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Chang C, Ton-That H. Detection of Cell Wall-Anchoring Machinery by Immunogold-Labeling Thin-Section Electron Microscopy. Methods Mol Biol 2024; 2727:145-152. [PMID: 37815715 DOI: 10.1007/978-1-0716-3491-2_12] [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] [Indexed: 10/11/2023]
Abstract
Cell wall anchoring of surface proteins and pili in Gram-positive bacteria is mediated by sortase - a highly conserved transpeptidase enzyme. Early studies have demonstrated the membrane-associated nature of this enzyme in close proximity with its cognate substrates, using immunogold-labeling thin-section electron microscopy. Here, we provide a detail protocol of this methodology, including specimen preparation, ultrathin sectioning, and immunogold-labeling electron microscopic procedures, with an experimental model of sortase enzymes from Actinomyces oris. In principle, this protocol can be employed for any bacterial ultrathin-section samples to detect subcellular localization of proteins and organelles by immuno-electron microscopy.
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Affiliation(s)
- Chungyu Chang
- Division of Oral & Systemic Health Sciences, School of Dentistry, University of California, Los Angeles, CA, USA.
| | - Hung Ton-That
- Division of Oral & Systemic Health Sciences, School of Dentistry, University of California, Los Angeles, CA, USA
- Molecular Biology Institute, University of California, Los Angeles, CA, USA
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA
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2
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Group B Streptococcus: Virulence Factors and Pathogenic Mechanism. Microorganisms 2022; 10:microorganisms10122483. [PMID: 36557736 PMCID: PMC9784991 DOI: 10.3390/microorganisms10122483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Revised: 12/10/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
Group B Streptococcus (GBS) or Streptococcus agalactiae is a major cause of neonatal mortality. When colonizing the lower genital tract of pregnant women, GBS may cause premature birth and stillbirth. If transmitted to the newborn, it may result in life-threatening illnesses, including sepsis, meningitis, and pneumonia. Moreover, through continuous evolution, GBS can use its original structure and unique factors to greatly improve its survival rate in the human body. This review discusses the key virulence factors that facilitate GBS invasion and colonization and their action mechanisms. A comprehensive understanding of the role of virulence factors in GBS infection is crucial to develop better treatment options and screen potential candidate molecules for the development of the vaccine.
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3
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Ognenovska S, Mukerjee C, Sanderson-Smith M, Moore KH, Mansfield KJ. Virulence Mechanisms of Common Uropathogens and Their Intracellular Localisation within Urothelial Cells. Pathogens 2022; 11:pathogens11080926. [PMID: 36015046 PMCID: PMC9415470 DOI: 10.3390/pathogens11080926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 08/12/2022] [Accepted: 08/15/2022] [Indexed: 11/29/2022] Open
Abstract
A recurrent urinary tract infection (UTI) is a common debilitating condition whereby uropathogens are able to survive within the urinary tract. In this study, we aimed to determine if the common uropathogens Escherichia coli, Enterococcus faecalis, and Group B Streptococcus possessed virulence mechanisms that enable the invasion of urothelial cells. Urothelial cells were isolated from women with detrusor overactivity and recurrent UTIs; the intracellular localisation of the uropathogens was determined by confocal microscopy. Uropathogens were also isolated from women with acute UTIs and their intracellular localisation and virulence mechanisms were examined (yeast agglutination, biofilm formation, and haemolysis). Fluorescent staining and imaging of urothelial cells isolated from women with refractory detrusor overactivity and recurrent UTIs demonstrated that all three uropathogens were capable of intracellular colonisation. Similarly, the bacterial isolates from women with acute UTIs were also seen to intracellularly localise using an in vitro model. All Enterococcus and Streptococcus isolates possessed a haemolytic capacity and displayed a strong biofilm formation whilst yeast cell agglutination was unique to Escherichia coli. The expression of virulence mechanisms by these uropathogenic species was observed to correlate with successful urothelial cell invasion. Invasion into the bladder urothelium was seen to be a common characteristic of uropathogens, suggesting that bacterial reservoirs within the bladder contribute to the incidence of recurrent UTIs.
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Affiliation(s)
- Samantha Ognenovska
- Detrusor Muscle Laboratory, Department of Urogynaecology, University of New South Wales, St. George Hospital, Sydney, NSW 2217, Australia
| | - Chinmoy Mukerjee
- Department of Microbiology, St. George Hospital, Sydney, NSW 2217, Australia
| | - Martina Sanderson-Smith
- Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
- Molecular Horizons, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Kate H. Moore
- Detrusor Muscle Laboratory, Department of Urogynaecology, University of New South Wales, St. George Hospital, Sydney, NSW 2217, Australia
| | - Kylie J. Mansfield
- Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
- Graduate School of Medicine, University of Wollongong, Wollongong, NSW 2522, Australia
- Correspondence:
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4
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Cho H, Masters T, Greenwood‐Quaintance KE, Johnson S, Jeraldo PR, Chia N, Pu M, Abdel MP, Patel R. Transcriptomic analysis of Streptococcus agalactiae periprosthetic joint infection. Microbiologyopen 2021; 10:e1256. [PMID: 34964296 PMCID: PMC8678771 DOI: 10.1002/mbo3.1256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 09/09/2021] [Accepted: 11/22/2021] [Indexed: 11/08/2022] Open
Abstract
Although Streptococcus agalactiae periprosthetic joint infection (PJI) is not as prevalent as staphylococcal PJI, invasive S. agalactiae infection is not uncommon. Here, RNA-seq was used to perform transcriptomic analysis of S. agalactiae PJI using fluid derived from sonication of explanted arthroplasties of subjects with S. agalactiae PJI, with results compared to those of S. agalactiae strain NEM316 grown in vitro. A total of 227 genes with outlier expression were found (164 upregulated and 63 downregulated) between PJI sonicate fluid and in vitro conditions. Functional enrichment analysis showed genes involved in mobilome and inorganic ion transport and metabolism to be most enriched. Genes involved in nickel, copper, and zinc transport, were upregulated. Among known virulence factors, cyl operon genes, encoding β-hemolysin/cytolysin, were consistently highly expressed in PJI versus in vitro. The data presented provide insight into S. agalactiae PJI pathogenesis and may be a resource for identification of novel PJI therapeutics or vaccines against invasive S. agalactiae infections.
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Affiliation(s)
- Hye‐Kyung Cho
- Division of Clinical Microbiology, Department of Laboratory Medicine and PathologyMayo ClinicRochesterMinnesotaUSA
| | - Thao Masters
- Division of Clinical Microbiology, Department of Laboratory Medicine and PathologyMayo ClinicRochesterMinnesotaUSA
| | | | - Stephen Johnson
- Department of Health Sciences ResearchMayo ClinicRochesterMinnesotaUSA
| | - Patricio R. Jeraldo
- Center for Individualized MedicineMayo ClinicRochesterMinnesotaUSA
- Department of SurgeryMayo ClinicRochesterMinnesotaUSA
| | - Nicholas Chia
- Center for Individualized MedicineMayo ClinicRochesterMinnesotaUSA
- Department of SurgeryMayo ClinicRochesterMinnesotaUSA
| | - Meng Pu
- Department of Medicine, Division of Gastroenterology and HepatologyMayo ClinicRochesterMinnesotaUSA
| | - Matthew P. Abdel
- Department of Orthopedic SurgeryMayo ClinicRochesterMinnesotaUSA
| | - Robin Patel
- Division of Clinical Microbiology, Department of Laboratory Medicine and PathologyMayo ClinicRochesterMinnesotaUSA
- Division of Infectious Diseases, Department of MedicineMayo ClinicRochesterMinnesotaUSA
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5
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Complete Genome Sequence of Streptococcus agalactiae Strain 01173, Isolated from Kuwaiti Wild Fish. Microbiol Resour Announc 2020; 9:9/36/e00674-20. [PMID: 32883783 PMCID: PMC7471378 DOI: 10.1128/mra.00674-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Here, we report the complete genome of piscine Streptococcus agalactiae 01173 serotype Ia, which was generated using long-read sequencing technology. The bacteria were isolated from wild fish displaying signs of streptococcosis, from a fish kill incident in Kuwait. Here, we report the complete genome of piscine Streptococcus agalactiae 01173 serotype Ia, which was generated using long-read sequencing technology. The bacteria were isolated from wild fish displaying signs of streptococcosis, from a fish kill incident in Kuwait.
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6
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Chatzikleanthous D, Schmidt ST, Buffi G, Paciello I, Cunliffe R, Carboni F, Romano MR, O'Hagan DT, D'Oro U, Woods S, Roberts CW, Perrie Y, Adamo R. Design of a novel vaccine nanotechnology-based delivery system comprising CpGODN-protein conjugate anchored to liposomes. J Control Release 2020; 323:125-137. [DOI: 10.1016/j.jconrel.2020.04.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 03/27/2020] [Accepted: 04/01/2020] [Indexed: 12/24/2022]
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7
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Ramirez NA, Das A, Ton-That H. New Paradigms of Pilus Assembly Mechanisms in Gram-Positive Actinobacteria. Trends Microbiol 2020; 28:999-1009. [PMID: 32499101 DOI: 10.1016/j.tim.2020.05.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 05/08/2020] [Accepted: 05/14/2020] [Indexed: 02/06/2023]
Abstract
Adhesive pili in Gram-positive bacteria represent a variety of extracellular multiprotein polymers that mediate bacterial colonization of specific host tissues and associated pathogenesis. Pili are assembled in two distinct but coupled steps, an orderly crosslinking of pilin monomers and subsequent anchoring of the polymer to peptidoglycan, catalyzed by two transpeptidase enzymes - the pilus-specific sortase and the housekeeping sortase. Here, we review this biphasic assembly mechanism based on studies of two prototypical models, the heterotrimeric pili in Corynebacterium diphtheriae and the heterodimeric pili in Actinomyces oris, highlighting some newly emerged basic paradigms. The disparate mechanisms of protein ligation mediated by the pilus-specific sortase and the spatial positioning of adhesive pili on the cell surface modulated by the housekeeping sortase are among the notable highlights.
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Affiliation(s)
- Nicholas A Ramirez
- Molecular Biology Institute, University of California, Los Angeles, CA, USA
| | - Asis Das
- Department of Medicine, Neag Comprehensive Cancer Center, University of Connecticut Health Center, Farmington, CT, USA
| | - Hung Ton-That
- Molecular Biology Institute, University of California, Los Angeles, CA, USA; Division of Oral Biology and Medicine, School of Dentistry, University of California, Los Angeles, CA, USA.
