactomic in vivo and in vitro studies. During the last years, a few plasmid vectors have been developed aimed at the fluorescent labeling of specific members of the lactic acid bacteria (LAB), a heterogeneous group that includes microorganisms used in the food industry, as probiotics, or as live vectors for mucosal vaccines. Successful and versatile labeling of a broad range of LAB not only requires a vector containing a promiscuous replicon and a widely recognized expression system for the constitutive or regulated expression of the fluorescence determinant, but also the knowledge of the main features of the entire plasmid/host/fluorescent protein ensemble. By using the LAB model species Lactococcus lactis, we have compared the utility properties of a set of labeling vectors constructed by combining a promiscuous replicon (pMV158 or pSH71) of the pMV158 plasmid family with the gene encoding either the EGFP or the mCherry fluorescent protein placed under control of promoter PX or PM from the pneumococcal mal gene cluster for maltosaccharide uptake and utilization, respectively. Some vectors carrying PM also harbor the malR gene, whose product represses transcription from this promoter, thus enabling maltose-inducible synthesis of the fluorescent proteins. We have determined the plasmid copy number (PCN) and segregational stability of the different constructs, as well as the effect of these features on the fitness and fluorescence intensity of the lactococcal host. Constructs based on the pSH71 replicon had a high copy number (∼115) and were segregationally stable. The copy number of vectors based on the pMV158 replicon was lower (∼8–45) and varied substantially depending on the genetic context of the plasmid and on the bacterial growth conditions; as a consequence, inheritance of these vectors was less stable. Synthesis of the fluorescent proteins encoded by these plasmids did not significantly decrease the host fitness. By employing inducible expression vectors, the fluorescent proteins were shown to be very stable in this bacterium. Importantly, conditions for accurate quantification of the emitted fluorescence were established based on the maturation times of the fluorescent proteins.
Collapse
Affiliation(s)
- Javier Nicolás Garay-Novillo
- Departamento de Biotecnología Microbiana y de Plantas, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.,Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC-CONICET), Córdoba, Argentina
| | - Diego García-Morena
- Departamento de Biotecnología Microbiana y de Plantas, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - José Ángel Ruiz-Masó
- Departamento de Biotecnología Microbiana y de Plantas, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - José Luis Barra
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC-CONICET), Córdoba, Argentina
| | - Gloria Del Solar
- Departamento de Biotecnología Microbiana y de Plantas, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| |
Collapse
|
19
|
Mauri M, Vecchione S, Fritz G. Deconvolution of Luminescence Cross-Talk in High-Throughput Gene Expression Profiling. ACS Synth Biol 2019; 8:1361-1370. [PMID: 31095908 DOI: 10.1021/acssynbio.9b00032] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Luciferase reporters have become standard genetic tools to monitor gene expression in real time and in high-throughput using microplate readers. Compared to reporter gene assays based on fluorescence proteins, luciferase reporters have a superior signal-to-noise ratio, since they do not suffer from the high autofluorescence background of the bacterial cell. However, at the same time luciferase reporters have the drawback of constant light emission, which leads to undesired cross-talk between neighboring wells on a microplate. To overcome this limitation, we developed a computational method to correct for luminescence bleed-through and to estimate the "true" luminescence activity for each well of a microplate. As the sole input our algorithm uses the signals measured from a calibration plate, in which the light emitted from a single luminescent well serves as an estimate for the "light-spread function". We show that this light-spread function can be used to deconvolve any other measurement obtained under the same technical conditions. Our analysis demonstrates that the correction preserves low-level signals close to the background and shows that it is universally applicable to different kinds of microplate readers and plate types.
Collapse
Affiliation(s)
- Marco Mauri
- LOEWE Center for Synthetic Microbiology and Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Stefano Vecchione
- LOEWE Center for Synthetic Microbiology and Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Georg Fritz
- LOEWE Center for Synthetic Microbiology and Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
| |
Collapse
|
20
|
Kusmierek M, Hoßmann J, Witte R, Opitz W, Vollmer I, Volk M, Heroven AK, Wolf-Watz H, Dersch P. A bacterial secreted translocator hijacks riboregulators to control type III secretion in response to host cell contact. PLoS Pathog 2019; 15:e1007813. [PMID: 31173606 PMCID: PMC6583979 DOI: 10.1371/journal.ppat.1007813] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 06/19/2019] [Accepted: 05/02/2019] [Indexed: 02/05/2023] Open
Abstract
Numerous Gram-negative pathogens use a Type III Secretion System (T3SS) to promote virulence by injecting effector proteins into targeted host cells, which subvert host cell processes. Expression of T3SS and the effectors is triggered upon host cell contact, but the underlying mechanism is poorly understood. Here, we report a novel strategy of Yersinia pseudotuberculosis in which this pathogen uses a secreted T3SS translocator protein (YopD) to control global RNA regulators. Secretion of the YopD translocator upon host cell contact increases the ratio of post-transcriptional regulator CsrA to its antagonistic small RNAs CsrB and CsrC and reduces the degradosome components PNPase and RNase E levels. This substantially elevates the amount of the common transcriptional activator (LcrF) of T3SS/Yop effector genes and triggers the synthesis of associated virulence-relevant traits. The observed hijacking of global riboregulators allows the pathogen to coordinate virulence factor expression and also readjusts its physiological response upon host cell contact.
Collapse
Affiliation(s)
- Maria Kusmierek
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Jörn Hoßmann
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Rebekka Witte
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Wiebke Opitz
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Ines Vollmer
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
- Institute for Infectiology, University of Münster, Germany
| | - Marcel Volk
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
- Institute for Infectiology, University of Münster, Germany
| | - Ann Kathrin Heroven
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Hans Wolf-Watz
- Department of Molecular Biology, Umea University, Sweden
| | - Petra Dersch
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
- Institute for Infectiology, University of Münster, Germany
- * E-mail:
| |
Collapse
|
21
|
Comparative Transcriptomic Profiling of Yersinia enterocolitica O:3 and O:8 Reveals Major Expression Differences of Fitness- and Virulence-Relevant Genes Indicating Ecological Separation. mSystems 2019; 4:mSystems00239-18. [PMID: 31020044 PMCID: PMC6478967 DOI: 10.1128/msystems.00239-18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 02/27/2019] [Indexed: 01/16/2023] Open
Abstract
Yersinia enterocolitica is a major diarrheal pathogen and is associated with a large range of gut-associated diseases. Members of this species have evolved into different phylogroups with genotypic variations. We performed the first characterization of the Y. enterocolitica transcriptional landscape and tracked the consequences of the genomic variations between two different pathogenic phylogroups by comparing their RNA repertoire, promoter usage, and expression profiles under four different virulence-relevant conditions. Our analysis revealed major differences in the transcriptional outputs of the closely related strains, pointing to an ecological separation in which one is more adapted to an environmental lifestyle and the other to a mostly mammal-associated lifestyle. Moreover, a variety of pathoadaptive alterations, including alterations in acid resistance genes, colonization factors, and toxins, were identified which affect virulence and host specificity. This illustrates that comparative transcriptomics is an excellent approach to discover differences in the functional output from closely related genomes affecting niche adaptation and virulence, which cannot be directly inferred from DNA sequences. Yersinia enterocolitica is a zoonotic pathogen and an important cause of bacterial gastrointestinal infections in humans. Large-scale population genomic analyses revealed genetic and phenotypic diversity of this bacterial species, but little is known about the differences in the transcriptome organization, small RNA (sRNA) repertoire, and transcriptional output. Here, we present the first comparative high-resolution transcriptome analysis of Y. enterocolitica strains representing highly pathogenic phylogroup 2 (serotype O:8) and moderately pathogenic phylogroup 3 (serotype O:3) grown under four infection-relevant conditions. Our transcriptome sequencing (RNA-seq) approach revealed 1,299 and 1,076 transcriptional start sites and identified strain-specific sRNAs that could contribute to differential regulation among the phylogroups. Comparative transcriptomics further uncovered major gene expression differences, in particular, in the temperature-responsive regulon. Multiple virulence-relevant genes are differentially regulated between the two strains, supporting an ecological separation of phylogroups with certain niche-adapted properties. Strong upregulation of the ystA enterotoxin gene in combination with constitutive high expression of cell invasion factor InvA further showed that the toxicity of recent outbreak O:3 strains has increased. Overall, our report provides new insights into the specific transcriptome organization of phylogroups 2 and 3 and reveals gene expression differences contributing to the substantial phenotypic differences that exist between the lineages. IMPORTANCEYersinia enterocolitica is a major diarrheal pathogen and is associated with a large range of gut-associated diseases. Members of this species have evolved into different phylogroups with genotypic variations. We performed the first characterization of the Y. enterocolitica transcriptional landscape and tracked the consequences of the genomic variations between two different pathogenic phylogroups by comparing their RNA repertoire, promoter usage, and expression profiles under four different virulence-relevant conditions. Our analysis revealed major differences in the transcriptional outputs of the closely related strains, pointing to an ecological separation in which one is more adapted to an environmental lifestyle and the other to a mostly mammal-associated lifestyle. Moreover, a variety of pathoadaptive alterations, including alterations in acid resistance genes, colonization factors, and toxins, were identified which affect virulence and host specificity. This illustrates that comparative transcriptomics is an excellent approach to discover differences in the functional output from closely related genomes affecting niche adaptation and virulence, which cannot be directly inferred from DNA sequences.
