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Navarro-Garcia F. Serine proteases autotransporter of Enterobacteriaceae: Structures, subdomains, motifs, functions, and targets. Mol Microbiol 2023; 120:178-193. [PMID: 37392318 DOI: 10.1111/mmi.15116] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 06/12/2023] [Accepted: 06/13/2023] [Indexed: 07/03/2023]
Abstract
Serine protease autotransporters of Enterobacteriaceae (SPATE) constitute a superfamily of virulence factors, resembling the trypsin-like superfamily of serine proteases. SPATEs accomplish multiple functions associated to disease development of their hosts, which could be the consequence of SPATE cleavage of host cell components. SPATEs have been divided into class-1 and class-2 based on structural differences and biological effects, including similar substrate specificity, cytotoxic effects on cultured cells, and enterotoxin activity on intestinal tissues for class-1 SPATEs, whereas most class-2 SPATEs exhibit a lectin-like activity with a predilection to degrade a variety of mucins, including leukocyte surface O-glycoproteins and soluble host proteins, resulting in mucosal colonization and immune modulation. In this review, the structure of class-1 and class-2 are analyzed, making emphasis on their putative functional subdomains as well as a description of their function is provided, including prototypical mechanism of action.
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Affiliation(s)
- Fernando Navarro-Garcia
- Department of Cell Biology, Centro de Investigación y de Estudios Avanzados del IPN, Mexico, Mexico
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2
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Sankey N, Merrick H, Singh P, Rogers J, Reddi A, Hartson SD, Mitra A. Role of the Mycobacterium tuberculosis ESX-4 Secretion System in Heme Iron Utilization and Pore Formation by PPE Proteins. mSphere 2023; 8:e0057322. [PMID: 36749044 PMCID: PMC10117145 DOI: 10.1128/msphere.00573-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 01/16/2023] [Indexed: 02/08/2023] Open
Abstract
Mycobacterium tuberculosis (Mtb) is transmitted through aerosols and primarily colonizes within the lung. The World Health Organization estimates that Mtb kills ~1.4 million people every year. A key aspect that makes Mtb such a successful pathogen is its ability to overcome iron limitation mounted by the host immune response. In our previous studies, we have shown that Mtb can utilize iron from heme, the largest source of iron in the human host, and that it uses two redundant heme utilization pathways. In this study, we show that the ESX-4 type VII secretion system (T7SS) is necessary for extracellular heme uptake into the Mtb cell through both heme utilization pathways. ESX-4 influences the secretion of the culture filtrate proteins Rv0125 and Rv1085c, which are also necessary for efficient heme utilization. We also discovered that deletion of the alternative sigma factor SigM significantly reduced Mtb heme utilization through both pathways and predict that SigM is a global positive regulator of core heme utilization genes of both pathways. Finally, we present the first direct evidence that some mycobacterial PPE (proline-proline-glutamate motif) proteins of the PPE protein family are pore-forming membrane proteins. Altogether, we identified core components of both Mtb Heme utilization pathways that were previously unknown and identified a novel channel-forming membrane protein of Mtb. IMPORTANCE M. tuberculosis (Mtb) is completely dependent on iron acquisition in the host to cause disease. The largest source of iron for Mtb in the human host is heme. Here, we show that the ancestral ESX-4 type VII secretion system is required for the efficient utilization of heme as a source of iron, which is an essential nutrient. This is another biological function identified for ESX-4 in Mtb, whose contribution to Mtb physiology is poorly understood. A most exciting finding is that some mycobacterial PPE (proline-proline-glutamate motif) proteins that have been implicated in the nutrient acquisition are membrane proteins that can form channels in a lipid bilayer. These observations have far-reaching implications because they support an emerging theme that PPE proteins can function as channel proteins in the outer mycomembrane for nutrient acquisition. Mtb has evolved a heme uptake system that is drastically different from all other known bacterial heme acquisition systems.
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Affiliation(s)
- November Sankey
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Haley Merrick
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Padam Singh
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Janet Rogers
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Amit Reddi
- School of Chemistry and Biochemistry, Parker Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Steven D. Hartson
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Avishek Mitra
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
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Abstract
Microbial communities are shaped by positive and negative interactions ranging from competition to mutualism. In the context of the mammalian gut and its microbial inhabitants, the integrated output of the community has important impacts on host health. Cross-feeding, the sharing of metabolites between different microbes, has emergent roles in establishing communities of gut commensals that are stable, resistant to invasion, and resilient to external perturbation. In this review, we first explore the ecological and evolutionary implications of cross-feeding as a cooperative interaction. We then survey mechanisms of cross-feeding across trophic levels, from primary fermenters to H2 consumers that scavenge the final metabolic outputs of the trophic network. We extend this analysis to also include amino acid, vitamin, and cofactor cross-feeding. Throughout, we highlight evidence for the impact of these interactions on each species' fitness as well as host health. Understanding cross-feeding illuminates an important aspect of microbe-microbe and host-microbe interactions that establishes and shapes our gut communities.
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Affiliation(s)
- Elizabeth J Culp
- Department of Microbial Pathogenesis and Microbial Sciences Institute, Yale University School of Medicine, New Haven, CT, USA
| | - Andrew L Goodman
- Department of Microbial Pathogenesis and Microbial Sciences Institute, Yale University School of Medicine, New Haven, CT, USA.
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Huynh DT, Jong WSP, Oudejans MAH, van den Berg van Saparoea HB, Luirink J, van Ulsen P. Heterologous Display of Chlamydia trachomatis PmpD Passenger at the Surface of Salmonella OMVs. MEMBRANES 2023; 13:366. [PMID: 37103793 PMCID: PMC10145130 DOI: 10.3390/membranes13040366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 03/17/2023] [Accepted: 03/21/2023] [Indexed: 06/19/2023]
Abstract
Chlamydia trachomatis is the bacterial pathogen that causes most cases of sexually transmitted diseases annually. To combat the global spread of asymptomatic infection, development of effective (mucosal) vaccines that offer both systemic and local immune responses is considered a high priority. In this study, we explored the expression of C. trachomatis full-length (FL) PmpD, as well as truncated PmpD passenger constructs fused to a "display" autotransporter (AT) hemoglobin protease (HbpD) and studied their inclusion into outer membrane vesicles (OMVs) of Escherichia coli and Salmonella Typhimurium. OMVs are considered safe vaccine vectors well-suited for mucosal delivery. By using E. coli AT HbpD-fusions of chimeric constructs we improved surface display and successfully generated Salmonella OMVs decorated with a secreted and immunogenic PmpD passenger fragment (aa68-629) to 13% of the total protein content. Next, we investigated whether a similar chimeric surface display strategy could be applied to other AT antigens, i.e., secreted fragments of Prn (aa35-350) of Bordetella pertussis and VacA (aa65-377) of Helicobacter pylori. The data provided information on the complexity of heterologous expression of AT antigens at the OMV surface and suggested that optimal expression strategies should be developed on an antigen-to-antigen basis.
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Affiliation(s)
- Dung T. Huynh
- Abera Bioscience AB, 750 26 Uppsala, Sweden
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
| | | | - Manon A. H. Oudejans
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
| | | | - Joen Luirink
- Abera Bioscience AB, 750 26 Uppsala, Sweden
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
| | - Peter van Ulsen
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
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5
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Pan X, Chen R, Zhang Y, Zhu Y, Zhao J, Yao H, Ma J. Porcine extraintestinal pathogenic Escherichia coli delivers two serine protease autotransporters coordinately optimizing the bloodstream infection. Front Cell Infect Microbiol 2023; 13:1138801. [PMID: 36875517 PMCID: PMC9978103 DOI: 10.3389/fcimb.2023.1138801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 01/31/2023] [Indexed: 02/18/2023] Open
Abstract
Extraintestinal pathogenic Escherichia coli (ExPEC) is one of the leading causes of bloodstream infections in a broad spectrum of birds and mammals, thus poses a great threat to public health, while its underlying mechanism causing sepsis is not fully understood. Here we reported a high virulent ExPEC strain PU-1, which has a robust ability to colonize within host bloodstream, while induced a low level of leukocytic activation. Two serine protease autotransporters of Enterobacteriaceae (SPATEs), VatPU-1 and TshPU-1, were found to play critical roles for the urgent blood infection of strain PU-1. Although the Vat and Tsh homologues have been identified as virulence factors of ExPEC, their contributions to bloodstream infection are still unclear. In this study, VatPU-1 and TshPU-1 were verified to interact with the hemoglobin (a well-known mucin-like glycoprotein in red blood cell), degrade the mucins of host respiratory tract, and cleave the CD43 (a major cell surface component sharing similar O-glycosylated modifications with other glycoprotein expressed on leukocytes), suggesting that these two SPATEs have the common activity to cleave a broad array of mucin-like O-glycoproteins. These cleavages significantly impaired the chemotaxis and transmigration of leukocytes, and then inhibited the activation of diverse immune responses coordinately, especially downregulated the leukocytic and inflammatory activation during bloodstream infection, thus might mediate the evasion of ExPEC from immune clearance of blood leukocytes. Taken together, these two SPATEs play critical roles to cause a heavy bacterial load within bloodstream via immunomodulation of leukocytes, which provides a more comprehensive understanding how ExPEC colonize within host bloodstream and cause severe sepsis.
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Affiliation(s)
- Xinming Pan
- Ministry of Education (MOE) Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China
- Office International Des (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing, China
| | - Rong Chen
- Ministry of Education (MOE) Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China
- Office International Des (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing, China
| | - Yating Zhang
- Ministry of Education (MOE) Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China
- Office International Des (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing, China
| | - Yinchu Zhu
- Institute of Animal Husbandry and Veterinary Sciences, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Jin Zhao
- Department of Animal Science, Yuxi Agriculture Vocation-Technical College, Yuxi, China
| | - Huochun Yao
- Ministry of Education (MOE) Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China
- Office International Des (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing, China
| | - Jiale Ma
- Ministry of Education (MOE) Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China
- Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing, China
- Office International Des (OIE) Reference Lab for Swine Streptococcosis, Nanjing Agricultural University, Nanjing, China
- *Correspondence: Jiale Ma,
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SurA-like and Skp-like Proteins as Important Virulence Determinants of the Gram Negative Bacterial Pathogens. Int J Mol Sci 2022; 24:ijms24010295. [PMID: 36613738 PMCID: PMC9820271 DOI: 10.3390/ijms24010295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 12/19/2022] [Accepted: 12/20/2022] [Indexed: 12/28/2022] Open
Abstract
In the Gram-negative bacteria, many important virulence factors reach their destination via two-step export systems, and they must traverse the periplasmic space before reaching the outer membrane. Since these proteins must be maintained in a structure competent for transport into or across the membrane, they frequently require the assistance of chaperones. Based on the results obtained for the model bacterium Escherichia coli and related species, it is assumed that in the biogenesis of the outer membrane proteins and the periplasmic transit of secretory proteins, the SurA peptidyl-prolyl isomerase/chaperone plays a leading role, while the Skp chaperone is rather of secondary importance. However, detailed studies carried out on several other Gram-negative pathogens indicate that the importance of individual chaperones in the folding and transport processes depends on the properties of client proteins and is species-specific. Taking into account the importance of SurA functions in bacterial virulence and severity of phenotypes due to surA mutations, this folding factor is considered as a putative therapeutic target to combat microbial infections. In this review, we present recent findings regarding SurA and Skp proteins: their mechanisms of action, involvement in processes related to virulence, and perspectives to use them as therapeutic targets.