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8
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Niu Z, Chen YH, Zhang K. Polymorphonuclear Leukocyte Transendothelial Migration Proceeds at Blood-Brain Barrier in Neonatal Meningitis. Front Microbiol 2020; 11:969. [PMID: 32528436 PMCID: PMC7264371 DOI: 10.3389/fmicb.2020.00969] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Accepted: 04/22/2020] [Indexed: 11/29/2022] Open
Abstract
Neonatal bacterial meningitis remains a life-threatening and causative sequelae disease in newborns, despite the effective usage of antibiotics and improved critical medical care. Polymorphonuclear leukocyte (PMN) transendothelial migration across the blood-brain barrier, one of the three hallmarks of bacterial meningitis, now is considered as a “double-edge sword”. When participating in host immune system defending against virulent pathogens, it results in tissue inflammation and following severe damage of central nervous system at the same time, which contributes to a disastrous consequence. Recently, several researches have focused on this multi-step process and the mechanism of how the virulent factors of different pathogens influence PMN migration. The great progression they made has enlightened a new research hotspot and a novel therapeutic strategy. This mini review outlines the determinants and progression of PMN transmigration in neonatal meningitis caused by different predominant pathogens.
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Affiliation(s)
- Zhuo Niu
- Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, Shenyang, China.,Department of Surgical Oncology and General Surgery, Key Laboratory of Precision Diagnosis and Treatment of Gastrointestinal Tumors, Ministry of Education, The First Affiliated Hospital of China Medical University, Shenyang, China
| | - Yu-Hua Chen
- Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, Shenyang, China
| | - Ke Zhang
- Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, Shenyang, China
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9
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Chang C, Wu C, Osipiuk J, Siegel SD, Zhu S, Liu X, Joachimiak A, Clubb RT, Das A, Ton-That H. Cell-to-cell interaction requires optimal positioning of a pilus tip adhesin modulated by gram-positive transpeptidase enzymes. Proc Natl Acad Sci U S A 2019; 116:18041-18049. [PMID: 31427528 PMCID: PMC6731673 DOI: 10.1073/pnas.1907733116] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Assembly of pili on the gram-positive bacterial cell wall involves 2 conserved transpeptidase enzymes named sortases: One for polymerization of pilin subunits and another for anchoring pili to peptidoglycan. How this machine controls pilus length and whether pilus length is critical for cell-to-cell interactions remain unknown. We report here in Actinomyces oris, a key colonizer in the development of oral biofilms, that genetic disruption of its housekeeping sortase SrtA generates exceedingly long pili, catalyzed by its pilus-specific sortase SrtC2 that possesses both pilus polymerization and cell wall anchoring functions. Remarkably, the srtA-deficient mutant fails to mediate interspecies interactions, or coaggregation, even though the coaggregation factor CafA is present at the pilus tip. Increasing ectopic expression of srtA in the mutant progressively shortens pilus length and restores coaggregation accordingly, while elevated levels of shaft pilins and SrtC2 produce long pili and block coaggregation by SrtA+ bacteria. With structural studies, we uncovered 2 key structural elements in SrtA that partake in recognition of pilin substrates and regulate pilus length by inducing the capture and transfer of pilus polymers to the cell wall. Evidently, coaggregation requires proper positioning of the tip adhesin CafA via modulation of pilus length by the housekeeping sortase SrtA.
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Affiliation(s)
- Chungyu Chang
- Division of Oral Biology and Medicine, School of Dentistry, University of California, Los Angeles, CA 90095;
| | - Chenggang Wu
- Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX 77030
| | - Jerzy Osipiuk
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and Engineering, University of Chicago, Chicago, IL 60637
- Structural Biology Center, Argonne National Laboratory, Lemont, IL 60439
| | - Sara D Siegel
- Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX 77030
| | - Shiwei Zhu
- Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06510
| | - Xiangan Liu
- Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX 77030
| | - Andrzej Joachimiak
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and Engineering, University of Chicago, Chicago, IL 60637
- Structural Biology Center, Argonne National Laboratory, Lemont, IL 60439
| | - Robert T Clubb
- Department of Chemistry and Biochemistry, University of California, Los Angeles-Department of Energy Institute of Genomics and Proteomics, University of California, Los Angeles, CA 90095
| | - Asis Das
- Department of Medicine, Neag Comprehensive Cancer Center, University of Connecticut Health Center, Farmington, CT 06030
| | - Hung Ton-That
- Division of Oral Biology and Medicine, School of Dentistry, University of California, Los Angeles, CA 90095;
- Molecular Biology Institute, University of California, Los Angeles, CA 90095
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10
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Armistead B, Oler E, Adams Waldorf K, Rajagopal L. The Double Life of Group B Streptococcus: Asymptomatic Colonizer and Potent Pathogen. J Mol Biol 2019; 431:2914-2931. [PMID: 30711542 DOI: 10.1016/j.jmb.2019.01.035] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Revised: 01/22/2019] [Accepted: 01/23/2019] [Indexed: 12/22/2022]
Abstract
Group B streptococcus (GBS) is a β-hemolytic gram-positive bacterium that colonizes the lower genital tract of approximately 18% of women globally as an asymptomatic member of the gastrointestinal and/or vaginal flora. If established in other host niches, however, GBS is highly pathogenic. During pregnancy, ascending GBS infection from the vagina to the intrauterine space is associated with preterm birth, stillbirth, and fetal injury. In addition, vertical transmission of GBS during or after birth results in life-threatening neonatal infections, including pneumonia, sepsis, and meningitis. Although the mechanisms by which GBS traffics from the lower genital tract to vulnerable host niches are not well understood, recent advances have revealed that many of the same bacterial factors that promote asymptomatic vaginal carriage also facilitate dissemination and virulence. Furthermore, highly pathogenic GBS strains have acquired unique factors that enhance survival in invasive niches. Several host factors also exist that either subdue GBS upon vaginal colonization or alternatively permit invasive infection. This review summarizes the GBS and host factors involved in GBS's state as both an asymptomatic colonizer and an invasive pathogen. Gaining a better understanding of these mechanisms is key to overcoming the challenges associated with vaccine development and identification of novel strategies to mitigate GBS virulence.
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Affiliation(s)
- Blair Armistead
- Department of Global Health, University of Washington, Seattle 98195, WA, USA; Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle 98101, WA, USA
| | - Elizabeth Oler
- Department of Obstetrics and Gynecology, University of Washington School of Medicine, Seattle 98195, WA, USA
| | - Kristina Adams Waldorf
- Department of Global Health, University of Washington, Seattle 98195, WA, USA; Department of Obstetrics and Gynecology, University of Washington School of Medicine, Seattle 98195, WA, USA; Center for Innate Immunity and Immune Disease, University of Washington, Seattle 98109, WA, USA; Sahlgrenska Academy, Gothenburg University, Gothenburg 413 90, Sweden
| | - Lakshmi Rajagopal
- Department of Global Health, University of Washington, Seattle 98195, WA, USA; Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle 98101, WA, USA; Department of Pediatrics, University of Washington School of Medicine, Seattle 98195, WA, USA.
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11
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Pietrocola G, Arciola CR, Rindi S, Montanaro L, Speziale P. Streptococcus agalactiae Non-Pilus, Cell Wall-Anchored Proteins: Involvement in Colonization and Pathogenesis and Potential as Vaccine Candidates. Front Immunol 2018; 9:602. [PMID: 29686667 PMCID: PMC5900788 DOI: 10.3389/fimmu.2018.00602] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 03/09/2018] [Indexed: 11/13/2022] Open
Abstract
Group B Streptococcus (GBS) remains an important etiological agent of several infectious diseases including neonatal septicemia, pneumonia, meningitis, and orthopedic device infections. This pathogenicity is due to a variety of virulence factors expressed by Streptococcus agalactiae. Single virulence factors are not sufficient to provoke a streptococcal infection, which is instead promoted by the coordinated activity of several pathogenicity factors. Such determinants, mostly cell wall-associated and secreted proteins, include adhesins that mediate binding of the pathogen to host extracellular matrix/plasma ligands and cell surfaces, proteins that cooperate in the invasion of and survival within host cells and factors that neutralize phagocytosis and/or modulate the immune response. The genome-based approaches and bioinformatics tools and the extensive use of biophysical and biochemical methods and animal model studies have provided a great wealth of information on the molecular structure and function of these virulence factors. In fact, a number of new GBS surface-exposed or secreted proteins have been identified (GBS immunogenic bacterial adhesion protein, leucine-rich repeat of GBS, serine-rich repeat proteins), the three-dimensional structures of known streptococcal proteins (αC protein, C5a peptidase) have been solved and an understanding of the pathogenetic role of "old" and new determinants has been better defined in recent years. Herein, we provide an update of our current understanding of the major surface cell wall-anchored proteins from GBS, with emphasis on their biochemical and structural properties and the pathogenetic roles they may have in the onset and progression of host infection. We also focus on the antigenic profile of these compounds and discuss them as targets for therapeutic intervention.
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Affiliation(s)
- Giampiero Pietrocola
- Unit of Biochemistry, Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Carla Renata Arciola
- Research Unit on Implant Infections, Rizzoli Orthopaedic Institute, Bologna, Italy.,Department of Experimental, Diagnostic, and Specialty Medicine, University of Bologna, Bologna, Italy
| | - Simonetta Rindi
- Unit of Biochemistry, Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Lucio Montanaro
- Research Unit on Implant Infections, Rizzoli Orthopaedic Institute, Bologna, Italy.,Department of Experimental, Diagnostic, and Specialty Medicine, University of Bologna, Bologna, Italy
| | - Pietro Speziale
- Unit of Biochemistry, Department of Molecular Medicine, University of Pavia, Pavia, Italy.,Department of Industrial and Information Engineering, University of Pavia, Pavia, Italy
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12
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A Vaginal Tract Signal Detected by the Group B Streptococcus SaeRS System Elicits Transcriptomic Changes and Enhances Murine Colonization. Infect Immun 2018; 86:IAI.00762-17. [PMID: 29378799 DOI: 10.1128/iai.00762-17] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 01/19/2018] [Indexed: 01/08/2023] Open
Abstract
Streptococcus agalactiae (group B streptococcus [GBS]) can colonize the human vaginal tract, leading to both superficial and serious infections in adults and neonates. To study bacterial colonization of the reproductive tract in a mammalian system, we employed a murine vaginal carriage model. Using transcriptome sequencing (RNA-Seq), the transcriptome of GBS growing in vivo during vaginal carriage was determined. Over one-quarter of the genes in GBS were found to be differentially regulated during in vivo colonization compared to laboratory cultures. A two-component system (TCS) homologous to the staphylococcal virulence regulator SaeRS was identified as being upregulated in vivo One of the SaeRS targets, pbsP, a proposed GBS vaccine candidate, is shown to be important for colonization of the vaginal tract. A component of vaginal lavage fluid acts as a signal to turn on pbsP expression via SaeRS. These data demonstrate the ability to quantify RNA expression directly from the murine vaginal tract and identify novel genes involved in vaginal colonization by GBS. They also provide more information about the regulation of an important virulence and colonization factor of GBS, pbsP, by the TCS SaeRS.
