1
|
Su T, Chua WZ, Liu Y, Fan J, Tan SY, Yang DW, Sham LT. Rewiring the pneumococcal capsule pathway for investigating glycosyltransferase specificity and genetic glycoengineering. SCIENCE ADVANCES 2023; 9:eadi8157. [PMID: 37672581 PMCID: PMC10482335 DOI: 10.1126/sciadv.adi8157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 08/03/2023] [Indexed: 09/08/2023]
Abstract
Virtually all living cells are covered with glycans. Their structures are primarily controlled by the specificities of glycosyltransferases (GTs). GTs typically adopt one of the three folds, namely, GT-A, GT-B, and GT-C. However, what defines their specificities remain poorly understood. Here, we developed a genetic glycoengineering platform by reprogramming the capsular polysaccharide pathways in Streptococcus pneumoniae to interrogate GT specificity and manipulate glycan structures. Our findings suggest that the central cleft of GT-B enzymes is important for determining acceptor specificity. The constraint of the glycoengineering platform was partially alleviated when the specificity of the precursor transporter was reduced, indicating that the transporter contributes to the overall fidelity of glycan synthesis. We also modified the pneumococcal capsule to produce several medically important mammalian glycans, as well as demonstrated the importance of regiochemistry in a glycosidic linkage on binding lung epithelial cells. Our work provided mechanistic insights into GT specificity and an approach for investigating glycan functions.
Collapse
Affiliation(s)
- Tong Su
- Infectious Diseases Translational Research Programme and Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545, Singapore
| | - Wan-Zhen Chua
- Infectious Diseases Translational Research Programme and Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545, Singapore
| | - Yao Liu
- Infectious Diseases Translational Research Programme and Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545, Singapore
| | - Jingsong Fan
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore 117545, Singapore
| | - Si-Yin Tan
- Infectious Diseases Translational Research Programme and Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545, Singapore
| | - Dai-wen Yang
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore 117545, Singapore
| | - Lok-To Sham
- Infectious Diseases Translational Research Programme and Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545, Singapore
- Infectious Diseases Translational Research Programme and Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545, Singapore
| |
Collapse
|
2
|
Nakamoto R, Bamyaci S, Blomqvist K, Normark S, Henriques-Normark B, Sham LT. The divisome but not the elongasome organizes capsule synthesis in Streptococcus pneumoniae. Nat Commun 2023; 14:3170. [PMID: 37264013 DOI: 10.1038/s41467-023-38904-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 05/16/2023] [Indexed: 06/03/2023] Open
Abstract
The bacterial cell envelope consists of multiple layers, including the peptidoglycan cell wall, one or two membranes, and often an external layer composed of capsular polysaccharides (CPS) or other components. How the synthesis of all these layers is precisely coordinated remains unclear. Here, we identify a mechanism that coordinates the synthesis of CPS and peptidoglycan in Streptococcus pneumoniae. We show that CPS synthesis initiates from the division septum and propagates along the long axis of the cell, organized by the tyrosine kinase system CpsCD. CpsC and the rest of the CPS synthesis complex are recruited to the septum by proteins associated with the divisome (a complex involved in septal peptidoglycan synthesis) but not the elongasome (involved in peripheral peptidoglycan synthesis). Assembly of the CPS complex starts with CpsCD, then CpsA and CpsH, the glycosyltransferases, and finally CpsJ. Remarkably, targeting CpsC to the cell pole is sufficient to reposition CPS synthesis, leading to diplococci that lack CPS at the septum. We propose that septal CPS synthesis is important for chain formation and complement evasion, thereby promoting bacterial survival inside the host.
Collapse
Affiliation(s)
- Rei Nakamoto
- Infectious Diseases Translational Research Programme and Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117545, Singapore
| | - Sarp Bamyaci
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, SE-17177, Sweden
| | - Karin Blomqvist
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, SE-17177, Sweden
- Clinical Microbiology, Karolinska University Hospital Solna, SE-17176, Stockholm, Sweden
| | - Staffan Normark
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, SE-17177, Sweden
| | - Birgitta Henriques-Normark
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, SE-17177, Sweden
- Clinical Microbiology, Karolinska University Hospital Solna, SE-17176, Stockholm, Sweden
| | - Lok-To Sham
- Infectious Diseases Translational Research Programme and Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117545, Singapore.
| |
Collapse
|
3
|
Chun YY, Tan KS, Yu L, Pang M, Wong MHM, Nakamoto R, Chua WZ, Huee-Ping Wong A, Lew ZZR, Ong HH, Chow VT, Tran T, Yun Wang D, Sham LT. Influence of glycan structure on the colonization of Streptococcus pneumoniae on human respiratory epithelial cells. Proc Natl Acad Sci U S A 2023; 120:e2213584120. [PMID: 36943879 PMCID: PMC10068763 DOI: 10.1073/pnas.2213584120] [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: 08/08/2022] [Accepted: 02/10/2023] [Indexed: 03/23/2023] Open
Abstract
Virtually all living cells are encased in glycans. They perform key cellular functions such as immunomodulation and cell-cell recognition. Yet, how their composition and configuration affect their functions remains enigmatic. Here, we constructed isogenic capsule-switch mutants harboring 84 types of capsular polysaccharides (CPSs) in Streptococcus pneumoniae. This collection enables us to systematically measure the affinity of structurally related CPSs to primary human nasal and bronchial epithelial cells. Contrary to the paradigm, the surface charge does not appreciably affect epithelial cell binding. Factors that affect adhesion to respiratory cells include the number of rhamnose residues and the presence of human-like glycomotifs in CPS. Besides, pneumococcal colonization stimulated the production of interleukin 6 (IL-6), granulocyte-macrophage colony-stimulating factor (GM-CSF), and monocyte chemoattractantprotein-1 (MCP-1) in nasal epithelial cells, which also appears to be dependent on the serotype. Together, our results reveal glycomotifs of surface polysaccharides that are likely to be important for colonization and survival in the human airway.
Collapse
Affiliation(s)
- Ye-Yu Chun
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| | - Kai Sen Tan
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Otolaryngology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117597
| | - Lisa Yu
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- College of Art and Sciences, Cornell University, Ithaca, NY14853
| | - Michelle Pang
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| | - Ming Hui Millie Wong
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| | - Rei Nakamoto
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| | - Wan-Zhen Chua
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| | - Amanda Huee-Ping Wong
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117593
| | - Zhe Zhang Ryan Lew
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| | - Hsiao Hui Ong
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| | - Vincent T. Chow
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| | - Thai Tran
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117593
| | - De Yun Wang
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| | - Lok-To Sham
- Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117545
| |
Collapse
|
4
|
York A, Huynh E, Mbodj S, Yolda-Carr D, Hislop MS, Echlin H, Rosch JW, Weinberger DM, Wyllie AL. Magnetic bead-based separation of pneumococcal serotypes. CELL REPORTS METHODS 2023; 3:100410. [PMID: 36936076 PMCID: PMC10014298 DOI: 10.1016/j.crmeth.2023.100410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 11/18/2022] [Accepted: 01/26/2023] [Indexed: 02/23/2023]
Abstract
The separation of pneumococcal serotypes from a complex polymicrobial mixture may be required for different applications. For instance, a minority strain could be present at a low frequency in a clinical sample, making it difficult to identify and isolate by traditional culture-based methods. We therefore developed an assay to separate mixed pneumococcal samples using serotype-specific antiserum and a magnetic bead-based separation method. Using qPCR and colony counting methods, we first show that serotypes (12F, 23F, 3, 14, 19A, and 15A) present at ∼0.1% of a dual serotype mixture can be enriched to between 10% and 90% of the final sample. We demonstrate two applications for this method: extraction of known pneumococcal serotypes from saliva samples and efficient purification of capsule switch variants from experimental transformation experiments. This method may have further laboratory or clinical applications when the selection of specific serotypes is required.