Collapse
|
22
|
Mastrodonato AC, Favier GI, Lucero Estrada CSM, Vidal R, Escudero ME. Bioserotypes, virulence genes, antimicrobial susceptibility and genomic diversity ofYersinia enterocoliticaisolates from Argentina and Chile. J Food Saf 2018. [DOI: 10.1111/jfs.12491] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Anna Chiara Mastrodonato
- Microbiologia Area Faculty of Chemistry Biochemistry and Pharmacy, National University of San Luis, Ejército de los Andes 950 Bloque 1 Piso 1, 5700; San Luis Argentina
| | - Gabriela I. Favier
- Microbiologia Area Faculty of Chemistry Biochemistry and Pharmacy, National University of San Luis, Ejército de los Andes 950 Bloque 1 Piso 1, 5700; San Luis Argentina
| | - Cecilia S. M. Lucero Estrada
- Microbiologia Area Faculty of Chemistry Biochemistry and Pharmacy, National University of San Luis, Ejército de los Andes 950 Bloque 1 Piso 1, 5700; San Luis Argentina
- Multidisciplinary Institute of Biological Researches of San Luis National Council of Scientific and Technological Researches (IMIBIO-SL-CONICET); San Luis Argentina
| | - Roberto Vidal
- Microbiology and Mycology Program; Institute of Biomedical Sciences, Faculty of Medicine, Universidad of Chile; Santiago Chile
| | - María E. Escudero
- Microbiologia Area Faculty of Chemistry Biochemistry and Pharmacy, National University of San Luis, Ejército de los Andes 950 Bloque 1 Piso 1, 5700; San Luis Argentina
| |
Collapse
|
23
|
Salmonella exploits the host endolysosomal tethering factor HOPS complex to promote its intravacuolar replication. PLoS Pathog 2017; 13:e1006700. [PMID: 29084291 PMCID: PMC5679646 DOI: 10.1371/journal.ppat.1006700] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 11/09/2017] [Accepted: 10/18/2017] [Indexed: 12/22/2022] Open
Abstract
Salmonella enterica serovar typhimurium extensively remodels the host late endocytic compartments to establish its vacuolar niche within the host cells conducive for its replication, also known as the Salmonella-containing vacuole (SCV). By maintaining a prolonged interaction with late endosomes and lysosomes of the host cells in the form of interconnected network of tubules (Salmonella-induced filaments or SIFs), Salmonella gains access to both membrane and fluid-phase cargo from these compartments. This is essential for maintaining SCV membrane integrity and for bacterial intravacuolar nutrition. Here, we have identified the multisubunit lysosomal tethering factor—HOPS (HOmotypic fusion and Protein Sorting) complex as a crucial host factor facilitating delivery of late endosomal and lysosomal content to SCVs, providing membrane for SIF formation, and nutrients for intravacuolar bacterial replication. Accordingly, depletion of HOPS subunits significantly reduced the bacterial load in non-phagocytic and phagocytic cells as well as in a mouse model of Salmonella infection. We found that Salmonella effector SifA in complex with its binding partner; SKIP, interacts with HOPS subunit Vps39 and mediates recruitment of this tethering factor to SCV compartments. The lysosomal small GTPase Arl8b that binds to, and promotes membrane localization of Vps41 (and other HOPS subunits) was also required for HOPS recruitment to SCVs and SIFs. Our findings suggest that Salmonella recruits the host late endosomal and lysosomal membrane fusion machinery to its vacuolar niche for access to host membrane and nutrients, ensuring its intracellular survival and replication. Intracellular pathogens have devised various strategies to subvert the host membrane trafficking pathways for their growth and survival inside the host cells. Salmonella is one such successful intracellular pathogen that redirects membrane and nutrients from the host endocytic compartments to its replicative niche known as the Salmonella-containing vacuole (SCV) via establishing an interconnected network of tubules (Salmonella-induced filaments or SIFs) that form a continuum with the SCVs. How Salmonella ensures a constant supply of endocytic cargo required for its survival and growth remained unexplored. Our work uncovers a strategy evolved by Salmonella wherein it secretes a bacterial effector into the host cytosol that recruits component of host vesicle fusion machinery-HOPS complex to SCVs and SIFs. HOPS complex promotes docking of the late endocytic compartments at the SCV membrane, prior to their fusion. Thus, depletion of HOPS subunits both in cultured cell lines as well as a mouse model inhibits Salmonella replication, likely due to reduced access to host membranes and nutrients by the vacuolar bacteria. These findings provide mechanistic insights into how this pathogen reroutes the host’s endocytic transport towards its vacuole, ensuring its own intracellular survival and replication.
Collapse
|
24
|
van Rossum T, Muras A, Baur MJ, Creutzburg SC, van der Oost J, Kengen SW. A growth- and bioluminescence-based bioreporter for the in vivo detection of novel biocatalysts. Microb Biotechnol 2017; 10:625-641. [PMID: 28393499 PMCID: PMC5404197 DOI: 10.1111/1751-7915.12612] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/10/2017] [Accepted: 01/13/2017] [Indexed: 11/28/2022] Open
Abstract
The use of bioreporters in high-throughput screening for small molecules is generally laborious and/or expensive. The technology can be simplified by coupling the generation of a desired compound to cell survival, causing only positive cells to stay in the pool of generated variants. Here, a dual selection/screening system was developed for the in vivo detection of novel biocatalysts. The sensor part of the system is based on the transcriptional regulator AraC, which controls expression of both a selection reporter (LeuB or KmR; enabling growth) for rapid reduction of the initially large library size and a screening reporter (LuxCDABE; causing bioluminescence) for further quantification of the positive variants. Of four developed systems, the best system was the medium copy system with KmR as selection reporter. As a proof of principle, the system was tested for the selection of cells expressing an l-arabinose isomerase derived from mesophilic Escherichia coli or thermophilic Geobacillus thermodenitrificans. A more than a millionfold enrichment of cells with l-arabinose isomerase activity was demonstrated by selection and exclusion of false positives by screening. This dual selection/screening system is an important step towards an improved detection method for small molecules, and thereby for finding novel biocatalysts.