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7
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Kim B, Kim JH, Lee Y. Virulence Factors Associated With Escherichia coli Bacteremia and Urinary Tract Infection. Ann Lab Med 2022; 42:203-212. [PMID: 34635614 PMCID: PMC8548248 DOI: 10.3343/alm.2022.42.2.203] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/05/2021] [Accepted: 09/13/2021] [Indexed: 01/03/2023] Open
Abstract
Background Extraintestinal pathogenic Escherichia coli (ExPEC) causes various infections, including urinary tract infection (UTI), sepsis, and neonatal meningitis. ExPEC strains have virulence factors (VFs) that facilitate infection by allowing bacterial cells to migrate into and multiply within the host. We compared the microbiological characteristics of ExPEC isolates from blood and urine specimens from UTI patients. Methods We conducted a single-center, prospective study in an 855-bed tertiary-care hospital in Korea. We consecutively recruited 80 hospitalized UTI patients with E. coli isolates, which were isolated from blood and/or urine, and urine alone between March 2019 and May 2020. We evaluated the 80 E. coli isolates for the presence of bacterial genes encoding the sequence types (STs), antimicrobial resistance, and VFs using whole-genome sequencing (WGS). Results We found no significant differences in STs, antimicrobial resistance patterns, or VFs between isolates from blood and urine specimens. ST131, a pandemic multidrug-resistant clone present in both blood and urine, was the most frequent ST (N=19/80, 24%), and ST131 isolates carried more virulence genes, especially, tsh and espC, than non-ST131 isolates. The virulence scores of the ST131 group and the ST69, ST95, and ST1193 groups differed significantly (P<0.05). Conclusions We found no STs and VFs associated with bacteremia in WGS data of E. coli isolates from UTI patients. ST131 was the most frequent ST among UTI causing isolates and carried more VF genes than non-ST131 isolates.
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Affiliation(s)
- Bongyoung Kim
- Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea
| | - Jin-Hong Kim
- Department of Laboratory Medicine, Hanyang University College of Medicine, Seoul, Korea
| | - Yangsoon Lee
- Department of Laboratory Medicine, Hanyang University College of Medicine, Seoul, Korea
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8
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Huus KE, Hoang TT, Creus-Cuadros A, Cirstea M, Vogt SL, Knuff-Janzen K, Sansonetti PJ, Vonaesch P, Finlay BB. Cross-feeding between intestinal pathobionts promotes their overgrowth during undernutrition. Nat Commun 2021; 12:6860. [PMID: 34824233 PMCID: PMC8617199 DOI: 10.1038/s41467-021-27191-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 11/08/2021] [Indexed: 12/18/2022] Open
Abstract
Child undernutrition is a global health issue associated with a high burden of infectious disease. Undernourished children display an overabundance of intestinal pathogens and pathobionts, and these bacteria induce enteric dysfunction in undernourished mice; however, the cause of their overgrowth remains poorly defined. Here, we show that disease-inducing human isolates of Enterobacteriaceae and Bacteroidales spp. are capable of multi-species symbiotic cross-feeding, resulting in synergistic growth of a mixed community in vitro. Growth synergy occurs uniquely under malnourished conditions limited in protein and iron: in this context, Bacteroidales spp. liberate diet- and mucin-derived sugars and Enterobacteriaceae spp. enhance the bioavailability of iron. Analysis of human microbiota datasets reveals that Bacteroidaceae and Enterobacteriaceae are strongly correlated in undernourished children, but not in adequately nourished children, consistent with a diet-dependent growth synergy in the human gut. Together these data suggest that dietary cross-feeding fuels the overgrowth of pathobionts in undernutrition.
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Affiliation(s)
- K. E. Huus
- grid.17091.3e0000 0001 2288 9830Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC Canada
| | - T. T. Hoang
- grid.17091.3e0000 0001 2288 9830Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC Canada
| | - A. Creus-Cuadros
- grid.17091.3e0000 0001 2288 9830Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC Canada
| | - M. Cirstea
- grid.17091.3e0000 0001 2288 9830Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC Canada
| | - S. L. Vogt
- grid.17091.3e0000 0001 2288 9830Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC Canada
| | - K. Knuff-Janzen
- grid.17091.3e0000 0001 2288 9830Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC Canada
| | - P. J. Sansonetti
- grid.428999.70000 0001 2353 6535Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, Paris, France ,grid.429007.80000 0004 0627 2381Present Address: Center for Microbes, Development and Health, Institut Pasteur de Shanghai, Shanghai, China
| | - P. Vonaesch
- grid.428999.70000 0001 2353 6535Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, Paris, France ,grid.416786.a0000 0004 0587 0574Present Address: Human and Animal Health Unit, Swiss Tropical and Public Health Institute & University of Basel, Basel, Switzerland
| | - B. B. Finlay
- grid.17091.3e0000 0001 2288 9830Michael Smith Laboratories and Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC Canada ,grid.440050.50000 0004 0408 2525Canadian Institute for Advanced Research, Toronto, Ontario Canada
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Analysis of six tonB gene homologs in Bacteroides fragilis revealed that tonB3 is essential for survival in experimental intestinal colonization and intra-abdominal infection. Infect Immun 2021; 90:e0046921. [PMID: 34662212 DOI: 10.1128/iai.00469-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The opportunistic, anaerobic pathogen and commensal of the human large intestinal tract, Bacteroides fragilis strain 638R, contains six predicted TonB proteins, termed TonB1-6, four ExbBs orthologs, ExbB1-4, and five ExbDs orthologs, ExbD1-5. The inner membrane TonB/ExbB/ExbD complex harvests energy from the proton motive force (Δp) and the TonB C-terminal domain interacts with and transduces energy to outer membrane TonB-dependent transporters (TBDTs). However, TonB's role in activating nearly one hundred TBDTs for nutrient acquisition in B. fragilis during intestinal colonization and extraintestinal infection has not been established. In this study, we show that growth was abolished in the ΔtonB3 mutant when heme, vitamin B12, Fe(III)-ferrichrome, starch, mucin-glycans, or N-linked glycans were used as a substrate for growth in vitro. Genetic complementation of the ΔtonB3 mutant with the tonB3 gene restored growth on these substrates. The ΔtonB1, ΔtonB2, ΔtonB4, ΔtonB5, and ΔtonB6 single mutants did not show a growth defect. This indicates that there was no functional compensation for the lack of TonB3, and it demonstrates that TonB3, alone, drives the TBDTs involved in the transport of essential nutrients. The ΔtonB3 mutant had a severe growth defect in a mouse model of intestinal colonization compared to the parent strain. This intestinal growth defect was enhanced in the ΔtonB3 ΔtonB6 double mutant strain which completely lost its ability to colonize the mouse intestinal tract compared to the parent strain. The ΔtonB1, ΔtonB2, ΔtonB4, and ΔtonB5 mutants did not significantly affect intestinal colonization. Moreover, the survival of the ΔtonB3 mutant strain was completely eradicated in a rat model of intra-abdominal infection. Taken together, these findings show that TonB3 was essential for survival in vivo. The genetic organization of tonB1, tonB2, tonB4, tonB5, and tonB6 gene orthologs indicates that they may interact with periplasmic and nonreceptor outer membrane proteins, but the physiological relevance of this has not been defined. Because anaerobic fermentation metabolism yields a lower Δp than aerobic respiration and B. fragilis has a reduced redox state in its periplasmic space - in contrast to an oxidative environment in aerobes - it remains to be determined if the diverse system of TonB/ExbB/ExbD orthologs encoded by B. fragilis have an increased sensitivity to PMF (relative to aerobic bacteria) to allow for the harvesting of energy under anaerobic conditions.
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Do Primocolonizing Bacteria Enable Bacteroides thetaiotaomicron Intestinal Colonization Independently of the Capacity To Consume Oxygen? mSphere 2021; 6:6/3/e00232-19. [PMID: 33952662 PMCID: PMC8103986 DOI: 10.1128/msphere.00232-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Aerobic bacteria are frequent primocolonizers of the human naive intestine. Their generally accepted role is to eliminate oxygen, which would allow colonization by anaerobes that subsequently dominate bacterial gut populations. Aerobic bacteria are frequent primocolonizers of the human naive intestine. Their generally accepted role is to eliminate oxygen, which would allow colonization by anaerobes that subsequently dominate bacterial gut populations. In this hypothesis-based study, we revisited this dogma experimentally in a germfree mouse model as a mimic of the germfree newborn. We varied conditions leading to the establishment of the dominant intestinal anaerobe Bacteroides thetaiotaomicron. Two variables were introduced: Bacteroides inoculum size and preestablishment by bacteria capable or not of consuming oxygen. High Bacteroides inoculum size enabled its primocolonization. At low inocula, we show that bacterial preestablishment was decisive for subsequent Bacteroides colonization. However, even non-oxygen-respiring bacteria, a hemAEscherichia coli mutant and the intestinal obligate anaerobe Clostridium scindens, facilitated Bacteroides establishment. These findings, which are supported by recent reports, revise the long-held assumption that oxygen scavenging is the main role for aerobic primocolonizing bacteria. Instead, we suggest that better survival of aerobic bacteria ex vivo during vectorization between hosts could be a reason for their frequent primocolonization.