Collapse
Affiliation(s)
- Anna York
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA
| | - Emily Huynh
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA
| | - Sidiya Mbodj
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA
| | - Devyn Yolda-Carr
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA
| | - Maikel S. Hislop
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA
- Department of Life Sciences and Chemistry, Utrecht University of Applied Sciences, 3584 CS Utrecht, the Netherlands
| | - Haley Echlin
- Department of Infectious Disease, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Jason W. Rosch
- Department of Infectious Disease, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Daniel M. Weinberger
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA
| | - Anne L. Wyllie
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA
| |
Collapse
|
5
|
Nyongesa S, Chenal M, Bernet È, Coudray F, Veyrier FJ. Sequential markerless genetic manipulations of species from the Neisseria genus. Can J Microbiol 2022; 68:551-560. [PMID: 35512370 DOI: 10.1139/cjm-2022-0024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The development of simple and highly efficient strategies for genetic modifications are essential for post-genetic studies aimed at characterizing gene functions for various applications. We sought to develop a reliable system for Neisseria species that allows for both unmarked and accumulation of multiple genetic modifications in a single strain. In this work we developed and validated three-gene cassettes named RPLK and RPCC, comprising of an antibiotic resistance marker for positive selection, the phenotypic selection marker lacZ or mCherry, and the counter selection gene rpsL. These cassettes can be transformed with high efficiency across the Neisseria genus while significantly reducing the number of false positives compared to similar approaches. We exemplify the versatility and application of these systems by obtaining unmarked luminescent strains (knock-in) or mutants (knock-out) in different pathogenic and commensal species across the Neisseria genus in addition to the cumulative deletion of six loci in a single strain of Neisseria elongata.
Collapse
Affiliation(s)
- Sammy Nyongesa
- INRS, 14851, Centre Armand-Frappier Santé Biotechnologie, Quebec, Quebec, Canada;
| | - Martin Chenal
- INRS, 14851, Centre Armand-Frappier Santé Biotechnologie, Quebec, Quebec, Canada;
| | - Ève Bernet
- INRS, 14851, Centre Armand-Frappier Santé Biotechnologie, Quebec, Quebec, Canada;
| | - Florian Coudray
- INRS, 14851, Centre Armand-Frappier Santé Biotechnologie, Quebec, Quebec, Canada;
| | - Frédéric J Veyrier
- INRS, 14851, Centre Armand-Frappier Santé Biotechnologie, Quebec, Quebec, Canada;
| |
Collapse
|
6
|
The bacterial tyrosine kinase system CpsBCD governs the length of capsule polymers. Proc Natl Acad Sci U S A 2021; 118:2103377118. [PMID: 34732571 DOI: 10.1073/pnas.2103377118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/16/2021] [Indexed: 12/17/2022] Open
Abstract
Many pathogenic bacteria are encased in a layer of capsular polysaccharide (CPS). This layer is important for virulence by masking surface antigens, preventing opsonophagocytosis, and avoiding mucus entrapment. The bacterial tyrosine kinase (BY-kinase) regulates capsule synthesis and helps bacterial pathogens to survive different host niches. BY-kinases autophosphorylate at the C-terminal tyrosine residues upon external stimuli, but the role of phosphorylation is still unclear. Here, we report that the BY-kinase CpsCD is required for growth in Streptococcus pneumoniae Cells lacking a functional cpsC or cpsD accumulated low molecular weight CPS and lysed because of the lethal sequestration of the lipid carrier undecaprenyl phosphate, resulting in inhibition of peptidoglycan (PG) synthesis. CpsC interacts with CpsD and the polymerase CpsH. CpsD phosphorylation reduces the length of CPS polymers presumably by controlling the activity of CpsC. Finally, pulse-chase experiments reveal the spatiotemporal coordination between CPS and PG synthesis. This coordination is dependent on CpsC and CpsD. Together, our study provides evidence that BY-kinases regulate capsule polymer length by fine-tuning CpsC activity through autophosphorylation.
Collapse
|
7
|
Anatomical site-specific carbohydrate availability impacts Streptococcus pneumoniae virulence and fitness during colonization and disease. Infect Immun 2021; 90:e0045121. [PMID: 34748366 DOI: 10.1128/iai.00451-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptococcus pneumoniae (Spn) colonizes the nasopharynx asymptomatically but can also cause severe life-threatening disease. Importantly, stark differences in carbohydrate availability exist between the nasopharynx and invasive disease sites, such as the bloodstream, which most likely impact Spn's behavior. Herein, using chemically-defined media (CDM) supplemented with physiological levels of carbohydrates, we examined how anatomical-site specific carbohydrate availability impacted Spn physiology and virulence. Spn grown in CDM modeling the nasopharynx (CDM-N) had reduced metabolic activity, slower growth rate, demonstrated mixed acid fermentation with marked H2O2 production, and were in a carbon-catabolite repression (CCR)-derepressed state versus Spn grown in CDM modeling blood (CDM-B). Using RNA-seq, we determined the transcriptome for Spn WT and its isogenic CCR deficient mutant in CDM-N and CDM-B. Genes with altered expression as a result of changes in carbohydrate availability or catabolite control protein deficiency, respectively, were primarily involved in carbohydrate metabolism, but also encoded for established virulence determinants such polysaccharide capsule and surface adhesins. We confirmed that anatomical site-specific carbohydrate availability directly influenced established Spn virulence traits. Spn grown in CDM-B formed shorter chains, produced more capsule, were less adhesive, and were more resistant to macrophage killing in an opsonophagocytosis assay. Moreover, growth of Spn in CDM-N or CDM-B prior to the challenge of mice impacted relative fitness in a colonization and invasive disease model, respectively. Thus, anatomical site-specific carbohydrate availability alters Spn physiology and virulence, in turn promoting anatomical-site specific fitness.
Collapse
|
8
|
High-Throughput Mutagenesis and Cross-Complementation Experiments Reveal Substrate Preference and Critical Residues of the Capsule Transporters in Streptococcus pneumoniae. mBio 2021; 12:e0261521. [PMID: 34724815 PMCID: PMC8561386 DOI: 10.1128/mbio.02615-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
MOP (Multidrug/Oligosaccharidyl-lipid/Polysaccharide) family transporters are found in almost all life forms. They are responsible for transporting lipid-linked precursors across the cell membrane to support the synthesis of various glycoconjugates. While significant progress has been made in elucidating their transport mechanism, how these transporters select their substrates remains unclear. Here, we systematically tested the MOP transporters in the Streptococcus pneumoniae capsule pathway for their ability to translocate noncognate capsule precursors. Sequence similarity cannot predict whether these transporters are interchangeable. We showed that subtle changes in the central aqueous cavity of the transporter are sufficient to accommodate a different cargo. These changes can occur naturally, suggesting a potential mechanism of expanding substrate selectivity. A directed evolution experiment was performed to identify gain-of-function variants that translocate a noncognate cargo. Coupled with a high-throughput mutagenesis and sequencing (Mut-seq) experiment, residues that are functionally important for the capsule transporter were revealed. Lastly, we showed that the expression of a flippase that can transport unfinished precursors resulted in an increased susceptibility to bacitracin and mild cell shape defects, which may be a driving force to maintain transporter specificity. IMPORTANCE All licensed pneumococcal vaccines target the capsular polysaccharide (CPS). This layer is highly variable and is important for virulence in many bacterial pathogens. Most of the CPSs are produced by the Wzx/Wzy mechanism. In this pathway, CPS repeating units are synthesized in the cytoplasm, which must be flipped across the cytoplasmic membrane before polymerization. This step is mediated by the widely conserved MOP (Multidrug/Oligosaccharidyl-lipid/Polysaccharide) family transporters. Here, we systematically evaluated the interchangeability of these transporters and identified the residues important for substrate specificity and function. Understanding how CPS is synthesized will inform glycoengineering, vaccine development, and antimicrobial discovery.
