1
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Jastrab JB, Kagan JC. Strategies of bacterial detection by inflammasomes. Cell Chem Biol 2024; 31:835-850. [PMID: 38636521 PMCID: PMC11103797 DOI: 10.1016/j.chembiol.2024.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/09/2024] [Accepted: 03/26/2024] [Indexed: 04/20/2024]
Abstract
Mammalian innate immunity is regulated by pattern-recognition receptors (PRRs) and guard proteins, which use distinct strategies to detect infections. PRRs detect bacterial molecules directly, whereas guards detect host cell manipulations by microbial virulence factors. Despite sensing infection through different mechanisms, both classes of innate immune sensors can activate the inflammasome, an immune complex that can mediate cell death and inflammation. Inflammasome-mediated immune responses are crucial for host defense against many bacterial pathogens and prevent invasion by non-pathogenic organisms. In this review, we discuss the mechanisms by which inflammasomes are stimulated by PRRs and guards during bacterial infection, and the strategies used by virulent bacteria to evade inflammasome-mediated immunity.
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Affiliation(s)
- Jordan B Jastrab
- Division of Gastroenterology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; Division of Infectious Diseases, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Jonathan C Kagan
- Division of Gastroenterology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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2
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Bryant OJ, Fraser GM. Identification of a new export signal that targets early subunits to the flagellar type III secretion export machinery. mBio 2024; 15:e0306723. [PMID: 38376149 PMCID: PMC10936197 DOI: 10.1128/mbio.03067-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 01/26/2024] [Indexed: 02/21/2024] Open
Abstract
Type III secretion systems (T3SSs) are essential for motility and virulence in many bacterial pathogens. Proteins destined for the flagellar T3SS contain at least two export signals in their N-terminal D0 domain. Here, we describe a third carboxy (C)-terminal signal in early flagellar subunits that facilitates subunit targeting to the export machinery. Mutational analysis identified critical residues within the flagellar hook subunit C-terminal export signal. The flagellar ATPase and cytoplasmic ring components were not required for this targeting, indicating that core export machinery components facilitate substrate targeting via the C-terminal export signal. More broadly, these results demonstrate that multiple distinct export signals within type III secretion substrates facilitate distinct export events at the T3SS export machinery. Our data establish key events in the export mechanism of type III secretion systems: targeting of subunits to and their sequential interactions with key components of the export machinery. IMPORTANCE Many bacterial pathogens utilize T3SS to inject virulence proteins (effectors) into host cells or to assemble flagella on the bacterial cell surface. Bacterial flagella present a paradigm for how cells build and operate complex cell-surface "nanomachines." Efficient subunit targeting from the bacterial cytosol to type III secretion systems is essential for rapid assembly and secretion by T3SSs. Subunits are thought to dock at the export machinery before being unfolded and translocated into the export channel. However, little is known about how subunits dock at the export machinery and the events that occur post docking. Here, we identified a new export signal within the C-termini of subunits that is essential for targeting of subunits to the type III export machinery. We show that this new export signal and previously identified export signals are recognized separately and sequentially, revealing a pathway for subunit transit through the type III export machinery in which sequential recognition events carry out different roles at major steps in the export pathway.
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Affiliation(s)
- Owain J. Bryant
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Gillian M. Fraser
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom
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3
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Halte M, Andrianova EP, Goosmann C, Chevance FFV, Hughes KT, Zhulin IB, Erhardt M. FlhE functions as a chaperone to prevent formation of periplasmic flagella in Gram-negative bacteria. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.11.584431. [PMID: 38558991 PMCID: PMC10979839 DOI: 10.1101/2024.03.11.584431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The bacterial flagellum is an organelle utilized by many Gram-negative bacteria to facilitate motility. The flagellum is composed of a several µm long, extracellular filament that is connected to a cytoplasmic rotor-stator complex via a periplasmic rod. Composed of ∼20 structural proteins, ranging from a few subunits to several thousand building blocks, the flagellum is a paradigm of a complex macromolecular structure that utilizes a highly regulated assembly process. This process is governed by multiple checkpoints that ensure an ordered gene expression pattern coupled to the assembly of the various flagellar building blocks in order to produce a functional flagellum. Using epifluorescence, super-resolution STED and transmission electron microscopy, we discovered that in Salmonella , the absence of one periplasmic protein, FlhE, prevents proper flagellar morphogenesis and results in the formation of periplasmic flagella. The periplasmic flagella disrupt cell wall synthesis, leading to a loss of the standard cell morphology resulting in cell lysis. We propose a model where FlhE functions as a periplasmic chaperone to control assembly of the periplasmic rod to prevent formation of periplasmic flagella. Our results highlight that bacteria evolved sophisticated regulatory mechanisms to control proper flagellar assembly and minor deviations from this highly regulated process can cause dramatic physiological consequences.
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4
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Einenkel R, Halte M, Erhardt M. Quantifying Substrate Protein Secretion via the Type III Secretion System of the Bacterial Flagellum. Methods Mol Biol 2024; 2715:577-592. [PMID: 37930553 DOI: 10.1007/978-1-0716-3445-5_36] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
Protein transport across the cytoplasmic membrane is coupled to energy derived from ATP hydrolysis or the proton motive force. A sophisticated, multi-component type III secretion system (T3SS) exports substrate proteins of both the bacterial flagellum and virulence-associated injectisome system of many Gram-negative pathogens. The T3SS is primarily a proton motive force-driven protein exporter. Here, we describe a method to investigate the export of substrate proteins of the flagellar T3SS into the culture supernatant under conditions that manipulate the proton motive force. Further, we describe methods to precisely quantify flagellar protein export into the culture supernatant using a split NanoLuc luciferase, and how fluorescence labeling of the extracellular flagellar filament can bring insights into the protein export rate of individual flagellar T3SS.
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Affiliation(s)
| | | | - Marc Erhardt
- Humboldt Universität zu Berlin, Berlin, Germany.
- Max Planck Unit for the Science of Pathogens, Berlin, Germany.
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5
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Minamino T, Kinoshita M. Structure, Assembly, and Function of Flagella Responsible for Bacterial Locomotion. EcoSal Plus 2023; 11:eesp00112023. [PMID: 37260402 DOI: 10.1128/ecosalplus.esp-0011-2023] [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: 01/18/2023] [Accepted: 04/14/2023] [Indexed: 01/28/2024]
Abstract
Many motile bacteria use flagella for locomotion under a variety of environmental conditions. Because bacterial flagella are under the control of sensory signal transduction pathways, each cell is able to autonomously control its flagellum-driven locomotion and move to an environment favorable for survival. The flagellum of Salmonella enterica serovar Typhimurium is a supramolecular assembly consisting of at least three distinct functional parts: a basal body that acts as a bidirectional rotary motor together with multiple force generators, each of which serves as a transmembrane proton channel to couple the proton flow through the channel with torque generation; a filament that functions as a helical propeller that produces propulsion; and a hook that works as a universal joint that transmits the torque produced by the rotary motor to the helical propeller. At the base of the flagellum is a type III secretion system that transports flagellar structural subunits from the cytoplasm to the distal end of the growing flagellar structure, where assembly takes place. In recent years, high-resolution cryo-electron microscopy (cryoEM) image analysis has revealed the overall structure of the flagellum, and this structural information has made it possible to discuss flagellar assembly and function at the atomic level. In this article, we describe what is known about the structure, assembly, and function of Salmonella flagella.
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Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
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6
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Worrall LJ, Majewski DD, Strynadka NCJ. Structural Insights into Type III Secretion Systems of the Bacterial Flagellum and Injectisome. Annu Rev Microbiol 2023; 77:669-698. [PMID: 37713458 DOI: 10.1146/annurev-micro-032521-025503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/17/2023]
Abstract
Two of the most fascinating bacterial nanomachines-the broadly disseminated rotary flagellum at the heart of cellular motility and the eukaryotic cell-puncturing injectisome essential to specific pathogenic species-utilize at their core a conserved export machinery called the type III secretion system (T3SS). The T3SS not only secretes the components that self-assemble into their extracellular appendages but also, in the case of the injectisome, subsequently directly translocates modulating effector proteins from the bacterial cell into the infected host. The injectisome is thought to have evolved from the flagellum as a minimal secretory system lacking motility, with the subsequent acquisition of additional components tailored to its specialized role in manipulating eukaryotic hosts for pathogenic advantage. Both nanomachines have long been the focus of intense interest, but advances in structural and functional understanding have taken a significant step forward since 2015, facilitated by the revolutionary advances in cryo-electron microscopy technologies. With several seminal structures of each nanomachine now captured, we review here the molecular similarities and differences that underlie their diverse functions.
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Affiliation(s)
- Liam J Worrall
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia, Canada; , ,
| | - Dorothy D Majewski
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia, Canada; , ,
- Current affiliation: Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
| | - Natalie C J Strynadka
- Department of Biochemistry and Molecular Biology and Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia, Canada; , ,
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7
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Kint N, Viollier PH. Extracellular transfer of a conserved polymerization factor for multi-flagellin filament assembly in Caulobacter. Cell Rep 2023; 42:112890. [PMID: 37515768 DOI: 10.1016/j.celrep.2023.112890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 06/15/2023] [Accepted: 07/12/2023] [Indexed: 07/31/2023] Open
Abstract
Unidirectional growth of filamentous protein assemblies including the bacterial flagellum relies on dedicated polymerization factors (PFs). The molecular determinants and structural transitions imposed by PFs on multi-subunit assembly are poorly understood. Here, we unveil FlaY from the polarized α-proteobacterium Caulobacter crescentus as a defining member of an alternative class of specialized flagellin PFs. Unlike the paradigmatic FliD capping protein, FlaY relies on a funnel-like β-propeller fold for flagellin polymerization. FlaY binds flagellin and is secreted by the flagellar secretion apparatus, yet it can also promote flagellin polymerization exogenously when donated from flagellin-deficient cells, serving as a transferable, extracellular public good. While the surge in FlaY abundance precedes bulk flagellin synthesis, FlaY-independent filament assembly is enhanced by mutation of a conserved region in multiple flagellin paralogs. We suggest that FlaYs are (multi-)flagellin PFs that evolved convergently to FliDs yet appropriated the versatile β-propeller fold implicated in human diseases for chaperone-assisted filament assembly.
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Affiliation(s)
- Nicolas Kint
- Department of Microbiology & Molecular Medicine and Geneva Center for Inflammation Research (GCIR), Faculty of Medicine, University of Geneva, Rue Michel Servet 1, 1211 Genève, Switzerland.
| | - Patrick H Viollier
- Department of Microbiology & Molecular Medicine and Geneva Center for Inflammation Research (GCIR), Faculty of Medicine, University of Geneva, Rue Michel Servet 1, 1211 Genève, Switzerland.