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13
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Anchoring of LPXTG-Like Proteins to the Gram-Positive Cell Wall Envelope. Curr Top Microbiol Immunol 2017; 404:159-175. [PMID: 27097813 DOI: 10.1007/82_2016_8] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In Gram-positive bacteria, protein precursors with a signal peptide and a cell wall sorting signal (CWSS)-which begins with an LPXTG motif, followed by a hydrophobic domain and a tail of positively charged residues-are targeted to the cell envelope by a transpeptidase enzyme call sortase. Evolution and selective pressure gave rise to six classes of sortase, i.e., SrtA-F. Only class C sortases are capable of polymerizing substrates harboring the pilin motif and CWSS into protein polymers known as pili or fimbriae, whereas the others perform cell wall anchoring functions. Regardless of the products generated from these sortases, the basic principle of sortase-catalyzed transpeptidation is the same. It begins with the cleavage of the LPXTG motif, followed by the cross-linking of this cleaved product at the threonine residue to a nucleophile, i.e., an active amino group of the peptidoglycan stem peptide or the lysine residue of the pilin motif. This chapter will summarize the efforts to identify and characterize sortases and their associated pathways with emphasis on the cell wall anchoring function.
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14
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Electron Transport Chain Is Biochemically Linked to Pilus Assembly Required for Polymicrobial Interactions and Biofilm Formation in the Gram-Positive Actinobacterium Actinomyces oris. mBio 2017. [PMID: 28634238 PMCID: PMC5478893 DOI: 10.1128/mbio.00399-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The Gram-positive actinobacteria Actinomyces spp. are key colonizers in the development of oral biofilms due to the inherent ability of Actinomyces to adhere to receptor polysaccharides on the surface of oral streptococci and host cells. This receptor-dependent bacterial interaction, or coaggregation, requires a unique sortase-catalyzed pilus consisting of the pilus shaft FimA and the coaggregation factor CafA forming the pilus tip. While the essential role of the sortase machine SrtC2 in pilus assembly, biofilm formation, and coaggregation has been established, little is known about trans-acting factors contributing to these processes. We report here a large-scale Tn5 transposon screen for mutants defective in Actinomyces oris coaggregation with Streptococcus oralis. We obtained 33 independent clones, 13 of which completely failed to aggregate with S. oralis, and the remainder of which exhibited a range of phenotypes from severely to weakly defective coaggregation. The former had Tn5 insertions in fimA, cafA, or srtC2, as expected; the latter were mapped to genes coding for uncharacterized proteins and various nuo genes encoding the NADH dehydrogenase subunits. Electron microscopy and biochemical analyses of mutants with nonpolar deletions of nuo genes and ubiE, a menaquinone C-methyltransferase-encoding gene downstream of the nuo locus, confirmed the pilus and coaggregation defects. Both nuoA and ubiE mutants were defective in oxidation of MdbA, the major oxidoreductase required for oxidative folding of pilus proteins. Furthermore, supplementation of the ubiE mutant with exogenous menaquinone-4 rescued the cell growth and pilus defects. Altogether, we propose that the A. oris electron transport chain is biochemically linked to pilus assembly via oxidative protein folding. The Gram-positive actinobacterium A. oris expresses adhesive pili, or fimbriae, that are essential to biofilm formation and Actinomyces interactions with other bacteria, termed coaggregation. While the critical role of the conserved sortase machine in pilus assembly and the disulfide bond-forming catalyst MdbA in oxidative folding of pilins has been established, little is known about other trans-acting factors involved in these processes. Using a Tn5 transposon screen for mutants defective in coaggregation with Streptococcus oralis, we found that genetic disruption of the NADH dehydrogenase and menaquinone biosynthesis detrimentally alters pilus assembly. Further biochemical characterizations determined that menaquinone is important for reactivation of MdbA. This study supports the notion that the electron transport chain is biochemically linked to pilus assembly in A. oris via oxidative folding of pilin precursors.
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15
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Khare B, V L Narayana S. Pilus biogenesis of Gram-positive bacteria: Roles of sortases and implications for assembly. Protein Sci 2017; 26:1458-1473. [PMID: 28493331 DOI: 10.1002/pro.3191] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 04/28/2017] [Accepted: 05/03/2017] [Indexed: 12/26/2022]
Abstract
Successful adherence, colonization, and survival of Gram-positive bacteria require surface proteins, and multiprotein assemblies called pili. These surface appendages are attractive pharmacotherapeutic targets and understanding their assembly mechanisms is essential for identifying a new class of 'anti-infectives' that do not elicit microbial resistance. Molecular details of the Gram-negative pilus assembly are available indepth, but the Gram-positive pilus biogenesis is still an emerging field and investigations continue to reveal novel insights into this process. Pilus biogenesis in Gram-positive bacteria is a biphasic process that requires enzymes called pilus-sortases for assembly and a housekeeping sortase for covalent attachment of the assembled pilus to the peptidoglycan cell wall. Emerging structural and functional data indicate that there are at least two groups of Gram-positive pili, which require either the Class C sortase or Class B sortase in conjunction with LepA/SipA protein for major pilin polymerization. This observation suggests two distinct modes of sortase-mediated pilus biogenesis in Gram-positive bacteria. Here we review the structural and functional biology of the pilus-sortases from select streptococcal pilus systems and their role in Gram-positive pilus assembly.
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Affiliation(s)
- Baldeep Khare
- Center for Structural Biology, School of Optometry, University of Alabama at Birmingham, Birmingham, USA
| | - Sthanam V L Narayana
- Center for Structural Biology, School of Optometry, University of Alabama at Birmingham, Birmingham, USA
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16
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Isiaku AI, Sabri MY, Ina-Salwany MY, Hassan MD, Tanko PN, Bello MB. Biofilm is associated with chronic streptococcal meningoencephalitis in fish. Microb Pathog 2016; 102:59-68. [PMID: 27890651 DOI: 10.1016/j.micpath.2016.10.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/15/2016] [Accepted: 10/17/2016] [Indexed: 02/06/2023]
Abstract
Biofilms are aggregates of attached microbial organisms whose existence on tissues is often recognised as a mechanism for the establishment of most chronic diseases. Herein we investigated the ability of piscine Streptococcus agalactiae, an important aquatic pathogen, for adaptation to this sessile lifestyle in vitro and in the brain of a tilapia fish model. Piscine S. agalactiae exhibited a weak attachment to polystyrene plates and expressed a low biofilm phenotype under the study conditions. Furthermore, fluorescent in situ hybridization and confocal laser scanning microscopy revealed discrete aggregates of attached S. agalactiae within brain tissues and around meningeal surfaces. They were embedded in an exopolysaccharide containing matrix, intractable to inflammatory response and showed some level of resistance to penicillin despite proven susceptibility on sensitivity test. Intracellular bacterial aggregates were also observed, moreover, antibody mediated response was not demonstrated during infection. Nucleated erythrocytes appear to facilitate brain invasion possibly via the Trojan horse mechanism leading to a granulomatous inflammation. We have demonstrated that biofilm is associated with persistence of S. agalactiae and the development of chronic meningoencephalitis in fish.
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Affiliation(s)
- A I Isiaku
- Molecular Pathology Laboratory, Department of Veterinary Pathology and Microbiology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
| | - M Y Sabri
- Molecular Pathology Laboratory, Department of Veterinary Pathology and Microbiology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
| | - M Y Ina-Salwany
- Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
| | - M D Hassan
- Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
| | - P N Tanko
- Molecular Pathology Laboratory, Department of Veterinary Pathology and Microbiology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
| | - M B Bello
- Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
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17
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A distinct sortase SrtB anchors and processes a streptococcal adhesin AbpA with a novel structural property. Sci Rep 2016; 6:30966. [PMID: 27492581 PMCID: PMC4974636 DOI: 10.1038/srep30966] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 07/06/2016] [Indexed: 02/06/2023] Open
Abstract
Surface display of proteins by sortases in Gram-positive bacteria is crucial for bacterial fitness and virulence. We found a unique gene locus encoding an amylase-binding adhesin AbpA and a sortase B in oral streptococci. AbpA possesses a new distinct C-terminal cell wall sorting signal. We demonstrated that this C-terminal motif is required for anchoring AbpA to cell wall. In vitro and in vivo studies revealed that SrtB has dual functions, anchoring AbpA to the cell wall and processing AbpA into a ladder profile. Solution structure of AbpA determined by NMR reveals a novel structure comprising a small globular α/β domain and an extended coiled-coil heliacal domain. Structural and biochemical studies identified key residues that are crucial for amylase binding. Taken together, our studies document a unique sortase/adhesion substrate system in streptococci adapted to the oral environment rich in salivary amylase.
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18
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Si L, Li P, Liu X, Luo L. Chinese herb medicine against Sortase A catalyzed transformations, a key role in gram-positive bacterial infection progress. J Enzyme Inhib Med Chem 2016; 31:184-196. [PMID: 27162091 DOI: 10.1080/14756366.2016.1178639] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Many Gram-positive bacteria can anchor their surface proteins to the cell wall peptidoglycan covalently by a common mechanism with Sortase A (SrtA), thus escaping from the host's identification of immune cells. SrtA can complete this anchoring process by cleaving LPXTG motif conserved among these surface proteins and thus these proteins anchor on the cell wall. Moreover, those SrtA mutants lose this capability to anchor these relative proteins, with these bacteria no longer infectious. Therefore, SrtA inhibitors can be promising anti-infective agents to cure bacterial infections. Chinese herb medicines (CHMs) (chosen from Science Citation Index) have exhibited inhibition on SrtA of Gram-positive pathogens irreversibly or reversibly. In general, CHMs are likely to have important long-term impact as new antibacterial compounds and sought after by academia and the pharmaceutical industry. This review mainly focuses on SrtA inhibitors from CHMs and the potential inhibiting mechanism related to chemical structures of compounds in CHMs.
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Affiliation(s)
- Lifang Si
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
| | - Pan Li
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
| | - Xiong Liu
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
| | - Lixin Luo
- a School of Bioscience & Bioengineering, South China University of Technology, Guangzhou University Town , Panyu , Guangzhou , China
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Avilés-Reyes A, Miller JH, Lemos JA, Abranches J. Collagen-binding proteins of Streptococcus mutans and related streptococci. Mol Oral Microbiol 2016; 32:89-106. [PMID: 26991416 DOI: 10.1111/omi.12158] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/03/2016] [Indexed: 12/13/2022]
Abstract
The ability of Streptococcus mutans to interact with collagen through the expression of collagen-binding proteins (CBPs) bestows this oral pathogen with an alternative to the sucrose-dependent mechanism of colonization classically attributed to caries development. Based on the abundance and distribution of collagen throughout the human body, stringent adherence to this molecule grants S. mutans with the opportunity to establish infection at different host sites. Surface proteins, such as SpaP, WapA, Cnm and Cbm, have been shown to bind collagen in vitro, and it has been suggested that these molecules play a role in colonization of oral and extra-oral tissues. However, robust collagen binding is not achieved by all strains of S. mutans, particularly those that lack Cnm or Cbm. These observations merit careful dissection of the contribution from these different CBPs towards tissue colonization and virulence. In this review, we will discuss the current understanding of mechanisms used by S. mutans and related streptococci to colonize collagenous tissues, and the possible contribution of CBPs to infections in different sites of the host.