Collapse
|
9
|
Biochemical reconstitution defines new functions for membrane-bound glycosidases in assembly of the bacterial cell wall. Proc Natl Acad Sci U S A 2021; 118:2103740118. [PMID: 34475211 DOI: 10.1073/pnas.2103740118] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 07/30/2021] [Indexed: 01/25/2023] Open
Abstract
The peptidoglycan cell wall is a macromolecular structure that encases bacteria and is essential for their survival. Proper assembly of the cell wall requires peptidoglycan synthases as well as membrane-bound cleavage enzymes that control where new peptidoglycan is made and inserted. Previous studies have shown that two membrane-bound proteins in Streptococcus pneumoniae, here named MpgA and MpgB, are important in maintaining cell wall integrity. MpgA was predicted to be a lytic transglycosylase based on its homology to Escherichia coli MltG, while the enzymatic activity of MpgB was unclear. Using nascent peptidoglycan substrates synthesized in vitro from the peptidoglycan precursor Lipid II, we report that both MpgA and MpgB are muramidases. We show that replacing a single amino acid in E. coli MltG with the corresponding amino acid from MpgA results in muramidase activity, allowing us to predict from the presence of this amino acid that other putative lytic transglycosylases actually function as muramidases. Strikingly, we report that MpgA and MpgB cut nascent peptidoglycan at different positions along the sugar backbone relative to the reducing end, with MpgA producing much longer peptidoglycan oligomers. We show that the cleavage site selectivity of MpgA is controlled by the LysM-like subdomain, which is required for its full functionality in cells. We propose that MltG's ability to complement the loss of MpgA in S. pneumoniae despite performing different cleavage chemistry is because it can cleave nascent peptidoglycan at the same distance from the lipid anchor.
Collapse
|
10
|
Green AE, Howarth D, Chaguza C, Echlin H, Langendonk RF, Munro C, Barton TE, Hinton JCD, Bentley SD, Rosch JW, Neill DR. Pneumococcal Colonization and Virulence Factors Identified Via Experimental Evolution in Infection Models. Mol Biol Evol 2021; 38:2209-2226. [PMID: 33502519 PMCID: PMC8136498 DOI: 10.1093/molbev/msab018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Streptococcus pneumoniae is a commensal of the human nasopharynx and a major cause of respiratory and invasive disease. We examined adaptation and evolution of pneumococcus, within nasopharynx and lungs, in an experimental system where the selective pressures associated with transmission were removed. This was achieved by serial passage of pneumococci, separately, in mouse models of nasopharyngeal carriage or pneumonia. Passaged pneumococci became more effective colonizers of the respiratory tract and we observed several examples of potential parallel evolution. The cell wall-modifying glycosyltransferase LafA was under strong selection during lung passage, whereas the surface expressed pneumococcal vaccine antigen gene pvaA and the glycerol-3-phosphate dehydrogenase gene gpsA were frequent targets of mutation in nasopharynx-passaged pneumococci. These mutations were not identified in pneumococci that were separately evolved by serial passage on laboratory agar. We focused on gpsA, in which the same single nucleotide polymorphism arose in two independently evolved nasopharynx-passaged lineages. We describe a new role for this gene in nasopharyngeal carriage and show that the identified single nucleotide change confers resistance to oxidative stress and enhanced nasopharyngeal colonization potential. We demonstrate that polymorphisms in gpsA arise and are retained during human colonization. These findings highlight how within-host environmental conditions can determine trajectories of bacterial evolution. Relative invasiveness or attack rate of pneumococcal lineages may be defined by genes that make niche-specific contributions to bacterial fitness. Experimental evolution in animal infection models is a powerful tool to investigate the relative roles played by pathogen virulence and colonization factors within different host niches.
Collapse
Affiliation(s)
- Angharad E Green
- Department of Clinical Infection, Microbiology and Immunology, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Deborah Howarth
- Department of Clinical Infection, Microbiology and Immunology, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Chrispin Chaguza
- Parasites and Microbes Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Cambridge, United Kingdom
| | - Haley Echlin
- Department of Infectious Disease, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - R Frèdi Langendonk
- Department of Clinical Infection, Microbiology and Immunology, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Connor Munro
- Department of Clinical Infection, Microbiology and Immunology, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Thomas E Barton
- Department of Clinical Infection, Microbiology and Immunology, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Jay C D Hinton
- Department of Clinical Infection, Microbiology and Immunology, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Stephen D Bentley
- Parasites and Microbes Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Cambridge, United Kingdom
| | - Jason W Rosch
- Department of Infectious Disease, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Daniel R Neill
- Department of Clinical Infection, Microbiology and Immunology, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom
| |
Collapse
|
11
|
Structural, Genetic, and Serological Elucidation of Streptococcus pneumoniae Serogroup 24 Serotypes: Discovery of a New Serotype, 24C, with a Variable Capsule Structure. J Clin Microbiol 2021; 59:e0054021. [PMID: 33883183 DOI: 10.1128/jcm.00540-21] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Pneumococcal capsules are important in pneumococcal pathogenesis and vaccine development. Although conjugate vaccines have brought about a significant reduction in invasive pneumococcal disease (IPD) caused by vaccine serotypes, the relative serotype prevalence has shifted with the dramatic emergence of serotype 24F in some countries. Here, we describe 14 isolates (13 IPD and 1 non-IPD) expressing a new capsule type, 24C, which resembles 24F but has a novel serological profile. We also describe the antigenic, biochemical, and genetic basis of 24F and 24C and the related serotypes 24A and 24B. Structural studies show that 24B, 24C, and 24F have identical polysaccharide backbones [β-Ribf-(1→4)-α-Rhap-(1→3)-β-GlcpNAc-(1→4)-β-Rhap-(1→4)-β-Glcp] but with different side chains, as follows: 24F has arabinitol-phosphate and 24B has ribitol-phosphate. 24C has a mixture of 24F and 24B repeating units, with the ratio of ribitol to arabinitol being strain dependent. In contrast, the 24A capsule has a backbone without β-Ribf but with arabinitol-phosphate and phosphocholine side chains. These structures indicate that factor-sera 24d and 24e recognize arabinitol and ribitol, respectively, which explains the serology of serogroup 24, including those of 24C. The structures can be genetically described by the bispecificity of wcxG, which is capable of transferring arabinitol or ribitol when arabinitol is limiting. Arabinitol is likely not produced in 24B but is produced in reduced amounts in 24C due to various mutations in abpA or abpB genes. Our findings demonstrate how pneumococci modulate their capsule structure and immunologic properties with small genetic changes, thereby evading host immune responses. Our findings also suggest a potential for new capsule types within serogroup 24.
Collapse
|
12
|
Dong W, Rasid O, Chevalier C, Connor M, Eldridge MJG, Hamon MA. Streptococcus pneumoniae Infection Promotes Histone H3 Dephosphorylation by Modulating Host PP1 Phosphatase. Cell Rep 2021; 30:4016-4026.e4. [PMID: 32209465 DOI: 10.1016/j.celrep.2020.02.116] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 01/15/2020] [Accepted: 02/21/2020] [Indexed: 10/24/2022] Open
Abstract
Pathogenic bacteria can alter host gene expression through post-translational modifications of histones. We show that a natural colonizer, Streptococcus pneumoniae, induces specific histone modifications, including robust dephosphorylation of histone H3 on serine 10 (H3S10), during infection of respiratory epithelial cells. The bacterial pore-forming toxin pneumolysin (PLY), along with the pyruvate oxidase SpxB responsible for H2O2 production, play important roles in the induction of this modification. The combined effects of PLY and H2O2 trigger host signaling that culminates in H3S10 dephosphorylation, which is mediated by the host cell phosphatase PP1. Strikingly, S. pneumoniae infection induces dephosphorylation and subsequent activation of PP1 catalytic activity. Colonization of PP1 catalytically deficient cells results in impaired intracellular S. pneumoniae survival and infection. Interestingly, PP1 activation and H3S10 dephosphorylation are not restricted to S. pneumoniae and appear to be general epigenomic mechanisms favoring intracellular survival of pathogenic bacteria.