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8
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Nedeljković M, Kreutzberger MAB, Postel S, Bonsor D, Xing Y, Jacob N, Schuler WJ, Egelman EH, Sundberg EJ. An unbroken network of interactions connecting flagellin domains is required for motility in viscous environments. PLoS Pathog 2023; 19:e1010979. [PMID: 37253071 PMCID: PMC10256154 DOI: 10.1371/journal.ppat.1010979] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 06/09/2023] [Accepted: 05/08/2023] [Indexed: 06/01/2023] Open
Abstract
In its simplest form, bacterial flagellar filaments are composed of flagellin proteins with just two helical inner domains, which together comprise the filament core. Although this minimal filament is sufficient to provide motility in many flagellated bacteria, most bacteria produce flagella composed of flagellin proteins with one or more outer domains arranged in a variety of supramolecular architectures radiating from the inner core. Flagellin outer domains are known to be involved in adhesion, proteolysis and immune evasion but have not been thought to be required for motility. Here we show that in the Pseudomonas aeruginosa PAO1 strain, a bacterium that forms a ridged filament with a dimerization of its flagellin outer domains, motility is categorically dependent on these flagellin outer domains. Moreover, a comprehensive network of intermolecular interactions connecting the inner domains to the outer domains, the outer domains to one another, and the outer domains back to the inner domain filament core, is required for motility. This inter-domain connectivity confers PAO1 flagella with increased stability, essential for its motility in viscous environments. Additionally, we find that such ridged flagellar filaments are not unique to Pseudomonas but are, instead, present throughout diverse bacterial phyla.
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Affiliation(s)
- Marko Nedeljković
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Mark A. B. Kreutzberger
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
| | - Sandra Postel
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Daniel Bonsor
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Yingying Xing
- School of Life Science and Technology, China Pharmaceutical University, Nanjing, China
| | - Neil Jacob
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - William J. Schuler
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Edward H. Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America
| | - Eric J. Sundberg
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, United States of America
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9
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Bizic M, Brad T, Ionescu D, Barbu-Tudoran L, Zoccarato L, Aerts JW, Contarini PE, Gros O, Volland JM, Popa R, Ody J, Vellone D, Flot JF, Tighe S, Sarbu SM. Cave Thiovulum (Candidatus Thiovulum stygium) differs metabolically and genomically from marine species. THE ISME JOURNAL 2023; 17:340-353. [PMID: 36528730 PMCID: PMC9938260 DOI: 10.1038/s41396-022-01350-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 11/29/2022] [Accepted: 12/02/2022] [Indexed: 12/23/2022]
Abstract
Thiovulum spp. (Campylobacterota) are large sulfur bacteria that form veil-like structures in aquatic environments. The sulfidic Movile Cave (Romania), sealed from the atmosphere for ~5 million years, has several aqueous chambers, some with low atmospheric O2 (~7%). The cave's surface-water microbial community is dominated by bacteria we identified as Thiovulum. We show that this strain, and others from subsurface environments, are phylogenetically distinct from marine Thiovulum. We assembled a closed genome of the Movile strain and confirmed its metabolism using RNAseq. We compared the genome of this strain and one we assembled from public data from the sulfidic Frasassi caves to four marine genomes, including Candidatus Thiovulum karukerense and Ca. T. imperiosus, whose genomes we sequenced. Despite great spatial and temporal separation, the genomes of the Movile and Frasassi Thiovulum were highly similar, differing greatly from the very diverse marine strains. We concluded that cave Thiovulum represent a new species, named here Candidatus Thiovulum stygium. Based on their genomes, cave Thiovulum can switch between aerobic and anaerobic sulfide oxidation using O2 and NO3- as electron acceptors, the latter likely via dissimilatory nitrate reduction to ammonia. Thus, Thiovulum is likely important to both S and N cycles in sulfidic caves. Electron microscopy analysis suggests that at least some of the short peritrichous structures typical of Thiovulum are type IV pili, for which genes were found in all strains. These pili may play a role in veil formation, by connecting adjacent cells, and in the motility of these exceptionally fast swimmers.
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Affiliation(s)
- Mina Bizic
- Leibniz Institute for Freshwater Ecology and Inland Fisheries, IGB, Dep 3, Plankton and Microbial Ecology, Zur Alte Fischerhütte 2, OT Neuglobsow, 16775, Stechlin, Germany. .,Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), Berlin, Germany.
| | - Traian Brad
- "Emil Racoviţă" Institute of Speleology, Clinicilor 5-7, 400006, Cluj-Napoca Romania, Romania.
| | - Danny Ionescu
- Leibniz Institute for Freshwater Ecology and Inland Fisheries, IGB, Dep 3, Plankton and Microbial Ecology, Zur Alte Fischerhütte 2, OT Neuglobsow, 16775, Stechlin, Germany. .,Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), Berlin, Germany.
| | - Lucian Barbu-Tudoran
- grid.7399.40000 0004 1937 1397Center for Electron Microscopy, “Babeș-Bolyai” University, Clinicilor 5, 400006 Cluj-Napoca, Romania
| | - Luca Zoccarato
- Leibniz Institute for Freshwater Ecology and Inland Fisheries, IGB, Dep 3, Plankton and Microbial Ecology, Zur Alte Fischerhütte 2, OT Neuglobsow, 16775 Stechlin, Germany ,grid.5173.00000 0001 2298 5320Institute of Computational Biology, University of Natural Resources and Life Sciences, Gregor-Mendel-Straße 3, 31180 Vienna, Austria
| | - Joost W. Aerts
- grid.12380.380000 0004 1754 9227Department of Molecular Cell Physiology, Faculty of Earth and Life sciences, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
| | - Paul-Emile Contarini
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, 97110 Pointe-à-Pitre, France ,Laboratory for Research in Complex Systems, Menlo Park, CA USA
| | - Olivier Gros
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d’Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, 97110 Pointe-à-Pitre, France
| | - Jean-Marie Volland
- Laboratory for Research in Complex Systems, Menlo Park, CA USA ,grid.184769.50000 0001 2231 4551Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, 94720 Berkeley, CA USA
| | - Radu Popa
- River Road Research, 62 Leslie St, Buffalo, NY 1421 USA
| | - Jessica Ody
- grid.4989.c0000 0001 2348 0746Evolutionary Biology and Ecology, Université libre de Bruxelles (ULB), C.P. 160/12, Avenue F.D. Roosevelt 50, 1050 Brussels, Belgium
| | - Daniel Vellone
- grid.59062.380000 0004 1936 7689Vermont Integrative Genomics Lab, University of Vermont Cancer Center, Health Science Research Facility, Burlington, Vermont, VT 05405 USA
| | - Jean-François Flot
- grid.4989.c0000 0001 2348 0746Evolutionary Biology and Ecology, Université libre de Bruxelles (ULB), C.P. 160/12, Avenue F.D. Roosevelt 50, 1050 Brussels, Belgium ,Interuniversity Institute of Bioinformatics in Brussels—(IB)², Brussels, Belgium
| | - Scott Tighe
- grid.59062.380000 0004 1936 7689Vermont Integrative Genomics Lab, University of Vermont Cancer Center, Health Science Research Facility, Burlington, Vermont, VT 05405 USA
| | - Serban M. Sarbu
- grid.501624.40000 0001 2260 1489“Emil Racoviţă” Institute of Speleology, Frumoasă 31-B, 010986 Bucureşti, Romania ,grid.253555.10000 0001 2297 1981Department of Biological Sciences, California State University, Chico, CA 95929 USA
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10
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Zhuang XY, Tseng CK, Lo CJ. Live-Cell Imaging of the Assembly and Ejection Processes of the Bacterial Flagella by Fluorescence Microscopy. Methods Mol Biol 2023; 2646:35-42. [PMID: 36842104 DOI: 10.1007/978-1-0716-3060-0_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
Abstract
Bacterial flagella are molecular machines used for motility and chemotaxis. The flagellum consists of a thin extracellular helical filament as a propeller, a short hook as a universal joint, and a basal body as a rotary motor. The filament is made up of more than 20,000 flagellin molecules and can grow to several micrometers long but only 20 nanometers thick. The regulation of flagellar assembly and ejection is important for bacterial environmental adaptation. However, due to the technical difficulty to observe these nanostructures in live cells, our understanding of the flagellar growth and loss is limited. In the last three decades, the development of fluorescence microscopy and fluorescence labeling of specific cellular structure has made it possible to perform the real-time observation of bacterial flagellar assembly and ejection processes. Furthermore, flagella are not only critical for bacterial motility but also important antigens stimulating host immune responses. The complete understanding of bacterial flagellar production and ejection is valuable for understanding macromolecular self-assembly, cell adaptation, and pathogen-host interactions.
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Affiliation(s)
- Xiang-Yu Zhuang
- Department of Physics, National Central University, Taoyuan, Taiwan
| | - Chao-Kai Tseng
- Department of Physics, National Central University, Taoyuan, Taiwan
| | - Chien-Jung Lo
- Department of Physics, National Central University, Taoyuan, Taiwan. .,Center for Complex Systems, National Central University, Taoyuan, Taiwan.
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11
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Chen P, Goldberg MB. Recent insights into type-3 secretion system injectisome structure and mechanism of human enteric pathogens. Curr Opin Microbiol 2023; 71:102232. [PMID: 36368294 PMCID: PMC10510281 DOI: 10.1016/j.mib.2022.102232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 10/06/2022] [Accepted: 10/19/2022] [Indexed: 11/10/2022]
Abstract
Type-3 secretion system injectisomes are multiprotein complexes that translocate bacterial effector proteins from the cytoplasm of gram-negative bacteria directly into the cytosol of eukaryotic host cells. These systems are present in more than 30 bacterial species, including numerous human, animal, and plant pathogens. We review recent discoveries of structural and molecular mechanisms of effector protein translocation through the injectisomes and recent advances in the understanding of mechanisms of activation of effector protein secretion.
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Affiliation(s)
- Poyin Chen
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA, USA; Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Marcia B Goldberg
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA, USA; Department of Microbiology, Harvard Medical School, Boston, MA, USA; Broad Institute, Cambridge, MA, USA.
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12
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Qu D, Jiang M, Duffin C, Hughes KT, Chevance FFV. Targeting early proximal-rod component substrate FlgB to FlhB for flagellar-type III secretion in Salmonella. PLoS Genet 2022; 18:e1010313. [PMID: 35819991 PMCID: PMC9307174 DOI: 10.1371/journal.pgen.1010313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 07/22/2022] [Accepted: 06/24/2022] [Indexed: 11/18/2022] Open
Abstract
The Salmonella flagellar secretion apparatus is a member of the type III secretion (T3S) family of export systems in bacteria. After completion of the flagellar motor structure, the hook-basal body (HBB), the flagellar T3S system undergoes a switch from early to late substrate secretion, which results in the expression and assembly of the external, filament propeller-like structure. In order to characterize early substrate secretion-signals in the flagellar T3S system, the FlgB, and FlgC components of the flagellar rod, which acts as the drive-shaft within the HBB, were subject to deletion mutagenesis to identify regions of these proteins that were important for secretion. The β-lactamase protein lacking its Sec-dependent secretion signal (Bla) was fused to the C-terminus of FlgB and FlgC and used as a reporter to select for and quantify the secretion of FlgB and FlgC into the periplasm. Secretion of Bla into the periplasm confers resistance to ampicillin. In-frame deletions of amino acids 9 through 18 and amino acids 39 through 58 of FlgB decreased FlgB secretion levels while deleting amino acid 6 through 14 diminished FlgC secretion levels. Further PCR-directed mutagenesis indicated that amino acid F45 of FlgB was critical for secretion. Single amino acid mutagenesis revealed that all amino acid substitutions at F45 of FlgB position impaired rod assembly, which was due to a defect of FlgB secretion. An equivalent F49 position in FlgC was essential for assembly but not for secretion. This study also revealed that a hydrophobic patch in the cleaved C-terminal domain of FlhB is critical for recognition of FlgB at F45. Type III secretion (T3S) is the means by which proteins are secreted from the bacterial cytoplasm to build flagella for motility and injectisome structures that facilitate pathogenesis. T3S is the only secretion system known to date that undergoes a secretion-specificity switch. For the assembly of the bacterial flagellum, the T3S system initially secretes early substrates to build the hook-basal body (HBB), which is the main component that makes up the flagellar motor. Upon HBB completion, the flagellar T3S system becomes specific for late substrates, which make up the long external filament that acts as the propeller of the motility organelle. This work identifies important sites of interaction between an early substrate, FlgB and a target site at the cytoplasmic base of T3S apparatus. A second early substrate, FlgC, lacks the targeting interaction found for FlgB suggesting a mechanism that distinguishes early substrates, and may indicate an order to early substrate secretion to facilitate the order of protein subunit assembly for the flagellum.