Collapse
Affiliation(s)
- Teunke van Rossum
- Laboratory of MicrobiologyWageningen University and ResearchStippeneng 46708WE WageningenThe Netherlands
| | - Aleksandra Muras
- Laboratory of MicrobiologyWageningen University and ResearchStippeneng 46708WE WageningenThe Netherlands
| | - Marco J.J. Baur
- Laboratory of MicrobiologyWageningen University and ResearchStippeneng 46708WE WageningenThe Netherlands
| | - Sjoerd C.A. Creutzburg
- Laboratory of MicrobiologyWageningen University and ResearchStippeneng 46708WE WageningenThe Netherlands
| | - John van der Oost
- Laboratory of MicrobiologyWageningen University and ResearchStippeneng 46708WE WageningenThe Netherlands
| | - Servé W.M. Kengen
- Laboratory of MicrobiologyWageningen University and ResearchStippeneng 46708WE WageningenThe Netherlands
| |
Collapse
|
25
|
Bozcal E, Dagdeviren M, Uzel A, Skurnik M. LuxCDE-luxAB-based promoter reporter system to monitor the Yersinia enterocolitica O:3 gene expression in vivo. PLoS One 2017; 12:e0172877. [PMID: 28235077 PMCID: PMC5325538 DOI: 10.1371/journal.pone.0172877] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 02/11/2017] [Indexed: 12/19/2022] Open
Abstract
It is crucial to understand the in vitro and in vivo regulation of the virulence factor genes of bacterial pathogens. In this study, we describe the construction of a versatile reporter system for Yersinia enterocolitica serotype O:3 (YeO3) based on the luxCDABE operon. In strain YeO3-luxCDE we integrated the luciferase substrate biosynthetic genes, luxCDE, into the genome of the bacterium so that the substrate is constitutively produced. The luxAB genes that encode the luciferase enzyme were cloned into a suicide vector to allow cloning of any promoter-containing fragment upstream the genes. When the obtained suicide-construct is mobilized into YeO3-luxCDE bacteria, it integrates into the recipient genome via homologous recombination between the cloned promoter fragment and the genomic promoter sequence and thereby generates a single-copy and stable promoter reporter. Lipopolysaccharide (LPS) O-antigen (O-ag) and outer core hexasaccharide (OC) of YeO3 are virulence factors necessary to colonization of the intestine and establishment of infection. To monitor the activities of the OC and O-ag gene cluster promoters we constructed the reporter strains YeO3-Poc::luxAB and YeO3-Pop1::luxAB, respectively. In vitro, at 37°C both promoter activities were highest during logarithmic growth and decreased when the bacteria entered stationary growth phase. At 22°C the OC gene cluster promoter activity increased during the late logarithmic phase. Both promoters were more active in late stationary phase. To monitor the promoter activities in vivo, mice were infected intragastrically and the reporter activities monitored by the IVIS technology. The mouse experiments revealed that both LPS promoters were well expressed in vivo and could be detected by IVIS, mainly from the intestinal region of orally infected mice.
Collapse
Affiliation(s)
- Elif Bozcal
- Istanbul University, Faculty of Science, Department of Biology, Basic and Industrial Microbiology Section, Istanbul, Turkey
- Ege University, Faculty of Science, Department of Biology, Basic and Industrial Microbiology Section, Izmir, Turkey
- Department of Bacteriology and Immunology, Medicum, and Research Programs Unit, Immunobiology, University of Helsinki, Helsinki, Finland
| | - Melih Dagdeviren
- Ege University, Faculty of Science, Department of Biology, General Biology Section, Izmir, Turkey
- Ege University, Center for Drug Research and Development and Pharmacokinetic Applications, Izmir, Turkey
| | - Atac Uzel
- Ege University, Faculty of Science, Department of Biology, Basic and Industrial Microbiology Section, Izmir, Turkey
| | - Mikael Skurnik
- Department of Bacteriology and Immunology, Medicum, and Research Programs Unit, Immunobiology, University of Helsinki, Helsinki, Finland
- Division of Clinical Microbiology, Helsinki University Hospital, HUSLAB, Helsinki, Finland
| |
Collapse
|
26
|
Engel Y, Windhorst C, Lu X, Goodrich-Blair H, Bode HB. The Global Regulators Lrp, LeuO, and HexA Control Secondary Metabolism in Entomopathogenic Bacteria. Front Microbiol 2017; 8:209. [PMID: 28261170 PMCID: PMC5313471 DOI: 10.3389/fmicb.2017.00209] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 01/30/2017] [Indexed: 11/13/2022] Open
Abstract
Photorhabdus luminescens TTO1 and Xenorhabdus nematophila HGB081 are insect pathogenic bacteria and producers of various structurally diverse bioactive natural products. In these entomopathogenic bacteria we investigated the role of the global regulators Lrp, LeuO, and HexA in the production of natural products. Lrp is a general activator of natural product biosynthesis in X. nematophila and for most compounds in TTO1. Microarray analysis confirmed these results in X. nematophila and enabled the identification of additional biosynthesis gene clusters (BGC) regulated by Lrp. Moreover, when promoters of two X. nematophila BGC were analyzed, transcriptional activation by Lrp was observed. In contrast, LeuO in X. nematophila and P. luminescens has both repressing and activating features, depending on the natural product examined. Furthermore, heterologous overexpression of leuO from X. nematophila in the closely related Xenorhabdus szentirmaii resulted in overproduction of several natural products including novel compounds. The presented findings could be of importance for establishing a tool for overproduction of secondary metabolites and subsequent identification of novel compounds.