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The uroS and yifB Genes Conserved among Tetrapyrrole Synthesizing-Deficient Bacteroidales Are Involved in Bacteroides fragilis Heme Assimilation and Survival in Experimental Intra-abdominal Infection and Intestinal Colonization. Infect Immun 2020; 88:IAI.00103-20. [PMID: 32457103 DOI: 10.1128/iai.00103-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/15/2020] [Indexed: 01/01/2023] Open
Abstract
The human intestinal anaerobic commensal and opportunistic pathogen Bacteroides fragilis does not synthesize the tetrapyrrole protoporphyrin IX in order to form heme that is required for growth stimulation and survival in vivo Consequently, B. fragilis acquires essential heme from host tissues during extraintestinal infection. The absence of several genes necessary for de novo heme biosynthesis is a common characteristic of many anaerobic bacteria; however, the uroS gene, encoding a uroporphyrinogen III synthase for an early step of heme biosynthesis, is conserved among the heme-requiring Bacteroidales that inhabit the mammalian gastrointestinal tract. In this study, we show that the ability of B. fragilis to utilize heme or protoporphyrin IX for growth was greatly reduced in a ΔuroS mutant. This growth defect appears to be linked to the suppression of reverse chelatase and ferrochelatase activities in the absence of uroS In addition, this ΔuroS suppressive effect was enhanced by the deletion of the yifB gene, which encodes an Mg2+-chelatase protein belonging to the ATPases associated with various cellular activities (AAA+) superfamily of proteins. Furthermore, the ΔuroS mutant and the ΔuroS ΔyifB double mutant had a severe survival defect compared to the parent strain in competitive infection assays using animal models of intra-abdominal infection and intestinal colonization. This shows that the presence of the uroS and yifB genes in B. fragilis seems to be linked to pathophysiological and nutritional competitive fitness for survival in host tissues. Genetic complementation studies and enzyme kinetics assays indicate that B. fragilis UroS is functionally different from canonical bacterial UroS proteins. Taken together, these findings show that heme assimilation and metabolism in the anaerobe B. fragilis have diverged from those of aerobic and facultative anaerobic pathogenic bacteria.
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Habouria H, Pokharel P, Maris S, Garénaux A, Bessaiah H, Houle S, Veyrier FJ, Guyomard-Rabenirina S, Talarmin A, Dozois CM. Three new serine-protease autotransporters of Enterobacteriaceae (SPATEs) from extra-intestinal pathogenic Escherichia coli and combined role of SPATEs for cytotoxicity and colonization of the mouse kidney. Virulence 2020; 10:568-587. [PMID: 31198092 PMCID: PMC6592367 DOI: 10.1080/21505594.2019.1624102] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Serine protease autotransporters of Enterobacteriaceae (SPATEs) are secreted proteins that contribute to virulence and function as proteases, toxins, adhesins, and/or immunomodulators. An extra-intestinal pathogenic E. coli (ExPEC) O1:K1 strain, QT598, isolated from a turkey, was shown to contain vat, tsh, and three uncharacterized SPATE-encoding genes. Uncharacterized SPATEs: Sha (Serine-protease hemagglutinin autotransporter), TagB and TagC (tandem autotransporter genes B and C) were tested for activities including hemagglutination, autoaggregation, and cytotoxicity when expressed in E. coli K-12. Sha and TagB conferred autoaggregation and hemagglutination activities. TagB, TagC, and Sha all exhibited cytopathic effects on a bladder epithelial cell line. In QT598, tagB and tagC are tandemly encoded on a genomic island, and were present in 10% of UTI isolates and 4.7% of avian E. coli. Sha is encoded on a virulence plasmid and was present in 1% of UTI isolates and 20% of avian E. coli. To specifically examine the role of SPATEs for infection, the 5 SPATE genes were deleted from strain QT598 and tested for cytotoxicity. Loss of all five SPATEs abrogated the cytopathic effect on bladder epithelial cells, although derivatives producing any of the 5 SPATEs retained cytopathic activity. In mouse infections, sha gene-expression was up-regulated a mean of sixfold in the bladder compared to growth in vitro. Loss of either tagBC or sha did not reduce urinary tract colonization. Deletion of all 5 SPATEs, however, significantly reduced competitive colonization of the kidney supporting a cumulative role of SPATEs for QT598 in the mouse UTI model.
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Affiliation(s)
- Hajer Habouria
- a Institut national de recherche scientifique (INRS)-Institut Armand Frappier , Laval , Quebec , Canada.,b Centre de recherche en infectiologie porcine et avicole (CRIPA)
| | - Pravil Pokharel
- a Institut national de recherche scientifique (INRS)-Institut Armand Frappier , Laval , Quebec , Canada.,b Centre de recherche en infectiologie porcine et avicole (CRIPA)
| | - Segolène Maris
- a Institut national de recherche scientifique (INRS)-Institut Armand Frappier , Laval , Quebec , Canada.,b Centre de recherche en infectiologie porcine et avicole (CRIPA)
| | - Amélie Garénaux
- a Institut national de recherche scientifique (INRS)-Institut Armand Frappier , Laval , Quebec , Canada.,b Centre de recherche en infectiologie porcine et avicole (CRIPA)
| | - Hicham Bessaiah
- a Institut national de recherche scientifique (INRS)-Institut Armand Frappier , Laval , Quebec , Canada.,b Centre de recherche en infectiologie porcine et avicole (CRIPA)
| | - Sébastien Houle
- a Institut national de recherche scientifique (INRS)-Institut Armand Frappier , Laval , Quebec , Canada.,b Centre de recherche en infectiologie porcine et avicole (CRIPA)
| | - Frédéric J Veyrier
- a Institut national de recherche scientifique (INRS)-Institut Armand Frappier , Laval , Quebec , Canada.,c Institut Pasteur International Network
| | - Stéphanie Guyomard-Rabenirina
- c Institut Pasteur International Network.,d Unité Environnement Santé , Institut Pasteur de Guadeloupe , Les Abymes , Guadeloupe , France
| | - Antoine Talarmin
- c Institut Pasteur International Network.,d Unité Environnement Santé , Institut Pasteur de Guadeloupe , Les Abymes , Guadeloupe , France
| | - Charles M Dozois
- a Institut national de recherche scientifique (INRS)-Institut Armand Frappier , Laval , Quebec , Canada.,b Centre de recherche en infectiologie porcine et avicole (CRIPA).,c Institut Pasteur International Network
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Pokharel P, Habouria H, Bessaiah H, Dozois CM. Serine Protease Autotransporters of the Enterobacteriaceae (SPATEs): Out and About and Chopping It Up. Microorganisms 2019; 7:E594. [PMID: 31766493 PMCID: PMC6956023 DOI: 10.3390/microorganisms7120594] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 11/13/2019] [Indexed: 02/06/2023] Open
Abstract
Autotransporters are secreted proteins with multiple functions produced by a variety of Gram-negative bacteria. In Enterobacteriaceae, a subgroup of these autotransporters are the SPATEs (serine protease autotransporters of Enterobacteriaceae). SPATEs play a crucial role in survival and virulence of pathogens such as Escherichia coli and Shigella spp. and contribute to intestinal and extra-intestinal infections. These high molecular weight proteases are transported to the external milieu by the type Va secretion system and function as proteases with diverse substrate specificities and biological functions including adherence and cytotoxicity. Herein, we provide an overview of SPATEs and discuss recent findings on the biological roles of these secreted proteins, including proteolysis of substrates, adherence to cells, modulation of the immune response, and virulence in host models. In closing, we highlight recent insights into the regulation of expression of SPATEs that could be exploited to understand fundamental SPATE biology.
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Affiliation(s)
- Pravil Pokharel
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Hajer Habouria
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Hicham Bessaiah
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Charles M. Dozois
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
- Institut Pasteur International Network, Laval, QC H7V 1B7, Canada
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Secreted proteases: A new insight in the pathogenesis of extraintestinal pathogenic Escherichia coli. Int J Med Microbiol 2019; 309:159-168. [DOI: 10.1016/j.ijmm.2019.03.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 02/19/2019] [Accepted: 03/04/2019] [Indexed: 11/20/2022] Open
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Rocha ER, Bergonia HA, Gerdes S, Jeffrey Smith C. Bacteroides fragilis requires the ferrous-iron transporter FeoAB and the CobN-like proteins BtuS1 and BtuS2 for assimilation of iron released from heme. Microbiologyopen 2019; 8:e00669. [PMID: 29931811 PMCID: PMC6460266 DOI: 10.1002/mbo3.669] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 04/13/2018] [Accepted: 05/07/2018] [Indexed: 12/17/2022] Open
Abstract
The intestinal commensal and opportunistic anaerobic pathogen Bacteroides fragilis has an essential requirement for both heme and free iron to support growth in extraintestinal infections. In the absence of free iron, B. fragilis can utilize heme as the sole source of iron. However, the mechanisms to remove iron from heme are not completely understood. In this study, we show that the inner membrane ferrous iron transporter ∆feoAB mutant strain is no longer able to grow with heme as the sole source of iron. Genetic complementation with the feoAB gene operon completely restored growth. Our data indicate that iron is removed from heme in the periplasmic space, and the released iron is transported by the FeoAB system. Interestingly, when B. fragilis utilizes iron from heme, it releases heme-derived porphyrins by a dechelatase activity which is upregulated under low iron conditions. This is supported by the findings showing that formation of heme-derived porphyrins in the ∆feoAB mutant and the parent strain increased 30-fold and fivefold (respectively) under low iron conditions compared to iron replete conditions. Moreover, the btuS1 btuS2 double-mutant strain (lacking the predicted periplasmic, membrane anchored CobN-like proteins) also showed growth defect with heme as the sole source of iron, suggesting that BtuS1 and BtuS2 are involved in heme-iron assimilation. Though the dechelatase mechanism remains uncharacterized, assays performed in bacterial crude extracts show that BtuS1 and BtuS2 affect the regulation of the dechelatase-specific activities in an iron-dependent manner. These findings suggest that the mechanism to extract iron from heme in Bacteroides requires a group of proteins, which spans the periplasmic space to make iron available for cellular functions.
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Affiliation(s)
- Edson R. Rocha
- Department of Microbiology and ImmunologyBrody School of MedicineGreenvilleNorth Carolina
| | - Hector A. Bergonia
- Iron and Heme CoreDivision of HematologyUniversity of Utah School of MedicineSalt Lake CityUtah
| | | | - Charles Jeffrey Smith
- Department of Microbiology and ImmunologyBrody School of MedicineGreenvilleNorth Carolina
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Abstract
Iron is an essential micronutrient for both microbes and humans alike. For well over half a century we have known that this element, in particular, plays a pivotal role in health and disease and, most especially, in shaping host-pathogen interactions. Intracellular iron concentrations serve as a critical signal in regulating the expression not only of high-affinity iron acquisition systems in bacteria, but also of toxins and other noted virulence factors produced by some major human pathogens. While we now are aware of many strategies that the host has devised to sequester iron from invading microbes, there are as many if not more sophisticated mechanisms by which successful pathogens overcome nutritional immunity imposed by the host. This review discusses some of the essential components of iron sequestration and scavenging mechanisms of the host, as well as representative Gram-negative and Gram-positive pathogens, and highlights recent advances in the field. Last, we address how the iron acquisition strategies of pathogenic bacteria may be exploited for the development of novel prophylactics or antimicrobials.