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Affiliation(s)
- Daofeng Qu
- Key Laboratory of Food Quality and Safety, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Mengxue Jiang
- Key Laboratory of Food Quality and Safety, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Calder Duffin
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Kelly T. Hughes
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Fabienne F. V. Chevance
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America
- * E-mail:
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13
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Kaplan M, Oikonomou CM, Wood CR, Chreifi G, Subramanian P, Ortega DR, Chang Y, Beeby M, Shaffer CL, Jensen GJ. Novel transient cytoplasmic rings stabilize assembling bacterial flagellar motors. EMBO J 2022; 41:e109523. [PMID: 35301732 PMCID: PMC9108667 DOI: 10.15252/embj.2021109523] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Revised: 01/31/2022] [Accepted: 02/16/2022] [Indexed: 12/20/2022] Open
Abstract
The process by which bacterial cells build their intricate flagellar motility apparatuses has long fascinated scientists. Our understanding of this process comes mainly from studies of purified flagella from two species, Escherichia coli and Salmonella enterica. Here, we used electron cryo-tomography (cryo-ET) to image the assembly of the flagellar motor in situ in diverse Proteobacteria: Hylemonella gracilis, Helicobacter pylori, Campylobacter jejuni, Pseudomonas aeruginosa, Pseudomonas fluorescens, and Shewanella oneidensis. Our results reveal the in situ structures of flagellar intermediates, beginning with the earliest flagellar type III secretion system core complex (fT3SScc) and MS-ring. In high-torque motors of Beta-, Gamma-, and Epsilon-proteobacteria, we discovered novel cytoplasmic rings that interact with the cytoplasmic torque ring formed by FliG. These rings, associated with the MS-ring, assemble very early and persist until the stators are recruited into their periplasmic ring; in their absence the stator ring does not assemble. By imaging mutants in Helicobacter pylori, we found that the fT3SScc proteins FliO and FliQ are required for the assembly of these novel cytoplasmic rings. Our results show that rather than a simple accretion of components, flagellar motor assembly is a dynamic process in which accessory components interact transiently to assist in building the complex nanomachine.
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Affiliation(s)
- Mohammed Kaplan
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaCAUSA
| | - Catherine M Oikonomou
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaCAUSA
| | - Cecily R Wood
- Department of Veterinary ScienceUniversity of KentuckyLexingtonKYUSA
| | - Georges Chreifi
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaCAUSA
| | - Poorna Subramanian
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaCAUSA
| | - Davi R Ortega
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaCAUSA
| | - Yi‐Wei Chang
- Department of Biochemistry and BiophysicsPerelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Morgan Beeby
- Department of Life SciencesImperial College LondonLondonUK
| | - Carrie L Shaffer
- Department of Veterinary ScienceUniversity of KentuckyLexingtonKYUSA
- Department of Microbiology, Immunology, and Molecular GeneticsUniversity of KentuckyLexingtonKYUSA
- Department of Pharmaceutical SciencesUniversity of KentuckyLexingtonKYUSA
| | - Grant J Jensen
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaCAUSA
- Department of Chemistry and BiochemistryBrigham Young UniversityProvoUTUSA
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14
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Minamino T, Morimoto YV, Kinoshita M, Namba K. Multiple Roles of Flagellar Export Chaperones for Efficient and Robust Flagellar Filament Formation in Salmonella. Front Microbiol 2021; 12:756044. [PMID: 34691007 PMCID: PMC8527033 DOI: 10.3389/fmicb.2021.756044] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 09/08/2021] [Indexed: 11/30/2022] Open
Abstract
FlgN, FliS, and FliT are flagellar export chaperones specific for FlgK/FlgL, FliC, and FliD, respectively, which are essential component proteins for filament formation. These chaperones facilitate the docking of their cognate substrates to a transmembrane export gate protein, FlhA, to facilitate their subsequent unfolding and export by the flagellar type III secretion system (fT3SS). Dynamic interactions of the chaperones with FlhA are thought to determine the substrate export order. To clarify the role of flagellar chaperones in filament assembly, we constructed cells lacking FlgN, FliS, and/or FliT. Removal of either FlgN, FliS, or FliT resulted in leakage of a large amount of unassembled FliC monomers into the culture media, indicating that these chaperones contribute to robust and efficient filament formation. The ∆flgN ∆fliS ∆fliT (∆NST) cells produced short filaments similarly to the ∆fliS mutant. Suppressor mutations of the ∆NST cells, which lengthened the filament, were all found in FliC and destabilized the folded structure of FliC monomer. Deletion of FliS inhibited FliC export and filament elongation only after FliC synthesis was complete. We propose that FliS is not involved in the transport of FliC upon onset of filament formation, but FliS-assisted unfolding of FliC by the fT3SS becomes essential for its rapid and efficient export to form a long filament when FliC becomes fully expressed in the cytoplasm.
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Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Yusuke V Morimoto
- Department of Physics and Information Technology, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Iizuka, Japan.,Japan Science and Technology Agency, PRESTO, Kawaguchi, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan.,RIKEN SPring-8 Center and Center for Biosystems Dynamics Research, Suita, Japan.,JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, Suita, Japan
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15
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Guse A, Halte M, Hüsing S, Erhardt M. Hook-basal-body assembly state dictates substrate specificity of the flagellar type-III secretion system. Mol Microbiol 2021; 116:1189-1200. [PMID: 34467587 DOI: 10.1111/mmi.14805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 08/27/2021] [Accepted: 08/28/2021] [Indexed: 12/01/2022]
Abstract
The assembly of the bacterial flagellum is orchestrated by the secretion of distinct early and late secretion substrates via the flagellar-specific type-III secretion system (fT3SS). However, how the fT3SS is able to distinguish between the different (early and late) substrate classes during flagellar assembly remains poorly understood. In this study, we investigated the substrate selectivity and specificity of the fT3SS of Salmonella enterica at different assembly stages. For this, we developed an experimental setup that allowed us to synchronize hook-basal-body assembly and to monitor early and late substrate secretion of fT3SSs operating in either early or late secretion mode, respectively. Our results demonstrate that the fT3SS features a remarkable specificity for only the substrates required at the respective assembly stage. No crosstalk of substrates was observed for fT3SSs operating in the opposing secretion mode. We further found that a substantial fraction of fT3SS surprisingly remained in early secretion mode. Our results thus suggest that the secretion substrate specificity switch of the fT3SS is unidirectional and irreversible. The developed secretion substrate reporter system further provides a platform for future investigations of the underlying molecular mechanisms of the elusive substrate recognition of the T3SS.
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Affiliation(s)
- Alina Guse
- Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Manuel Halte
- Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Svenja Hüsing
- Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Marc Erhardt
- Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany.,Max Planck Unit for the Science of Pathogens, Berlin, Germany
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16
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Bacterial Flagellar Filament: A Supramolecular Multifunctional Nanostructure. Int J Mol Sci 2021; 22:ijms22147521. [PMID: 34299141 PMCID: PMC8306008 DOI: 10.3390/ijms22147521] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/06/2021] [Accepted: 07/10/2021] [Indexed: 02/07/2023] Open
Abstract
The bacterial flagellum is a complex and dynamic nanomachine that propels bacteria through liquids. It consists of a basal body, a hook, and a long filament. The flagellar filament is composed of thousands of copies of the protein flagellin (FliC) arranged helically and ending with a filament cap composed of an oligomer of the protein FliD. The overall structure of the filament core is preserved across bacterial species, while the outer domains exhibit high variability, and in some cases are even completely absent. Flagellar assembly is a complex and energetically costly process triggered by environmental stimuli and, accordingly, highly regulated on transcriptional, translational and post-translational levels. Apart from its role in locomotion, the filament is critically important in several other aspects of bacterial survival, reproduction and pathogenicity, such as adhesion to surfaces, secretion of virulence factors and formation of biofilms. Additionally, due to its ability to provoke potent immune responses, flagellins have a role as adjuvants in vaccine development. In this review, we summarize the latest knowledge on the structure of flagellins, capping proteins and filaments, as well as their regulation and role during the colonization and infection of the host.
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17
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Zhang W, Luo M, Feng C, Liu H, Zhang H, Bennett RR, Utada AS, Liu Z, Zhao K. Crash landing of Vibrio cholerae by MSHA pili-assisted braking and anchoring in a viscoelastic environment. eLife 2021; 10:60655. [PMID: 34212857 PMCID: PMC8282333 DOI: 10.7554/elife.60655] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 07/01/2021] [Indexed: 11/19/2022] Open
Abstract
Mannose-sensitive hemagglutinin (MSHA) pili and flagellum are critical for the surface attachment of Vibrio cholerae, the first step of V. cholerae colonization on host surfaces. However, the cell landing mechanism remains largely unknown, particularly in viscoelastic environments such as the mucus layers of intestines. Here, combining the cysteine-substitution-based labeling method with single-cell tracking techniques, we quantitatively characterized the landing of V. cholerae by directly observing both pili and flagellum of cells in a viscoelastic non-Newtonian solution consisting of 2% Luria-Bertani and 1% methylcellulose (LB+MC). The results show that MSHA pili are evenly distributed along the cell length and can stick to surfaces at any point along the filament. With such properties, MSHA pili are observed to act as a brake and anchor during cell landing which includes three phases: running, lingering, and attaching. Importantly, loss of MSHA pili results in a more dramatic increase in mean path length in LB+MC than in 2% LB only or in 20% Ficoll solutions, indicating that the role of MSHA pili during cell landing is more apparent in viscoelastic non-Newtonian fluids than viscous Newtonian ones. Our work provides a detailed picture of the landing dynamics of V. cholerae under viscoelastic conditions, which can provide insights into ways to better control V. cholerae infections in a real mucus-like environment.
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Affiliation(s)
- Wenchao Zhang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Mei Luo
- Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Chunying Feng
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Huaqing Liu
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Hong Zhang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Rachel R Bennett
- School of Mathematics, University of Bristol, Bristol, United Kingdom
| | - Andrew S Utada
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan.,The Microbiology Research Center for Sustainability, University of Tsukuba, Ibaraki, Japan
| | - Zhi Liu
- Department of Biotechnology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Kun Zhao
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
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18
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Hüsing S, Halte M, van Look U, Guse A, Gálvez EJC, Charpentier E, Blair DF, Erhardt M, Renault TT. Control of membrane barrier during bacterial type-III protein secretion. Nat Commun 2021; 12:3999. [PMID: 34183670 PMCID: PMC8239009 DOI: 10.1038/s41467-021-24226-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 06/02/2021] [Indexed: 11/09/2022] Open
Abstract
Type-III secretion systems (T3SSs) of the bacterial flagellum and the evolutionarily related injectisome are capable of translocating proteins with a remarkable speed of several thousand amino acids per second. Here, we investigate how T3SSs are able to transport proteins at such a high rate while preventing the leakage of small molecules. Our mutational and evolutionary analyses demonstrate that an ensemble of conserved methionine residues at the cytoplasmic side of the T3SS channel create a deformable gasket (M-gasket) around fast-moving substrates undergoing export. The unique physicochemical features of the M-gasket are crucial to preserve the membrane barrier, to accommodate local conformational changes during active secretion, and to maintain stability of the secretion pore in cooperation with a plug domain (R-plug) and a network of salt-bridges. The conservation of the M-gasket, R-plug, and salt-bridge network suggests a universal mechanism by which the membrane integrity is maintained during high-speed protein translocation in all T3SSs. Type-III secretion systems (T3SSs) are capable of translocating proteins with high speed while maintaining the membrane barrier for small molecules. Here, a structure-function analysis of the T3SS pore complex elucidates the precise mechanisms enabling the gating and the conformational changes required for protein substrate secretion.