Collapse
Affiliation(s)
- Wenyang Dong
- G5 Chromatine et Infection, Institut Pasteur, Paris 75015, France; Université de Paris, Sorbonne Paris Cité, Paris, France
| | - Orhan Rasid
- G5 Chromatine et Infection, Institut Pasteur, Paris 75015, France
| | | | - Michael Connor
- G5 Chromatine et Infection, Institut Pasteur, Paris 75015, France
| | | | | |
Collapse
|
13
|
Eichner H, Karlsson J, Spelmink L, Pathak A, Sham LT, Henriques-Normark B, Loh E. RNA thermosensors facilitate Streptococcus pneumoniae and Haemophilus influenzae immune evasion. PLoS Pathog 2021; 17:e1009513. [PMID: 33914847 PMCID: PMC8084184 DOI: 10.1371/journal.ppat.1009513] [Citation(s) in RCA: 5] [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: 03/02/2021] [Accepted: 03/29/2021] [Indexed: 11/18/2022] Open
Abstract
Bacterial meningitis is a major cause of death and disability in children worldwide. Two human restricted respiratory pathogens, Streptococcus pneumoniae and Haemophilus influenzae, are the major causative agents of bacterial meningitis, attributing to 200,000 deaths annually. These pathogens are often part of the nasopharyngeal microflora of healthy carriers. However, what factors elicit them to disseminate and cause invasive diseases, remain unknown. Elevated temperature and fever are hallmarks of inflammation triggered by infections and can act as warning signals to pathogens. Here, we investigate whether these respiratory pathogens can sense environmental temperature to evade host complement-mediated killing. We show that productions of two vital virulence factors and vaccine components, the polysaccharide capsules and factor H binding proteins, are temperature dependent, thus influencing serum/opsonophagocytic killing of the bacteria. We identify and characterise four novel RNA thermosensors in S. pneumoniae and H. influenzae, responsible for capsular biosynthesis and production of factor H binding proteins. Our data suggest that these bacteria might have independently co-evolved thermosensing abilities with different RNA sequences but distinct secondary structures to evade the immune system.
Collapse
Affiliation(s)
- Hannes Eichner
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden
| | - Jens Karlsson
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden
| | - Laura Spelmink
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden
| | - Anuj Pathak
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden
| | - Lok-To Sham
- Infectious Disease Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Birgitta Henriques-Normark
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden
- Clinical Microbiology, Bioclinicum, Karolinska University Hospital, Solna, Sweden
- Lee Kong Chian School of Medicine and Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
| | - Edmund Loh
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden
- Clinical Microbiology, Bioclinicum, Karolinska University Hospital, Solna, Sweden
- Lee Kong Chian School of Medicine and Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
| |
Collapse
|
14
|
Middleton DR, Aceil J, Mustafa S, Paschall AV, Avci FY. Glycosyltransferases within the psrP Locus Facilitate Pneumococcal Virulence. J Bacteriol 2021; 203:e00389-20. [PMID: 33468592 PMCID: PMC8088515 DOI: 10.1128/jb.00389-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 12/23/2020] [Indexed: 11/20/2022] Open
Abstract
The pneumococcal serine-rich repeat protein (PsrP) is a high-molecular-weight, glycosylated adhesin that promotes the attachment of Streptococcus pneumoniae to host cells. PsrP, its associated glycosyltransferases (GTs), and dedicated secretion machinery are encoded in a 37-kb genomic island that is present in many invasive clinical isolates of S. pneumoniae PsrP has been implicated in establishment of lung infection in murine models, although specific roles of the PsrP glycans in disease progression or bacterial physiology have not been elucidated. Moreover, enzymatic specificities of associated glycosyltransferases are yet to be fully characterized. We hypothesized that the glycosyltransferases that modify PsrP are critical for the adhesion properties and infectivity of S. pneumoniae Here, we characterize the putative S. pneumoniaepsrP locus glycosyltransferases responsible for PsrP glycosylation. We also begin to elucidate their roles in S. pneumoniae virulence. We show that four glycosyltransferases within the psrP locus are indispensable for S. pneumoniae biofilm formation, lung epithelial cell adherence, and establishment of lung infection in a mouse model of pneumococcal pneumonia.IMPORTANCE PsrP has previously been identified as a necessary virulence factor for many serotypes of S. pneumoniae and studied as a surface glycoprotein. Thus, studying the effects on virulence of each glycosyltransferase (GT) that builds the PsrP glycan is of high importance. Our work elucidates the influence of GTs in vivo We have identified at least four GTs that are required for lung infection, an indication that it is worthwhile to consider glycosylated PsrP as a candidate for serotype-independent pneumococcal vaccine design.
Collapse
Affiliation(s)
- Dustin R Middleton
- Department of Biochemistry and Molecular Biology, Center for Molecular Medicine, The University of Georgia, Athens, Georgia, USA
| | - Javid Aceil
- Department of Biochemistry and Molecular Biology, Center for Molecular Medicine, The University of Georgia, Athens, Georgia, USA
| | - Seema Mustafa
- Department of Biochemistry and Molecular Biology, Center for Molecular Medicine, The University of Georgia, Athens, Georgia, USA
| | - Amy V Paschall
- Department of Biochemistry and Molecular Biology, Center for Molecular Medicine, The University of Georgia, Athens, Georgia, USA
| | - Fikri Y Avci
- Department of Biochemistry and Molecular Biology, Center for Molecular Medicine, The University of Georgia, Athens, Georgia, USA
| |
Collapse
|
15
|
Harnessing CRISPR-Cas9 for Genome Editing in Streptococcus pneumoniae D39V. Appl Environ Microbiol 2021; 87:AEM.02762-20. [PMID: 33397704 PMCID: PMC8105017 DOI: 10.1128/aem.02762-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 12/21/2020] [Indexed: 11/20/2022] Open
Abstract
Streptococcus pneumoniae (the pneumococcus) is an important opportunistic human pathogen killing more than 1 million people each year. Having the availability of a system capable of easy genome editing would significantly facilitate drug discovery and efforts to identify new vaccine candidates. CRISPR-Cas systems provide bacteria and archaea with adaptive immunity against viruses and plasmids by the detection and cleavage of invading foreign DNA. Modified versions of this system can be exploited as a biotechnological tool for precise genome editing at a targeted locus. Here, we developed a replicative plasmid that carries the CRISPR-Cas9 system for RNA-programmable genome editing by counterselection in the opportunistic human pathogen Streptococcus pneumoniae. Specifically, we demonstrate an approach for making targeted markerless gene knockouts and large genome deletions. After a precise double-stranded break (DSB) is introduced, the cells’ DNA repair mechanism of homology-directed repair (HDR) is exploited to select successful transformants. This is achieved through the transformation of a template DNA fragment that will recombine in the genome and eliminate recognition of the target of the Cas9 endonuclease. Next, the newly engineered strain can be easily cured from the plasmid, which is temperature sensitive for replication, by growing it at the nonpermissive temperature. This allows for consecutive rounds of genome editing. Using this system, we engineered a strain with three major virulence factors deleted. The approaches developed here could potentially be adapted for use with other Gram-positive bacteria. IMPORTANCEStreptococcus pneumoniae (the pneumococcus) is an important opportunistic human pathogen killing more than 1 million people each year. Having the availability of a system capable of easy genome editing would significantly facilitate drug discovery and efforts to identify new vaccine candidates. Here, we introduced an easy-to-use system to perform multiple rounds of genome editing in the pneumococcus by putting the CRISPR-Cas9 system on a temperature-sensitive replicative plasmid. The approaches used here will advance genome editing projects in this important human pathogen.
Collapse
|
16
|
Synthetic gene-regulatory networks in the opportunistic human pathogen Streptococcus pneumoniae. Proc Natl Acad Sci U S A 2020; 117:27608-27619. [PMID: 33087560 PMCID: PMC7959565 DOI: 10.1073/pnas.1920015117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Streptococcus pneumoniae is a major human pathogen responsible for enormous global morbidity and mortality. Despite this, the pneumococcus makes up part of the commensal nasopharyngeal flora. How the pneumococcus switches from this commensal to pathogenic state and causes disease is unclear and very likely involves variability in expression of its virulence factors. Here, we used synthetic biology approaches to generate complex gene-regulatory networks such as logic gates and toggle switches. We show that these networks are functional in vivo to control capsule production in an influenza-superinfection model. This opens the field of systematically testing the role of phenotypic variation in pneumococcal virulence. The approaches used here may serve as an example for synthetic biology projects in unrelated organisms. Streptococcus pneumoniae can cause disease in various human tissues and organs, including the ear, the brain, the blood, and the lung, and thus in highly diverse and dynamic environments. It is challenging to study how pneumococci control virulence factor expression, because cues of natural environments and the presence of an immune system are difficult to simulate in vitro. Here, we apply synthetic biology methods to reverse-engineer gene expression control in S. pneumoniae. A selection platform is described that allows for straightforward identification of transcriptional regulatory elements out of combinatorial libraries. We present TetR- and LacI-regulated promoters that show expression ranges of four orders of magnitude. Based on these promoters, regulatory networks of higher complexity are assembled, such as logic AND gates and IMPLY gates. We demonstrate single-copy genome-integrated toggle switches that give rise to bimodal population distributions. The tools described here can be used to mimic complex expression patterns, such as the ones found for pneumococcal virulence factors. Indeed, we were able to rewire gene expression of the capsule operon, the main pneumococcal virulence factor, to be externally inducible (YES gate) or to act as an IMPLY gate (only expressed in absence of inducer). Importantly, we demonstrate that these synthetic gene-regulatory networks are functional in an influenza A virus superinfection murine model of pneumonia, paving the way for in vivo investigations of the importance of gene expression control on the pathogenicity of S. pneumoniae.