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Affiliation(s)
- A Avilés-Reyes
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - J H Miller
- Department of Anesthesiology, School of Medicine and Dentistry, University of Rochester, Rochester, NY, USA
| | - J A Lemos
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - J Abranches
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA
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Morello E, Mallet A, Konto-Ghiorghi Y, Chaze T, Mistou MY, Oliva G, Oliveira L, Di Guilmi AM, Trieu-Cuot P, Dramsi S. Evidence for the Sialylation of PilA, the PI-2a Pilus-Associated Adhesin of Streptococcus agalactiae Strain NEM316. PLoS One 2015; 10:e0138103. [PMID: 26407005 PMCID: PMC4583379 DOI: 10.1371/journal.pone.0138103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 08/25/2015] [Indexed: 01/20/2023] Open
Abstract
Streptococcus agalactiae (or Group B Streptococcus, GBS) is a commensal bacterium present in the intestinal and urinary tracts of approximately 30% of humans. We and others previously showed that the PI-2a pilus polymers, made of the backbone pilin PilB, the tip adhesin PilA and the cell wall anchor protein PilC, promote adhesion to host epithelia and biofilm formation. Affinity-purified PI-2a pili from GBS strain NEM316 were recognized by N-acetylneuraminic acid (NeuNAc, also known as sialic acid) specific lectins such as Elderberry Bark Lectin (EBL) suggesting that pili are sialylated. Glycan profiling with twenty different lectins combined with monosaccharide composition by HPLC suggested that affinity-purified PI-2a pili are modified by N-glycosylation and decorated with sialic acid attached to terminal galactose. Analysis of various relevant mutants in the PI-2a pilus operon by flow-cytometry and electron microscopy analyses pointed to PilA as the pilus subunit modified by glycosylation. Double labeling using PilB antibody and EBL lectin, which specifically recognizes N-acetylneuraminic acid attached to galactose in α-2, 6, revealed a characteristic binding of EBL at the tip of the pilus structures, highly reminiscent of PilA localization. Expression of a secreted form of PilA using an inducible promoter showed that this recombinant PilA binds specifically to EBL lectin when produced in the native GBS context. In silico search for potentially glycosylated asparagine residues in PilA sequence pointed to N427 and N597, which appear conserved and exposed in the close homolog RrgA from S. pneumoniae, as likely candidates. Conversion of these two asparagyl residues to glutamyl resulted in a higher instability of PilA. Our results provide the first evidence that the tip PilA adhesin can be glycosylated, and suggest that this modification is critical for PilA stability and may potentially influence interactions with the host.
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Affiliation(s)
- Eric Morello
- Institut Pasteur, Unité des Bactéries Pathogènes à Gram positif, Paris, France
- Centre National de la Recherche Scientifique (CNRS ERL 3526), Paris, France
| | - Adeline Mallet
- Institut Pasteur, Imagopole, Ultrastructural Microscopy Platform, Paris, France
| | - Yoan Konto-Ghiorghi
- Institut Pasteur, Unité des Bactéries Pathogènes à Gram positif, Paris, France
- Centre National de la Recherche Scientifique (CNRS ERL 3526), Paris, France
| | - Thibault Chaze
- Institut Pasteur, Spectrométrie de Masse Structurale et Protéomique, Paris, France
- INRA UMR 1319, MICALIS, Jouy-en-Josas, France
| | | | - Giulia Oliva
- Institut Pasteur, Unité des Bactéries Pathogènes à Gram positif, Paris, France
- Centre National de la Recherche Scientifique (CNRS ERL 3526), Paris, France
| | - Liliana Oliveira
- Institut Pasteur, Unité des Bactéries Pathogènes à Gram positif, Paris, France
- Centre National de la Recherche Scientifique (CNRS ERL 3526), Paris, France
| | - Anne-Marie Di Guilmi
- Université Grenoble Alpes, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Patrick Trieu-Cuot
- Institut Pasteur, Unité des Bactéries Pathogènes à Gram positif, Paris, France
- Centre National de la Recherche Scientifique (CNRS ERL 3526), Paris, France
| | - Shaynoor Dramsi
- Institut Pasteur, Unité des Bactéries Pathogènes à Gram positif, Paris, France
- Centre National de la Recherche Scientifique (CNRS ERL 3526), Paris, France
- * E-mail:
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21
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Lazzarin M, Cozzi R, Malito E, Martinelli M, D'Onofrio M, Maione D, Margarit I, Rinaudo CD. Noncanonical sortase‐mediated assembly of pilus type 2b in group B
Streptococcus. FASEB J 2015. [DOI: 10.1096/fj.15-272500] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Roberta Cozzi
- Novartis Vaccines and Diagnostics, GlaxoSmithKlineSienaItaly
| | - Enrico Malito
- Novartis Vaccines and Diagnostics, GlaxoSmithKlineSienaItaly
| | | | - Mariapina D'Onofrio
- Nuclear Magnetic Resonance LaboratoryDepartment of BiotechnologyUniversity of VeronaVeronaItaly
| | - Domenico Maione
- Novartis Vaccines and Diagnostics, GlaxoSmithKlineSienaItaly
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22
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Stoner TD, Weston TA, Trejo J, Doran KS. Group B streptococcal infection and activation of human astrocytes. PLoS One 2015; 10:e0128431. [PMID: 26030618 PMCID: PMC4452173 DOI: 10.1371/journal.pone.0128431] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 04/27/2015] [Indexed: 01/08/2023] Open
Abstract
Background Streptococcus agalactiae (Group B Streptococcus, GBS) is the leading cause of life-threatening meningitis in human newborns in industrialized countries. Meningitis results from neonatal infection that occurs when GBS leaves the bloodstream (bacteremia), crosses the blood-brain barrier (BBB), and enters the central nervous system (CNS), where the bacteria contact the meninges. Although GBS is known to invade the BBB, subsequent interaction with astrocytes that physically associate with brain endothelium has not been well studied. Methodology/Principal Findings We hypothesize that human astrocytes play a unique role in GBS infection and contribute to the development of meningitis. To address this, we used a well- characterized human fetal astrocyte cell line, SVG-A, and examined GBS infection in vitro. We observed that all GBS strains of representative clinically dominant serotypes (Ia, Ib, III, and V) were able to adhere to and invade astrocytes. Cellular invasion was dependent on host actin cytoskeleton rearrangements, and was specific to GBS as Streptococcus gordonii failed to enter astrocytes. Analysis of isogenic mutant GBS strains deficient in various cell surface organelles showed that anchored LTA, serine-rich repeat protein (Srr1) and fibronectin binding (SfbA) proteins all contribute to host cell internalization. Wild-type GBS also displayed an ability to persist and survive within an intracellular compartment for at least 12 h following invasion. Moreover, GBS infection resulted in increased astrocyte transcription of interleukin (IL)-1β, IL-6 and VEGF. Conclusions/Significance This study has further characterized the interaction of GBS with human astrocytes, and has identified the importance of specific virulence factors in these interactions. Understanding the role of astrocytes during GBS infection will provide important information regarding BBB disruption and the development of neonatal meningitis.
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Affiliation(s)
- Terri D. Stoner
- Department of Biology, Center for Microbial Sciences, San Diego State University, San Diego, CA, United States of America
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, United States of America
| | - Thomas A. Weston
- Department of Biology, Center for Microbial Sciences, San Diego State University, San Diego, CA, United States of America
| | - JoAnn Trejo
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, United States of America
| | - Kelly S. Doran
- Department of Biology, Center for Microbial Sciences, San Diego State University, San Diego, CA, United States of America
- Departmant of Pediatrics, School of Medicine, University of California San Diego, La Jolla, CA, United States of America
- * E-mail:
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23
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Cozzi R, Malito E, Lazzarin M, Nuccitelli A, Castagnetti A, Bottomley MJ, Margarit I, Maione D, Rinaudo CD. Structure and assembly of group B streptococcus pilus 2b backbone protein. PLoS One 2015; 10:e0125875. [PMID: 25942637 PMCID: PMC4420484 DOI: 10.1371/journal.pone.0125875] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 03/26/2015] [Indexed: 12/03/2022] Open
Abstract
Group B Streptococcus (GBS) is a major cause of invasive disease in infants. Like other Gram-positive bacteria, GBS uses a sortase C-catalyzed transpeptidation mechanism to generate cell surface pili from backbone and ancillary pilin precursor substrates. The three pilus types identified in GBS contain structural subunits that are highly immunogenic and are promising candidates for the development of a broadly-protective vaccine. Here we report the X-ray crystal structure of the backbone protein of pilus 2b (BP-2b) at 1.06Å resolution. The structure reveals a classical IgG-like fold typical of the pilin subunits of other Gram-positive bacteria. The crystallized portion of the protein (residues 185-468) encompasses domains D2 and D3 that together confer high stability to the protein due to the presence of an internal isopeptide bond within each domain. The D2+D3 region, lacking the N-terminal D1 domain, was as potent as the entire protein in conferring protection against GBS challenge in a well-established mouse model. By site-directed mutagenesis and complementation studies in GBS knock-out strains we identified the residues and motives essential for assembly of the BP-2b monomers into high-molecular weight complexes, thus providing new insights into pilus 2b polymerization.
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Lu B, Wang D, Zhou H, Zhu F, Li D, Zhang S, Shi Y, Cui Y, Huang L, Wu H. Distribution of pilus islands and alpha-like protein genes of group B Streptococcus colonized in pregnant women in Beijing, China. Eur J Clin Microbiol Infect Dis 2015; 34:1173-9. [PMID: 25669160 DOI: 10.1007/s10096-015-2342-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 01/27/2015] [Indexed: 11/30/2022]
Abstract
Group B Streptococcus (GBS) is one of the major pathogens of severe newborn sepsis and meningitis. Understanding its regional molecular epidemiology is helpful for regulating efficient prevention practice. A total of 160 GBS strains were collected from colonized pregnant women in six hospital settings in Beijing, China. Polymerase chain reaction (PCR) assays were used to identify the pilus island (PI), alp genes profiling of the alpha-like protein family, and capsular polysaccharide (cps) serotyping. The clonal relationships between strains were investigated using multilocus sequence typing (MLST). All isolates carried at least one pilus island. The most frequently detected pilus island was PI-2a alone (70 isolates, 43.8 %). The most prevalent alp gene was rib (60 isolates, 37.5 %). Moreover, a strong association was noted between alp genes, serotyping, and pilus island profiles. The GBS isolates under study hinted similar molecular epidemical characteristics in Beijing to those reported worldwide, but having their regional distributional features.