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Affiliation(s)
- Svenja Hüsing
- Institute for Biology-Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany.,Max Planck Unit for the Science of Pathogens, Berlin, Germany
| | - Manuel Halte
- Institute for Biology-Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ulf van Look
- Institute for Biology-Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany.,Max Planck Unit for the Science of Pathogens, Berlin, Germany
| | - Alina Guse
- Institute for Biology-Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Eric J C Gálvez
- Max Planck Unit for the Science of Pathogens, Berlin, Germany
| | | | - David F Blair
- School of Biology, University of Utah, Salt Lake City, UT, USA
| | - Marc Erhardt
- Institute for Biology-Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany. .,Max Planck Unit for the Science of Pathogens, Berlin, Germany.
| | - Thibaud T Renault
- Institute for Biology-Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany. .,Max Planck Unit for the Science of Pathogens, Berlin, Germany. .,CNRS, UMR 5234, Université de Bordeaux, Bordeaux, France. .,Institut Européen de Chimie et Biologie, Université de Bordeaux, Pessac, France.
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19
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Ozer E, Yaniv K, Chetrit E, Boyarski A, Meijler MM, Berkovich R, Kushmaro A, Alfonta L. An inside look at a biofilm: Pseudomonas aeruginosa flagella biotracking. SCIENCE ADVANCES 2021; 7:eabg8581. [PMID: 34117070 PMCID: PMC8195488 DOI: 10.1126/sciadv.abg8581] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 04/28/2021] [Indexed: 05/28/2023]
Abstract
The opportunistic pathogen, Pseudomonas aeruginosa, a flagellated bacterium, is one of the top model organisms for biofilm studies. To elucidate the location of bacterial flagella throughout the biofilm life cycle, we developed a new flagella biotracking tool. Bacterial flagella were site-specifically labeled via genetic code expansion. This enabled us to track bacterial flagella during biofilm maturation. Live flagella imaging revealed the presence and synthesis of flagella throughout the biofilm life cycle. To study the possible role of flagella in a biofilm, we produced a flagella knockout strain and compared its biofilm to that of the wild-type strain. Results showed a one order of magnitude stronger biofilm structure in the wild type in comparison with the flagella knockout strain. This suggests a possible structural role for flagella in a biofilm, conceivably as a scaffold. Our findings suggest a new model for biofilm maturation dynamic which underscores the importance of direct evidence from within the biofilm.
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Affiliation(s)
- Eden Ozer
- Department of Life Sciences, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
| | - Karin Yaniv
- Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
| | - Einat Chetrit
- Department of Chemical Engineering, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
| | - Anastasya Boyarski
- Department of Chemistry, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
| | - Michael M Meijler
- Department of Chemistry, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
- National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
| | - Ronen Berkovich
- Department of Chemical Engineering, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
- Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
| | - Ariel Kushmaro
- Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel.
- Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
| | - Lital Alfonta
- Department of Life Sciences, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel.
- Department of Chemistry, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
- Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 8410501, Israel
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20
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Minamino T, Morimoto YV, Kinoshita M, Namba K. Membrane voltage-dependent activation mechanism of the bacterial flagellar protein export apparatus. Proc Natl Acad Sci U S A 2021; 118:e2026587118. [PMID: 34035173 PMCID: PMC8179193 DOI: 10.1073/pnas.2026587118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The proton motive force (PMF) consists of the electric potential difference (Δψ), which is measured as membrane voltage, and the proton concentration difference (ΔpH) across the cytoplasmic membrane. The flagellar protein export machinery is composed of a PMF-driven transmembrane export gate complex and a cytoplasmic ATPase ring complex consisting of FliH, FliI, and FliJ. ATP hydrolysis by the FliI ATPase activates the export gate complex to become an active protein transporter utilizing Δψ to drive proton-coupled protein export. An interaction between FliJ and a transmembrane ion channel protein, FlhA, is a critical step for Δψ-driven protein export. To clarify how Δψ is utilized for flagellar protein export, we analyzed the export properties of the export gate complex in the absence of FliH and FliI. The protein transport activity of the export gate complex was very low at external pH 7.0 but increased significantly with an increase in Δψ by an upward shift of external pH from 7.0 to 8.5. This observation suggests that the export gate complex is equipped with a voltage-gated mechanism. An increase in the cytoplasmic level of FliJ and a gain-of-function mutation in FlhA significantly reduced the Δψ dependency of flagellar protein export by the export gate complex. However, deletion of FliJ decreased Δψ-dependent protein export significantly. We propose that Δψ is required for efficient interaction between FliJ and FlhA to open the FlhA ion channel to conduct protons to drive flagellar protein export in a Δψ-dependent manner.
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Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan;
| | - Yusuke V Morimoto
- Department of Physics and Information Technology, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Fukuoka 820-8502, Japan
- Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
| | - Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan;
- SPring-8 Center, RIKEN, Osaka 565-0871, Japan
- Center for Biosystems Dynamics Research, RIKEN, Osaka 565-0871, Japan
- JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, Osaka 565-0871, Japan
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21
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Clopés J, Winkler RG. Flagellar arrangements in elongated peritrichous bacteria: bundle formation and swimming properties. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:17. [PMID: 33683543 PMCID: PMC7940165 DOI: 10.1140/epje/s10189-021-00027-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 01/25/2021] [Indexed: 05/26/2023]
Abstract
The surface distribution of flagella in peritrichous bacterial cells has been traditionally assumed to be random. Recently, the presence of a regular grid-like pattern of basal bodies has been suggested. Experimentally, the manipulation of the anchoring points of flagella in the cell membrane is difficult, and thus, elucidation of the consequences of a particular pattern on bacterial locomotion is challenging. We analyze the bundle formation process and swimming properties of Bacillus subtilis-like cells considering random, helical, and ring-like arrangements of flagella by means of mesoscale hydrodynamics simulations. Helical and ring patterns preferentially yield configurations with a single bundle, whereas configurations with no clear bundles are most likely for random anchoring. For any type of pattern, there is an almost equally low probability to form V-shaped bundle configurations with at least two bundles. Variation of the flagellum length yields a clear preference for a single major bundle in helical and ring patterns as soon as the flagellum length exceeds the body length. The average swimming speed of cells with a single or two bundles is rather similar, and approximately [Formula: see text] larger than that of cells of other types of flagellar organization. Considering the various anchoring patterns, rings yield the smallest average swimming speed independent of the type of bundle, followed by helical arrangements, and largest speeds are observed for random anchoring. Hence, a regular pattern provides no advantage in terms of swimming speed compared to random anchoring of flagella, but yields more likely single-bundle configurations.
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Affiliation(s)
- Judit Clopés
- Theoretical Physics of Living Matter, Institute of Biological Information Processing and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany
- Institute for Theoretical Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - Roland G Winkler
- Theoretical Physics of Living Matter, Institute of Biological Information Processing and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany.
- Institute for Theoretical Physics, RWTH Aachen University, 52074, Aachen, Germany.
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22
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Protein Export via the Type III Secretion System of the Bacterial Flagellum. Biomolecules 2021; 11:biom11020186. [PMID: 33572887 PMCID: PMC7911332 DOI: 10.3390/biom11020186] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/25/2021] [Accepted: 01/26/2021] [Indexed: 12/15/2022] Open
Abstract
The bacterial flagellum and the related virulence-associated injectisome system of pathogenic bacteria utilize a type III secretion system (T3SS) to export substrate proteins across the inner membrane in a proton motive force-dependent manner. The T3SS is composed of an export gate (FliPQR/FlhA/FlhB) located in the flagellar basal body and an associated soluble ATPase complex in the cytoplasm (FliHIJ). Here, we summarise recent insights into the structure, assembly and protein secretion mechanisms of the T3SS with a focus on energy transduction and protein transport across the cytoplasmic membrane.
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23
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Milne-Davies B, Wimmi S, Diepold A. Adaptivity and dynamics in type III secretion systems. Mol Microbiol 2020; 115:395-411. [PMID: 33251695 DOI: 10.1111/mmi.14658] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/17/2020] [Accepted: 11/23/2020] [Indexed: 01/07/2023]
Abstract
The type III secretion system is the common core of two bacterial molecular machines: the flagellum and the injectisome. The flagellum is the most widely distributed prokaryotic locomotion device, whereas the injectisome is a syringe-like apparatus for inter-kingdom protein translocation, which is essential for virulence in important human pathogens. The successful concept of the type III secretion system has been modified for different bacterial needs. It can be adapted to changing conditions, and was found to be a dynamic complex constantly exchanging components. In this review, we highlight the flexibility, adaptivity, and dynamic nature of the type III secretion system.
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Affiliation(s)
- Bailey Milne-Davies
- Department of Ecophysiology, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany
| | - Stephan Wimmi
- Department of Ecophysiology, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany
| | - Andreas Diepold
- Department of Ecophysiology, Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany
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24
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Cambré A, Aertsen A. Bacterial Vivisection: How Fluorescence-Based Imaging Techniques Shed a Light on the Inner Workings of Bacteria. Microbiol Mol Biol Rev 2020; 84:e00008-20. [PMID: 33115939 PMCID: PMC7599038 DOI: 10.1128/mmbr.00008-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The rise in fluorescence-based imaging techniques over the past 3 decades has improved the ability of researchers to scrutinize live cell biology at increased spatial and temporal resolution. In microbiology, these real-time vivisections structurally changed the view on the bacterial cell away from the "watery bag of enzymes" paradigm toward the perspective that these organisms are as complex as their eukaryotic counterparts. Capitalizing on the enormous potential of (time-lapse) fluorescence microscopy and the ever-extending pallet of corresponding probes, initial breakthroughs were made in unraveling the localization of proteins and monitoring real-time gene expression. However, later it became clear that the potential of this technique extends much further, paving the way for a focus-shift from observing single events within bacterial cells or populations to obtaining a more global picture at the intra- and intercellular level. In this review, we outline the current state of the art in fluorescence-based vivisection of bacteria and provide an overview of important case studies to exemplify how to use or combine different strategies to gain detailed information on the cell's physiology. The manuscript therefore consists of two separate (but interconnected) parts that can be read and consulted individually. The first part focuses on the fluorescent probe pallet and provides a perspective on modern methodologies for microscopy using these tools. The second section of the review takes the reader on a tour through the bacterial cell from cytoplasm to outer shell, describing strategies and methods to highlight architectural features and overall dynamics within cells.