Collapse
Affiliation(s)
- Yvonne Engel
- Merck-Stiftungsprofessur Molekulare Biotechnologie, Molekulare Biowissenschaften, Goethe Universität Frankfurt Frankfurt am Main, Germany
| | - Carina Windhorst
- Merck-Stiftungsprofessur Molekulare Biotechnologie, Molekulare Biowissenschaften, Goethe Universität Frankfurt Frankfurt am Main, Germany
| | - Xiaojun Lu
- Department of Bacteriology, University of Wisconsin-Madison, Madison WI, USA
| | - Heidi Goodrich-Blair
- Department of Bacteriology, University of Wisconsin-Madison, MadisonWI, USA; Department of Microbiology, University of Tennessee, Knoxville, KnoxvilleTN, USA
| | - Helge B Bode
- Merck-Stiftungsprofessur Molekulare Biotechnologie, Molekulare Biowissenschaften, Goethe Universität FrankfurtFrankfurt am Main, Germany; Buchmann Institute for Molecular Life Sciences (BMLS), Goethe Universität FrankfurtFrankfurt am Main, Germany
| |
Collapse
|
27
|
Nuss AM, Schuster F, Roselius L, Klein J, Bücker R, Herbst K, Heroven AK, Pisano F, Wittmann C, Münch R, Müller J, Jahn D, Dersch P. A Precise Temperature-Responsive Bistable Switch Controlling Yersinia Virulence. PLoS Pathog 2016; 12:e1006091. [PMID: 28006011 PMCID: PMC5179001 DOI: 10.1371/journal.ppat.1006091] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 11/27/2016] [Indexed: 11/19/2022] Open
Abstract
Different biomolecules have been identified in bacterial pathogens that sense changes in temperature and trigger expression of virulence programs upon host entry. However, the dynamics and quantitative outcome of this response in individual cells of a population, and how this influences pathogenicity are unknown. Here, we address these questions using a thermosensing virulence regulator of an intestinal pathogen (RovA of Yersinia pseudotuberculosis) as a model. We reveal that this regulator is part of a novel thermoresponsive bistable switch, which leads to high- and low-invasive subpopulations within a narrow temperature range. The temperature range in which bistability is observed is defined by the degradation and synthesis rate of the regulator, and is further adjustable via a nutrient-responsive regulator. The thermoresponsive switch is also characterized by a hysteretic behavior in which activation and deactivation occurred on vastly different time scales. Mathematical modeling accurately mirrored the experimental behavior and predicted that the thermoresponsiveness of this sophisticated bistable switch is mainly determined by the thermo-triggered increase of RovA proteolysis. We further observed RovA ON and OFF subpopulations of Y. pseudotuberculosis in the Peyer’s patches and caecum of infected mice, and that changes in the RovA ON/OFF cell ratio reduce tissue colonization and overall virulence. This points to a bet-hedging strategy in which the thermoresponsive bistable switch plays a key role in adapting the bacteria to the fluctuating conditions encountered as they pass through the host’s intestinal epithelium and suggests novel strategies for the development of antimicrobial therapies. The ability of pathogens to sense temperature changes when they enter their mammalian hosts from the environment is crucial to optimize their fitness and adjust expression of their virulence programs. Until now it has been assumed that all cells within a population participate in the thermo-triggered adaptive response. Here, we show that a small subpopulation of an enteric pathogen does not follow thermo-induced reprogramming when the bacteria pass the intestinal epithelial layer. Observed heterogeneity is promoted by a new type of bistable switch, implicating a highly precise, thermoresponsive control element. Moreover, we demonstrate that this regulatory implement is important for virulence as it prepares the pathogen for sudden, unpredictable fluctuations encountered during host entry and exit.
Collapse
Affiliation(s)
- Aaron Mischa Nuss
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Franziska Schuster
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Louisa Roselius
- Institute of Microbiology, Technical University Braunschweig, Braunschweig, Germany
| | - Johannes Klein
- Institute of Microbiology, Technical University Braunschweig, Braunschweig, Germany
| | - René Bücker
- Institute of Systems Biotechnology, Saarland University, Saarbrücken, Germany
| | - Katharina Herbst
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Ann Kathrin Heroven
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Fabio Pisano
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Christoph Wittmann
- Institute of Systems Biotechnology, Saarland University, Saarbrücken, Germany
| | - Richard Münch
- Institute of Microbiology, Technical University Braunschweig, Braunschweig, Germany
| | - Johannes Müller
- Institute of Mathematics, Technical University Munich, Munich, Germany
- Institute of Computational Biology, Helmholtz Centre Munich, Neuherberg, Germany
| | - Dieter Jahn
- Institute of Microbiology, Technical University Braunschweig, Braunschweig, Germany
| | - Petra Dersch
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
- * E-mail:
| |
Collapse
|
28
|
Abstract
The human pathogens
Yersinia pseudotuberculosis and
Yersinia enterocolitica cause enterocolitis, while
Yersinia pestis is responsible for pneumonic, bubonic, and septicaemic plague. All three share an infection strategy that relies on a virulence factor arsenal to enable them to enter, adhere to, and colonise the host while evading host defences to avoid untimely clearance. Their arsenal includes a number of adhesins that allow the invading pathogens to establish a foothold in the host and to adhere to specific tissues later during infection. When the host innate immune system has been activated, all three pathogens produce a structure analogous to a hypodermic needle. In conjunction with the translocon, which forms a pore in the host membrane, the channel that is formed enables the transfer of six ‘effector’ proteins into the host cell cytoplasm. These proteins mimic host cell proteins but are more efficient than their native counterparts at modifying the host cell cytoskeleton, triggering the host cell suicide response. Such a sophisticated arsenal ensures that yersiniae maintain the upper hand despite the best efforts of the host to counteract the infecting pathogen.
Collapse
Affiliation(s)
- Steve Atkinson
- Centre for Biomolecular Sciences, School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Paul Williams
- Centre for Biomolecular Sciences, School of Life Sciences, University of Nottingham, Nottingham, UK
| |
Collapse
|
29
|
Rees CA, Smolinska A, Hill JE. The volatile metabolome of
Klebsiella pneumoniae
in human blood. J Breath Res 2016; 10:027101. [DOI: 10.1088/1752-7155/10/2/027101] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
|
30
|
Yang R, Cui Y, Bi Y. Perspectives on Yersinia pestis: A Model for Studying Zoonotic Pathogens. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 918:377-391. [PMID: 27722871 DOI: 10.1007/978-94-024-0890-4_14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Yersinia pestis is a typical zoonotic bacterial pathogen. The following reasons make this pathogen a model for studying zoonotic pathogens: (1) Its unique lifestyle makes Y. pestis an ideal model for studying host-vector-environment-pathogen interactions; (2) population diversity characters in Y. pestis render it a model species for studying monomorphic bacterial evolution; (3) the pathogenic features of bacteria provide us with good opportunities to study human immune responses; (4) typical animal and vector models of Y. pestis infection create opportunities for experimental studies on pathogenesis and evolution; and (5) repeated pandemics and local outbreaks provide us with clues about the infectious disease outbreaks that have occurred in human history.
Collapse
Affiliation(s)
- Ruifu Yang
- Beijing Institute of Microbiology and Epidemiology, No. 20, Dongdajie, Fengtai, Beijing, 100071, China.
| | - Yujun Cui
- Beijing Institute of Microbiology and Epidemiology, No. 20, Dongdajie, Fengtai, Beijing, 100071, China
| | - Yujing Bi
- Beijing Institute of Microbiology and Epidemiology, No. 20, Dongdajie, Fengtai, Beijing, 100071, China
| |
Collapse
|
31
|
The secreted autotransporter toxin (Sat) does not act as a virulence factor in the probiotic Escherichia coli strain Nissle 1917. BMC Microbiol 2015; 15:250. [PMID: 26518156 PMCID: PMC4628265 DOI: 10.1186/s12866-015-0591-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 10/25/2015] [Indexed: 12/11/2022] Open
Abstract
Background Escherichia coli Nissle 1917 (EcN) is a probiotic used in the treatment of intestinal diseases. Although it is considered safe, EcN is closely related to the uropathogenic E. coli strain CFT073 and contains many of its predicted virulence elements. Thus, it is relevant to assess whether virulence-associated genes are functional in EcN. One of these genes encodes the secreted autotransporter toxin (Sat), a member of the serine protease autotransporters of Enterobacteriaceae (SPATEs) that are secreted following the type V autotransporter pathway. Sat is highly prevalent in certain E. coli pathogenic groups responsible for urinary and intestinal infections. In these pathogens Sat promotes cytotoxic effects in several lines of undifferentiated epithelial cells, but not in differentiated Caco-2 cells. Results Here we provide evidence that sat is expressed by EcN during the colonization of mouse intestine. The EcN protein is secreted as an active serine protease, with its 107 kDa-passenger domain released into the medium as a soluble protein. Expression of recombinant EcN Sat protein in strain HB101 increases paracellular permeability to mannitol in polarized Caco-2 monolayers. This effect, also reported for the Sat protein of diffusely adherent E. coli, is not observed when this protein is expressed in the EcN background. In addition, we show that EcN supernatants confer protection against Sat-mediated effects on paracellular permeability, thus indicating that other secreted EcN factors are able to prevent barrier disruption caused by pathogen-related factors. Sat is not required for intestinal colonization, but the EcNsat::cat mutant outcompetes wild-type EcN in the streptomycin-treated mouse model. Analysis of the presence of sat in 29 strains of the ECOR collection isolated from stools of healthy humans shows 34.8 % positives, with high prevalence of strains of the phylogenetic groups D and B2, related with extra-intestinal infections. Conclusions Sat does not act as a virulence factor in EcN. The role of Sat in intestinal pathogenesis relies on other genetic determinants responsible for the bacterial pathotype. Electronic supplementary material The online version of this article (doi:10.1186/s12866-015-0591-5) contains supplementary material, which is available to authorized users.