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Affiliation(s)
- B Lu
- Department of Laboratory Medicine, Civil Aviation General Hospital, No. 1 Gaojing Street, Chaoyang District, Beijing, 100123, People's Republic of China,
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25
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Wu C, Huang IH, Chang C, Reardon-Robinson ME, Das A, Ton-That H. Lethality of sortase depletion in Actinomyces oris caused by excessive membrane accumulation of a surface glycoprotein. Mol Microbiol 2014; 94:1227-41. [PMID: 25230351 DOI: 10.1111/mmi.12780] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/29/2014] [Indexed: 01/03/2023]
Abstract
Sortase, a cysteine-transpeptidase conserved in Gram-positive bacteria, anchors on the cell wall many surface proteins that facilitate bacterial pathogenesis and fitness. Genetic disruption of the housekeeping sortase in several Gram-positive pathogens reported thus far attenuates virulence, but not bacterial growth. Paradoxically, we discovered that depletion of the housekeeping sortase SrtA was lethal for Actinomyces oris; yet, all of its predicted cell wall-anchored protein substrates (AcaA-N) were individually dispensable for cell viability. Using Tn5-transposon mutagenesis to identify factors that upend lethality of srtA deletion, we uncovered a set of genetic suppressors harbouring transposon insertions within genes of a locus encoding AcaC and a LytR-CpsA-Psr (LCP)-like protein. AcaC was shown to be highly glycosylated and dependent on LCP for its glycosylation. Upon SrtA depletion, the glycosylated form of AcaC, hereby renamed GspA, was accumulated in the membrane. Overexpression of GspA in a mutant lacking gspA and srtA was lethal; conversely, cells overexpressing a GspA mutant missing a membrane-localization domain were viable. The results reveal a unique glycosylation pathway in A. oris that is coupled to cell wall anchoring catalysed by sortase SrtA. Significantly, this novel phenomenon of glyco-stress provides convenient cell-based assays for developing a new class of inhibitors against Gram-positive pathogens.
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Affiliation(s)
- Chenggang Wu
- Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA
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26
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Shaik MM, Maccagni A, Tourcier G, Di Guilmi AM, Dessen A. Structural basis of pilus anchoring by the ancillary pilin RrgC of Streptococcus pneumoniae. J Biol Chem 2014; 289:16988-97. [PMID: 24755220 DOI: 10.1074/jbc.m114.555854] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Pili are surface-attached, fibrous virulence factors that play key roles in the pathogenesis process of a number of bacterial agents. Streptococcus pneumoniae is a causative agent of pneumonia and meningitis, and the appearance of drug-resistance organisms has made its treatment challenging, especially in developing countries. Pneumococcus-expressed pili are composed of three structural proteins: RrgB, which forms the polymerized backbone, RrgA, the tip-associated adhesin, and RrgC, which presumably associates the pilus with the bacterial cell wall. Despite the fact that the structures of both RrgA and RrgB were known previously, structural information for RrgC was still lacking, impeding the analysis of a complete model of pilus architecture. Here, we report the structure of RrgC to 1.85 Å and reveal that it is a three-domain molecule stabilized by two intradomain isopeptide bonds. RrgC does not depend on pilus-specific sortases to become attached to the cell wall; instead, it binds the preformed pilus to the peptidoglycan by employing the catalytic activity of SrtA. A comprehensive model of the type 1 pilus from S. pneumoniae is also presented.
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Affiliation(s)
- Md Munan Shaik
- From the Institut de Biologie Structurale (IBS), Université Grenoble Alpes, 41 avenue des Martyrs, 38044 Grenoble, France, the Commissariat à l'Energie Atomique (CEA), 38000 Grenoble, France, the Centre National de la Recherche Scientifique (CNRS), UMR 5075, Grenoble, France, and
| | - Amandine Maccagni
- From the Institut de Biologie Structurale (IBS), Université Grenoble Alpes, 41 avenue des Martyrs, 38044 Grenoble, France, the Commissariat à l'Energie Atomique (CEA), 38000 Grenoble, France, the Centre National de la Recherche Scientifique (CNRS), UMR 5075, Grenoble, France, and
| | - Guillaume Tourcier
- From the Institut de Biologie Structurale (IBS), Université Grenoble Alpes, 41 avenue des Martyrs, 38044 Grenoble, France, the Commissariat à l'Energie Atomique (CEA), 38000 Grenoble, France, the Centre National de la Recherche Scientifique (CNRS), UMR 5075, Grenoble, France, and
| | - Anne Marie Di Guilmi
- From the Institut de Biologie Structurale (IBS), Université Grenoble Alpes, 41 avenue des Martyrs, 38044 Grenoble, France, the Commissariat à l'Energie Atomique (CEA), 38000 Grenoble, France, the Centre National de la Recherche Scientifique (CNRS), UMR 5075, Grenoble, France, and
| | - Andréa Dessen
- From the Institut de Biologie Structurale (IBS), Université Grenoble Alpes, 41 avenue des Martyrs, 38044 Grenoble, France, the Commissariat à l'Energie Atomique (CEA), 38000 Grenoble, France, the Centre National de la Recherche Scientifique (CNRS), UMR 5075, Grenoble, France, and the Brazilian National Laboratory for Biosciences (LNBio), CNPEM, Campinas, 13083-100 São Paulo, Brazil
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27
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Pilin and sortase residues critical for endocarditis- and biofilm-associated pilus biogenesis in Enterococcus faecalis. J Bacteriol 2013; 195:4484-95. [PMID: 23913319 DOI: 10.1128/jb.00451-13] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Enterococci commonly cause hospital-acquired infections, such as infective endocarditis and catheter-associated urinary tract infections. In animal models of these infections, a long hairlike extracellular protein fiber known as the endocarditis- and biofilm-associated (Ebp) pilus is an important virulence factor for Enterococcus faecalis. For Ebp and other sortase-assembled pili, the pilus-associated sortases are essential for fiber formation as they create covalent isopeptide bonds between the sortase recognition motif and the pilin-like motif of the pilus subunits. However, the molecular requirements governing the incorporation of the three pilus subunits (EbpA, EbpB, and EbpC) have not been investigated in E. faecalis. Here, we show that a Lys residue within the pilin-like motif of the EbpC subunit was necessary for EbpC polymerization. However, incorporation of EbpA into the pilus fiber only required its sortase recognition motif (LPXTG), while incorporation of EbpB only required its pilin-like motif. Only the sortase recognition motif would be required for incorporation of the pilus tip subunit, while incorporation of the base subunit would only require the pilin recognition motif. Thus, these data support a model with EbpA at the tip and EbpB at the base of an EbpC polymer. In addition, the housekeeping sortase, SrtA, was found to process EbpB and its predicted catalytic Cys residue was required for efficient cell wall anchoring of mature Ebp pili. Thus, we have defined molecular interactions involved in fiber polymerization, minor subunit organization, and pilus subcellular compartmentalization in the E. faecalis Ebp pilus system. These studies advance our understanding of unique molecular mechanisms of sortase-assembled pilus biogenesis.
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28
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Contribution of individual Ebp Pilus subunits of Enterococcus faecalis OG1RF to pilus biogenesis, biofilm formation and urinary tract infection. PLoS One 2013; 8:e68813. [PMID: 23874774 PMCID: PMC3708956 DOI: 10.1371/journal.pone.0068813] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 05/31/2013] [Indexed: 11/25/2022] Open
Abstract
The endocarditis and biofilm-associated pilus (Ebp) operon is a component of the core genome of Enterococcus faecalis that has been shown to be important for biofilm formation, adherence to host fibrinogen, collagen and platelets, and in experimental endocarditis and urinary tract infection models. Here, we created single and double deletion mutants of the pilus subunits and sortases; next, by combining western blotting, immunoelectron microscopy, and using ebpR in trans to increase pilus production, we identified EbpA as the tip pilin and EbpB as anchor at the pilus base, the latter attached to cell wall by the housekeeping sortase, SrtA. We also confirmed EbpC and Bps as the major pilin and pilin-specific sortase, respectively, both required for pilus polymerization. Interestingly, pilus length was increased and the number of pili decreased by deleting ebpA, while control overexpression of ebpA in trans restored wild-type levels, suggesting a dual role for EbpA in both initiation and termination of pilus polymerization. We next investigated the contribution of each pilin subunit to biofilm formation and UTI. Significant reduction in biofilm formation was observed with deletion of ebpA or ebpC (P<0.001) while ebpB was found to be dispensable; a similar result was seen in kidney CFUs in experimental UTI (ΔebpA, ΔebpC, P≤0.0093; ΔebpB, non-significant, each vs. OG1RF). Hence, our data provide important structural and functional information about these ubiquitous E. faecalis pili and, based on their demonstrated importance in biofilm and infection, suggest EbpA and EbpC as potential targets for antibody-based therapeutic approaches.
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Understanding the molecular determinants driving the immunological specificity of the protective pilus 2a backbone protein of group B streptococcus. PLoS Comput Biol 2013; 9:e1003115. [PMID: 23825940 PMCID: PMC3694817 DOI: 10.1371/journal.pcbi.1003115] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 05/10/2013] [Indexed: 11/19/2022] Open
Abstract
The pilus 2a backbone protein (BP-2a) is one of the most structurally and functionally characterized components of a potential vaccine formulation against Group B Streptococcus. It is characterized by six main immunologically distinct allelic variants, each inducing variant-specific protection. To investigate the molecular determinants driving the variant immunogenic specificity of BP-2a, in terms of single residue contributions, we generated six monoclonal antibodies against a specific protein variant based on their capability to recognize the polymerized pili structure on the bacterial surface. Three mAbs were also able to induce complement-dependent opsonophagocytosis killing of live GBS and target the same linear epitope present in the structurally defined and immunodominant domain D3 of the protein. Molecular docking between the modelled scFv antibody sequences and the BP-2a crystal structure revealed the potential role at the binding interface of some non-conserved antigen residues. Mutagenesis analysis confirmed the necessity of a perfect balance between charges, size and polarity at the binding interface to obtain specific binding of mAbs to the protein antigen for a neutralizing response. Group B Streptococcus (GBS) is the leading cause of neonatal invasive diseases and pili, as long filamentous fibers protruding from the bacterial surface, have been discovered as important virulence factors and potential vaccine candidates. The bacterial surface is the main interface between host and pathogen, and the ability of the host to identify molecular determinants that are unique to pathogens has a crucial role for microbial clearance. Here, we describe a strategy to investigate the immunological and structural proprieties of a protective pilus protein, by elucidating the molecular mechanisms, in terms of single residue contributions, by which functional epitopes guide bacterial clearance. We generated neutralizing monoclonal antibodies raised against the protein and identified the epitope region in the antigen. Then, we performed computational docking analysis of the antibodies in complex with the target antigen and identified specific residues on the target protein that mediate hydrophobic interactions at the binding interface. Our results suggest that a perfect balance of shape and charges at the binding interface in antibody/antigen interactions is crucial for the antibody/antigen complex in driving a successful neutralizing response. Knowing the native molecular architecture of protective determinants might be useful to selectively engineer the antigens for effective vaccine formulations.