Collapse
|
17
|
Binsker U, Lees JA, Hammond AJ, Weiser JN. Immune exclusion by naturally acquired secretory IgA against pneumococcal pilus-1. J Clin Invest 2020; 130:927-941. [PMID: 31687974 DOI: 10.1172/jci132005] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 10/30/2019] [Indexed: 02/06/2023] Open
Abstract
Successful infection by mucosal pathogens requires overcoming the mucus barrier. To better understand this key step, we performed a survey of the interactions between human respiratory mucus and the human pathogen Streptococcus pneumoniae. Pneumococcal adherence to adult human nasal fluid was seen only by isolates expressing pilus-1. Robust binding was independent of pilus-1 adhesive properties but required Fab-dependent recognition of RrgB, the pilus shaft protein, by naturally acquired secretory IgA (sIgA). Pilus-1 binding by specific sIgA led to bacterial agglutination, but adherence required interaction of agglutinated pneumococci and entrapment in mucus particles. To test the effect of these interactions in vivo, pneumococci were preincubated with human sIgA before intranasal challenge in a mouse model of colonization. sIgA treatment resulted in rapid immune exclusion of pilus-expressing pneumococci. Our findings predict that immune exclusion would select for nonpiliated isolates in individuals who acquired RrgB-specific sIgA from prior episodes of colonization with piliated strains. Accordingly, genomic data comparing isolates carried by mothers and their children showed that mothers are less likely to be colonized with pilus-expressing strains. Our study provides a specific example of immune exclusion involving naturally acquired antibody in the human host, a major factor driving pneumococcal adaptation.
Collapse
|
18
|
Echlin H, Rosch JW. Advancing Genetic Tools in Streptococcus pneumoniae. Genes (Basel) 2020; 11:genes11090965. [PMID: 32825523 PMCID: PMC7563404 DOI: 10.3390/genes11090965] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 08/10/2020] [Accepted: 08/15/2020] [Indexed: 11/16/2022] Open
Abstract
Streptococcus pneumoniae is the causative agent of a multitude of diseases, and further study into its pathogenies is vital. The pneumococcus is genetically malleable, and several tools are available to manipulate this pathogen. In this study, we attempted to utilize one such tool, the Sweet Janus cassette, to replace the capsule locus with other capsule loci in our strain background and found that the efficiency of allelic replacement was low and the number of revertant false-positive colonies was high. We determined that the capacity to recombine capsule varied by the initial isolated colony, suggesting that frequency of reversion is dependent on the bacterial clone. Alternative selection markers may further expand the application of Sweet Janus. We created novel cassettes that utilized chlorinated phenylalanine as an alternative counter-selection agent in conjunction with the Janus or Sweet Janus cassette, providing a new dual or triple selection marker. Moreover, we created cassettes that do not require engineered resistance in the background strain, including both single and dual selection markers. We were able to utilize all constructs in allelic replacement of the capsule loci. These novel constructs provide a new means for generating gene deletions in S. pneumoniae that expand experimental applications.
Collapse
|
19
|
Cooper VS, Honsa E, Rowe H, Deitrick C, Iverson AR, Whittall JJ, Neville SL, McDevitt CA, Kietzman C, Rosch JW. Experimental Evolution In Vivo To Identify Selective Pressures during Pneumococcal Colonization. mSystems 2020; 5:e00352-20. [PMID: 32398278 PMCID: PMC7219553 DOI: 10.1128/msystems.00352-20] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 04/30/2020] [Indexed: 12/20/2022] Open
Abstract
Experimental evolution is a powerful technique to understand how populations evolve from selective pressures imparted by the surrounding environment. With the advancement of whole-population genomic sequencing, it is possible to identify and track multiple contending genotypes associated with adaptations to specific selective pressures. This approach has been used repeatedly with model species in vitro, but only rarely in vivo Herein we report results of replicate experimentally evolved populations of Streptococcus pneumoniae propagated by repeated murine nasal colonization with the aim of identifying gene products under strong selection as well as the population genetic dynamics of infection cycles. Frameshift mutations in one gene, dltB, responsible for incorporation of d-alanine into teichoic acids on the bacterial surface, evolved repeatedly and swept to high frequency. Targeted deletions of dltB produced a fitness advantage during initial nasal colonization coupled with a corresponding fitness disadvantage in the lungs during pulmonary infection. The underlying mechanism behind the fitness trade-off between these two niches was found to be enhanced adherence to respiratory cells balanced by increased sensitivity to host-derived antimicrobial peptides, a finding recapitulated in the murine model. Additional mutations that are predicted to affect trace metal transport, central metabolism, and regulation of biofilm production and competence were also selected. These data indicate that experimental evolution can be applied to murine models of pathogenesis to gain insight into organism-specific tissue tropisms.IMPORTANCE Evolution is a powerful force that can be experimentally harnessed to gain insight into how populations evolve in response to selective pressures. Herein we tested the applicability of experimental evolutionary approaches to gain insight into how the major human pathogen Streptococcus pneumoniae responds to repeated colonization events using a murine model. These studies revealed the population dynamics of repeated colonization events and demonstrated that in vivo experimental evolution resulted in highly reproducible trajectories that reflect the environmental niche encountered during nasal colonization. Mutations impacting the surface charge of the bacteria were repeatedly selected during colonization and provided a fitness benefit in this niche that was counterbalanced by a corresponding fitness defect during lung infection. These data indicate that experimental evolution can be applied to models of pathogenesis to gain insight into organism-specific tissue tropisms.
Collapse
Affiliation(s)
- Vaughn S Cooper
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Center for Evolutionary Biology and Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Erin Honsa
- St. Jude Children's Research Hospital, Department of Infectious Diseases, Memphis, Tennessee, USA
| | - Hannah Rowe
- St. Jude Children's Research Hospital, Department of Infectious Diseases, Memphis, Tennessee, USA
| | - Christopher Deitrick
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Center for Evolutionary Biology and Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Amy R Iverson
- St. Jude Children's Research Hospital, Department of Infectious Diseases, Memphis, Tennessee, USA
| | - Jonathan J Whittall
- Department of Molecular and Biomedical Science, School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Stephanie L Neville
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, Victoria, Australia
| | - Christopher A McDevitt
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, Victoria, Australia
| | - Colin Kietzman
- St. Jude Children's Research Hospital, Department of Infectious Diseases, Memphis, Tennessee, USA
| | - Jason W Rosch
- St. Jude Children's Research Hospital, Department of Infectious Diseases, Memphis, Tennessee, USA
| |
Collapse
|
20
|
Vimberg V, Zieglerová L, Buriánková K, Branny P, Balíková Novotná G. VanZ Reduces the Binding of Lipoglycopeptide Antibiotics to Staphylococcus aureus and Streptococcus pneumoniae Cells. Front Microbiol 2020; 11:566. [PMID: 32318043 PMCID: PMC7146870 DOI: 10.3389/fmicb.2020.00566] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 03/16/2020] [Indexed: 11/30/2022] Open
Abstract
vanZ, a member of the VanA glycopeptide resistance gene cluster, confers resistance to lipoglycopeptide antibiotics independent of cell wall precursor modification by the vanHAX genes. Orthologs of vanZ are present in the genomes of many clinically relevant bacteria, including Enterococcus faecium and Streptococcus pneumoniae; however, vanZ genes are absent in Staphylococcus aureus. Here, we show that the expression of enterococcal vanZ paralogs in S. aureus increases the minimal inhibitory concentrations of lipoglycopeptide antibiotics teicoplanin, dalbavancin, oritavancin and new teicoplanin pseudoaglycone derivatives. The reduction in the binding of fluorescently labeled teicoplanin to the cells suggests the mechanism of VanZ-mediated resistance. In addition, using a genomic vanZ gene knockout mutant of S. pneumoniae, we have shown that the ability of VanZ proteins to compromise the activity of lipoglycopeptide antibiotics by reducing their binding is a more general feature of VanZ-superfamily proteins.