Collapse
|
32
|
Earl SC, Rogers MT, Keen J, Bland DM, Houppert AS, Miller C, Temple I, Anderson DM, Marketon MM. Resistance to Innate Immunity Contributes to Colonization of the Insect Gut by Yersinia pestis. PLoS One 2015; 10:e0133318. [PMID: 26177454 PMCID: PMC4503695 DOI: 10.1371/journal.pone.0133318] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 06/25/2015] [Indexed: 01/29/2023] Open
Abstract
Yersinia pestis, the causative agent of bubonic and pneumonic plague, is typically a zoonotic vector-borne disease of wild rodents. Bacterial biofilm formation in the proventriculus of the flea contributes to chronic infection of fleas and facilitates efficient disease transmission. However prior to biofilm formation, ingested bacteria must survive within the flea midgut, and yet little is known about vector-pathogen interactions that are required for flea gut colonization. Here we establish a Drosophila melanogaster model system to gain insight into Y. pestis colonization of the insect vector. We show that Y. pestis establishes a stable infection in the anterior midgut of fly larvae, and we used this model system to study the roles of genes involved in biofilm production and/or resistance to gut immunity stressors. We find that PhoP and GmhA both contribute to colonization and resistance to antimicrobial peptides in flies, and furthermore, the data suggest biofilm formation may afford protection against antimicrobial peptides. Production of reactive oxygen species in the fly gut, as in fleas, also serves to limit bacterial infection, and OxyR mediates Y. pestis survival in both insect models. Overall, our data establish the fruit fly as an informative model to elucidate the relationship between Y. pestis and its flea vector.
Collapse
Affiliation(s)
- Shaun C. Earl
- Department of Biology, Indiana University, Bloomington, IN, United States of America
| | - Miles T. Rogers
- Department of Biology, Indiana University, Bloomington, IN, United States of America
| | - Jennifer Keen
- Department of Biology, Indiana University, Bloomington, IN, United States of America
| | - David M. Bland
- Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri, United States of America
| | - Andrew S. Houppert
- Department of Biology, Indiana University, Bloomington, IN, United States of America
| | - Caitlynn Miller
- Department of Biology, Indiana University, Bloomington, IN, United States of America
| | - Ian Temple
- Department of Biology, Indiana University, Bloomington, IN, United States of America
| | - Deborah M. Anderson
- Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri, United States of America
| | - Melanie M. Marketon
- Department of Biology, Indiana University, Bloomington, IN, United States of America
- * E-mail:
| |
Collapse
|
33
|
Keller R, Ariöz C, Hansmeier N, Stenberg-Bruzell F, Burstedt M, Vikström D, Kelly A, Wieslander Å, Daley DO, Hunke S. The Escherichia coli Envelope Stress Sensor CpxA Responds to Changes in Lipid Bilayer Properties. Biochemistry 2015; 54:3670-6. [PMID: 25993101 DOI: 10.1021/acs.biochem.5b00242] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Cpx stress response system is induced by various environmental and cellular stimuli. It is also activated in Escherichia coli strains lacking the major phospholipid, phosphatidylethanolamine (PE). However, it is not known whether CpxA directly senses changes in the lipid bilayer or the presence of misfolded proteins due to the lack of PE in their membranes. To address this question, we used an in vitro reconstitution system and vesicles with different lipid compositions to track modulations in the activity of CpxA in different lipid bilayers. Moreover, the Cpx response was validated in vivo by monitoring expression of a PcpxP-gfp reporter in lipid-engineered strains of E. coli. Our combined data indicate that CpxA responds specifically to different lipid compositions.
Collapse
Affiliation(s)
- Rebecca Keller
- †Department of Pharmacy and Biochemistry, Johannes Gutenberg-University, D-55128 Mainz, Germany
| | - Candan Ariöz
- ‡Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Nicole Hansmeier
- §Department of Microbiology, University of Osnabrück, D-49076 Osnabrück, Germany
| | - Filippa Stenberg-Bruzell
- ‡Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Malin Burstedt
- ‡Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - David Vikström
- ‡Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Amelie Kelly
- ‡Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Åke Wieslander
- ‡Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Daniel O Daley
- ‡Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
| | - Sabine Hunke
- ∥Molecular Microbiology, University of Osnabrück, D-49076 Osnabrück, Germany
| |
Collapse
|
34
|
Cell Differentiation in a Bacillus thuringiensis Population during Planktonic Growth, Biofilm Formation, and Host Infection. mBio 2015; 6:e00138-15. [PMID: 25922389 PMCID: PMC4436061 DOI: 10.1128/mbio.00138-15] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Bacillus thuringiensis (Bt) is armed to complete a full cycle in its insect host. During infection, virulence factors are expressed under the control of the quorum sensor PlcR to kill the host. After the host’s death, the quorum sensor NprR controls a necrotrophic lifestyle, allowing the vegetative cells to use the insect cadaver as a bioincubator and to survive. Only a part of the Bt population sporulates in the insect cadaver, and the precise composition of the whole population and its evolution over time are unknown. Using fluorescent reporters to record gene expression at the single-cell level, we have determined the differentiation course of a Bt population and explored the lineage existing among virulent, necrotrophic, and sporulating cells. The dynamics of cell differentiation were monitored during growth in homogenized medium, biofilm formation, and colonization of insect larvae. We demonstrated that in the insect host and in planktonic culture in rich medium, the virulence, necrotrophism, and sporulation regulators are successively activated in the same cell. In contrast, in biofilms, activation of PlcR is dispensable for NprR activation and we observed a greater heterogeneity than under the other two growth conditions. We also showed that sporulating cells arise almost exclusively from necrotrophic cells. In biofilm and in the insect cadaver, we identified an as-yet-uncharacterized category of cells that do not express any of the reporters used. Overall, we showed that PlcR, NprR, and Spo0A act as interconnected integrators to allow finely tuned adaptation of the pathogen to its environment. Bt is an entomopathogen found ubiquitously in the environment and is a widely used biopesticide. Studies performed at the population level suggest that the infection process of Bt includes three successive steps (virulence, necrotrophism, and sporulation) controlled by different regulators. This study aimed to determine how these phenotypes are activated at the cellular level and if they are switched on in all cells. We used an insect model of infection and biofilms to decipher the cellular differentiation of this bacterium under naturalistic conditions. Our study reveals the connection and lineage existing among virulent, necrotrophic, and sporulating cells. It also shows that the complex conditions encountered in biofilms and during infection generate great heterogeneity inside the population, which might reflect a bet-hedging strategy to ameliorate survival. These data generate new insights into the role of regulatory networks in the adaptation of a pathogen to its host.