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Jin D, Chen C, Li L, Lu S, Li Z, Zhou Z, Jing H, Xu Y, Du P, Wang H, Xiong Y, Zheng H, Bai X, Sun H, Wang L, Ye C, Gottschalk M, Xu J. Dynamics of fecal microbial communities in children with diarrhea of unknown etiology and genomic analysis of associated Streptococcus lutetiensis. BMC Microbiol 2013; 13:141. [PMID: 23782707 PMCID: PMC3716944 DOI: 10.1186/1471-2180-13-141] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 06/10/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The sequences of the 16S rRNA genes extracted from fecal samples provide insights into the dynamics of fecal microflora. This potentially gives valuable etiological information for patients whose conditions have been ascribed to unknown pathogens, which cannot be accomplished using routine culture methods. We studied 33 children with diarrhea who were admitted to the Children's Hospital in Shanxi Province during 2006. RESULTS Nineteen of 33 children with diarrhea could not be etiologically diagnosed by routine culture and polymerase chain reaction methods. Eleven of 19 children with diarrhea of unknown etiology had Streptococcus as the most dominant fecal bacterial genus at admission. Eight of nine children whom three consecutive fecal samples were collected had Streptococcus as the dominant fecal bacterial genus, including three in the Streptococcus bovis group and three Streptococcus sp., which was reduced during and after recovery. We isolated strains that were possibly from the S. bovis group from feces sampled at admission, which were then identified as Streptococcus lutetiensis from one child and Streptococcus gallolyticus subsp. pasteurianus from two children. We sequenced the genome of S. lutetiensis and identified five antibiotic islands, two pathogenicity islands, and five unique genomic islands. The identified virulence genes included hemolytic toxin cylZ of Streptococcus agalactiae and sortase associated with colonization of pathogenic streptococci. CONCLUSIONS We identified S. lutetiensis and S. gallolyticus subsp. pasteurianus from children with diarrhea of unknown etiology, and found pathogenic islands and virulence genes in the genome of S. lutetiensis.
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Affiliation(s)
- Dong Jin
- State Key Laboratory for Infectious Disease Prevention and Control, and National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China
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Pilus gene pool variation and the virulence of Corynebacterium diphtheriae clinical isolates during infection of a nematode. J Bacteriol 2013; 195:3774-83. [PMID: 23772071 DOI: 10.1128/jb.00500-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Toxigenic Corynebacterium diphtheriae strains cause diphtheria in humans. The toxigenic C. diphtheriae isolate NCTC13129 produces three distinct heterotrimeric pili that contain SpaA, SpaD, and SpaH, making up the shaft structure. The SpaA pili are known to mediate bacterial adherence to pharyngeal epithelial cells. However, to date little is known about the expression of different pili in various clinical isolates and their importance in bacterial pathogenesis. Here, we characterized a large collection of C. diphtheriae clinical isolates for their pilin gene pool by PCR and for the expression of the respective pilins by immunoblotting with antibodies against Spa pilins. Consistent with the role of a virulence factor, the SpaA-type pili were found to be prevalent among the isolates, and most significantly, corynebacterial adherence to pharyngeal epithelial cells was strictly correlated with isolates that were positive for the SpaA pili. By comparison, the isolates were heterogeneous for the presence of SpaD- and SpaH-type pili. Importantly, using Caenorhabditis elegans as a model host for infection, we show here that strain NCTC13129 rapidly killed the nematodes, the phenotype similar to isolates that were positive for toxin and all pilus types. In contrast, isogenic mutants of NCTC13129 lacking SpaA-type pili or devoid of toxin and SpaA pili exhibited delayed killing of nematodes with similar kinetics. Consistently, nontoxigenic or toxigenic isolates that lack one, two, or all three pilus types were also attenuated in virulence. This work signifies the important role of pili in corynebacterial pathogenesis and provides a simple host model to identify additional virulence factors.
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Cozzi R, Zerbini F, Assfalg M, D'Onofrio M, Biagini M, Martinelli M, Nuccitelli A, Norais N, Telford JL, Maione D, Rinaudo CD. Group B Streptococcus pilus sortase regulation: a single mutation in the lid region induces pilin protein polymerization in vitro. FASEB J 2013; 27:3144-54. [PMID: 23631841 DOI: 10.1096/fj.13-227793] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Gram-positive bacteria build pili on their cell surface via a class C sortase-catalyzed transpeptidation mechanism from pilin protein substrates. Despite the availability of several crystal structures, pilus-related C sortases remain poorly characterized to date, and their mechanisms of transpeptidation and regulation need to be further investigated. The available 3-dimensional structures of these enzymes reveal a typical sortase fold, except for the presence of a unique feature represented by an N-terminal highly flexible loop known as the "lid." This region interacts with the residues composing the catalytic triad and covers the active site, thus maintaining the enzyme in an autoinhibited state and preventing the accessibility to the substrate. It is believed that enzyme activation may occur only after lid displacement from the catalytic domain. In this work, we provide the first direct evidence of the regulatory role of the lid, demonstrating that it is possible to obtain in vitro an efficient polymerization of pilin subunits using an active C sortase lid mutant carrying a single residue mutation in the lid region. Moreover, biochemical analyses of this recombinant mutant reveal that the lid confers thermodynamic and proteolytic stability to the enzyme.
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Affiliation(s)
- Roberta Cozzi
- Novartis Vaccines and Diagnostics, Via Fiorentina 1, 53100 Siena, Italy
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Abstract
Pili or fimbriae are recognized as essential virulence determinants assembled on the bacterial surface. Gram-positive bacteria produce covalently linked pilus structures that are distinct from gram-negative counterparts. In this chapter, we describe three commonly used techniques to extract, detect, and visualize pili from gram-positive bacteria: (1) Western blot analysis, (2) Immuno-Electron Microscopy, and (3) Atomic Force Microscopy.
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Complete genome sequence of Streptococcus agalactiae ZQ0910, a pathogen causing meningoencephalitis in the GIFT strain of Nile tilapia (Oreochromis niloticus). J Bacteriol 2012; 194:5132-3. [PMID: 22933761 DOI: 10.1128/jb.01080-12] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptococcus agalactiae (group B streptococcus [GBS]) is a pathogen that causes meningoencephalitis in Nile tilapia (Oreochromis niloticus). Here, we reported the complete genome sequence of S. agalactiae strain ZQ0910, which was isolated from the GIFT strain of Nile tilapia in Guangdong, China.
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Structural basis for group B streptococcus pilus 1 sortases C regulation and specificity. PLoS One 2012; 7:e49048. [PMID: 23145064 PMCID: PMC3493515 DOI: 10.1371/journal.pone.0049048] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 10/03/2012] [Indexed: 11/19/2022] Open
Abstract
Gram-positive bacteria assemble pili through class C sortase enzymes specialized in polymerizing pilin subunits into covalently linked, high-molecular-weight, elongated structures. Here we report the crystal structures of two class C sortases (SrtC1 and SrtC2) from Group B Streptococcus (GBS) Pilus Island 1. The structures show that both sortases are comprised of two domains: an 8-stranded β-barrel catalytic core conserved among all sortase family members and a flexible N-terminal region made of two α-helices followed by a loop, known as the lid, which acts as a pseudo-substrate. In vitro experiments performed with recombinant SrtC enzymes lacking the N-terminal portion demonstrate that this region of the enzyme is dispensable for catalysis but may have key roles in substrate specificity and regulation. Moreover, in vitro FRET-based assays show that the LPXTG motif common to many sortase substrates is not the sole determinant of sortase C specificity during pilin protein recognition.
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Danne C, Dramsi S. Pili of gram-positive bacteria: roles in host colonization. Res Microbiol 2012; 163:645-58. [PMID: 23116627 DOI: 10.1016/j.resmic.2012.10.012] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 10/11/2012] [Indexed: 02/06/2023]
Abstract
In the last decade, pili, which are encoded within pathogenicity islands, have been found in many Gram-positive bacteria, including the major streptococcal and enterococcal pathogens. These long proteinaceous polymers extending from the bacterial surface are constituted of covalently linked pilin subunits, which play major roles in adhesion and host colonization. They are also involved in biofilm formation, a characteristic life-style of the bacteria constituting the oral flora. Pili are highly immunogenic structures that are under the selective pressure of host immune responses. Indeed, pilus expression was found to be heterogeneous in several bacteria with the co-existence of two subpopulations expressing various levels of pili. The molecular mechanisms underlying this complex regulation are poorly characterized except for Streptococcus pneumoniae. In this review, we will discuss the roles of Gram-positive bacteria pili in adhesion to host extracellular matrix proteins, tissue tropism, biofilm formation, modulation of innate immune responses and their contribution to virulence, and in a second part the regulation of their expression. This overview should help to understand the rise of pili as an intensive field of investigation and pinpoints the areas that need further study.
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Affiliation(s)
- Camille Danne
- Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram-positif, Paris F-75015, France
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Madzivhandila M, Adrian PV, Cutland CL, Kuwanda L, Madhi SA. Distribution of pilus islands of group B streptococcus associated with maternal colonization and invasive disease in South Africa. J Med Microbiol 2012; 62:249-253. [PMID: 23065545 DOI: 10.1099/jmm.0.052951-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Group B streptococcus (GBS) is a leading cause of neonatal sepsis. Sortase-dependent pilus-like structures have been identified on the surface of GBS, and have been found to be important in the adhesion and attachment of GBS to host cells. Three pilus island alleles, PI-1, PI-2a and PI-2b, have been described, and their proteins are being explored as vaccine candidates. The pilus islands from 541 colonization isolates and 284 invasive isolates were characterized by PCR. All isolates carried at least one pilus island, and they were identified alone or in combinations at the following overall frequencies: PI-2a, 29.8 %; PI-2b, 0.2 %; PI-1+PI-2a, 24.8 %; and PI-1+PI-2b, 45.1 %. A combination of PI-1+PI-2a (28.7 vs 17.6 %) was more common among colonizing compared with invasive isolates. Conversely, a combination of PI-1+PI-2b (37.2 vs 60.2 %) was more frequently associated with invasive disease compared to colonization. There was a strong association between pilus islands when adjusted for serotype distribution, PI-2a was identified in 92.6 % of colonizing and 90.0 % of invasive serotype Ia isolates, whereas serotype III was associated with co-expression of a PI-1 and PI-2b among 84.6 % of colonizing and 96.5 % of invasive isolates. Based on this homogeneity of pilus island distribution, a pilus-based vaccine developed for Europe and the USA will have similar coverage in South Africa.
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Affiliation(s)
- Mashudu Madzivhandila
- Department of Science and Technology/National Research Foundation: Vaccine Preventable Diseases, University of the Witwatersrand, Johannesburg, South Africa
| | - Peter V Adrian
- Department of Science and Technology/National Research Foundation: Vaccine Preventable Diseases, University of the Witwatersrand, Johannesburg, South Africa
| | - Clare L Cutland
- Department of Science and Technology/National Research Foundation: Vaccine Preventable Diseases, University of the Witwatersrand, Johannesburg, South Africa
| | - Locadiah Kuwanda
- Department of Science and Technology/National Research Foundation: Vaccine Preventable Diseases, University of the Witwatersrand, Johannesburg, South Africa
| | - Shabir A Madhi
- National Institute for Communicable Diseases, Johannesburg, South Africa
- Department of Science and Technology/National Research Foundation: Vaccine Preventable Diseases, University of the Witwatersrand, Johannesburg, South Africa
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Dramsi S, Morello E, Poyart C, Trieu-Cuot P. Epidemiologically and clinically relevant Group B Streptococcus isolates do not bind collagen but display enhanced binding to human fibrinogen. Microbes Infect 2012; 14:1044-8. [DOI: 10.1016/j.micinf.2012.07.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 07/02/2012] [Accepted: 07/02/2012] [Indexed: 11/26/2022]
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Becherelli M, Manetti AGO, Buccato S, Viciani E, Ciucchi L, Mollica G, Grandi G, Margarit I. The ancillary protein 1 of Streptococcus pyogenes FCT-1 pili mediates cell adhesion and biofilm formation through heterophilic as well as homophilic interactions. Mol Microbiol 2012; 83:1035-47. [PMID: 22320452 PMCID: PMC3490378 DOI: 10.1111/j.1365-2958.2012.07987.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Gram-positive pili are known to play a role in bacterial adhesion to epithelial cells and in the formation of biofilm microbial communities. In the present study we undertook the functional characterization of the pilus ancillary protein 1 (AP1_M6) from Streptococcus pyogenes isolates expressing the FCT-1 pilus variant, known to be strong biofilm formers. Cell binding and biofilm formation assays using S. pyogenes in-frame deletion mutants, Lactococcus expressing heterologous FCT-1 pili and purified recombinant AP1_M6, indicated that this pilin is a strong cell adhesin that is also involved in bacterial biofilm formation. Moreover, we show that AP1_M6 establishes homophilic interactions that mediate inter-bacterial contact, possibly promoting bacterial colonization of target epithelial cells in the form of three-dimensional microcolonies. Finally, AP1_M6 knockout mutants were less virulent in mice, indicating that this protein is also implicated in GAS systemic infection.