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Stacy A, Abraham N, Jorth P, Whiteley M. Microbial Community Composition Impacts Pathogen Iron Availability during Polymicrobial Infection. PLoS Pathog 2016; 12:e1006084. [PMID: 27973608 PMCID: PMC5156373 DOI: 10.1371/journal.ppat.1006084] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 11/21/2016] [Indexed: 01/07/2023] Open
Abstract
Iron is an essential nutrient for bacterial pathogenesis, but in the host, iron is tightly sequestered, limiting its availability for bacterial growth. Although this is an important arm of host immunity, most studies examine how bacteria respond to iron restriction in laboratory rather than host settings, where the microbiome can potentially alter pathogen strategies for acquiring iron. One of the most important transcriptional regulators controlling bacterial iron homeostasis is Fur. Here we used a combination of RNA-seq and chromatin immunoprecipitation (ChIP)-seq to characterize the iron-restricted and Fur regulons of the biofilm-forming opportunistic pathogen Aggregatibacter actinomycetemcomitans. We discovered that iron restriction and Fur regulate 4% and 3.5% of the genome, respectively. While most genes in these regulons were related to iron uptake and metabolism, we found that Fur also directly regulates the biofilm-dispersing enzyme Dispersin B, allowing A. actinomycetemcomitans to escape from iron-scarce environments. We then leveraged these datasets to assess the availability of iron to A. actinomycetemcomitans in its primary infection sites, abscesses and the oral cavity. We found that A. actinomycetemcomitans is not restricted for iron in a murine abscess mono-infection, but becomes restricted for iron upon co-infection with the oral commensal Streptococcus gordonii. Furthermore, in the transition from health to disease in human gum infection, A. actinomycetemcomitans also becomes restricted for iron. These results suggest that host iron availability is heterogeneous and dependent on the infecting bacterial community. One of the most well-studied phenomena in microbiology is nutritional immunity, or how the host withholds nutrients such as iron to combat infection. As part of this, researchers have characterized how many pathogens respond to iron restriction. However, these studies are often conducted in laboratory media rather than the host. As a result, they overlook how the host environment, such as its microbiome, might alter pathogen behavior regarding iron during infection. To address this gap, we used an opportunistic pathogen that causes abscess and oral cavity infections. We defined how it responds to iron restriction in vitro and then used this data to assess its iron status in vivo. Our results show that in mono-culture abscesses the pathogen is not starved for iron but in co-culture abscesses and multispecies gum disease it is starved for iron. Therefore, host environments are not uniformly restricted for iron, and the microbiome can modulate iron availability to pathogens.
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Affiliation(s)
- Apollo Stacy
- Department of Molecular Biosciences, Institute of Cellular and Molecular Biology, John Ring LaMontagne Center for Infectious Disease, The University of Texas at Austin, Austin, TX United States of America
| | - Nader Abraham
- Department of Molecular Biosciences, Institute of Cellular and Molecular Biology, John Ring LaMontagne Center for Infectious Disease, The University of Texas at Austin, Austin, TX United States of America
| | - Peter Jorth
- Department of Molecular Biosciences, Institute of Cellular and Molecular Biology, John Ring LaMontagne Center for Infectious Disease, The University of Texas at Austin, Austin, TX United States of America
| | - Marvin Whiteley
- Department of Molecular Biosciences, Institute of Cellular and Molecular Biology, John Ring LaMontagne Center for Infectious Disease, The University of Texas at Austin, Austin, TX United States of America
- * E-mail:
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18
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Jong WSP, Daleke-Schermerhorn MH, Vikström D, Ten Hagen-Jongman CM, de Punder K, van der Wel NN, van de Sandt CE, Rimmelzwaan GF, Follmann F, Agger EM, Andersen P, de Gier JW, Luirink J. An autotransporter display platform for the development of multivalent recombinant bacterial vector vaccines. Microb Cell Fact 2014; 13:162. [PMID: 25421093 PMCID: PMC4252983 DOI: 10.1186/s12934-014-0162-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 11/02/2014] [Indexed: 01/02/2023] Open
Abstract
Background The Autotransporter pathway, ubiquitous in Gram-negative bacteria, allows the efficient secretion of large passenger proteins via a relatively simple mechanism. Capitalizing on its crystal structure, we have engineered the Escherichia coli autotransporter Hemoglobin protease (Hbp) into a versatile platform for secretion and surface display of multiple heterologous proteins in one carrier molecule. Results As proof-of-concept, we demonstrate efficient secretion and high-density display of the sizeable Mycobacterium tuberculosis antigens ESAT6, Ag85B and Rv2660c in E. coli simultaneously. Furthermore, we show stable multivalent display of these antigens in an attenuated Salmonella Typhimurium strain upon chromosomal integration. To emphasize the versatility of the Hbp platform, we also demonstrate efficient expression of multiple sizeable antigenic fragments from Chlamydia trachomatis and the influenza A virus at the Salmonella cell surface. Conclusions The successful efficient cell surface display of multiple antigens from various pathogenic organisms highlights the potential of Hbp as a universal platform for the development of multivalent recombinant bacterial vector vaccines. Electronic supplementary material The online version of this article (doi:10.1186/s12934-014-0162-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Wouter S P Jong
- Department of Molecular Cell Biology, Section Molecular Microbiology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081, HV, Amsterdam, The Netherlands. .,Abera Bioscience AB, SE-111 45, Stockholm, Sweden.
| | - Maria H Daleke-Schermerhorn
- Department of Molecular Cell Biology, Section Molecular Microbiology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081, HV, Amsterdam, The Netherlands. .,Abera Bioscience AB, SE-111 45, Stockholm, Sweden.
| | - David Vikström
- Xbrane Bioscience AB, SE-111 45, Stockholm, Sweden. .,Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91, Stockholm, Sweden.
| | - Corinne M Ten Hagen-Jongman
- Department of Molecular Cell Biology, Section Molecular Microbiology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081, HV, Amsterdam, The Netherlands. .,Abera Bioscience AB, SE-111 45, Stockholm, Sweden.
| | - Karin de Punder
- The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, 1066, CX, Amsterdam, The Netherlands. .,Present Address: Institute for Medical Psychology, Charité Universitätsmedizin, 10117, Berlin, Germany.
| | - Nicole N van der Wel
- The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, 1066, CX, Amsterdam, The Netherlands. .,Present Address: Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, 1105, AZ, Amsterdam, The Netherlands.
| | | | - Guus F Rimmelzwaan
- Department of Viroscience, Erasmus Medical Center, 3015, GE, Rotterdam, The Netherlands.
| | - Frank Follmann
- Department of Infectious Disease & Immunology, Statens Serum Institut, Copenhagen, Denmark.
| | - Else Marie Agger
- Department of Infectious Disease & Immunology, Statens Serum Institut, Copenhagen, Denmark.
| | - Peter Andersen
- Department of Infectious Disease & Immunology, Statens Serum Institut, Copenhagen, Denmark.
| | - Jan-Willem de Gier
- Xbrane Bioscience AB, SE-111 45, Stockholm, Sweden. .,Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91, Stockholm, Sweden.
| | - Joen Luirink
- Department of Molecular Cell Biology, Section Molecular Microbiology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081, HV, Amsterdam, The Netherlands. .,Abera Bioscience AB, SE-111 45, Stockholm, Sweden.
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van Ulsen P, Rahman SU, Jong WS, Daleke-Schermerhorn MH, Luirink J. Type V secretion: From biogenesis to biotechnology. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1592-611. [DOI: 10.1016/j.bbamcr.2013.11.006] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 11/01/2013] [Accepted: 11/13/2013] [Indexed: 12/13/2022]
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Decoration of outer membrane vesicles with multiple antigens by using an autotransporter approach. Appl Environ Microbiol 2014; 80:5854-65. [PMID: 25038093 DOI: 10.1128/aem.01941-14] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Outer membrane vesicles (OMVs) are spherical nanoparticles that naturally shed from Gram-negative bacteria. They are rich in immunostimulatory proteins and lipopolysaccharide but do not replicate, which increases their safety profile and renders them attractive vaccine vectors. By packaging foreign polypeptides in OMVs, specific immune responses can be raised toward heterologous antigens in the context of an intrinsic adjuvant. Antigens exposed at the vesicle surface have been suggested to elicit protection superior to that from antigens concealed inside OMVs, but hitherto robust methods for targeting heterologous proteins to the OMV surface have been lacking. We have exploited our previously developed hemoglobin protease (Hbp) autotransporter platform for display of heterologous polypeptides at the OMV surface. One, two, or three of the Mycobacterium tuberculosis antigens ESAT6, Ag85B, and Rv2660c were targeted to the surface of Escherichia coli OMVs upon fusion to Hbp. Furthermore, a hypervesiculating ΔtolR ΔtolA derivative of attenuated Salmonella enterica serovar Typhimurium SL3261 was generated, enabling efficient release and purification of OMVs decorated with multiple heterologous antigens, exemplified by the M. tuberculosis antigens and epitopes from Chlamydia trachomatis major outer membrane protein (MOMP). Also, we showed that delivery of Salmonella OMVs displaying Ag85B to antigen-presenting cells in vitro results in processing and presentation of an epitope that is functionally recognized by Ag85B-specific T cell hybridomas. In conclusion, the Hbp platform mediates efficient display of (multiple) heterologous antigens, individually or combined within one molecule, at the surface of OMVs. Detection of antigen-specific immune responses upon vesicle-mediated delivery demonstrated the potential of our system for vaccine development.
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21
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Ruiz-Perez F, Nataro JP. Bacterial serine proteases secreted by the autotransporter pathway: classification, specificity, and role in virulence. Cell Mol Life Sci 2013; 71:745-70. [PMID: 23689588 DOI: 10.1007/s00018-013-1355-8] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 04/25/2013] [Accepted: 04/29/2013] [Indexed: 01/07/2023]
Abstract
Serine proteases exist in eukaryotic and prokaryotic organisms and have emerged during evolution as the most abundant and functionally diverse group. In Gram-negative bacteria, there is a growing family of high molecular weight serine proteases secreted to the external milieu by a fascinating and widely employed bacterial secretion mechanism, known as the autotransporter pathway. They were initially found in Neisseria, Shigella, and pathogenic Escherichia coli, but have now also been identified in Citrobacter rodentium, Salmonella, and Edwardsiella species. Here, we focus on proteins belonging to the serine protease autotransporter of Enterobacteriaceae (SPATEs) family. Recent findings regarding the predilection of serine proteases to host intracellular or extracellular protein-substrates involved in numerous biological functions, such as those implicated in cytoskeleton stability, autophagy or innate and adaptive immunity, have helped provide a better understanding of SPATEs' contributions in pathogenesis. Here, we discuss their classification, substrate specificity, and potential roles in pathogenesis.