Collapse
|
35
|
Community behavior and spatial regulation within a bacterial microcolony in deep tissue sites serves to protect against host attack. Cell Host Microbe 2014; 17:21-31. [PMID: 25500192 DOI: 10.1016/j.chom.2014.11.008] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 09/09/2014] [Accepted: 10/27/2014] [Indexed: 12/20/2022]
Abstract
Bacterial pathogens express virulence-specific transcriptional programs that allow tissue colonization. Although phenotypic variation has been noted in the context of antibiotic exposure, no direct evidence exists for heterogeneity in virulence-specific transcriptional programs within tissues. In a mouse model of Yersinia pseudotuberculosis infection, we show that at least three subpopulations of bacteria develop within a single tissue site in response to distinct host signals. Bacteria growing on the exterior of spleen microcolonies responded to soluble signals and induced the nitric oxide (NO)-detoxifying gene, hmp. Hmp effectively eliminated NO diffusion and protected the interior bacterial population from exposure to NO-derived inducing signals. A third subpopulation, constituting the most peripherally localized bacteria, directly contacted neutrophils and transcriptionally upregulated a virulence factor. These studies demonstrate that growth within tissues results in transcriptional specialization within a single focus of microbial replication, facilitating directed pathogen counterattack against the host response.
Collapse
|
36
|
Influence of PhoP and intra-species variations on virulence of Yersinia pseudotuberculosis during the natural oral infection route. PLoS One 2014; 9:e103541. [PMID: 25075520 PMCID: PMC4116203 DOI: 10.1371/journal.pone.0103541] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 07/03/2014] [Indexed: 01/02/2023] Open
Abstract
The two-component regulatory system PhoP/PhoQ has been shown to (i) control expression of virulence-associated traits, (ii) confer survival and growth within macrophages and (iii) play a role in Yersinia infections. However, the influence of PhoP on virulence varied greatly between different murine models of infection and its role in natural oral infections with frequently used representative isolates of Y. pseudotuberculosis was unknown. To address this issue, we constructed an isogenic set of phoP+ and phoP− variants of strain IP32953 and YPIII and analyzed the impact of PhoP using in vitro functionality experiments and a murine oral infection model, whereby we tested for bacterial dissemination and influence on the host immune response. Our results revealed that PhoP has a low impact on virulence, lymphatic and systemic organ colonization, and on immune response modulation by IP32953 and YPIII, indicating that PhoP is not absolutely essential for oral infections but may be involved in fine-tuning the outcome. Our work further revealed certain strain-specific differences in virulence properties, which do not strongly rely on the function of PhoP, but affect tissue colonization, dissemination and/or persistence of the bacteria. Highlighted intra-species variations may provide a potential means to rapidly adjust to environmental changes inside and outside of the host.
Collapse
|
37
|
Evidence of autoinducer-dependent and -independent heterogeneous gene expression in Sinorhizobium fredii NGR234. Appl Environ Microbiol 2014; 80:5572-82. [PMID: 25002427 DOI: 10.1128/aem.01689-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Populations of genetically identical Sinorhizobium fredii NGR234 cells differ significantly in their expression profiles of autoinducer (AI)-dependent and AI-independent genes. Promoter fusions of the NGR234 AI synthase genes traI and ngrI showed high levels of phenotypic heterogeneity during growth in TY medium on a single-cell level. However, adding very high concentrations of N-(3-oxooctanoyl-)-l-homoserine lactone resulted in a more homogeneous expression profile. Similarly, the lack of internally synthesized AIs in the background of the NGR234-ΔtraI or the NGR234-ΔngrI mutant resulted in a highly homogenous expression of the corresponding promoter fusions in the population. Expression studies with reporter fusions of the promoter regions of the quorum-quenching genes dlhR and qsdR1 and the type IV pilus gene cluster located on pNGR234b suggested that factors other than AI molecules affect NGR234 phenotypic heterogeneity. Further studies with root exudates and developing Arabidopsis thaliana seedlings provide the first evidence that plant root exudates have strong effects on the heterogeneity of AI synthase and quorum-quenching genes in NGR234. Therefore, plant-released octopine appears to play a key role in modulation of heterogeneous gene expression.
Collapse
|
38
|
Trauth S, Bischofs IB. Ectopic integration vectors for generating fluorescent promoter fusions in Bacillus subtilis with minimal dark noise. PLoS One 2014; 9:e98360. [PMID: 24874808 PMCID: PMC4038550 DOI: 10.1371/journal.pone.0098360] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 05/01/2014] [Indexed: 11/19/2022] Open
Abstract
Fluorescent protein promoter reporters are important tools that are widely used for diverse purposes in microbiology, systems biology and synthetic biology and considerable engineering efforts are still geared at improving the sensitivity of the reporter systems. Here we focus on dark noise, i.e. the signal that is generated by the empty vector control. We quantitatively characterize the dark noise of a few common bacterial reporter systems by single cell microscopy. All benchmarked reporter systems generated significant amounts of dark noise that exceed the cellular autofluorescence to different extents. We then reengineered a multicolor set of fluorescent ectopic integration vectors for Bacillus subtilis by introducing a terminator immediately upstream of the promoter insertion site, resulting in an up to 2.7-fold reduction of noise levels. The sensitivity and dynamic range of the new high-performance pXFP_Star reporter system is only limited by cellular autofluorescence. Moreover, based on studies of the rapE promoter of B. subtilis we show that the new pXFP_Star reporter system reliably reports on the weak activity of the rapE promoter whereas the original reporter system fails because of transcriptional interference. Since the pXFP_Star reporter system properly isolates the promoter from spurious transcripts, it is a particularly suitable tool for quantitative characterization of weak promoters in B. subtilis.
Collapse
Affiliation(s)
- Stephanie Trauth
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Heidelberg, Germany
- Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), University of Heidelberg, Heidelberg, Germany
| | - Ilka B. Bischofs
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Heidelberg, Germany
- Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), University of Heidelberg, Heidelberg, Germany
- * E-mail:
| |
Collapse
|
39
|
Swarts DC, Jore MM, Westra ER, Zhu Y, Janssen JH, Snijders AP, Wang Y, Patel DJ, Berenguer J, Brouns SJJ, van der Oost J. DNA-guided DNA interference by a prokaryotic Argonaute. Nature 2014; 507:258-261. [PMID: 24531762 DOI: 10.1038/nature12971] [Citation(s) in RCA: 311] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 12/19/2013] [Indexed: 12/19/2022]
Abstract
RNA interference is widely distributed in eukaryotes and has a variety of functions, including antiviral defence and gene regulation. All RNA interference pathways use small single-stranded RNA (ssRNA) molecules that guide proteins of the Argonaute (Ago) family to complementary ssRNA targets: RNA-guided RNA interference. The role of prokaryotic Ago variants has remained elusive, although bioinformatics analysis has suggested their involvement in host defence. Here we demonstrate that Ago of the bacterium Thermus thermophilus (TtAgo) acts as a barrier for the uptake and propagation of foreign DNA. In vivo, TtAgo is loaded with 5'-phosphorylated DNA guides, 13-25 nucleotides in length, that are mostly plasmid derived and have a strong bias for a 5'-end deoxycytidine. These small interfering DNAs guide TtAgo to cleave complementary DNA strands. Hence, despite structural homology to its eukaryotic counterparts, TtAgo functions in host defence by DNA-guided DNA interference.