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Affiliation(s)
- Marco Becherelli
- Novartis Vaccines and Diagnostics, Via Fiorentina 1, Siena, Italy
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Cozzi R, Nuccitelli A, D'Onofrio M, Necchi F, Rosini R, Zerbini F, Biagini M, Norais N, Beier C, Telford JL, Grandi G, Assfalg M, Zacharias M, Maione D, Rinaudo CD. New insights into the role of the glutamic acid of the E‐box motif in group B
Streptococcus
pilus 2a assembly. FASEB J 2012; 26:2008-18. [DOI: 10.1096/fj.11-196378] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Mariapina D'Onofrio
- Nuclear Magnetic Resonance LaboratoryDepartment of BiotechnologyUniversity of VeronaVeronaItaly
| | | | | | | | | | | | | | | | | | - Michael Assfalg
- Nuclear Magnetic Resonance LaboratoryDepartment of BiotechnologyUniversity of VeronaVeronaItaly
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Abstract
In Gram-positive bacteria proteins are displayed on the cell surface using sortase enzymes. These cysteine transpeptidases join proteins bearing an appropriate sorting signal to strategically positioned amino groups on the cell surface. Working alone, or in concert with other enzymes, sortases either attach proteins to the cross-bridge peptide of the cell wall or they link proteins together to form pili. Because surface proteins play a fundamental role in microbial physiology and are frequently virulence factors, sortase enzymes have been intensely studied since their discovery a little more than a decade ago. Based on their primary sequences and functions sortases can be partitioned into distinct families called class A to F enzymes. Most bacteria elaborate their surfaces using more than one type of sortase that function non-redundantly by recognizing unique sorting signals within their protein substrates. Here we review what is known about the functions of these enzymes and the molecular basis of catalysis. Particular emphasis is placed on 'pilin' specific class C sortases that construct structurally complex pili. Exciting new data have revealed that these enzymes are amazingly promiscuous in the substrates that they can employ and that there is a startling degree of diversity in their mechanism of action. We also review recent data that suggest that sortases are targeted to specific sites on the cell surface where they work with other sortases and accessory factors to properly function.
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Affiliation(s)
- Thomas Spirig
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
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Khare B, Fu ZQ, Huang IH, Ton-That H, Narayana SVL. The crystal structure analysis of group B Streptococcus sortase C1: a model for the "lid" movement upon substrate binding. J Mol Biol 2011; 414:563-77. [PMID: 22033482 DOI: 10.1016/j.jmb.2011.10.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 10/06/2011] [Accepted: 10/12/2011] [Indexed: 01/15/2023]
Abstract
A unique feature of the class-C-type sortases, enzymes essential for Gram-positive pilus biogenesis, is the presence of a flexible "lid" anchored in the active site. However, the mechanistic details of the "lid" displacement, suggested to be a critical prelude for enzyme catalysis, are not yet known. This is partly due to the absence of enzyme-substrate and enzyme-inhibitor complex crystal structures. We have recently described the crystal structures of the Streptococcus agalactiae SAG2603 V/R sortase SrtC1 in two space groups (type II and type III) and that of its "lid" mutant and proposed a role of the "lid" as a protector of the active-site hydrophobic environment. Here, we report the crystal structures of SAG2603 V/R sortase C1 in a different space group (type I) and that of its complex with a small-molecule cysteine protease inhibitor. We observe that the catalytic Cys residue is covalently linked to the small-molecule inhibitor without lid displacement. However, the type I structure provides a view of the sortase SrtC1 lid displacement while having structural elements similar to a substrate sorting motif suitably positioned in the active site. We propose that these major conformational changes seen in the presence of a substrate mimic in the active site may represent universal features of class C sortase substrate recognition and enzyme activation.
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Affiliation(s)
- Baldeep Khare
- Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Necchi F, Nardi-Dei V, Biagini M, Assfalg M, Nuccitelli A, Cozzi R, Norais N, Telford JL, Rinaudo CD, Grandi G, Maione D. Sortase A substrate specificity in GBS pilus 2a cell wall anchoring. PLoS One 2011; 6:e25300. [PMID: 21991306 PMCID: PMC3186789 DOI: 10.1371/journal.pone.0025300] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 08/31/2011] [Indexed: 11/18/2022] Open
Abstract
Streptococcus agalactiae, also referred to as Group B Streptococcus (GBS), is one of the most common causes of life-threatening bacterial infections in infants. In recent years cell surface pili have been identified in several Gram-positive bacteria, including GBS, as important virulence factors and promising vaccine candidates. In GBS, three structurally distinct types of pili have been discovered (pilus 1, 2a and 2b), whose structural subunits are assembled in high-molecular weight polymers by specific class C sortases. In addition, the highly conserved housekeeping sortase A (SrtA), whose main role is to link surface proteins to bacterial cell wall peptidoglycan by a transpeptidation reaction, is also involved in pili cell wall anchoring in many bacteria. Through in vivo mutagenesis, we demonstrate that the LPXTG sorting signal of the minor ancillary protein (AP2) is essential for pilus 2a anchoring. We successfully produced a highly purified recombinant SrtA (SrtA(ΔN40)) able to specifically hydrolyze the sorting signal of pilus 2a minor ancillary protein (AP2-2a) and catalyze in vitro the transpeptidation reaction between peptidoglycan analogues and the LPXTG motif, using both synthetic fluorescent peptides and recombinant proteins. By contrast, SrtA(ΔN40) does not catalyze the transpeptidation reaction with substrate-peptides mimicking sorting signals of the other pilus 2a subunits (the backbone protein and the major ancillary protein). Thus, our results add further insight into the proposed model of GBS pilus 2a assembly, in which SrtA is required for pili cell wall covalent attachment, acting exclusively on the minor accessory pilin, representing the terminal subunit located at the base of the pilus.
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Affiliation(s)
| | | | | | - Michael Assfalg
- Department of Biotechnology, University of Verona, Verona, Italy
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Banerjee A, Kim BJ, Carmona EM, Cutting AS, Gurney MA, Carlos C, Feuer R, Prasadarao NV, Doran KS. Bacterial Pili exploit integrin machinery to promote immune activation and efficient blood-brain barrier penetration. Nat Commun 2011; 2:462. [PMID: 21897373 PMCID: PMC3195231 DOI: 10.1038/ncomms1474] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 08/10/2011] [Indexed: 12/25/2022] Open
Abstract
Group B Streptococcus (GBS) is the leading cause of meningitis in newborn infants. Bacterial cell surface appendages, known as pili, have been recently described in streptococcal pathogens, including GBS. The pilus tip adhesin, PilA, contributes to GBS adherence to blood-brain barrier (BBB) endothelium; however, the host receptor and the contribution of PilA in central nervous system (CNS) disease pathogenesis are unknown. Here we show that PilA binds collagen, which promotes GBS interaction with the α₂β₁ integrin resulting in activation of host chemokine expression and neutrophil recruitment during infection. Mice infected with the PilA-deficient mutant exhibit delayed mortality, a decrease in neutrophil infiltration and bacterial CNS dissemination. We find that PilA-mediated virulence is dependent on neutrophil influx as neutrophil depletion results in a decrease in BBB permeability and GBS-BBB penetration. Our results suggest that the bacterial pilus, specifically the PilA adhesin, has a dual role in immune activation and bacterial entry into the CNS.
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Affiliation(s)
- Anirban Banerjee
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
| | - Brandon J. Kim
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
- These authors contributed equally to this work
| | - Ellese M. Carmona
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
- These authors contributed equally to this work
| | - Andrew S. Cutting
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
| | - Michael A. Gurney
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
| | - Chris Carlos
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
| | - Ralph Feuer
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
| | - Nemani V. Prasadarao
- Division of Infectious Diseases, Department of Pediatrics, Childrens Hospital Los Angeles and University of Southern California Keck School of Medicine, Los Angeles, California 90027, USA
| | - Kelly S. Doran
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
- Department of Pediatrics, University of California–San Diego School of Medicine, La Jolla, California 92093, USA
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Nakata M, Kimura KR, Sumitomo T, Wada S, Sugauchi A, Oiki E, Higashino M, Kreikemeyer B, Podbielski A, Okahashi N, Hamada S, Isoda R, Terao Y, Kawabata S. Assembly mechanism of FCT region type 1 pili in serotype M6 Streptococcus pyogenes. J Biol Chem 2011; 286:37566-77. [PMID: 21880740 DOI: 10.1074/jbc.m111.239780] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human pathogen Streptococcus pyogenes produces diverse pili depending on the serotype. We investigated the assembly mechanism of FCT type 1 pili in a serotype M6 strain. The pili were found to be assembled from two precursor proteins, the backbone protein T6 and ancillary protein FctX, and anchored to the cell wall in a manner that requires both a housekeeping sortase enzyme (SrtA) and pilus-associated sortase enzyme (SrtB). SrtB is primarily required for efficient formation of the T6 and FctX complex and subsequent polymerization of T6, whereas proper anchoring of the pili to the cell wall is mainly mediated by SrtA. Because motifs essential for polymerization of pilus backbone proteins in other Gram-positive bacteria are not present in T6, we sought to identify the functional residues involved in this process. Our results showed that T6 encompasses the novel VAKS pilin motif conserved in streptococcal T6 homologues and that the lysine residue (Lys-175) within the motif and cell wall sorting signal of T6 are prerequisites for isopeptide linkage of T6 molecules. Because Lys-175 and the cell wall sorting signal of FctX are indispensable for substantial incorporation of FctX into the T6 pilus shaft, FctX is suggested to be located at the pilus tip, which was also implied by immunogold electron microscopy findings. Thus, the elaborate assembly of FCT type 1 pili is potentially organized by sortase-mediated cross-linking between sorting signals and the amino group of Lys-175 positioned in the VAKS motif of T6, thereby displaying T6 and FctX in a temporospatial manner.