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Affiliation(s)
- Fernando Ruiz-Perez
- Department of Pediatrics, School of Medicine, University of Virginia, P.O.Box 800326, MR4 Room 4012C, 409 Lane Road, Charlottesville, VA, 22908, USA,
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Lobo LA, Jenkins AL, Jeffrey Smith C, Rocha ER. Expression of Bacteroides fragilis hemolysins in vivo and role of HlyBA in an intra-abdominal infection model. Microbiologyopen 2013; 2:326-37. [PMID: 23441096 PMCID: PMC3633356 DOI: 10.1002/mbo3.76] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 01/22/2013] [Accepted: 01/28/2013] [Indexed: 01/01/2023] Open
Abstract
Bacteroides fragilis is the most frequent opportunistic pathogen isolated from anaerobic infections. However, there is a paucity of information regarding the genetic and molecular aspects of gene expression of its virulence factors during extra-intestinal infections. A potential virulence factor that has received little attention is the ability of B. fragilis to produce hemolysins. In this study, an implanted perforated table tennis "ping-pong" ball was used as an intra-abdominal artificial abscess model in the rat. This procedure provided sufficient infected exudate for gene expression studies in vivo. Real-time reverse transcription polymerase chain reaction (RT-PCR) was used to quantify the relative expression of hlyA, hlyB, hlyC, hlyD, hlyE, hlyF, hlyG, and hlyIII mRNAs. The hlyA mRNA was induced approximately sixfold after 4 days postinfection compared with the mRNA levels in the inoculum culture prior to infection. The hlyB mRNA increased approximately sixfold after 4 days and 12-fold after 8 days postinfection. Expression of hlyC mRNA increased sixfold after 1 day, 45-fold after 4 days, and 16-fold after 8 days postinfection, respectively. The hlyD and hlyE mRNAs were induced approximately 40-fold and 30-fold, respectively, after 4-days postinfection. The hlyF expression increased approximately threefold after 4-days postinfection. hlyG was induced approximately fivefold after 4 and 8 days postinfection. The hlyIII mRNA levels had a steady increase of approximately four-, eight-, and 12-fold following 1, 4, and 8 days postinfection, respectively. These findings suggest that B. fragilis hemolysins are induced and differentially regulated in vivo. Both parent and hlyBA mutant strains reached levels of approximately 3-8 × 10(9) cfu/mL after 1 day postinfection. However, the hlyBA mutant strain lost 2 logs in viable cell counts compared with the parent strain after 8 days postinfection. This is the first study showing HlyBA is a virulence factor which plays a role in B. fragilis survival in an intra-abdominal abscess model.
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Affiliation(s)
- Leandro A Lobo
- Department of Microbiology and Immunology, East Carolina University Brody School of Medicine, Greenville, North Carolina 27834, USA
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23
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Byrne DP, Potempa J, Olczak T, Smalley JW. Evidence of mutualism between two periodontal pathogens: co-operative haem acquisition by the HmuY haemophore of Porphyromonas gingivalis and the cysteine protease interpain A (InpA) of Prevotella intermedia. Mol Oral Microbiol 2013; 28:219-29. [PMID: 23336115 DOI: 10.1111/omi.12018] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/27/2012] [Indexed: 11/27/2022]
Abstract
Haem (iron protoporphyrin IX) is both an essential growth factor and a virulence regulator of the periodontal pathogens Porphyromonas gingivalis and Prevotella intermedia, which acquire it through the proteolytic degradation of haemoglobin and other haem-carrying plasma proteins. The haem-binding lipoprotein HmuY haemophore and the gingipain proteases of P. gingivalis form a unique synthrophic system responsible for capture of haem from haemoglobin and methaemalbumin. In this system, methaemoglobin is formed from oxyhaemoglobin by the activities of gingipain proteases and serves as a facile substrate from which HmuY can capture haem. This study examined the possibility of cooperation between HmuY and the cysteine protease interpain A (InpA) of Pr. intermedia in the haem acquisition process. Using UV-visible spectroscopy and polyacrylamide gel electrophoresis, HmuY was demonstrated to be resistant to proteolysis and so able to cooperate with InpA to extract haem from haemoglobin, which was proteolytically converted to methaemoglobin by the protease. Spectroscopic pH titrations showed that both the iron(II) and iron(III) protoporphyrin IX-HmuY complexes were stable over the pH range 4-10, demonstrating that the haemophore could function over a range of pH that may be encountered in the dental plaque biofilm. This is the first demonstration of a bacterial haemophore working in conjunction with a protease from another bacterial species to acquire haem from haemoglobin and may represent mutualism between P. gingivalis and Pr. intermedia co-inhabiting the periodontal pocket.
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Affiliation(s)
- D P Byrne
- Department of Clinical Infection, Microbiology and Immunology, Institute of Infection and Global Health, University of Liverpool, Liverpool, UK
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A structurally informed autotransporter platform for efficient heterologous protein secretion and display. Microb Cell Fact 2012; 11:85. [PMID: 22709508 PMCID: PMC3521207 DOI: 10.1186/1475-2859-11-85] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 06/07/2012] [Indexed: 11/17/2022] Open
Abstract
Background The self-sufficient autotransporter (AT) pathway, ubiquitous in Gram-negative bacteria, combines a relatively simple protein secretion mechanism with a high transport capacity. ATs consist of a secreted passenger domain and a β-domain that facilitates transfer of the passenger across the cell-envelope. They have a great potential for the extracellular expression of recombinant proteins but their exploitation has suffered from the limited structural knowledge of carrier ATs. Capitalizing on its crystal structure, we have engineered the Escherichia coli AT Hemoglobin protease (Hbp) into a platform for the secretion and surface display of heterologous proteins, using the Mycobacterium tuberculosis vaccine target ESAT6 as a model protein. Results Based on the Hbp crystal structure, five passenger side domains were selected and one by one replaced by ESAT6, whereas a β-helical core structure (β-stem) was left intact. The resulting Hbp-ESAT6 chimeras were efficiently and stably secreted into the culture medium of E. coli. On the other hand, Hbp-ESAT6 fusions containing a truncated β-stem appeared unstable after translocation, demonstrating the importance of an intact β-stem. By interrupting the cleavage site between passenger and β-domain, Hbp-ESAT6 display variants were constructed that remain cell associated and facilitate efficient surface exposure of ESAT6 as judged by proteinase K accessibility and whole cell immuno-EM analysis. Upon replacement of the passenger side domain of an alternative AT, EspC, ESAT6 was also efficiently secreted, showing the approach is more generally applicable to ATs. Furthermore, Hbp-ESAT6 was efficiently displayed in an attenuated Salmonella typhimurium strain upon chromosomal integration of a single encoding gene copy, demonstrating the potential of the Hbp platform for live vaccine development. Conclusions We developed the first structurally informed AT platform for efficient secretion and surface display of heterologous proteins. The platform has potential with regard to the development of recombinant live vaccines and may be useful for other biotechnological applications that require high-level secretion or display of recombinant proteins by bacteria.
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Roussel-Jazédé V, Gelder PV, Sijbrandi R, Rutten L, Otto BR, Luirink J, Gros P, Tommassen J, Ulsen PV. Channel properties of the translocator domain of the autotransporter Hbp ofEscherichia coli. Mol Membr Biol 2011; 28:158-70. [DOI: 10.3109/09687688.2010.550328] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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26
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Soprova Z, Sauri A, van Ulsen P, Tame JRH, den Blaauwen T, Jong WSP, Luirink J. A conserved aromatic residue in the autochaperone domain of the autotransporter Hbp is critical for initiation of outer membrane translocation. J Biol Chem 2010; 285:38224-33. [PMID: 20923769 DOI: 10.1074/jbc.m110.180505] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Autotransporters are bacterial virulence factors that share a common mechanism by which they are transported to the cell surface. They consist of an N-terminal passenger domain and a C-terminal β-barrel, which has been implicated in translocation of the passenger across the outer membrane (OM). The mechanism of passenger translocation and folding is still unclear but involves a conserved region at the C terminus of the passenger domain, the so-called autochaperone domain. This domain functions in the stepwise translocation process and in the folding of the passenger domain after translocation. In the autotransporter hemoglobin protease (Hbp), the autochaperone domain consists of the last rung of the β-helix and a capping domain. To examine the role of this region, we have mutated several conserved aromatic residues that are oriented toward the core of the β-helix. We found that non-conservative mutations affected secretion with Trp(1015) in the cap region as the most critical residue. Substitution at this position yielded a DegP-sensitive intermediate that is located at the periplasmic side of the OM. Further analysis revealed that Trp(1015) is most likely required for initiation of processive folding of the β-helix at the cell surface, which drives sequential translocation of the Hbp passenger across the OM.
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Affiliation(s)
- Zora Soprova
- Department of Molecular Microbiology, Institute of Molecular Cell Biology, VU University, 1081 HV Amsterdam, The Netherlands
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27
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Abstract
The innate immune system of the human body has developed numerous mechanisms to control endogenous and exogenous bacteria and thus prevent infections by these microorganisms. These mechanisms range from physical barriers such as the skin or mucosal epithelium to a sophisticated array of molecules and cells that function to suppress or prevent bacterial infection. Many bacteria express a variety of proteases, ranging from non-specific and powerful enzymes that degrade many proteins involved in innate immunity to proteases that are extremely precise and specific in their mode of action. Here we have assembled a comprehensive picture of how bacterial proteases affect the host's innate immune system to gain advantage and cause infection. This picture is far from being complete since the numbers of mechanisms utilized are as astonishing as they are diverse, ranging from degradation of molecules vital to innate immune mechanisms to subversion of the mechanisms to allow the bacterium to hide from the system or take advantage of it. It is vital that such mechanisms are elucidated to allow strategies to be developed to aid the innate immune system in controlling bacterial infections.
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Affiliation(s)
- Jan Potempa
- Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland.
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Dautin N. Serine protease autotransporters of enterobacteriaceae (SPATEs): biogenesis and function. Toxins (Basel) 2010; 2:1179-206. [PMID: 22069633 PMCID: PMC3153244 DOI: 10.3390/toxins2061179] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 05/17/2010] [Accepted: 05/27/2010] [Indexed: 01/19/2023] Open
Abstract
Serine Protease Autotransporters of Enterobacteriaceae (SPATEs) constitute a large family of proteases secreted by Escherichia coli and Shigella. SPATEs exhibit two distinct proteolytic activities. First, a C-terminal catalytic site triggers an intra-molecular cleavage that releases the N-terminal portion of these proteins in the extracellular medium. Second, the secreted N-terminal domains of SPATEs are themselves proteases; each contains a canonical serine-protease catalytic site. Some of these secreted proteases are toxins, eliciting various effects on mammalian cells. Here, we discuss the biogenesis of SPATEs and their function as toxins.