Collapse
Affiliation(s)
- Daan C Swarts
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, the Netherlands
| | - Matthijs M Jore
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, the Netherlands
| | - Edze R Westra
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, the Netherlands
| | - Yifan Zhu
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, the Netherlands
| | - Jorijn H Janssen
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, the Netherlands
| | - Ambrosius P Snijders
- Clare Hall Laboratories, Cancer Research UK, London Research Institute, South Mimms EN6 3LD, UK
| | - Yanli Wang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Dinshaw J Patel
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA
| | - José Berenguer
- Centro de Biología Molecular Severo Ochoa, UAM-CSIC, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Stan J J Brouns
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, the Netherlands
| | - John van der Oost
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, the Netherlands
| |
Collapse
|
40
|
Schweer J, Kulkarni D, Kochut A, Pezoldt J, Pisano F, Pils MC, Genth H, Huehn J, Dersch P. The cytotoxic necrotizing factor of Yersinia pseudotuberculosis (CNFY) enhances inflammation and Yop delivery during infection by activation of Rho GTPases. PLoS Pathog 2013; 9:e1003746. [PMID: 24244167 PMCID: PMC3820761 DOI: 10.1371/journal.ppat.1003746] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 09/20/2013] [Indexed: 12/19/2022] Open
Abstract
Some isolates of Yersinia pseudotuberculosis produce the cytotoxic necrotizing factor (CNFY), but the functional consequences of this toxin for host-pathogen interactions during the infection are unknown. In the present study we show that CNFY has a strong influence on virulence. We demonstrate that the CNFY toxin is thermo-regulated and highly expressed in all colonized lymphatic tissues and organs of orally infected mice. Most strikingly, we found that a cnfY knock-out variant of a naturally toxin-expressing Y. pseudotuberculosis isolate is strongly impaired in its ability to disseminate into the mesenteric lymph nodes, liver and spleen, and has fully lost its lethality. The CNFY toxin contributes significantly to the induction of acute inflammatory responses and to the formation of necrotic areas in infected tissues. The analysis of the host immune response demonstrated that presence of CNFY leads to a strong reduction of professional phagocytes and natural killer cells in particular in the spleen, whereas loss of the toxin allows efficient tissue infiltration of these immune cells and rapid killing of the pathogen. Addition of purified CNFY triggers formation of actin-rich membrane ruffles and filopodia, which correlates with the activation of the Rho GTPases, RhoA, Rac1 and Cdc42. The analysis of type III effector delivery into epithelial and immune cells in vitro and during the course of the infection further demonstrated that CNFY enhances the Yop translocation process and supports a role for the toxin in the suppression of the antibacterial host response. In summary, we highlight the importance of CNFY for pathogenicity by showing that this toxin modulates inflammatory responses, protects the bacteria from attacks of innate immune effectors and enhances the severity of a Yersinia infection. Various toxins and effector proteins of bacterial pathogens have been found to manipulate eukaryotic cell machineries to promote persistence and proliferation within their hosts. Many of these virulence factors target small Rho GTPases, but their role in pathogenesis is often unknown. Here, we addressed the expression and functional consequences of the CNFY toxin found in some isolates of Y. pseudotuberculosis. We found that CNFY besides modulating the cell cytoskeleton by activation of the GTPases RhoA, Rac1 and Cdc42, contributes to increased inflammation and tissue damage. Moreover, CNFY increases the ability of Yersinia to prevent the attack of the immune system, by enhancing the delivery of antiphagocytic and cytotoxic effectors into professional phagocytes. Our findings provide the first insights into the multi-functional action and severe consequences of the CNFY toxin on the inflammatory response and disease-associated tissue damage during the natural course of the infection.
Collapse
Affiliation(s)
- Janina Schweer
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Devesha Kulkarni
- Department of Experimental Immunology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Annika Kochut
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Joern Pezoldt
- Department of Experimental Immunology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Fabio Pisano
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Marina C. Pils
- Mouse Pathology, Animal Experimental Unit, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Harald Genth
- Institute for Toxicology, Medical School Hannover, Hannover, Germany
| | - Jochen Huehn
- Department of Experimental Immunology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Petra Dersch
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
- * E-mail:
| |
Collapse
|
41
|
Heroven AK, Sest M, Pisano F, Scheb-Wetzel M, Steinmann R, Böhme K, Klein J, Münch R, Schomburg D, Dersch P. Crp induces switching of the CsrB and CsrC RNAs in Yersinia pseudotuberculosis and links nutritional status to virulence. Front Cell Infect Microbiol 2012; 2:158. [PMID: 23251905 PMCID: PMC3523269 DOI: 10.3389/fcimb.2012.00158] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 11/27/2012] [Indexed: 12/18/2022] Open
Abstract
Colonization of the intestinal tract and dissemination into deeper tissues by the enteric pathogen Yersinia pseudotuberculosis demands expression of a special set of virulence factors important for the initiation and the persistence of the infection. In this study we demonstrate that many virulence-associated functions are coregulated with the carbohydrate metabolism. This link is mediated by the carbon storage regulator (Csr) system, including the regulatory RNAs CsrB and CsrC, and the cAMP receptor protein (Crp), which both control virulence gene expression in response to the nutrient composition of the medium. Here, we show that Crp regulates the synthesis of both Csr RNAs in an opposite manner. A loss of the crp gene resulted in a strong upregulation of CsrB synthesis, whereas CsrC levels were strongly reduced leading to downregulation of the virulence regulator RovA. Switching of the Csr RNA involves Crp-mediated repression of the response regulator UvrY which activates csrB transcription. To elucidate the regulatory links between virulence and carbon metabolism, we performed comparative metabolome, transcriptome, and phenotypic microarray analyses and found that Crp promotes oxidative catabolism of many different carbon sources, whereas fermentative patterns of metabolism are favored when crp is deleted. Mouse infection experiments further demonstrated that Crp is pivotal for a successful Y. pseudotuberculosis infection. In summary, placement of the Csr system and important virulence factors under control of Crp enables this pathogen to link its nutritional status to virulence in order to optimize biological fitness and infection efficiency through the infectious life cycle.
Collapse
Affiliation(s)
- Ann Kathrin Heroven
- Abteilung Molekulare Infektionsbiologie, Helmholtz-Zentrum für Infektionsforschung Braunschweig, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Ozawa T, Yoshimura H, Kim SB. Advances in Fluorescence and Bioluminescence Imaging. Anal Chem 2012; 85:590-609. [DOI: 10.1021/ac3031724] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Takeaki Ozawa
- Department of Chemistry, Graduate
School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hideaki Yoshimura
- Department of Chemistry, Graduate
School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Sung Bae Kim
- Research Institute for Environmental Management
Technology, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba
305-8569, Japan
| |
Collapse
|
43
|
Sun Y, Connor MG, Pennington JM, Lawrenz MB. Development of bioluminescent bioreporters for in vitro and in vivo tracking of Yersinia pestis. PLoS One 2012; 7:e47123. [PMID: 23071730 PMCID: PMC3469486 DOI: 10.1371/journal.pone.0047123] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 09/10/2012] [Indexed: 12/21/2022] Open
Abstract
Yersinia pestis causes an acute infection known as the plague. Conventional techniques to enumerate Y. pestis can be labor intensive and do not lend themselves to high throughput assays. In contrast, bioluminescent bioreporters produce light that can be detected using plate readers or optical imaging platforms to monitor bacterial populations as a function of luminescence. Here, we describe the development of two Y. pestis chromosomal-based luxCDABE bioreporters, Lux(PtolC) and Lux(PcysZK). These bioreporters use constitutive promoters to drive expression of luxCDABE that allow for sensitive detection of bacteria via bioluminescence in vitro. Importantly, both bioreporters demonstrate a direct correlation between bacterial numbers and bioluminescence, which allows for bioluminescence to be used to compare bacterial numbers. We demonstrate the use of these bioreporters to test antimicrobial inhibitors (Lux(PtolC)) and monitor intracellular survival (Lux(PtolC) and Lux(PcysZK)) in vitro. Furthermore, we show that Y. pestis infection of the mouse model can be monitored using whole animal optical imaging in real time. Using optical imaging, we observed Y. pestis dissemination and differentiated between virulence phenotypes in live animals via bioluminescence. Finally, we demonstrate that whole animal optical imaging can identify unexpected colonization patterns in mutant-infected animals.