Collapse
Affiliation(s)
- Vladimir Vimberg
- Laboratory for Biology of Secondary Metabolism, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Leona Zieglerová
- Laboratory for Biology of Secondary Metabolism, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Karolína Buriánková
- Laboratory of Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Pavel Branny
- Laboratory of Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| | - Gabriela Balíková Novotná
- Laboratory for Biology of Secondary Metabolism, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czechia
| |
Collapse
|
21
|
Wang CY, Medlin JS, Nguyen DR, Disbennett WM, Dawid S. Molecular Determinants of Substrate Selectivity of a Pneumococcal Rgg-Regulated Peptidase-Containing ABC Transporter. mBio 2020; 11:e02502-19. [PMID: 32047125 PMCID: PMC7018657 DOI: 10.1128/mbio.02502-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 12/23/2019] [Indexed: 01/31/2023] Open
Abstract
Peptidase-containing ABC transporters (PCATs) are a widely distributed family of transporters which secrete double-glycine (GG) peptides. In the opportunistic pathogen Streptococcus pneumoniae (pneumococcus), the PCATs ComAB and BlpAB have been shown to secrete quorum-sensing pheromones and bacteriocins related to the competence and pneumocin pathways. Here, we describe another pneumococcal PCAT, RtgAB, encoded by the rtg locus and found intact in 17% of strains. The Rgg/SHP-like quorum-sensing system RtgR/S, which uses a peptide pheromone with a distinctive Trp-X-Trp motif, regulates expression of the rtg locus and provides a competitive fitness advantage in a mouse model of nasopharyngeal colonization. RtgAB secretes a set of coregulated rtg GG peptides. ComAB and BlpAB, which share a substrate pool, do not secrete the rtg GG peptides. Similarly, RtgAB does not efficiently secrete ComAB/BlpAB substrates. We examined the molecular determinants of substrate selectivity between ComAB, BlpAB, and RtgAB and found that the GG peptide signal sequences contain all the information necessary to direct secretion through specific transporters. Secretion through ComAB and BlpAB depends largely on the identity of four conserved hydrophobic signal sequence residues previously implicated in substrate recognition by PCATs. In contrast, a motif situated at the N-terminal end of the signal sequence, found only in rtg GG peptides, directs secretion through RtgAB. These findings illustrate the complexity in predicting substrate-PCAT pairings by demonstrating specificity that is not dictated solely by signal sequence residues previously implicated in substrate recognition.IMPORTANCE The export of peptides from the cell is a fundamental process carried out by all bacteria. One method of bacterial peptide export relies on a family of transporters called peptidase-containing ABC transporters (PCATs). PCATs export so-called GG peptides which carry out diverse functions, including cell-to-cell communication and interbacterial competition. In this work, we describe a PCAT-encoding genetic locus, rtg, in the pathogen Streptococcus pneumoniae (pneumococcus). The rtg locus is linked to increased competitive fitness advantage in a mouse model of nasopharyngeal colonization. We also describe how the rtg PCAT preferentially secretes a set of coregulated GG peptides but not GG peptides secreted by other pneumococcal PCATs. These findings illuminate a relatively understudied part of PCAT biology: how these transporters discriminate between different subsets of GG peptides. Ultimately, expanding our knowledge of PCATs will advance our understanding of the many microbial processes dependent on these transporters.
Collapse
Affiliation(s)
- Charles Y Wang
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jennifer S Medlin
- Department of Pediatrics, University of Michigan, Ann Arbor, Michigan, USA
| | - Don R Nguyen
- Department of Pediatrics, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Suzanne Dawid
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, USA
- Department of Pediatrics, University of Michigan, Ann Arbor, Michigan, USA
| |
Collapse
|
22
|
Tóthpál A, Desobry K, Joshi SS, Wyllie AL, Weinberger DM. Variation of growth characteristics of pneumococcus with environmental conditions. BMC Microbiol 2019; 19:304. [PMID: 31878880 PMCID: PMC6933730 DOI: 10.1186/s12866-019-1671-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 12/02/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Pneumococcus is exposed to a variety of temperature and oxygen levels in the upper respiratory tract and as it invades the lung, tissues, and blood. We sought to determine the effect of environmental variability on growth in vitro and to assess variability between strains. We evaluated the effect of temperature and oxygen on the growth of 256 isolates representing 53 serotypes, recovered from healthy carriers and disease patients. Strains were grown at a range of temperatures, anaerobically or in ambient air with catalase, and were monitored by reading the optical density. Regression models evaluated variation in the characteristics of the growth curves. RESULTS Most isolates grew to the maximal density at low temperatures (~33C) and under aerobic conditions. There was considerable variability between strains, and some of this variability was linked to serotype. However, capsule-switch experiments suggest that the production of different capsules might not be sufficient to explain this variation, suggesting there could be interactions between the capsule and genetic background. CONCLUSIONS Pneumococcal strains vary in how they respond to environmental variations, some of this variation can be explained by the capsule type being produced, but capsule production itself is not sufficient to explain the variability. This variability could help to explain why different lineages of pneumococcus are more common in carriage or disease.
Collapse
Affiliation(s)
- Adrienn Tóthpál
- Epidemiology of Microbial Diseases, Yale School of Public Health, 60 College Street, New Haven, CT, 06510, USA. .,Institute of Medical Microbiology, Semmelweis University, Nagyvarad ter 4, Budapest, HU-1089, Hungary.
| | - Katherine Desobry
- Epidemiology of Microbial Diseases, Yale School of Public Health, 60 College Street, New Haven, CT, 06510, USA
| | - Shreyas S Joshi
- Epidemiology of Microbial Diseases, Yale School of Public Health, 60 College Street, New Haven, CT, 06510, USA
| | - Anne L Wyllie
- Epidemiology of Microbial Diseases, Yale School of Public Health, 60 College Street, New Haven, CT, 06510, USA
| | - Daniel M Weinberger
- Epidemiology of Microbial Diseases, Yale School of Public Health, 60 College Street, New Haven, CT, 06510, USA.
| |
Collapse
|
23
|
DprA-Dependent Exit from the Competent State Regulates Multifaceted Streptococcus pneumoniae Virulence. Infect Immun 2019; 87:IAI.00349-19. [PMID: 31451619 DOI: 10.1128/iai.00349-19] [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] [Received: 05/02/2019] [Accepted: 08/18/2019] [Indexed: 11/20/2022] Open
Abstract
Streptococcus pneumoniae (pneumococcus) causes multiple infectious diseases. The pneumococcal competence system facilitates genetic transformation, spreads antibiotic resistance, and contributes to virulence. DNA-processing protein A (DprA) regulates the exit of pneumococcus from the competent state. Previously, we have shown that DprA is important in both bacteremia and pneumonia infections. Here, we examined the mechanisms of virulence attenuation in a ΔdprA mutant. Compared to the parental wild-type D39, the ΔdprA mutant enters the competent state when exposed to lower concentrations of the competence-stimulating peptide CSP1. The ΔdprA mutant overexpresses ComM, which delays cell separation after division. Additionally, the ΔdprA mutant overexpresses allolytic factors LytA, CbpD, and CibAB and is more susceptible to detergent-triggered lysis. Disabling of the competent-state-specific induction of ComM and allolytic factors compensated for the virulence loss in the ΔdprA mutant, suggesting that overexpression of these factors contributes to virulence attenuation. Finally, the ΔdprA mutant fails to downregulate the expression of multiple competence-regulated genes, leading to the excessive energy consumption. Collectively, these results indicate that an inability to properly exit the competent state disrupts multiple cellular processes that cause virulence attenuation in the ΔdprA mutant.