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Affiliation(s)
- Nathalie Dautin
- Department of Biology, The Catholic University of America, 620 Michigan Avenue N.E., Washington, DC, 20064, USA.
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29
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Autotransporter passenger proteins: virulence factors with common structural themes. J Mol Med (Berl) 2010; 88:451-8. [DOI: 10.1007/s00109-010-0600-y] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 01/13/2010] [Accepted: 01/21/2010] [Indexed: 01/20/2023]
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30
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Sauri A, Soprova Z, Wickström D, de Gier JW, Van der Schors RC, Smit AB, Jong WSP, Luirink J. The Bam (Omp85) complex is involved in secretion of the autotransporter haemoglobin protease. Microbiology (Reading) 2009; 155:3982-3991. [DOI: 10.1099/mic.0.034991-0] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Autotransporters are large virulence factors secreted by Gram-negative bacteria. They are synthesized with a C-terminal domain that forms a β-barrel pore in the outer membrane implicated in translocation of the upstream ‘passenger’ domain across the outer membrane. However, recent structural data suggest that the diameter of the β-barrel pore is not sufficient to allow the passage of partly folded structures observed for several autotransporters. Here, we have used a stalled translocation intermediate of the autotransporter Hbp to identify components involved in insertion and translocation of the protein across the outer membrane. At this intermediate stage the β-domain was not inserted and folded as an integral β-barrel in the outer membrane whereas part of the passenger was surface exposed. The intermediate was copurified with the periplasmic chaperone SurA and subunits of the Bam (Omp85) complex that catalyse the insertion and assembly of outer-membrane proteins. The data suggest a critical role for this general machinery in the translocation of autotransporters across the outer membrane.
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Affiliation(s)
- Ana Sauri
- Department of Molecular Microbiology, Institute of Molecular Cell Biology, VU University, 1081 HV Amsterdam, The Netherlands
| | - Zora Soprova
- Department of Molecular Microbiology, Institute of Molecular Cell Biology, VU University, 1081 HV Amsterdam, The Netherlands
| | - David Wickström
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Jan-Willem de Gier
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Roel C. Van der Schors
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, 1081 HV Amsterdam, The Netherlands
| | - August B. Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, 1081 HV Amsterdam, The Netherlands
| | - Wouter S. P. Jong
- Department of Molecular Microbiology, Institute of Molecular Cell Biology, VU University, 1081 HV Amsterdam, The Netherlands
| | - Joen Luirink
- Department of Molecular Microbiology, Institute of Molecular Cell Biology, VU University, 1081 HV Amsterdam, The Netherlands
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31
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Pauer H, Ferreira EDO, dos Santos-Filho J, Portela MB, Zingali RB, Soares RMA, Domingues RMCP. A TonB-dependent outer membrane protein as a Bacteroides fragilis fibronectin-binding molecule. ACTA ACUST UNITED AC 2009; 55:388-95. [PMID: 19187219 DOI: 10.1111/j.1574-695x.2009.00532.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The binding of Bacteroides fragilis to plasmatic fibronectin was investigated using strains isolated from healthy subjects and from patients with bacteremia. They were cultivated in a synthetic media in which variations in cysteine concentrations determined alterations in the oxidation-reduction potential (Eh). All the strains assayed were capable of adhering to plasmatic fibronectin when cultivated under oxidizing and reducing conditions. Bacteroides fragilis 1405 showed the greatest difference when the results under these conditions were compared and it was selected for further investigations. Chemical treatments suggested the involvement of a protein in the interaction between B. fragilis and plasmatic fibronectin. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of outer membrane proteins (OMPs) revealed differences between the extracts obtained from cultures grown under the two conditions. Protein bands of c. 102, 100, 77, 73, 50 and 40 kDa were more highly expressed under oxidizing than reducing conditions. Dot blot analysis showed a stronger recognition of plasmatic fibronectin by OMPs obtained from cultures grown under higher Eh, and Western blot assays confirmed a band of c. 102 kDa as fibronectin-binding protein. This protein was sequenced and revealed to be a putative TonB-dependent OMPs. PCR analysis confirmed the presence of this gene in all the studied strains.
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Affiliation(s)
- Heidi Pauer
- Departamento de Microbiologia Médica, Laboratório de Biologia de Protistas, Instituto de Microbiologia Prof Paulo de Góes/UFRJ, Rio de Janeiro, Brazil.
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32
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Full sequence and comparative analysis of the plasmid pAPEC-1 of avian pathogenic E. coli chi7122 (O78:K80:H9). PLoS One 2009; 4:e4232. [PMID: 19156210 PMCID: PMC2626276 DOI: 10.1371/journal.pone.0004232] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Accepted: 12/06/2008] [Indexed: 12/04/2022] Open
Abstract
Background Extra-intestinal pathogenic E. coli (ExPEC), including Avian Pathogenic E. coli (APEC), are very diverse. They cause a complex of diseases in Human, animals, and birds. Even though large plasmids are often associated with the virulence of ExPEC, their characterization is still in its infancy. Methodology/Principal Findings We fully sequenced and analyzed the large plasmid pAPEC-1 (103,275-bp) associated with the APEC strain χ7122, from worldwide serogroup O78∶K80∶H9. A putative virulence region spanning an 80-kb region of pAPEC-1 possesses four iron acquisition systems (iutA iucABCD, sitABCD, iroBCDN, and temperature-sensitive hemagglutinin tsh), a colicin V operon, increasing serum sensitivity iss, ompT, hlyF, and etsABC. Thirty three ORFs in pAPEC-1 are identified as insertion sequences (ISs) that belong to nine families with diverse origins. The full length of the transfer region in pAPEC-1 (11 kb) is shorter compared to the tra region of other sequenced F plasmids; the absence of some tra genes in pAPEC-1 affects its self-transferability, and the conjugative function of the plasmid was effective only in the presence of other plasmids. Two-replicon systems, repFIIA-repFIC and repFIB, and two post-segregational systems, srnB and hok/sok, are also present in the sequence of pAPEC-1. The comparison of the pAPEC-1 sequence with the two available plasmid sequences reveals more gene loss and reorganization than previously appreciated. The presence of pAPEC-1-associated genes is assessed in human ExPEC by PCR. Many patterns of association between genes are found. Conclusions/Significance The pathotype typical of pAPEC-1 was present in some human strains, which indicates a horizontal transfer between strains and the zoonotic risk of APEC strains. ColV plasmids could have common virulence genes that could be acquired by transposition, without sharing genes of plasmid function.
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33
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Sijbrandi R, Stork M, Luirink J, Otto BR. Pbp, a cell-surface exposed plasminogen binding protein of Bacteroides fragilis. Microbes Infect 2008; 10:514-21. [PMID: 18403231 DOI: 10.1016/j.micinf.2008.01.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 01/24/2008] [Accepted: 01/25/2008] [Indexed: 11/29/2022]
Abstract
The Gram-negative anaerobic bacterium B. fragilis is a member of the commensal flora of the human intestine, but is also frequently found in severe intra-abdominal infections. Several B. fragilis virulence factors have been implicated in the development of these infections. A B. fragilis protein of circa 60-kDa was identified as a putative plasminogen binding protein (Pbp). The corresponding gene was located, cloned, sequenced and the subcellular localization of the protein was investigated. Pbp was both determined in the outer membrane of B. fragilis and of E. coli that expressed the cloned protein. Protease accessibility studies showed that the protein is expressed at the cell surface. Importantly, we demonstrated that Pbp is sufficient and required for plasminogen binding to whole cells in both E. coli and B. fragilis. Pbp-like proteins were also detected in some other Bacteroides subspecies. The role of this potential B. fragilis virulence factor in pathogenicity is discussed.
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Affiliation(s)
- Robert Sijbrandi
- Department of Molecular Microbiology, Faculty of Earth and Life Sciences, VU-University Amsterdam de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
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34
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Renn JP, Clark PL. A conserved stable core structure in the passenger domain β-helix of autotransporter virulence proteins. Biopolymers 2008; 89:420-7. [DOI: 10.1002/bip.20924] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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35
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Jong WSP, ten Hagen-Jongman CM, den Blaauwen T, Slotboom DJ, Tame JRH, Wickström D, de Gier JW, Otto BR, Luirink J. Limited tolerance towards folded elements during secretion of the autotransporter Hbp. Mol Microbiol 2007; 63:1524-36. [PMID: 17302825 DOI: 10.1111/j.1365-2958.2007.05605.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Many virulence factors secreted by pathogenic Gram-negative bacteria belong to the autotransporter (AT) family. ATs consist of a passenger domain, which is the actual secreted moiety, and a beta-domain that facilitates the transfer of the passenger domain across the outer membrane. Here, we analysed folding and translocation of the AT passenger, using Escherichia coli haemoglobin protease (Hbp) as a model protein. Dual cysteine mutagenesis, instigated by the unique crystal structure of the Hbp passenger, resulted in intramolecular disulphide bond formation dependent on the periplasmic enzyme DsbA. A small loop tied off by a disulphide bond did not interfere with secretion of Hbp. In contrast, a bond between different domains of the Hbp passenger completely blocked secretion resulting in degradation by the periplasmic protease DegP. In the absence of DegP, a translocation intermediate accumulated in the outer membrane. A similar jammed intermediate was formed upon insertion of a calmodulin folding moiety into Hbp. The data suggest that Hbp can fold in the periplasm but must retain a certain degree of flexibility and/or modest width to allow translocation across the outer membrane.
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Affiliation(s)
- Wouter S P Jong
- Department of Molecular Microbiology, Institute of Molecular Cell Biology, Vrije Universiteit, 1081 HV Amsterdam, the Netherlands
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36
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Durant L, Metais A, Soulama-Mouze C, Genevard JM, Nassif X, Escaich S. Identification of candidates for a subunit vaccine against extraintestinal pathogenic Escherichia coli. Infect Immun 2006; 75:1916-25. [PMID: 17145948 PMCID: PMC1865706 DOI: 10.1128/iai.01269-06] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Extraintestinal pathogenic Escherichia coli (ExPEC) strains cause a large spectrum of infections. The majority of ExPEC strains are closely related to the B2 or the D phylogenetic group. The aim of our study was to develop a protein-based vaccine against these ExPEC strains. To this end, we identified ExPEC-specific genomic regions, using a comparative genome analysis, between the nonpathogenic E. coli strain K-12 MG1655 and ExPEC strains C5 (meningitis isolate) and CFT073 (urinary tract infection isolate). The analysis of these genomic regions allowed the selection of 40 open reading frames, which are conserved among B2/D clinical isolates and encode proteins with putative outer membrane localization. These genes were cloned, and recombinant proteins were purified and assessed as vaccine candidates. After immunization of BALB/c mice, five proteins induced a significant protective immunity against a lethal challenge with a clinical E. coli strain of the B2 group. In passive immunization assays, antigen-specific antibodies afforded protection to naive mice against a lethal challenge. Three of these antigens were related to iron acquisition metabolism, an important virulence factor of the ExPEC, and two corresponded to new, uncharacterized proteins. Due to the large number of genetic differences that exists between commensal and pathogenic strains of E. coli, our results demonstrate that it is possible to identify targets that elicit protective immune responses specific to those strains. The five protective antigens could constitute the basis for a preventive subunit vaccine against diseases caused by ExPEC strains.