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Affiliation(s)
- Alexander Cambré
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Leuven, Belgium
| | - Abram Aertsen
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Leuven, Belgium
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25
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Zhuang XY, Lo CJ. Construction and Loss of Bacterial Flagellar Filaments. Biomolecules 2020; 10:E1528. [PMID: 33182435 PMCID: PMC7696725 DOI: 10.3390/biom10111528] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 10/26/2020] [Accepted: 11/04/2020] [Indexed: 11/16/2022] Open
Abstract
The bacterial flagellar filament is an extracellular tubular protein structure that acts as a propeller for bacterial swimming motility. It is connected to the membrane-anchored rotary bacterial flagellar motor through a short hook. The bacterial flagellar filament consists of approximately 20,000 flagellins and can be several micrometers long. In this article, we reviewed the experimental works and models of flagellar filament construction and the recent findings of flagellar filament ejection during the cell cycle. The length-dependent decay of flagellar filament growth data supports the injection-diffusion model. The decay of flagellar growth rate is due to reduced transportation of long-distance diffusion and jamming. However, the filament is not a permeant structure. Several bacterial species actively abandon their flagella under starvation. Flagellum is disassembled when the rod is broken, resulting in an ejection of the filament with a partial rod and hook. The inner membrane component is then diffused on the membrane before further breakdown. These new findings open a new field of bacterial macro-molecule assembly, disassembly, and signal transduction.
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Affiliation(s)
| | - Chien-Jung Lo
- Department of Physics and Graduate Institute of Biophysics, National Central University, Taoyuan City 32001, Taiwan;
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26
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de Oliveira Barbosa F, de Freitas Neto OC, Rodrigues Alves LB, Benevides VP, de Souza AIS, da Silva Rubio M, de Almeida AM, Saraiva MM, de Oliveira CJB, Olsen JE, Junior AB. Immunological and bacteriological shifts associated with a flagellin-hyperproducing Salmonella Enteritidis mutant in chickens. Braz J Microbiol 2020; 52:419-429. [PMID: 33150477 DOI: 10.1007/s42770-020-00399-7] [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: 05/13/2020] [Accepted: 10/27/2020] [Indexed: 11/30/2022] Open
Abstract
Salmonella Enteritidis causes infections in humans and animals which are often associated with extensive gut colonization and bacterial shedding in faeces. The natural presence of flagella in Salmonella enterica has been shown to be enough to induce pro-inflammatory responses in the gut, resulting in recruitment of polymorphonuclear cells, gut inflammation and, consequently, reducing the severity of systemic infection in chickens. On the other hand, the absence of flagellin in some Salmonella strains favours systemic infection as a result of the poor intestinal inflammatory responses elicited. The hypothesis that higher production of flagellin by certain Salmonella enterica strains could lead to an even more immunogenic and less pathogenic strain for chickens was here investigated. In the present study, a Salmonella Enteritidis mutant strain harbouring deletions in clpP and fliD genes (SE ΔclpPfliD), which lead to overexpression of flagellin, was generated, and its immunogenicity and pathogenicity were comparatively assessed to the wild type in chickens. Our results showed that SE ΔclpPfliD elicited more intense immune responses in the gut during early stages of infection than the wild type did, and that this correlated with earlier intestinal and systemic clearance of the bacterium.
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Affiliation(s)
- Fernanda de Oliveira Barbosa
- Department of Veterinary Pathology from the School of Agriculture and Veterinarian Sciences (FCAV), Jaboticabal, State University of São Paulo, Jaboticabal, Brazil
| | - Oliveiro Caetano de Freitas Neto
- Department of Preventive Veterinary Medicine, Veterinary School, Federal University of Minas Gerais (UFMG), Av. Antônio Carlos 6627, Belo Horizonte, Minas Gerais, 31270-901, Brazil.
| | - Lucas Bocchini Rodrigues Alves
- Department of Veterinary Pathology from the School of Agriculture and Veterinarian Sciences (FCAV), Jaboticabal, State University of São Paulo, Jaboticabal, Brazil
| | - Valdinete Pereira Benevides
- Department of Veterinary Pathology from the School of Agriculture and Veterinarian Sciences (FCAV), Jaboticabal, State University of São Paulo, Jaboticabal, Brazil
| | - Andrei Itajahy Secundo de Souza
- Department of Veterinary Pathology from the School of Agriculture and Veterinarian Sciences (FCAV), Jaboticabal, State University of São Paulo, Jaboticabal, Brazil
| | - Marcela da Silva Rubio
- Department of Veterinary Pathology from the School of Agriculture and Veterinarian Sciences (FCAV), Jaboticabal, State University of São Paulo, Jaboticabal, Brazil
| | - Adriana Maria de Almeida
- Department of Veterinary Pathology from the School of Agriculture and Veterinarian Sciences (FCAV), Jaboticabal, State University of São Paulo, Jaboticabal, Brazil
| | - Mauro Mesquita Saraiva
- Department of Veterinary Pathology from the School of Agriculture and Veterinarian Sciences (FCAV), Jaboticabal, State University of São Paulo, Jaboticabal, Brazil
| | - Celso José Bruno de Oliveira
- Department of Animal Science, Center for Agricultural Sciences, Federal University of Paraiba (CCA/UFPB), Areia, PB, Brazil
| | - John Elmerdahl Olsen
- Department of Veterinary and Animal Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark
| | - Angelo Berchieri Junior
- Department of Veterinary Pathology from the School of Agriculture and Veterinarian Sciences (FCAV), Jaboticabal, State University of São Paulo, Jaboticabal, Brazil
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27
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Burtchett T, Love C, Sarkar R, Tripp BC. A structure-function study of C-terminal residues predicted to line the export channel in Salmonella Flagellin. Biochim Biophys Acta Gen Subj 2020; 1865:129748. [PMID: 32980501 DOI: 10.1016/j.bbagen.2020.129748] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 09/16/2020] [Accepted: 09/18/2020] [Indexed: 10/23/2022]
Abstract
BACKGROUND Structural studies of a Salmonella Typhimurium flagellin protein indicated that four polar or charged C-terminal amino acid residues line the inner channel of the flagellum. The hydrophilic character of these putative channel-lining residues was predicted to be essential to facilitate the transport of unfolded flagellin monomers during flagellar assembly. The structure-function relationship of these putative channel-lining residues was investigated by site-directed mutagenesis to examine effects of side chain polarity and size on flagella assembly and function. METHODS Channel-lining residue variants were generated using site-directed mutagenesis to substitute alanine and other residues to examine the effects of altered side-chain polarity on export and assembly. The export, in vivo motility function, and flagellar structure of variants was characterized by agar motility, video microscopy, immunofluorescence, and SDS-PAGE. RESULTS Alanine substitution yielded decreased motility and flagellar assembly for three of the four residues. However, alanine substitution of residue Arg 494 did not alter export, although substitution with negatively charged glutamate decreased motility and flagellar filament length. Furthermore, many of the C-terminal mutations affected flagellar filament morphology and stability, often resulting in more tightly coiled and/or more brittle flagella than the wild type. CONCLUSIONS The four channel-lining C-terminal residues may facilitate monomer protein transport but also have structural roles in determining the stability and morphology of the flagellum. GENERAL SIGNIFICANCE These results provide further insight into the complex process of bacterial flagellin export and flagellar assembly and provide evidence of previously unknown structural functions for the four putative channel-lining residues.
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Affiliation(s)
- Troy Burtchett
- Western Michigan University, Department of Biological Sciences, 1903 W. Michigan Avenue, Kalamazoo, MI 49008, USA
| | - Chloe Love
- Kalamazoo College, Department of Biology, 1200 Academy St., Kalamazoo, MI 49006, USA
| | - Reshma Sarkar
- Western Michigan University, Department of Biological Sciences, 1903 W. Michigan Avenue, Kalamazoo, MI 49008, USA
| | - Brian C Tripp
- Western Michigan University, Department of Biological Sciences, 1903 W. Michigan Avenue, Kalamazoo, MI 49008, USA.
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28
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Zhuang X, Guo S, Li Z, Zhao Z, Kojima S, Homma M, Wang P, Lo C, Bai F. Live‐cell fluorescence imaging reveals dynamic production and loss of bacterial flagella. Mol Microbiol 2020; 114:279-291. [DOI: 10.1111/mmi.14511] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 03/10/2020] [Accepted: 03/30/2020] [Indexed: 02/02/2023]
Affiliation(s)
- Xiang‐Yu Zhuang
- Department of Physics and Graduate Institute of Biophysics National Central University Jhongli Taiwan, R.O.C
| | - Shihao Guo
- Biomedical Pioneering Innovation Center (BIOPIC) School of Life Sciences Peking University Beijing China
- Department of General Surgery Peking University First Hospital Peking University Beijing China
| | - Zhuoran Li
- Biomedical Pioneering Innovation Center (BIOPIC) School of Life Sciences Peking University Beijing China
| | - Ziyi Zhao
- Biomedical Pioneering Innovation Center (BIOPIC) School of Life Sciences Peking University Beijing China
| | - Seiji Kojima
- Division of Biological Science Graduate School of Science Nagoya University Nagoya Japan
| | - Michio Homma
- Division of Biological Science Graduate School of Science Nagoya University Nagoya Japan
| | - Pengyuan Wang
- Department of General Surgery Peking University First Hospital Peking University Beijing China
| | - Chien‐Jung Lo
- Department of Physics and Graduate Institute of Biophysics National Central University Jhongli Taiwan, R.O.C
| | - Fan Bai
- Biomedical Pioneering Innovation Center (BIOPIC) School of Life Sciences Peking University Beijing China
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29
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Kucera J, Terentjev EM. FliI 6-FliJ molecular motor assists with unfolding in the type III secretion export apparatus. Sci Rep 2020; 10:7127. [PMID: 32346005 PMCID: PMC7189227 DOI: 10.1038/s41598-020-63330-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 03/27/2020] [Indexed: 01/05/2023] Open
Abstract
The role of rotational molecular motors of the ATP synthase class is integral to the metabolism of cells. Yet the function of FliI6-FliJ complex, a homolog of the F1 ATPase motor, within the flagellar export apparatus remains unclear. We use a simple two-state model adapted from studies of linear molecular motors to identify key features of this motor. The two states are the 'locked' ground state where the FliJ coiled coil filament experiences angular fluctuations in an asymmetric torsional potential, and a 'free' excited state in which FliJ undergoes rotational diffusion. Michaelis-Menten kinetics was used to treat transitions between these two states, and obtain the average angular velocity of the unloaded FliJ filament within the FliI6 stator: ωmax ≈ 9.0 rps. The motor was then studied under external counter torque conditions in order to ascertain its maximal power output: Pmax ≈ 42 kBT/s (or 102 kW/mol), and the stall torque: Gstall ≈ 3 kBT/rad (or 0.01 nN·nm/rad). Two modes of action within the flagellar export apparatus are proposed, in which the motor performs useful work either by continuously 'grinding' through the resistive environment of the export gate, or by exerting equal and opposite stall force on it. In both cases, the resistance is provided by flagellin subunits entering the flagellar export channel prior to their unfolding. We therefore propose that the function of the FliI6-FliJ complex is to lower the energy barrier, and therefore assist in unfolding of the flagellar proteins before feeding them into the transport channel.