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Affiliation(s)
- Masanobu Nakata
- Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita-Osaka, 565-0871, Japan
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Khare B, Krishnan V, Rajashankar KR, I-Hsiu H, Xin M, Ton-That H, Narayana SV. Structural differences between the Streptococcus agalactiae housekeeping and pilus-specific sortases: SrtA and SrtC1. PLoS One 2011; 6:e22995. [PMID: 21912586 PMCID: PMC3166054 DOI: 10.1371/journal.pone.0022995] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Accepted: 07/06/2011] [Indexed: 11/19/2022] Open
Abstract
The assembly of pili on the cell wall of Gram-positive bacteria requires transpeptidase enzymes called sortases. In Streptococcus agalactiae, the PI-1 pilus island of strain 2603V/R encodes two pilus-specific sortases (SrtC1 and SrtC2) and three pilins (GBS80, GBS52 and GBS104). Although either pilus-specific sortase is sufficient for the polymerization of the major pilin, GBS80, incorporation of the minor pilins GBS52 and GBS104 into the pilus structure requires SrtC1 and SrtC2, respectively. The S. agalactiae housekeeping sortase, SrtA, whose gene is present at a different location and does not catalyze pilus polymerization, was shown to be involved in cell wall anchoring of pilus polymers. To understand the structural basis of sortases involved in such diverse functions, we determined the crystal structures of S. agalactiae SrtC1 and SrtA. Both enzymes are made of an eight-stranded beta-barrel core with variations in their active site architecture. SrtA exhibits a catalytic triad arrangement similar to that in Streptococcus pyogenes SrtA but different from that in Staphylococcus aureus SrtA. In contrast, the SrtC1 enzyme contains an N-terminal helical domain and a ‘lid’ in its putative active site, which is similar to that seen in Streptococcus pneumoniae pilus-specific sortases, although with subtle differences in positioning and composition. To understand the effect of such differences on substrate recognition, we have also determined the crystal structure of a SrtC1 mutant, in which the conserved DP(W/F/Y) motif was replaced with the sorting signal motif of GBS80, IPNTG. By comparing the structures of WT wild type SrtA and SrtC1 and the ‘lid’ mutant of SrtC1, we propose that structural elements within the active site and the lid may be important for defining the role of specific sortase in pili biogenesis.
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Affiliation(s)
- B. Khare
- Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - V. Krishnan
- Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - K. R. Rajashankar
- NE-CAT, Advanced Photon Source, Argonne National Laboratory, Chicago, Illinois, United States of America
| | - H. I-Hsiu
- University of Texas Health Science Center, Houston, Texas, United States of America
| | - M. Xin
- University of Texas Health Science Center, Houston, Texas, United States of America
| | - H. Ton-That
- University of Texas Health Science Center, Houston, Texas, United States of America
| | - S. V. Narayana
- Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- * E-mail:
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Papasergi S, Brega S, Mistou MY, Firon A, Oxaran V, Dover R, Teti G, Shai Y, Trieu-Cuot P, Dramsi S. The GBS PI-2a pilus is required for virulence in mice neonates. PLoS One 2011; 6:e18747. [PMID: 21525979 PMCID: PMC3078112 DOI: 10.1371/journal.pone.0018747] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 03/10/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Streptococcus agalactiae (Group B Streptococcus) is a leading cause of sepsis and meningitis in newborns. Most bacterial pathogens, including gram-positive bacteria, have long filamentous structures known as pili extending from their surface. Although pili are described as adhesive organelles, they have been also implicated in many other functions including thwarting the host immune responses. We previously characterized the pilus-encoding operon PI-2a (gbs1479-1474) in strain NEM316. This pilus is composed of three structural subunit proteins: PilA (Gbs1478), PilB (Gbs1477), and PilC (Gbs1474), and its assembly involves two class C sortases (SrtC3 and SrtC4). PilB, the bona fide pilin, is the major component whereas PilA, the pilus associated adhesin, and PilC the pilus anchor are both accessory proteins incorporated into the pilus backbone. METHODOLOGY/PRINCIPAL FINDINGS In this study, the role of the major pilin subunit PilB was tested in systemic virulence using 6-weeks old and newborn mice. Notably, the non-piliated ΔpilB mutant was less virulent than its wild-type counterpart in the newborn mice model. Next, we investigated the possible role(s) of PilB in resistance to innate immune host defenses, i.e. resistance to macrophage killing and to antimicrobial peptides. Phagocytosis and survival of wild-type NEM316 and its isogenic ΔpilB mutant in immortalized RAW 264.7 murine macrophages were not significantly different whereas the isogenic ΔsodA mutant was more susceptible to killing. These results were confirmed using primary peritoneal macrophages. We also tested the activities of five cationic antimicrobial peptides (AMP-1D, LL-37, colistin, polymyxin B, and mCRAMP) and found no significant difference between WT and ΔpilB strains whereas the isogenic dltA mutant showed increased sensitivity. CONCLUSIONS/SIGNIFICANCE These results question the previously described role of PilB pilus in resistance to the host immune defenses. Interestingly, PilB was found to be important for virulence in the neonatal context.
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Affiliation(s)
- Salvatore Papasergi
- Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram-Positif, Paris, France
- URA CNRS 2172, Paris, France
- The Elie Metchnikoff Deparment, University of Messina, Messina, Italy
| | - Sara Brega
- Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram-Positif, Paris, France
- URA CNRS 2172, Paris, France
| | - Michel-Yves Mistou
- Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram-Positif, Paris, France
- URA CNRS 2172, Paris, France
- INRA, MICALIS UMR 1319, Equipe Paroi, Jouy-en-Josas, France
| | - Arnaud Firon
- Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram-Positif, Paris, France
- URA CNRS 2172, Paris, France
| | - Virginie Oxaran
- INRA, MICALIS UMR1319, Equipe Protéines de Surface Utiles, Jouy-en-Josas, France
| | - Ron Dover
- Depatment of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Giuseppe Teti
- The Elie Metchnikoff Deparment, University of Messina, Messina, Italy
| | - Yechiel Shai
- Depatment of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Patrick Trieu-Cuot
- Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram-Positif, Paris, France
- URA CNRS 2172, Paris, France
| | - Shaynoor Dramsi
- Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram-Positif, Paris, France
- URA CNRS 2172, Paris, France
- * E-mail:
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Cozzi R, Malito E, Nuccitelli A, D'Onofrio M, Martinelli M, Ferlenghi I, Grandi G, Telford JL, Maione D, Rinaudo CD. Structure analysis and site-directed mutagenesis of defined key residues and motives for pilus-related sortase C1 in group B Streptococcus. FASEB J 2011; 25:1874-86. [PMID: 21357525 DOI: 10.1096/fj.10-174797] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In group B Streptococcus (GBS), 3 structurally distinct types of pili have been discovered as potential virulence factors and vaccine candidates. The pilus-forming proteins are assembled into high-molecular-weight polymers via a transpeptidation mechanism mediated by specific class C sortases. Using a multidisciplinary approach including bioinformatics, structural and biochemical studies, and in vivo mutagenesis, we performed a broad characterization of GBS sortase C1 of pilus island 2a. The high-resolution X-ray structure of the enzyme revealed that the active site, into the β-barrel core of the enzyme, is made of the catalytic triad His157-Cys219-Arg228 and covered by a loop, known as the "lid." We show that the catalytic triad and the predicted N- and C-terminal transmembrane regions are required for the enzyme activity. Interestingly, by in vivo complementation mutagenesis studies, we found that the deletion of the entire lid loop or mutations in specific lid key residues had no effect on catalytic activity of the enzyme. In addition, kinetic characterizations of recombinant enzymes indicate that the lid mutants can still recognize and cleave the substrate-mimicking peptide at least as well as the wild-type protein.
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Affiliation(s)
- Roberta Cozzi
- Novartis Vaccines and Diagnostics, Via Fiorentina 1, 53100 Siena, Italy
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Chang C, Mandlik A, Das A, Ton-That H. Cell surface display of minor pilin adhesins in the form of a simple heterodimeric assembly in Corynebacterium diphtheriae. Mol Microbiol 2011; 79:1236-47. [PMID: 21205008 DOI: 10.1111/j.1365-2958.2010.07515.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Pilus assembly in Gram-positive bacteria occurs by a two-step mechanism, whereby pilins are polymerized and then covalently anchored to the cell wall. In Corynebacterium diphtheriae, the pilin-specific sortase SrtA catalyses polymerization of the SpaA-type pilus, consisting of the shaft pilin SpaA, tip pilin SpaC and minor pilin SpaB. Cell wall anchoring of the SpaA polymers is triggered when SrtA incorporates SpaB into the pilus base via lysine-mediated transpeptidation; anchoring to the cell wall peptidoglycan is subsequently catalysed by the housekeeping sortase SrtF. Here we show that SpaB and SpaC formed a heterodimer independent of SpaA polymerization. SrtA was absolutely required for the formation of the SpaBC heterodimer, while SrtF facilitated the optimal cell wall anchoring of this heterodimer. Alanine substitution of the SpaB lysine residue K139 or truncation of the SpaB cell wall-sorting signal (CWSS) abolished assembly of the SpaBC heterodimer, hence underscoring SpaB function in transpeptidation and cell wall linkage. Importantly, sortase specificity for the cell wall-anchoring step was found to be dependent on the LAFTG motif within the SpaB CWSS. Thus, C. diphtheriae employs a common sortase-catalysed mechanism involving lysine-mediated transpeptidation to generate both adhesive pilus and simple heterodimeric structures on the bacterial the cell wall.
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Affiliation(s)
- Chungyu Chang
- Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USA
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50
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The minor pilin subunit Sgp2 is necessary for assembly of the pilus encoded by the srtG cluster of Streptococcus suis. J Bacteriol 2010; 193:822-31. [PMID: 21148736 DOI: 10.1128/jb.01555-09] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gram-positive pili are composed of covalently bound pilin subunits whose assembly is mediated via a pilus-specific sortase(s). Major subunits constitute the pilus backbone and are therefore essential for pilus formation. Minor subunits are also incorporated into the pilus, but they are considered to be dispensable for backbone formation. The srtG cluster is one of the putative pilus gene clusters identified in the major swine pathogen Streptococcus suis. It consists of one sortase gene (srtG) and two putative pilin subunit genes (sgp1 and sgp2). In this study, by constructing mutants for each of the genes in the cluster and by both immunoblotting and immunogold electron microscopic analysis with antibodies against Sgp1 and Sgp2, we found that the srtG cluster mediates the expression of pilus-like structures in S. suis strain 89/1591. In this pilus, Sgp1 forms the backbone, whereas Sgp2 is incorporated as the minor subunit. In accordance with the current model of pilus assembly by Gram-positive organisms, the major subunit Sgp1 was indispensable for backbone formation and the cognate sortase SrtG mediated the polymerization of both subunits. However, unlike other well-characterized Gram-positive bacterial pili, the minor subunit Sgp2 was required for polymerization of the major subunit Sgp1. Because Sgp2 homologues are encoded in several other Gram-positive bacterial pilus gene clusters, in some types of pili, minor pilin subunits may contribute to backbone formation by a novel mechanism.
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