Collapse
Affiliation(s)
| | | | | | - Matthew B. Lawrenz
- Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, Kentucky, United States of America
- * E-mail:
| |
Collapse
|
44
|
Rapid depletion of target proteins allows identification of coincident physiological responses. J Bacteriol 2012; 194:5932-40. [PMID: 22942249 DOI: 10.1128/jb.00913-12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Targeted protein degradation is a powerful tool that can be used to create unique physiologies depleted of important factors. Current strategies involve modifying a gene of interest such that a degradation peptide is added to an expressed target protein and then conditionally activating proteolysis, either by expressing adapters, unmasking cryptic recognition determinants, or regulating protease affinities using small molecules. For each target, substantial optimization may be required to achieve a practical depletion, in that the target remains present at a normal level prior to induction and is then rapidly depleted to levels low enough to manifest a physiological response. Here, we describe a simplified targeted degradation system that rapidly depletes targets and that can be applied to a wide variety of proteins without optimizing target protease affinities. The depletion of the target is rapid enough that a primary physiological response manifests that is related to the function of the target. Using ribosomal protein S1 as an example, we show that the rapid depletion of this essential translation factor invokes concomitant changes to the levels of several mRNAs, even before appreciable cell division has occurred.
Collapse
|
45
|
Imaging of bubonic plague dynamics by in vivo tracking of bioluminescent Yersinia pestis. PLoS One 2012; 7:e34714. [PMID: 22496846 PMCID: PMC3320629 DOI: 10.1371/journal.pone.0034714] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 03/09/2012] [Indexed: 01/25/2023] Open
Abstract
Yersinia pestis dissemination in a host is usually studied by enumerating bacteria in the tissues of animals sacrificed at different times. This laborious methodology gives only snapshots of the infection, as the infectious process is not synchronized. In this work we used in vivo bioluminescence imaging (BLI) to follow Y. pestis dissemination during bubonic plague. We first demonstrated that Y. pestis CO92 transformed with pGEN-luxCDABE stably emitted bioluminescence in vitro and in vivo, while retaining full virulence. The light produced from live animals allowed to delineate the infected organs and correlated with bacterial loads, thus validating the BLI tool. We then showed that the first step of the infectious process is a bacterial multiplication at the injection site (linea alba), followed by a colonization of the draining inguinal lymph node(s), and subsequently of the ipsilateral axillary lymph node through a direct connection between the two nodes. A mild bacteremia and an effective filtering of the blood stream by the liver and spleen probably accounted for the early bacterial blood clearance and the simultaneous development of bacterial foci within these organs. The saturation of the filtering capacity of the spleen and liver subsequently led to terminal septicemia. Our results also indicate that secondary lymphoid tissues are the main targets of Y. pestis multiplication and that colonization of other organs occurs essentially at the terminal phase of the disease. Finally, our analysis reveals that the high variability in the kinetics of infection is attributable to the time the bacteria remain confined at the injection site. However, once Y. pestis has reached the draining lymph nodes, the disease progresses extremely rapidly, leading to the invasion of the entire body within two days and to death of the animals. This highlights the extraordinary capacity of Y. pestis to annihilate the host innate immune response.
Collapse
|
46
|
Concerted actions of a thermo-labile regulator and a unique intergenic RNA thermosensor control Yersinia virulence. PLoS Pathog 2012; 8:e1002518. [PMID: 22359501 PMCID: PMC3280987 DOI: 10.1371/journal.ppat.1002518] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 12/19/2011] [Indexed: 11/19/2022] Open
Abstract
Expression of all Yersinia pathogenicity factors encoded on the virulence plasmid, including the yop effector and the ysc type III secretion genes, is controlled by the transcriptional activator LcrF in response to temperature. Here, we show that a protein- and RNA-dependent hierarchy of thermosensors induce LcrF synthesis at body temperature. Thermally regulated transcription of lcrF is modest and mediated by the thermo-sensitive modulator YmoA, which represses transcription from a single promoter located far upstream of the yscW-lcrF operon at moderate temperatures. The transcriptional response is complemented by a second layer of temperature-control induced by a unique cis-acting RNA element located within the intergenic region of the yscW-lcrF transcript. Structure probing demonstrated that this region forms a secondary structure composed of two stemloops at 25°C. The second hairpin sequesters the lcrF ribosomal binding site by a stretch of four uracils. Opening of this structure was favored at 37°C and permitted ribosome binding at host body temperature. Our study further provides experimental evidence for the biological relevance of an RNA thermometer in an animal model. Following oral infections in mice, we found that two different Y. pseudotuberculosis patient isolates expressing a stabilized thermometer variant were strongly reduced in their ability to disseminate into the Peyer's patches, liver and spleen and have fully lost their lethality. Intriguingly, Yersinia strains with a destabilized version of the thermosensor were attenuated or exhibited a similar, but not a higher mortality. This illustrates that the RNA thermometer is the decisive control element providing just the appropriate amounts of LcrF protein for optimal infection efficiency.
Collapse
|
47
|
In vivo-induced InvA-like autotransporters Ifp and InvC of Yersinia pseudotuberculosis promote interactions with intestinal epithelial cells and contribute to virulence. Infect Immun 2011; 80:1050-64. [PMID: 22158741 DOI: 10.1128/iai.05715-11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The Yersinia pseudotuberculosis Ifp and InvC molecules are putative autotransporter proteins with a high homology to the invasin (InvA) protein. To characterize the function of these surface proteins, we expressed both factors in Escherichia coli K-12 and demonstrated the attachment of Ifp- and InvC-expressing bacteria to human-, mouse-, and pig-derived intestinal epithelial cells. Ifp also was found to mediate microcolony formation and internalization into polarized human enterocytes. The ifp and invC genes were not expressed under in vitro conditions but were found to be induced in the Peyer's patches of the mouse intestinal tract. In a murine coinfection model, the colonization of the Peyer's patches and the mesenteric lymph nodes of mice by the ifp-deficient strain was significantly reduced, and considerably fewer bacteria reached liver and spleen. The absence of InvC did not have a severe influence on bacterial colonization in the murine infection model, and it resulted in only a slightly reduced number of invC mutants in the Peyer's patches. The analysis of the host immune response demonstrated that the presence of Ifp and InvC reduced the recruitment of professional phagocytes, especially neutrophils, in the Peyer's patches. These findings support a role for the adhesins in modulating host-pathogen interactions that are important for immune defense.
Collapse
|