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Affiliation(s)
- Jiri Kucera
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
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30
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Methylation of Salmonella Typhimurium flagella promotes bacterial adhesion and host cell invasion. Nat Commun 2020; 11:2013. [PMID: 32332720 PMCID: PMC7181671 DOI: 10.1038/s41467-020-15738-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 03/13/2020] [Indexed: 11/09/2022] Open
Abstract
The long external filament of bacterial flagella is composed of several thousand copies of a single protein, flagellin. Here, we explore the role played by lysine methylation of flagellin in Salmonella, which requires the methylase FliB. We show that both flagellins of Salmonella enterica serovar Typhimurium, FliC and FljB, are methylated at surface-exposed lysine residues by FliB. A Salmonella Typhimurium mutant deficient in flagellin methylation is outcompeted for gut colonization in a gastroenteritis mouse model, and methylation of flagellin promotes bacterial invasion of epithelial cells in vitro. Lysine methylation increases the surface hydrophobicity of flagellin, and enhances flagella-dependent adhesion of Salmonella to phosphatidylcholine vesicles and epithelial cells. Therefore, posttranslational methylation of flagellin facilitates adhesion of Salmonella Typhimurium to hydrophobic host cell surfaces, and contributes to efficient gut colonization and host infection. Flagellin proteins of Salmonella flagella are methylated. Here, the authors show that flagellin methylation facilitates adhesion of Salmonella to hydrophobic host-cell surfaces, and contributes to efficient gut colonization and host infection.
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31
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The substrate specificity switch FlhB assembles onto the export gate to regulate type three secretion. Nat Commun 2020; 11:1296. [PMID: 32157081 PMCID: PMC7064499 DOI: 10.1038/s41467-020-15071-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 02/15/2020] [Indexed: 11/24/2022] Open
Abstract
Protein secretion through type-three secretion systems (T3SS) is critical for motility and virulence of many bacteria. Proteins are transported through an export gate containing three proteins (FliPQR in flagella, SctRST in virulence systems). A fourth essential T3SS protein (FlhB/SctU) functions to “switch” secretion substrate specificity once the growing hook/needle reach their determined length. Here, we present the cryo-electron microscopy structure of an export gate containing the switch protein from a Vibrio flagellar system at 3.2 Å resolution. The structure reveals that FlhB/SctU extends the helical export gate with its four predicted transmembrane helices wrapped around FliPQR/SctRST. The unusual topology of the FlhB/SctU helices creates a loop wrapped around the bottom of the closed export gate. Structure-informed mutagenesis suggests that this loop is critical in gating secretion and we propose that a series of conformational changes in the T3SS trigger opening of the gate through interactions between FlhB/SctU and FliPQR/SctRST. Export of proteins by type three secretion systems occurs through an export gate that is localized in the periplasm. Here, the authors present the cryo-EM structure of the Vibrio mimicus export gate complex with FlhB, which plays a major role in switching of the specificity of secretion substrates and propose a mechanism for export gate opening.
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32
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Beeby M, Ferreira JL, Tripp P, Albers SV, Mitchell DR. Propulsive nanomachines: the convergent evolution of archaella, flagella and cilia. FEMS Microbiol Rev 2020; 44:253-304. [DOI: 10.1093/femsre/fuaa006] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 03/06/2020] [Indexed: 02/06/2023] Open
Abstract
ABSTRACT
Echoing the repeated convergent evolution of flight and vision in large eukaryotes, propulsive swimming motility has evolved independently in microbes in each of the three domains of life. Filamentous appendages – archaella in Archaea, flagella in Bacteria and cilia in Eukaryotes – wave, whip or rotate to propel microbes, overcoming diffusion and enabling colonization of new environments. The implementations of the three propulsive nanomachines are distinct, however: archaella and flagella rotate, while cilia beat or wave; flagella and cilia assemble at their tips, while archaella assemble at their base; archaella and cilia use ATP for motility, while flagella use ion-motive force. These underlying differences reflect the tinkering required to evolve a molecular machine, in which pre-existing machines in the appropriate contexts were iteratively co-opted for new functions and whose origins are reflected in their resultant mechanisms. Contemporary homologies suggest that archaella evolved from a non-rotary pilus, flagella from a non-rotary appendage or secretion system, and cilia from a passive sensory structure. Here, we review the structure, assembly, mechanism and homologies of the three distinct solutions as a foundation to better understand how propulsive nanomachines evolved three times independently and to highlight principles of molecular evolution.
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Affiliation(s)
- Morgan Beeby
- Department of Life Sciences, Frankland Road, Imperial College of London, London, SW7 2AZ, UK
| | - Josie L Ferreira
- Department of Life Sciences, Frankland Road, Imperial College of London, London, SW7 2AZ, UK
| | - Patrick Tripp
- Molecular Biology of Archaea, Institute of Biology, University of Freiburg, Schaenzlestrasse 1, 79211 Freiburg, Germany
| | - Sonja-Verena Albers
- Molecular Biology of Archaea, Institute of Biology, University of Freiburg, Schaenzlestrasse 1, 79211 Freiburg, Germany
| | - David R Mitchell
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA
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33
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Cryo-EM structure of the Shigella type III needle complex. PLoS Pathog 2020; 16:e1008263. [PMID: 32092125 PMCID: PMC7058355 DOI: 10.1371/journal.ppat.1008263] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 03/05/2020] [Accepted: 12/09/2019] [Indexed: 12/22/2022] Open
Abstract
The Type III Secretion Systems (T3SS) needle complex is a conserved syringe-shaped protein translocation nanomachine with a mass of about 3.5 MDa essential for the survival and virulence of many Gram-negative bacterial pathogens. This system is composed of a membrane-embedded basal body and an extracellular needle that deliver effector proteins into host cells. High-resolution structures of the T3SS from different organisms and infection stages are needed to understand the underlying molecular mechanisms of effector translocation. Here, we present the cryo-electron microscopy structure of the isolated Shigella T3SS needle complex. The inner membrane (IM) region of the basal body adopts 24-fold rotational symmetry and forms a channel system that connects the bacterial periplasm with the export apparatus cage. The secretin oligomer adopts a heterogeneous architecture with 16- and 15-fold cyclic symmetry in the periplasmic N-terminal connector and C-terminal outer membrane ring, respectively. Two out of three IM subunits bind the secretin connector via a β-sheet augmentation. The cryo-EM map also reveals the helical architecture of the export apparatus core, the inner rod, the needle and their intervening interfaces. Diarrheal diseases evoke about 2.2. million dead people annually and are the second leading cause of postneonatal child mortality worldwide. Shigella causing dysentery utilizes the type 3-secretion system (T3SS) to inject virulence factors into the gut cells. The T3SS needle complex is a syringe-shaped nanomachine consisting of two membrane-embedded ring systems that sheath a central export apparatus and a hollow needle-like structure through which the virulence factors are transported. We present here the structure of the Shigella T3SS needle complex obtained by high-end electron microscopy. The outer membrane (OM) ring system adopts a mixed 15- and 16-fold cyclic symmetry and the near-atomic structure shows the connection of the inner membrane (IM) and OM rings. Conserved channels in the IM ring connect the bacterial periplasm with the central export apparatus. Similar to the Salmonella flagellar system, the export apparatus and its connected needle-like structure assemble in a helical manner. This study advances our understanding of the role of essential structural elements in the T3SS assembly and function.
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34
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Detecting Salmonella Type II flagella production by transmission electron microscopy and immunocytochemistry. J Microbiol 2019; 58:245-251. [PMID: 31760612 DOI: 10.1007/s12275-020-9297-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 10/11/2019] [Accepted: 10/20/2019] [Indexed: 10/25/2022]
Abstract
The bacterial flagellum is an appendage structure that provides a means for motility to promote survival in fluctuating environments. For the intracellular pathogen Salmonella enterica serovar Typhimurium to survive within macrophages, flagellar gene expression must be tightly regulated, and thus, is controlled at multiple levels, including DNA recombination, transcription, post-transcription, protein synthesis, and assembly within host cells. To understand the contribution of flagella to Salmonella pathogenesis within the host, it is critical to detect flagella production within macrophages via microscopy. In this paper, we describe two methods for detecting bacterial flagella by microscopy both in vitro and in vivo infection models.
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35
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Abstract
Cells from all three domains of life on Earth utilize motile macromolecular devices that protrude from the cell surface to generate forces that allow them to swim through fluid media. Research carried out on archaea during the past decade or so has led to the recognition that, despite their common function, the motility devices of the three domains display fundamental differences in their properties and ancestry, reflecting a striking example of convergent evolution. Thus, the flagella of bacteria and the archaella of archaea employ rotary filaments that assemble from distinct subunits that do not share a common ancestor and generate torque using energy derived from distinct fuel sources, namely chemiosmotic ion gradients and FlaI motor-catalyzed ATP hydrolysis, respectively. The cilia of eukaryotes, however, assemble via kinesin-2-driven intraflagellar transport and utilize microtubules and ATP-hydrolyzing dynein motors to beat in a variety of waveforms via a sliding filament mechanism. Here, with reference to current structural and mechanistic information about these organelles, we briefly compare the evolutionary origins, assembly and tactic motility of archaella, flagella and cilia.
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Affiliation(s)
- Shahid Khan
- Molecular Biology Consortium, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
| | - Jonathan M Scholey
- Department of Molecular and Cell Biology, University of California @ Davis, CA 95616, USA.
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36
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Robust Stoichiometry of FliW-CsrA Governs Flagellin Homeostasis and Cytoplasmic Organization in Bacillus subtilis. mBio 2019; 10:mBio.00533-19. [PMID: 31113895 PMCID: PMC6529632 DOI: 10.1128/mbio.00533-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The intracellular concentration of flagellar filament protein Hag is restricted by the Hag-FliW-CsrA system in B. subtilis. Here we show that the Hag-FliW-CsrAdimer system functions at nearly 1:1:1 stoichiometry and that the system is both robust with respect to perturbation and hypersensitive to the Hag intracellular concentration. Moreover, restriction of cytoplasmic Hag levels is important for maintaining proper intracellular architecture, as artificial Hag hyperaccumulation led to generalized spatial defects and a high frequency of minicell production. The Hag-FliW-CsrA system is conserved in the deeper branches of bacterial phylogeny, and we note that the Hag-FliW-CsrA “homeostasis module” resembles a toxin-antitoxin system where, by analogy, CsrA is the “toxin,” FliW is the “antitoxin,” and Hag is the target. Flagellin (Hag) is one of the most abundant proteins in Bacillus subtilis. Here we show that each flagellar filament is assembled from ∼12,000 Hag monomers and that there is a cytoplasmic pool of Hag that is restricted to 5% of the total. Hag is thought to be restricted at the level of translation by a partner-switching mechanism involving FliW and the homodimeric RNA-binding protein CsrA (CsrAdimer). We further show that the mechanism of translation inhibition is hypersensitive due to a 1:1 ratio of Hag to FliW, a 1:1 inhibitory ratio of FliW to CsrAdimer, and a nearly 1:1 ratio of CsrAdimer to hag transcripts. Equimolarity of all components couples single-molecule detection of Hag export to compensatory translation and causes cytoplasmic Hag concentrations to oscillate around the level of FliW. We found that stoichiometry is ensured by genetic architecture, translational coupling, and the ability of CsrAdimer to restrict hag transcript accumulation. We further show that homeostasis prevents Hag hyperaccumulation that would otherwise cause severe defects in intracellular architecture, perhaps due to increased molecular crowding. We note that FliW-CsrA-mediated structural homeostasis has similarities to that seen with some toxin-antitoxin systems.