Collapse
|
24
|
Abstract
Ninety years after the discovery of pneumococcal Transformation, and 74 years after the work of Avery and colleagues that identified DNA as the genetic material, Streptococcus pneumoniae is still one of the most important model organism to understand Bacterial Genetics and Genomics. In this Chapter special emphasis has been given to Genomics and to Mobile Genetic Elements (the Mobilome) which greatly contribute to the dynamic variation of pneumococcal genomes by horizontal gene transfer. Other topics include molecular mechanisms of Genetic Transformation, Restriction/Modification Systems, Mismatch DNA Repair, and techniques for construction of genetically engineered pneumococcal strains.
Collapse
|
25
|
A Counterselectable Sucrose Sensitivity Marker Permits Efficient and Flexible Mutagenesis in Streptococcus agalactiae. Appl Environ Microbiol 2019; 85:AEM.03009-18. [PMID: 30658970 DOI: 10.1128/aem.03009-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 01/13/2019] [Indexed: 12/25/2022] Open
Abstract
Streptococcus agalactiae (group B Streptococcus [GBS]) is a cause of severe infections, particularly during the newborn period. While methods exist for generating chromosomal mutations in GBS, they are cumbersome and inefficient and present significant challenges if the goal is to study subtle mutations, such as single-base-pair polymorphisms. To address this problem, we have developed an efficient and flexible GBS mutagenesis protocol based on sucrose counterselection against levansucrase (SacB) expressed from a temperature-selective shuttle vector. GBS containing the SacB expression cassette demonstrates lethal sensitivity to supplemental sucrose whether the plasmid DNA is replicating outside of the chromosome or has been integrated during a crossover event. Transmission electron microscopy shows that SacB-mediated lethal sucrose sensitivity results from the accumulation of inclusion bodies that eventually lead to complete degradation of normal cellular architecture and subsequent lysis. We used this new mutagenesis technique to generate an in-frame, allelic exchange knockout of the GBS sortase gene srtA, demonstrating that >99% of colonies that emerge from our protocol had the expected knockout phenotype and that among a subset tested by sequencing, 100% had the correct genotype. We also generated barcoded nonsense mutations in the cylE gene in two GBS strains, showing that the approach can be used to make small, precise chromosomal mutations.IMPORTANCE The ability to generate chromosomal mutations is fundamental to microbiology. Historically, however, GBS pathogenesis research has been made challenging by the relative genetic intractability of the organism. Generating a single knockout in GBS using traditional techniques can take many months, with highly variable success rates. Furthermore, traditional methods do not offer a straightforward way to generate single-base-pair polymorphisms or other subtle changes, especially to noncoding regions of the chromosome. We have developed a new sucrose counterselection-based method that permits rapid, efficient, and flexible GBS mutagenesis. Our technique requires no additional equipment beyond what is needed for traditional approaches. We believe that it will catalyze rapid advances in GBS genetics research by significantly easing the path to generating mutants.
Collapse
|
26
|
Zhu Y, Dong W, Ma J, Zhang Y, Pan Z, Yao H. Utilization of the ComRS system for the rapid markerless deletion of chromosomal genes in Streptococcus suis. Future Microbiol 2019; 14:207-222. [DOI: 10.2217/fmb-2018-0279] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aim: To develop a markerless gene deletion strategy in Streptococcus suis to solve the problem that several serotypes against electrotransformation of foreign DNA. Materials & methods: Bioinformatics retrieval was performed to identified ComRS systems functioning for natural transformation. A sacB-spc cassette with the upper and lower homologous fragments was amplification by fusion-PCR for spectinomycin-positive and sucrose-negative selection during gene deletion. Results & conclusion: Three phylogenetic clusters of ComR were identified to function for natural transformation by specific recognition to competence pheromone in S. suis. Thus, they were employed to establish gene deletion method. Its efficiency for genetic replacement was dependent on the length of homologs fragment and the concentration of donor DNA. This rapid gene-editing technique may greatly facilitate molecular studies on S. suis.
Collapse
Affiliation(s)
- Yinchu Zhu
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China
- Office International Des Epizooties (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing 210095, PR China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Wenyang Dong
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China
- Office International Des Epizooties (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing 210095, PR China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Jiale Ma
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China
- Office International Des Epizooties (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing 210095, PR China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Yue Zhang
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China
- Office International Des Epizooties (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing 210095, PR China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Zihao Pan
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China
- Office International Des Epizooties (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing 210095, PR China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Huochun Yao
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China
- Office International Des Epizooties (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing 210095, PR China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, PR China
| |
Collapse
|
27
|
Genome-wide association analyses of invasive pneumococcal isolates identify a missense bacterial mutation associated with meningitis. Nat Commun 2019; 10:178. [PMID: 30643125 PMCID: PMC6331587 DOI: 10.1038/s41467-018-07997-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 12/11/2018] [Indexed: 11/10/2022] Open
Abstract
Bacterial mutations predisposing pneumococcus to causing meningitis, a more severe form of invasive pneumococcal disease (IPD), are largely unknown. Knowledge of such mutations may improve our understanding of pathogenesis and inform preventive strategies. Here we report a pneumococcal pbp1b gene mutation (pbp1bA641C causing N214T change in PBP1b transglycosylase domain) that is associated with meningitis in an exploratory cohort of IPD patients (n = 2054, p = 6.8 × 10−6), in an independent confirmatory cohort (n = 2518, p = 2.3 × 10−6), and in a combined analysis (n = 4572, p = 3.0 × 10−10). Patients infected by the pbp1b641C genotype pneumococci show 2.8-fold odds (95% CI 1.7 to 4.8) of meningitis compared to those infected by non-pbp1b641C pneumococci, after controlling for pneumococcal serotype, antibiotic resistance, and patient age. The pbp1bA641C change results in longer time needed for bacterial killing by antibiotic treatment and shows evidence of being under positive selection. Thus, a pneumococcal mutation conferring increased antibiotic tolerance is associated with meningitis among IPD patients. Meningitis is a severe form of invasive pneumococcal disease (IPD). To study the contribution of bacterial genomic variation, here Li et al. perform whole genome sequencing of pneumococcal isolates from IPD patients and identify an association for higher risk of meningitis with a pbp1bA641C variant
Collapse
|
28
|
ABC transporter content diversity in Streptococcus pneumoniae impacts competence regulation and bacteriocin production. Proc Natl Acad Sci U S A 2018; 115:E5776-E5785. [PMID: 29866828 PMCID: PMC6016807 DOI: 10.1073/pnas.1804668115] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The opportunistic pathogen Streptococcus pneumoniae (pneumococcus) participates in horizontal gene transfer through genetic competence and produces antimicrobial peptides called “bacteriocins.” Here, we show that the competence and bacteriocin-related ABC transporters ComAB and BlpAB share the same substrate pool, resulting in bidirectional crosstalk between competence and bacteriocin regulation. We also clarify the role of each transporter in bacteriocin secretion and show that, based on their transporter content, pneumococcal strains can be separated into a majority opportunist group that uses bacteriocins only to support competence and a minority aggressor group that uses bacteriocins in broader contexts. Our findings will impact how bacteriocin regulation and production is modeled in the many other bacterial species that use ComAB/BlpAB-type transporters. The opportunistic pathogen Streptococcus pneumoniae (pneumococcus) uses natural genetic competence to increase its adaptability through horizontal gene transfer. One method of acquiring DNA is through predation of neighboring strains with antimicrobial peptides called “bacteriocins.” Competence and production of the major family of pneumococcal bacteriocins, pneumocins, are regulated by the quorum-sensing systems com and blp, respectively. In the classical paradigm, the ABC transporters ComAB and BlpAB each secretes its own system’s signaling pheromone and in the case of BlpAB also secretes the pneumocins. While ComAB is found in all pneumococci, only 25% of strains encode an intact version of BlpAB [BlpAB(+)] while the rest do not [BlpAB(−)]. Contrary to the classical paradigm, it was previously shown that BlpAB(−) strains can activate blp through ComAB-mediated secretion of the blp pheromone during brief periods of competence. To better understand the full extent of com-blp crosstalk, we examined the contribution of each transporter to competence development and pneumocin secretion. We found that BlpAB(+) strains have a greater capacity for competence activation through BlpAB-mediated secretion of the com pheromone. Similarly, we show that ComAB and BlpAB are promiscuous and both can secrete pneumocins. Consequently, differences in pneumocin secretion between BlpAB(+) and BlpAB(−) strains derive from the regulation and kinetics of transporter expression rather than substrate specificity. We speculate that BlpAB(−) strains (opportunists) use pneumocins mainly in a narrowly tailored role for DNA acquisition and defense during competence while BlpAB(+) strains (aggressors) expand their use for the general inhibition of rival strains.