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Affiliation(s)
- Lionel Durant
- Mutabilis SA, 102 route de Noisy, 93230 Romainville, France
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37
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Borbone S, Cascone C, Santagati M, Mezzatesta ML, Stefani S. Bactericidal activity of ertapenem against major intra-abdominal pathogens. Int J Antimicrob Agents 2006; 28:396-401. [PMID: 17045463 DOI: 10.1016/j.ijantimicag.2006.07.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 07/17/2006] [Accepted: 07/20/2006] [Indexed: 10/24/2022]
Abstract
Treatment of intra-abdominal infections remains a challenge owing to their polymicrobial nature and associated mortality risk. Treatment regimens must provide broad-spectrum coverage, including Gram-positive and Gram-negative aerobic and anaerobic bacteria of gastrointestinal origin. Ertapenem is a long-acting 1-beta-methyl parenteral group 1 carbapenem antibiotic that has a broad antibacterial spectrum and once-daily dosing supported by clinical studies. It is active against Gram-positive and Gram-negative bacteria, including Enterobacteriaceae, Streptococcus pneumoniae and most species of anaerobic bacteria. The aim of this study was to measure the killing effects of ertapenem against a selected group of strains responsible for intra-abdominal infections. Gram-negative isolates comprised the following species: Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Klebsiella ozaenae, Enterobacter cloacae and Proteus mirabilis (extended-spectrum beta-lactamase (ESBL) producers and non-producers). Gram-positive isolates comprised methicillin-susceptible Staphylococcus aureus (MSSA), Enterococcus faecalis and anaerobic Bacteroides fragilis. Ertapenem activity was tested by determination of minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs). Killing curves were performed in monocultures and co-cultures at selected antibiotic concentrations. Ertapenem showed a rapid and potent bactericidal activity in the first few hours of the kinetic curves against E. coli (6 log(10) colony-forming unit (CFU) reduction in the first 2h), B. fragilis (4 log(10) CFU reduction in 4h), MSSA (3 log(10) CFU reduction in 4-6h), K. ozaenae (ESBL+), K. pneumoniae (ESBL+ and -), E. cloacae (ESBL-) in 1h and P. mirabilis (ESBL+) in the first 2h. The potent bactericidal activity of ertapenem compared with ceftriaxone and piperacillin/tazobactam was well demonstrated in the co-cultures of E. coli-B. fragilis and E. coli-B. fragilis-E. faecalis, whilst ertapenem was shown to be bactericidal at 24h in the mixed culture of S. aureus-P. mirabilis. These results support the potent in vitro bactericidal activity of ertapenem against all multiresistant strains selected in this study and the use of this drug in the treatment of intra-abdominal infections.
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Affiliation(s)
- Sonia Borbone
- Department of Microbiological and Gynaecological Science, University of Catania, Via Androne 81, 95124 Catania, Italy
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38
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Kilian M, Frandsen EVG, Haubek D, Poulsen K. The etiology of periodontal disease revisited by population genetic analysis. Periodontol 2000 2006; 42:158-79. [PMID: 16930310 DOI: 10.1111/j.1600-0757.2006.00159.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Mogens Kilian
- Department of Bacteriology, Institute of Medical Microbiology and Immunology, University of Aarhus, Aarhus, Denmark
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39
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Whitby PW, Vanwagoner TM, Seale TW, Morton DJ, Stull TL. Transcriptional profile of Haemophilus influenzae: effects of iron and heme. J Bacteriol 2006; 188:5640-5. [PMID: 16855256 PMCID: PMC1540045 DOI: 10.1128/jb.00417-06] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Haemophilus influenzae requires either heme or a porphyrin and iron source for growth. Microarray studies of H. influenzae strain Rd KW20 identified 162 iron/heme-regulated genes, representing approximately 10% of the genome, with > or =1.5-fold changes in transcription in response to iron/heme availability in vitro. Eighty genes were preferentially expressed under iron/heme restriction; 82 genes were preferentially expressed under iron/heme-replete conditions.
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Affiliation(s)
- Paul W Whitby
- Department of Pediatrics, CHO 2308, 940 NE 13th St., Oklahoma City, OK 73104, USA
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40
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Abstract
This review focuses on the function of the Escherichia coli and Salmonella autotransporters for which a considerable amount of literature is available. Members of the serine protease autotransporters of the Enterobacteriaceae (SPATEs) family are proteins from E. coli and Shigella spp., which, like the Neisseria and Haemophilus influenzae IgA1 proteases and Hap, possess a consensus serine protease motif. The largest subfamily of autotransporters is defined by the AidA conserved domain COG3468 and consists of members from a diverse range of animal and plant pathogens including E. coli, S. enterica, Yersinia pestis. This subfamily, which is composed of more than 55 proteins, possesses some of the best-characterized autotransporter proteins including the S. flexneri mediator of motility IcsA, the major phase-variable E. coli outer membrane protein antigen 43 (Ag43) and the diffuse adhering E. coli (DAEC) adhesin AIDA-I, from which this subfamily derives its name. Another member of the AIDA-I family, and one of the most studied autotransporter proteins, is IcsA. The autotransporter pathway is emerging as the most common mechanism of protein translocation across the gram-negative outer membrane.
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Affiliation(s)
- Ian R Henderson
- Bacterial Pathogenesis and Genomics Unit, Division of Immunity and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - James P Nataro
- Center for Vaccine Development, Department of Pediatrics, University of Maryland School of Medicine, 685 W. Baltimore St., Baltimore, MD 21201
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41
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Otto BR, Sijbrandi R, Luirink J, Oudega B, Heddle JG, Mizutani K, Park SY, Tame JRH. Crystal structure of hemoglobin protease, a heme binding autotransporter protein from pathogenic Escherichia coli. J Biol Chem 2005; 280:17339-45. [PMID: 15728184 DOI: 10.1074/jbc.m412885200] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The acquisition of iron is essential for the survival of pathogenic bacteria, which have consequently evolved a wide variety of uptake systems to extract iron and heme from host proteins such as hemoglobin. Hemoglobin protease (Hbp) was discovered as a factor involved in the symbiosis of pathogenic Escherichia coli and Bacteroides fragilis, which cause intra-abdominal abscesses. Released from E. coli, this serine protease autotransporter degrades hemoglobin and delivers heme to both bacterial species. The crystal structure of the complete passenger domain of Hbp (110 kDa) is presented, which is the first structure from this class of serine proteases and the largest parallel beta-helical structure yet solved.
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Affiliation(s)
- Ben R Otto
- Department of Molecular Microbiology, Faculty of Earth and Life Sciences, Vrije Universiteit de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
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42
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Sijbrandi R, Den Blaauwen T, Tame JRH, Oudega B, Luirink J, Otto BR. Characterization of an iron-regulated alpha-enolase of Bacteroides fragilis. Microbes Infect 2005; 7:9-18. [PMID: 15716066 DOI: 10.1016/j.micinf.2004.09.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Revised: 09/16/2004] [Accepted: 09/22/2004] [Indexed: 10/26/2022]
Abstract
This study describes the identification, cloning and molecular characterization of the alpha-enolase P46 of Bacteroides fragilis. The gram-negative anaerobic bacterium B. fragilis is a member of the commensal flora of the human intestine but is also frequently found in severe intra-abdominal infections. Several virulence factors have been described that may be involved in the development of these infections. Many of these virulence factors are upregulated under conditions of iron- or heme-starvation. We found a major protein of 46 kDa (P46) that is upregulated under iron-depleted conditions. This protein was identified as an alpha-enolase. Alpha-enolases in several gram-positive bacteria and eukaryotic cells are located at the cell surface and function as plasminogen-binding proteins. Localization studies demonstrated that P46 is mainly located in the cytoplasm and partly associated with the inner membrane (IM). Under iron-restricted conditions, however, P46 is localized primarily in the IM fraction. Plasminogen-binding to B. fragilis cells did occur but was not P46 dependent. A 60-kDa protein was identified as a putative plasminogen-binding protein in B. fragilis.
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Affiliation(s)
- Robert Sijbrandi
- Department of Molecular Microbiology, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
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43
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Tivendale KA, Allen JL, Ginns CA, Crabb BS, Browning GF. Association of iss and iucA, but not tsh, with plasmid-mediated virulence of avian pathogenic Escherichia coli. Infect Immun 2004; 72:6554-60. [PMID: 15501787 PMCID: PMC523064 DOI: 10.1128/iai.72.11.6554-6560.2004] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Avian pathogenic Escherichia coli (APEC) is an economically important respiratory pathogen of chickens worldwide. Factors previously associated with the virulence of APEC include adhesins, iron-scavenging mechanisms, the production of colicin V (ColV), serum resistance, and temperature-sensitive hemagglutination, but virulence has generally been assessed by parenteral inoculation, which does not replicate the normal respiratory route of infection. A large plasmid, pVM01, is essential for virulence in APEC strain E3 in chickens after aerosol exposure. Here we establish the size of pVM01 to be approximately 160 kb and show that the putative virulence genes iss (increased serum survival) and tsh (temperature-sensitive hemagglutinin) and the aerobactin operon are on the plasmid. These genes were not clustered on pVM01 but, rather, were each located in quite distinct regions. Examination of APEC strains with defined levels of respiratory pathogenicity after aerosol exposure showed that both the aerobactin operon and iss were associated with high levels of virulence in APEC but that the possession of either gene was sufficient for intermediate levels of virulence. In contrast, the presence of tsh was not necessary for high levels of virulence. Thus, both the aerobactin operon and iss are associated with virulence in APEC after exposure by the natural route of infection. The similarities between APEC and extraintestinal E. coli infection in other species suggests that they may be useful models for definition of the role of these virulence genes and of other novel virulence genes that may be located on their virulence plasmids.