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37
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Rudenko I, Ni B, Glatter T, Sourjik V. Inefficient Secretion of Anti-sigma Factor FlgM Inhibits Bacterial Motility at High Temperature. iScience 2019; 16:145-154. [PMID: 31170626 PMCID: PMC6551532 DOI: 10.1016/j.isci.2019.05.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 04/01/2019] [Accepted: 05/15/2019] [Indexed: 12/03/2022] Open
Abstract
Temperature is one of the key cues that enable microorganisms to adjust their physiology in response to environmental changes. Here we show that motility is the major cellular function of Escherichia coli that is differentially regulated between growth at normal host temperature of 37°C and the febrile temperature of 42°C. Expression of both class II and class III flagellar genes is reduced at 42°C because of lowered level of the upstream activator FlhD. Class III genes are additionally repressed because of the destabilization and malfunction of secretion apparatus at high temperature, which prevents secretion of the anti-sigma factor FlgM. This mechanism of repression apparently accelerates loss of motility at 42°C. We hypothesize that E. coli perceives high temperature as a sign of inflammation, downregulating flagella to escape detection by the immune system of the host. Secretion-dependent coupling of gene expression to the environmental temperature is likely common among many bacteria. E. coli motility is tightly turned off at febrile temperature (42°C) Repression of motility is achieved at two levels of hierarchical gene regulation Lowered FlhD level reduces expression of all flagellar genes Impaired FlgM secretion tightens repression of class III genes
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Affiliation(s)
- Iaroslav Rudenko
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg 35043, Germany
| | - Bin Ni
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg 35043, Germany
| | - Timo Glatter
- Core Facility for Mass Spectrometry & Proteomics, Max Planck Institute for Terrestrial Microbiology, Marburg 35043, Germany
| | - Victor Sourjik
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg 35043, Germany.
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38
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Export Mechanisms and Energy Transduction in Type-III Secretion Machines. Curr Top Microbiol Immunol 2019; 427:143-159. [PMID: 31218506 DOI: 10.1007/82_2019_166] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The remarkably complex architecture and organization of bacterial nanomachines originally raised the enigma to how they are assembled in a coordinated manner. Over the years, the assembly processes of the flagellum and evolutionary-related injectisome complexes have been deciphered and were shown to rely on a conserved protein secretion machine: the type-III secretion system. In this book chapter, we demonstrate how individually evolved mechanisms cooperate in highly versatile and robust secretion machinery to export and assemble the building blocks of those nanomachines.
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39
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Kühn MJ, Schmidt FK, Farthing NE, Rossmann FM, Helm B, Wilson LG, Eckhardt B, Thormann KM. Spatial arrangement of several flagellins within bacterial flagella improves motility in different environments. Nat Commun 2018; 9:5369. [PMID: 30560868 PMCID: PMC6299084 DOI: 10.1038/s41467-018-07802-w] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 11/22/2018] [Indexed: 11/26/2022] Open
Abstract
Bacterial flagella are helical proteinaceous fibers, composed of the protein flagellin, that confer motility to many bacterial species. The genomes of about half of all flagellated species include more than one flagellin gene, for reasons mostly unknown. Here we show that two flagellins (FlaA and FlaB) are spatially arranged in the polar flagellum of Shewanella putrefaciens, with FlaA being more abundant close to the motor and FlaB in the remainder of the flagellar filament. Observations of swimming trajectories and numerical simulations demonstrate that this segmentation improves motility in a range of environmental conditions, compared to mutants with single-flagellin filaments. In particular, it facilitates screw-like motility, which enhances cellular spreading through obstructed environments. Similar mechanisms may apply to other bacterial species and may explain the maintenance of multiple flagellins to form the flagellar filament.
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Affiliation(s)
- Marco J Kühn
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität Gießen, 35392, Gießen, Germany
| | - Felix K Schmidt
- Fachbereich Physik und LOEWE Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, 35032, Marburg, Germany
| | - Nicola E Farthing
- Department of Physics, University of York, Heslington, York, YO10 5DD, UK
- Department of Mathematics, University of York, Heslington, York, YO10 5DD, UK
| | - Florian M Rossmann
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität Gießen, 35392, Gießen, Germany
| | - Bina Helm
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität Gießen, 35392, Gießen, Germany
| | - Laurence G Wilson
- Department of Physics, University of York, Heslington, York, YO10 5DD, UK.
| | - Bruno Eckhardt
- Fachbereich Physik und LOEWE Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, 35032, Marburg, Germany.
| | - Kai M Thormann
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität Gießen, 35392, Gießen, Germany.
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40
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Multiple Flagellin Proteins Have Distinct and Synergistic Roles in Agrobacterium tumefaciens Motility. J Bacteriol 2018; 200:JB.00327-18. [PMID: 30201783 DOI: 10.1128/jb.00327-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 09/01/2018] [Indexed: 11/20/2022] Open
Abstract
Rotary flagella propel bacteria through liquid and across semisolid environments. Flagella are composed of the basal body that constitutes the motor for rotation, the curved hook that connects to the basal body, and the flagellar filament that propels the cell. Flagellar filaments can be composed of a single flagellin protein, such as in Escherichia coli, or made up of multiple flagellins, such as in Agrobacterium tumefaciens The four distinct flagellins FlaA, FlaB, FlaC, and FlaD produced by wild-type A. tumefaciens are not redundant in function but have specific properties. FlaA and FlaB are much more abundant than FlaC and FlaD and are readily observable in mature flagellar filaments, when either FlaA or FlaB is fluorescently labeled. Cells producing FlaA with any one of the other three flagellins can generate functional filaments and thus are motile, but FlaA alone cannot constitute a functional filament. In flaA mutants that manifest swimming deficiencies, there are multiple ways by which these mutations can be phenotypically suppressed. These suppressor mutations primarily occur within or upstream of the flaB flagellin gene or in the transcription factor sciP regulating flagellin expression. The helical conformation of the flagellar filament appears to require a key asparagine residue present in FlaA and absent in other flagellins. However, FlaB can be spontaneously mutated to render helical flagella in the absence of FlaA, reflecting their overall similarity and perhaps the subtle differences in the specific functions they have evolved to fulfill.IMPORTANCE Flagellins are abundant bacterial proteins comprising the flagellar filaments that propel bacterial movement. Several members of the alphaproteobacterial group express multiple flagellins, in contrast to model systems, such as with Escherichia coli, which has one type of flagellin. The plant pathogen Agrobacterium tumefaciens has four flagellins, the abundant and readily detected FlaA and FlaB, and lower levels of FlaC and FlaD. Mutational analysis reveals that FlaA requires at least one of the other flagellins to function, as flaA mutants produce nonhelical flagella and cannot swim efficiently. Suppressor mutations can rescue this swimming defect through mutations in the remaining flagellins, including structural changes imparting helical shape to the flagella, and putative regulators. Our findings shed light on how multiple flagellins contribute to motility.
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41
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Spöring I, Martinez VA, Hotz C, Schwarz-Linek J, Grady KL, Nava-Sedeño JM, Vissers T, Singer HM, Rohde M, Bourquin C, Hatzikirou H, Poon WCK, Dufour YS, Erhardt M. Hook length of the bacterial flagellum is optimized for maximal stability of the flagellar bundle. PLoS Biol 2018; 16:e2006989. [PMID: 30188886 PMCID: PMC6126814 DOI: 10.1371/journal.pbio.2006989] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 08/08/2018] [Indexed: 11/28/2022] Open
Abstract
Most bacteria swim in liquid environments by rotating one or several flagella. The long external filament of the flagellum is connected to a membrane-embedded basal body by a flexible universal joint, the hook, which allows the transmission of motor torque to the filament. The length of the hook is controlled on a nanometer scale by a sophisticated molecular ruler mechanism. However, why its length is stringently controlled has remained elusive. We engineered and studied a diverse set of hook-length variants of Salmonella enterica. Measurements of plate-assay motility, single-cell swimming speed, and directional persistence in quasi-2D and population-averaged swimming speed and body angular velocity in 3D revealed that the motility performance is optimal around the wild-type hook length. We conclude that too-short hooks may be too stiff to function as a junction and too-long hooks may buckle and create instability in the flagellar bundle. Accordingly, peritrichously flagellated bacteria move most efficiently as the distance travelled per body rotation is maximal and body wobbling is minimized. Thus, our results suggest that the molecular ruler mechanism evolved to control flagellar hook growth to the optimal length consistent with efficient bundle formation. The hook-length control mechanism is therefore a prime example of how bacteria evolved elegant but robust mechanisms to maximize their fitness under specific environmental constraints. Many bacteria use flagella for directed movement in liquid environments. The flexible hook connects the membrane-embedded basal body of the flagellum to the long, external filament. Flagellar function relies on self-assembly processes that define or self-limit the lengths of major parts. The length of the hook is precisely controlled on a nanometer scale by a molecular ruler mechanism. However, the physiological benefit of tight hook-length control remains unclear. Here, we show that the molecular ruler mechanism evolved to control the optimal length of the flagellar hook, which is consistent with efficient motility performance. These results highlight the evolutionary forces that enable flagellated bacteria to optimize their fitness in diverse environments and might have important implications for the design of swimming microrobots.
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Affiliation(s)
- Imke Spöring
- Institute for Biology – Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany
- Junior Research Group Infection Biology of Salmonella, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Vincent A. Martinez
- School of Physics and Astronomy, The University of Edinburgh, Edinburgh, United Kingdom
| | - Christian Hotz
- Department of Medicine/MED3 – Pharmacology, University of Fribourg, Fribourg, Switzerland
| | - Jana Schwarz-Linek
- School of Physics and Astronomy, The University of Edinburgh, Edinburgh, United Kingdom
| | - Keara L. Grady
- Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Josué M. Nava-Sedeño
- Braunschweig Integrated Centre of Systems Biology (BRICS), Braunschweig, Germany
| | - Teun Vissers
- School of Physics and Astronomy, The University of Edinburgh, Edinburgh, United Kingdom
| | - Hanna M. Singer
- Department of Medicine/MED3 – Microbiologie, University of Fribourg, Fribourg, Switzerland
| | - Manfred Rohde
- Central Facility for Microscopy, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Carole Bourquin
- Department of Medicine/MED3 – Pharmacology, University of Fribourg, Fribourg, Switzerland
- School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Switzerland
| | - Haralampos Hatzikirou
- Braunschweig Integrated Centre of Systems Biology (BRICS), Braunschweig, Germany
- Systems Immunology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Wilson C. K. Poon
- School of Physics and Astronomy, The University of Edinburgh, Edinburgh, United Kingdom
| | - Yann S. Dufour
- Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Marc Erhardt
- Institute for Biology – Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany
- Junior Research Group Infection Biology of Salmonella, Helmholtz Centre for Infection Research, Braunschweig, Germany
- Department of Medicine/MED3 – Microbiologie, University of Fribourg, Fribourg, Switzerland
- * E-mail:
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42
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Frequent pauses in Escherichia coli flagella elongation revealed by single cell real-time fluorescence imaging. Nat Commun 2018; 9:1885. [PMID: 29760469 PMCID: PMC5951861 DOI: 10.1038/s41467-018-04288-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 04/13/2018] [Indexed: 12/02/2022] Open
Abstract
The bacterial flagellum is a large extracellular protein organelle that extrudes from the cell surface. The flagellar filament is assembled from tens of thousands of flagellin subunits that are exported through the flagellar type III secretion system. Here, we measure the growth of Escherichia coli flagella in real time and find that, although the growth rate displays large variations at similar lengths, it decays on average as flagella lengthen. By tracking single flagella, we show that the large variations in growth rate occur as a result of frequent pauses. Furthermore, different flagella on the same cell show variable growth rates with correlation. Our observations are consistent with an injection-diffusion model, and we propose that an insufficient cytoplasmic flagellin supply is responsible for the pauses in flagellar growth in E. coli. The bacterial flagellar filament is assembled from tens of thousands of flagellin subunits that are exported by a dedicated secretion system. Here, the authors show that, on average, the growth rate of flagella in E. coli decays as flagella lengthen, with large variations due to frequent pauses.