Collapse
|
29
|
Abstract
The capsular polysaccharide (CPS) of Streptococcus pneumoniae is characterized by its diversity, as it has over 95 known serotypes, and the variation in its thickness as it surrounds an organism. While within-host effects of CPS have been studied in detail, there is no information about its contribution to host-to-host transmission. In this study, we used an infant mouse model of intralitter transmission, together with isogenic capsule switch and cps promoter switch constructs, to explore the effects of CPS type and amount. The determining factor in the transmission rate in this model is the number of pneumococci shed in nasal secretions by colonized hosts. Two of seven capsule switch constructs showed reduced shedding. These constructs were unimpaired in colonization and expressed capsules similar in size to those of the wild-type strain. A cps promoter switch mutant expressing ~50% of wild-type amounts of CPS also displayed reduced shedding without a defect in colonization. Since shedding from the mucosal surface may require escape from mucus entrapment, a mucin-binding assay was used to compare capsule switch and cps promoter switch mutants. The CPS type or amount constructs that shed poorly were bound more robustly by immobilized mucin. These capsule switch and cps promoter switch constructs with increased mucin-binding affinity and reduced shedding also had lower rates of pup-to-pup transmission. Our results demonstrate that CPS type and amount affect transmission dynamics and may contribute to the marked differences in prevalence among pneumococcal types.IMPORTANCEStreptococcus pneumoniae, a leading cause of morbidity and mortality, is readily transmitted, especially among young children. Its structurally and antigenically diverse capsular polysaccharide is the target of currently licensed pneumococcal vaccines. Epidemiology studies show that only a subset of the >95 distinct serotypes are prevalent in the human population, suggesting that certain capsular polysaccharide types might be more likely to be transmitted within the community. Herein, we used an infant mouse model to show that both capsule type and amount are important determinants in the spread of pneumococci from host to host. Transmission rates correlate with those capsule types that are better at escaping mucus entrapment, a key step in exiting the host upper respiratory tract. Hence, our study provides a better mechanistic understanding of why certain pneumococcal serotypes are more common in the human population.
Collapse
|
30
|
Echlin H, Frank MW, Iverson A, Chang TC, Johnson MDL, Rock CO, Rosch JW. Pyruvate Oxidase as a Critical Link between Metabolism and Capsule Biosynthesis in Streptococcus pneumoniae. PLoS Pathog 2016; 12:e1005951. [PMID: 27760231 PMCID: PMC5070856 DOI: 10.1371/journal.ppat.1005951] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Accepted: 09/23/2016] [Indexed: 01/12/2023] Open
Abstract
The pneumococcus is one of the most prodigious producers of hydrogen peroxide amongst bacterial pathogens. Hydrogen peroxide production by the pneumococcus has been implicated in antibiotic synergism, competition between other bacterial colonizers of the nasopharynx, and damage to epithelial cells. However, the role during invasive disease has been less clear with mutants defective in hydrogen peroxide production demonstrating both attenuation and heightened invasive disease capacity depending upon strain and serotype background. This work resolves these conflicting observations by demonstrating that the main hydrogen peroxide producing enzyme of the pneumococcus, SpxB, is required for capsule formation in a strain dependent manner. Capsule production by strains harboring capsules with acetylated sugars was dependent upon the presence of spxB while capsule production in serotypes lacking such linkages were not. The spxB mutant had significantly lower steady-state cellular levels of acetyl-CoA, suggesting that loss of capsule arises from dysregulation of this intermediary metabolite. This conclusion is corroborated by deletion of pdhC, which also resulted in lower steady-state acetyl-CoA levels and phenocopied the capsule expression profile of the spxB mutant. Capsule and acetyl-CoA levels were restored in the spxB and lctO (lactate oxidase) double mutant, supporting the connection between central metabolism and capsule formation. Taken together, these data show that the defect in pathogenesis in the spxB mutant is due to a metabolic imbalance that attenuates capsule formation and not to reduced hydrogen peroxide formation. The pneumococcus polysaccharide capsule is one of the most critical virulence determinants produced by this major human pathogen. The pneumococcus also produces prodigious amounts of hydrogen peroxide via the enzymatic reaction catalyzed by pyruvate oxidase, SpxB. Deletion of spxB resulted in the loss of surface polysaccharide capsule production in a serotype dependent manner with a mirrored effect on the virulence of the mutants. We observed that deletion of spxB reduced the steady-state levels of acetyl-CoA, a key metabolic intermediate in peptidoglycan, fatty acid biosynthesis, and in capsule biosynthesis in a subset of serotypes. These data suggest that the defect in capsule production was due to altered metabolism that results in reduced acetyl-CoA availability. Corroborating these data, we found that capsule biosynthesis was impaired upon loss of PDHC, an additional metabolic enzyme that generates acetyl-CoA. These data reveal a critical link between pneumococcal metabolism and capsule biosynthesis as well as provide a striking example of how a virulence gene can have a differential contribution to pathogenesis dependent upon strain background.
Collapse
Affiliation(s)
- Haley Echlin
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Matthew W. Frank
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Amy Iverson
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Ti-Cheng Chang
- Department of Computational Biology, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Michael D. L. Johnson
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Charles O. Rock
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Jason W. Rosch
- Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- * E-mail:
| |
Collapse
|
31
|
Zafar MA, Kono M, Wang Y, Zangari T, Weiser JN. Infant Mouse Model for the Study of Shedding and Transmission during Streptococcus pneumoniae Monoinfection. Infect Immun 2016; 84:2714-22. [PMID: 27400721 PMCID: PMC4995895 DOI: 10.1128/iai.00416-16] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 07/05/2016] [Indexed: 12/21/2022] Open
Abstract
One of the least understood aspects of the bacterium Streptococcus pneumoniae (pneumococcus) is its transmission from host to host, the critical first step in both the carrier state and the disease state. To date, transmission models have depended on influenza A virus coinfection, which greatly enhances pneumococcal shedding to levels that allow acquisition by a new host. Here, we describe an infant mouse model that can be utilized to study pneumococcal colonization, shedding, and transmission during bacterial monoinfection. Using this model, we demonstrated that the level of bacterial shedding is highest in pups infected intranasally at age 4 days and peaks over the first 4 days postchallenge. Shedding results differed among isolates of five different pneumococcal types. Colonization density was found to be a major factor in the level of pneumococcal shedding and required expression of capsule. Transmission within a litter occurred when there was a high ratio of colonized "index" pups to uncolonized "contact" pups. Transmission was observed for each of the well-colonizing pneumococcal isolates, with the rate of transmission proportional to the level of shedding. This model can be used to examine bacterial and host factors that contribute to pneumococcal transmission without the effects of viral coinfection.
Collapse
Affiliation(s)
- M Ammar Zafar
- Department of Microbiology, New York University, New York, New York, USA
| | - Masamitsu Kono
- Department of Microbiology, New York University, New York, New York, USA Department of Otolaryngology-Head and Neck Surgery, Wakayama Medical University, Wakayama, Japan
| | - Yang Wang
- Department of Microbiology, New York University, New York, New York, USA School of Medicine, Tsing Hua University, Beijing, China
| | - Tonia Zangari
- Department of Microbiology, New York University, New York, New York, USA
| | - Jeffrey N Weiser
- Department of Microbiology, New York University, New York, New York, USA
| |
Collapse
|