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Affiliation(s)
- Kelly A Tivendale
- Department of Veterinary Science, The University of Melbourne, Parkville, 3010 Victoria, Australia
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44
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Henderson IR, Navarro-Garcia F, Desvaux M, Fernandez RC, Ala'Aldeen D. Type V protein secretion pathway: the autotransporter story. Microbiol Mol Biol Rev 2004; 68:692-744. [PMID: 15590781 PMCID: PMC539010 DOI: 10.1128/mmbr.68.4.692-744.2004] [Citation(s) in RCA: 635] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Gram-negative bacteria possess an outer membrane layer which constrains uptake and secretion of solutes and polypeptides. To overcome this barrier, bacteria have developed several systems for protein secretion. The type V secretion pathway encompasses the autotransporter proteins, the two-partner secretion system, and the recently described type Vc or AT-2 family of proteins. Since its discovery in the late 1980s, this family of secreted proteins has expanded continuously, due largely to the advent of the genomic age, to become the largest group of secreted proteins in gram-negative bacteria. Several of these proteins play essential roles in the pathogenesis of bacterial infections and have been characterized in detail, demonstrating a diverse array of function including the ability to condense host cell actin and to modulate apoptosis. However, most of the autotransporter proteins remain to be characterized. In light of new discoveries and controversies in this research field, this review considers the autotransporter secretion process in the context of the more general field of bacterial protein translocation and exoprotein function.
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Affiliation(s)
- Ian R Henderson
- Division of Immunity and Infection, University of Birmingham, Birmingham B15 2TT, UK.
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Abstract
Few microorganisms are as versatile as Escherichia coli. An important member of the normal intestinal microflora of humans and other mammals, E. coli has also been widely exploited as a cloning host in recombinant DNA technology. But E. coli is more than just a laboratory workhorse or harmless intestinal inhabitant; it can also be a highly versatile, and frequently deadly, pathogen. Several different E. coli strains cause diverse intestinal and extraintestinal diseases by means of virulence factors that affect a wide range of cellular processes.
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Affiliation(s)
- James B Kaper
- Center for Vaccine Development, Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
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Heimer SR, Rasko DA, Lockatell CV, Johnson DE, Mobley HLT. Autotransporter genes pic and tsh are associated with Escherichia coli strains that cause acute pyelonephritis and are expressed during urinary tract infection. Infect Immun 2004; 72:593-7. [PMID: 14688142 PMCID: PMC343984 DOI: 10.1128/iai.72.1.593-597.2004] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have identified two chromosomal open reading frames in uropathogenic Escherichia coli (UPEC) strain CFT073 which are highly homologous to serine protease autotransporters Pic and Tsh. Both cloned determinants were correlated with the presence of 105- to 110-kDa proteins in the culture supernatants. Furthermore, in cellular fractionation experiments, 30-kDa polypeptides were identified in the outer membrane; we speculated that these proteins are the beta-barrel portions of the autotransporter homologues. Furthermore, Pic-containing culture supernatants have serine protease activity. In reverse transcription-PCR analyses, the expression of the pic and tsh genes in E. coli CFT073 was higher in broth cultures grown at 37 degrees C than at 25 degrees C. Moreover, pic and tsh were expressed by bacteria isolated from urine of transurethrally infected mice. The tsh determinant was identified in 63% of our clinical UPEC strain isolates (n = 87) and in 33% of fecal strains (n = 27), whereas pic was present in 31% of the pyelonephritis (n = 67) and 7% of the fecal strains. There was no significant correlation between cystitis strains (n = 20) and the pic determinant.
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Affiliation(s)
- Susan R Heimer
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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Bates CS, Montañez GE, Woods CR, Vincent RM, Eichenbaum Z. Identification and characterization of a Streptococcus pyogenes operon involved in binding of hemoproteins and acquisition of iron. Infect Immun 2003; 71:1042-55. [PMID: 12595414 PMCID: PMC148835 DOI: 10.1128/iai.71.3.1042-1055.2003] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The hemolytic Streptococcus pyogenes can use a variety of heme compounds as an iron source. In this study, we investigate hemoprotein utilization by S. pyogenes. We demonstrate that surface proteins contribute to the binding of hemoproteins to S. pyogenes. We identify an ABC transporter from the iron complex family named sia for streptococcal iron acquisition, which consists of a lipoprotein (siaA), membrane permease (siaB), and ATPase (siaC). The sia transporter is part of a highly conserved, iron regulated, 10-gene operon. SiaA, which was localized to the cell membrane, could specifically bind hemoglobin. The operon's first gene encodes a novel bacterial protein that bound hemoglobin, myoglobin, heme-albumin, and hemoglobin-haptoglobin (but not apo-haptoglobin) and therefore was named Shr, for streptococcal hemoprotein receptor. PhoZ fusion and Western blot analysis showed that Shr has a leader peptide and is found in both membrane-bound and soluble forms. An M1 SF370 strain with a polar mutation in shr was more resistant to streptonigrin and hydrogen peroxide, suggesting decreased iron uptake. The addition of hemoglobin to the culture medium increased cell resistance to hydrogen peroxide in SF370 but not in the mutant, implying the sia operon may be involved in hemoglobin-dependent resistance to oxidative stress. The shr mutant demonstrated reduced hemoglobin binding, though cell growth in iron-depleted medium supplemented with hemoglobin, whole blood, or ferric citrate was not affected, suggesting additional systems are involved in hemoglobin utilization. SiaA and Shr are the first hemoprotein receptors identified in S. pyogenes; their possible role in iron capture is discussed.
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Affiliation(s)
- Christopher S Bates
- Department of Biology, College of Arts and Sciences, Georgia State University, Atlanta, Georgia 30303, USA
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Sijbrandi R, Urbanus ML, ten Hagen-Jongman CM, Bernstein HD, Oudega B, Otto BR, Luirink J. Signal recognition particle (SRP)-mediated targeting and Sec-dependent translocation of an extracellular Escherichia coli protein. J Biol Chem 2003; 278:4654-9. [PMID: 12466262 DOI: 10.1074/jbc.m211630200] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hemoglobin protease (Hbp) is a hemoglobin-degrading protein that is secreted by a human pathogenic Escherichia coli strain via the autotransporter mechanism. Little is known about the earliest steps in autotransporter secretion, i.e. the targeting to and translocation across the inner membrane. Here, we present evidence that Hbp interacts with the signal recognition particle (SRP) and the Sec-translocon early during biogenesis. Furthermore, Hbp requires a functional SRP targeting pathway and Sec-translocon for optimal translocation across the inner membrane. SecB is not required for targeting of Hbp but can compensate to some extent for the lack of SRP. Hbp is synthesized with an unusually long signal peptide that is remarkably conserved among a subset of autotransporters. We propose that these autotransporters preferentially use the co-translational SRP/Sec route to avoid adverse effects of the exposure of their mature domains in the cytoplasm.
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Affiliation(s)
- Robert Sijbrandi
- Department of Molecular Microbiology, Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands
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Dozois CM, Daigle F, Curtiss R. Identification of pathogen-specific and conserved genes expressed in vivo by an avian pathogenic Escherichia coli strain. Proc Natl Acad Sci U S A 2003; 100:247-52. [PMID: 12506201 PMCID: PMC140941 DOI: 10.1073/pnas.232686799] [Citation(s) in RCA: 180] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Escherichia coli is a diverse bacterial species that comprises commensal nonpathogenic strains such as E. coli K-12 and pathogenic strains that cause a variety of diseases in different host species. Avian pathogenic E. coli strain chi7122 (O78:K80:H9) was used in a chicken infection model to identify bacterial genes that are expressed in infected tissues. By using the cDNA selection method of selective capture of transcribed sequences and enrichment for the isolation of pathogen-specific (non-E. coli K-12) transcripts, pathogen-specific cDNAs were identified. Pathogen-specific transcripts corresponded to putative adhesins, lipopolysaccharide core synthesis, iron-responsive, plasmid- and phage-encoded genes, and genes of unknown function. Specific deletion of the aerobactin siderophore system and E. coli iro locus, which were identified by selective capture of transcribed sequences, demonstrated that these pathogen-specific systems contribute to the virulence of strain chi7122. Consecutive blocking to enrich for selection of pathogen-specific genes did not completely eliminate the presence of transcripts that corresponded to sequences also present in E. coli K-12. These E. coli conserved genes are likely to be highly expressed in vivo and contribute to growth or virulence. Overall, the approach we have used simultaneously provided a means to identify novel pathogen-specific genes expressed in vivo and insight regarding the global gene expression and physiology of a pathogenic E. coli strain in a natural animal host during the infectious process.
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Affiliation(s)
- Charles M Dozois
- Department of Biology, Washington University, Campus Box 1137, One Brookings Drive, St. Louis, MO 63130, USA
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Hayashida H, Poulsen K, Kilian M. Differences in iron acquisition from human haemoglobin among strains of Actinobacillus actinomycetemcomitans. MICROBIOLOGY (READING, ENGLAND) 2002; 148:3993-4001. [PMID: 12480903 DOI: 10.1099/00221287-148-12-3993] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
To get a better insight into the physiology of the high-toxic JP2 clone of Actinobacillus actinomycetemcomitans serotype b, which is strongly associated with juvenile periodontitis in adolescents of African descent, the modes of iron acquisition in this clone were examined and compared to those of other strains of the species. None of the strains examined could utilize human transferrin as a source of iron. This was in accordance with the presence of a non-functional tbpA gene, which normally encodes the A subunit of the transferrin-binding-protein complex. Southern blot analysis indicated that functional duplications of tbpA were not present in the genome. Thus, A. actinomycetemcomitans seems to be in a process of evolution, in which iron acquisition from host transferrin is not essential as in many other members of the pasteurellaceae. All strains could utilize haem as a source of iron. All 11 A. actinomycetemcomitans strains examined harboured a single genomic sequence with homology to the hgpA gene encoding haemoglobin-binding protein A in Haemophilus influenzae. However, in all three strains belonging to the JP2 clone and in one serotype e strain hgpA was a pseudogene. Seven other strains possessed a functional hgpA gene which, according to insertion mutagenesis experiments, was responsible for the ability of these strains to utilize haemoglobin as a source of iron. Thus, the presence of an hgpA pseudogene and the inability to use human haemoglobin as an iron source discriminate the high-toxic JP2 clone from low-toxic serotype b strains and most other strains of A. actinomycetemcomitans.
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Affiliation(s)
- Hideaki Hayashida
- Division of Oral Health Services Research, Department of Public Health, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8588, Japan2
- Department of Medical Microbiology and Immunology, University of Aarhus, the Bartholin Building, DK-8000 Aarhus C, Denmark1
| | - Knud Poulsen
- Department of Medical Microbiology and Immunology, University of Aarhus, the Bartholin Building, DK-8000 Aarhus C, Denmark1
| | - Mogens Kilian
- Department of Medical Microbiology and Immunology, University of Aarhus, the Bartholin Building, DK-8000 Aarhus C, Denmark1
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