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43
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Minamino T. Hierarchical protein export mechanism of the bacterial flagellar type III protein export apparatus. FEMS Microbiol Lett 2018; 365:4993518. [DOI: 10.1093/femsle/fny117] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 05/04/2018] [Indexed: 12/18/2022] Open
Affiliation(s)
- Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
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44
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Regulation of Flagellum Biosynthesis in Response to Cell Envelope Stress in Salmonella enterica Serovar Typhimurium. mBio 2018; 9:mBio.00736-17. [PMID: 29717015 PMCID: PMC5930307 DOI: 10.1128/mbio.00736-17] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Flagellum-driven motility of Salmonella enterica serovar Typhimurium facilitates host colonization. However, the large extracellular flagellum is also a prime target for the immune system. As consequence, expression of flagella is bistable within a population of Salmonella, resulting in flagellated and nonflagellated subpopulations. This allows the bacteria to maximize fitness in hostile environments. The degenerate EAL domain protein RflP (formerly YdiV) is responsible for the bistable expression of flagella by directing the flagellar master regulatory complex FlhD4C2 with respect to proteolytic degradation. Information concerning the environmental cues controlling expression of rflP and thus about the bistable flagellar biosynthesis remains ambiguous. Here, we demonstrated that RflP responds to cell envelope stress and alterations of outer membrane integrity. Lipopolysaccharide (LPS) truncation mutants of Salmonella Typhimurium exhibited increasing motility defects due to downregulation of flagellar gene expression. Transposon mutagenesis and genetic profiling revealed that σ24 (RpoE) and Rcs phosphorelay-dependent cell envelope stress response systems sense modifications of the lipopolysaccaride, low pH, and activity of the complement system. This subsequently results in activation of RflP expression and degradation of FlhD4C2 via ClpXP. We speculate that the presence of diverse hostile environments inside the host might result in cell envelope damage and would thus trigger the repression of resource-costly and immunogenic flagellum biosynthesis via activation of the cell envelope stress response. Pathogenic bacteria such as Salmonella Typhimurium sense and adapt to a multitude of changing and stressful environments during host infection. At the initial stage of gastrointestinal colonization, Salmonella uses flagellum-mediated motility to reach preferred sites of infection. However, the flagellum also constitutes a prime target for the host’s immune response. Accordingly, the pathogen needs to determine the spatiotemporal stage of infection and control flagellar biosynthesis in a robust manner. We found that Salmonella uses signals from cell envelope stress-sensing systems to turn off production of flagella. We speculate that downregulation of flagellum synthesis after cell envelope damage in hostile environments aids survival of Salmonella during late stages of infection and provides a means to escape recognition by the immune system.
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45
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Inoue Y, Morimoto YV, Namba K, Minamino T. Novel insights into the mechanism of well-ordered assembly of bacterial flagellar proteins in Salmonella. Sci Rep 2018; 8:1787. [PMID: 29379125 PMCID: PMC5789064 DOI: 10.1038/s41598-018-20209-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 01/15/2018] [Indexed: 11/24/2022] Open
Abstract
The FliI ATPase of the flagellar type III protein export apparatus forms the FliH2FliI complex along with its regulator FliH. The FliH2FliI complex is postulated to bring export substrates from the cytoplasm to the docking platform made of FlhA and FlhB although not essential for flagellar protein export. Here, to clarify the role of the FliH2FliI complex in flagellar assembly, we analysed the effect of FliH and FliI deletion on flagellar protein export and assembly. The hook length was not controlled properly in the ∆fliH-fliI flhB(P28T) mutant compared to wild-type cells, whose hook length is controlled to about 55 nm within 10% error. The FlhA(F459A) mutation increased the export level of the hook protein FlgE and the ruler protein FliK by about 10-fold and 3-fold, respectively, and improved the hook length control in the absence of FliH and FliI. However, the ∆fliH-fliI flhB(P28T) flhA(F459A) mutant did not produce flagellar filaments efficiently, and a large amount of flagellin monomers were leaked out into the culture media. Neither the hook length control nor flagellin leakage was affected by the FlhB(P28T) and FlhA(F459A) mutations. We will discuss a hierarchical protein export mechanism of the bacterial flagellum.
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Affiliation(s)
- Yumi Inoue
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yusuke V Morimoto
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.,Quantitative Biology Center, RIKEN, 6-2-3 Furuedai, Suita, Osaka, 565-0874, Japan.,Department of Bioscience and Bioinformatics, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka, Fukuoka, 820-8502, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan. .,Quantitative Biology Center, RIKEN, 6-2-3 Furuedai, Suita, Osaka, 565-0874, Japan.
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
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46
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Bacterial Flagellins: Does Size Matter? Trends Microbiol 2017; 26:575-581. [PMID: 29258714 DOI: 10.1016/j.tim.2017.11.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 11/20/2017] [Accepted: 11/29/2017] [Indexed: 01/31/2023]
Abstract
The bacterial flagellum is the principal organelle of motility in bacteria. Here, we address the question of size when applied to the chief flagellar protein flagellin and the flagellar filament. Surprisingly, nature furnishes multiple examples of 'giant flagellins' greater than a thousand amino acids in length, with large surface-exposed hypervariable domains. We review the contexts in which these giant flagellins occur, speculate as to their functions, and highlight the potential for biotechnology to build on what nature provides.
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47
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Ward E, Renault TT, Kim EA, Erhardt M, Hughes KT, Blair DF. Type-III secretion pore formed by flagellar protein FliP. Mol Microbiol 2017; 107:94-103. [PMID: 29076571 DOI: 10.1111/mmi.13870] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 10/14/2017] [Accepted: 10/23/2017] [Indexed: 11/29/2022]
Abstract
During assembly of the bacterial flagellum, protein subunits that form the exterior structures are exported through a specialized secretion apparatus energized by the proton gradient. This category of protein transport, together with the similar process that occurs in the injectisomes of gram-negative pathogens, is termed type-III secretion. The membrane-embedded part of the flagellar export apparatus contains five essential proteins: FlhA, FlhB, FliP, FliQ and FliR. Here, we have undertaken a variety of experiments that together support the proposal that the protein-conducting conduit is formed primarily, and possibly entirely, by FliP. Chemical modification experiments demonstrate that positions near the center of certain FliP trans-membrane (TM) segments are accessible to polar reagents. FliP expression sensitizes cells to a number of chemical agents, and mutations at predicted channel-facing positions modulate this effect. Multiple assays are used to show that FliP suffices to form a channel that can conduct a variety of medium-sized, polar molecules. Conductance properties are strongly modulated by mutations in a methionine-rich loop that is predicted to lie at the inner mouth of the channel, which might form a gasket around cargo molecules undergoing export. The results are discussed in the framework of an hypothesis for the architecture and action of the cargo-conducting part of the type-III secretion apparatus.
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Affiliation(s)
- Elizabeth Ward
- Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA
| | - Thibaud T Renault
- Helmholtz Centre for Infection Research, Inhoffenstr. 7, Braunschweig, 38124, Germany.,Max Planck Institute for Infection Biology, Charitéplatz 1, Campus Charité Mitte, Berlin, 10117, Germany
| | - Eun A Kim
- Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA
| | - Marc Erhardt
- Helmholtz Centre for Infection Research, Inhoffenstr. 7, Braunschweig, 38124, Germany
| | - Kelly T Hughes
- Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA
| | - David F Blair
- Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA
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48
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Abstract
The bacterial flagellum is an organelle that self-assembles outside the cell body. Recent work has uncovered the mechanism for length control of this self-assembly process.
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Affiliation(s)
- Kelly T Hughes
- Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
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49
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Chien A, Shih SM, Bower R, Tritschler D, Porter ME, Yildiz A. Dynamics of the IFT machinery at the ciliary tip. eLife 2017; 6:28606. [PMID: 28930071 PMCID: PMC5662288 DOI: 10.7554/elife.28606] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 09/12/2017] [Indexed: 12/15/2022] Open
Abstract
Intraflagellar transport (IFT) is essential for the elongation and maintenance of eukaryotic cilia and flagella. Due to the traffic jam of multiple trains at the ciliary tip, how IFT trains are remodeled in these turnaround zones cannot be determined by conventional imaging. Using PhotoGate, we visualized the full range of movement of single IFT trains and motors in Chlamydomonas flagella. Anterograde trains split apart and IFT complexes mix with each other at the tip to assemble retrograde trains. Dynein-1b is carried to the tip by kinesin-II as inactive cargo on anterograde trains. Unlike dynein-1b, kinesin-II detaches from IFT trains at the tip and diffuses in flagella. As the flagellum grows longer, diffusion delays return of kinesin-II to the basal body, depleting kinesin-II available for anterograde transport. Our results suggest that dissociation of kinesin-II from IFT trains serves as a negative feedback mechanism that facilitates flagellar length control in Chlamydomonas.
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Affiliation(s)
- Alexander Chien
- Biophysics Graduate Group, University of California, Berkeley, Berkeley, United States
| | - Sheng Min Shih
- Physics Department, University of California, Berkeley, Berkeley, United States
| | - Raqual Bower
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, United States
| | - Douglas Tritschler
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, United States
| | - Mary E Porter
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, United States
| | - Ahmet Yildiz
- Biophysics Graduate Group, University of California, Berkeley, Berkeley, United States.,Physics Department, University of California, Berkeley, Berkeley, United States.,Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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50
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Kinoshita M, Aizawa SI, Inoue Y, Namba K, Minamino T. The role of intrinsically disordered C-terminal region of FliK in substrate specificity switching of the bacterial flagellar type III export apparatus. Mol Microbiol 2017; 105:572-588. [PMID: 28557186 DOI: 10.1111/mmi.13718] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2017] [Indexed: 01/06/2023]
Abstract
The bacterial flagellar export switching machinery consists of a ruler protein, FliK, and an export switch protein, FlhB and switches substrate specificity of the flagellar type III export apparatus upon completion of hook assembly. An interaction between the C-terminal domain of FliK (FliKC ) and the C-terminal cytoplasmic domain of FlhB (FlhBC ) is postulated to be responsible for this switch. FliKC has a compactly folded domain termed FliKT3S4 (residues 268-352) and an intrinsically disordered region composed of the last 53 residues, FliKCT (residues 353-405). Residues 301-350 of FliKT3S4 and the last five residues of FliKCT are critical for the switching function of FliK. FliKCT is postulated to regulate the interaction of FliKT3S4 with FlhBC , but it remains unknown how. Here we report the role of FliKCT in the export switching mechanism. Systematic deletion analyses of FliKCT revealed that residues of 351-370 are responsible for efficient switching of substrate specificity of the export apparatus. Suppressor mutant analyses showed that FliKCT coordinates FliKT3S4 action with the switching. Site-directed photo-cross-linking experiments showed that Val-302 and Ile-304 in the hydrophobic core of FliKT3S4 bind to FlhBC . We propose that FliKCT may induce conformational rearrangements of FliKT3S4 to bind to FlhBC .
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Affiliation(s)
- Miki Kinoshita
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Shin-Ichi Aizawa
- Department of Life Sciences, Prefectural University of Hiroshima, 562 Nanatsuka, Shobara, Hiroshima, 727-0023, Japan
| | - Yumi Inoue
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.,Quantitative Biology Center, RIKEN, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
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