Pili and Flagella: Current Research and Future Trends
"excellent book" (Microbiology Today) "recommended for all microbiology labs" (Int. J. Food. Microbiol.)
Caister Academic Press
Department of Microbiology and Immunology, Queen's University, Ontario, Canada
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Flagella-dependent motility is widespread throughout prokaryotes and is advantageous when nutrients are limited, as a mechanism to migrate to more favourable environments and to compete with other micro-organisms. Flagella systems can also play an important role in additional processes such as adhesion to substrates, biofilm formation and host invasion in pathogenic bacteria. A variety of different classes of pili are found in prokaryotes and these structures also possess a diverse array of functions. Pili are essential for host colonization, virulence and pathogenesis for many bacteria and, in the case of type IV pili, can also be employed for motility across solid surfaces.
This book, the first for many years on this important topic, brings together some of the top scientists in the field and describes the current knowledge and latest research on prokaryotic pili and flagella. The emphasis of the chapters is on the molecular biology, genetics, structure, assembly and function of these structures. Topics include biogenesis, structure, and function of various pili in Gram-negative and Gram-positive organisms, flagellar gene expression, structure and assembly, the flagella motor, posttranslational modifications of flagella systems, lateral flagella systems, the origin and evolution of flagella, applications of flagella as a surface display and expression system, and a chapter on the flagella and pili of Archaea.
A recommended text for all microbiology laboratories and an essential volume for anyone involved in microbial adhesion, pathogenesis, virulence, structural biology, host colonization and motility.
"the latest knowledge on prokaryotic pili and flagella" from SciTech Book News (September 2009)
"a recommended text for all microbiology laboratories and essential for anyone involved in microbial adhesion, pathogenesis, virulence, structural biology host colonization and motility. All the chapters are comprehensive and current, presented on a scientific very high level and you will enjoy the clarity and insight provided in all the chapters." from Int. J. Food. Microbiol. (2009) 135: 183.
"written by internationally outstanding experts and top scientists within this field ... outstanding colour plates ... references are restricted to really important primary publications and are absolutely up to date ... an essential monography for scientists especially involved in topics such as microbial adhesion, pathogenesis and virulence, host colonization, microbial motility, biofilm aspects, and structural biology of pili and flagella ... from the perspective of the excellent scientific, editorial and layout quality the price should be considered reasonable." from Arzneimittelforschung/Drug Research (2009) 59: 578.
"excellent book ... helpful explanations ... an ideal source ... the authors write with enthusiasm and authority ... a great purchase" from Microbiology Today
Table of contents
1. Type IV Pilus Structure
The Type IV pili are architectural marvels of biology. These helical arrays of thousands of copies of a single pilin subunit are extremely thin and flexible yet remarkably strong, and they possess a diverse array of functions. Type IV pili are essential for host colonization and virulence for many Gram negative bacteria, and may also play a role in pathogenesis for some Gram positive bacteria. High resolution structures of pilin subunits have been determined by X-ray crystallography and nuclear magnetic resonance spectroscopy both as full length proteins and as soluble fragments. These structures have been used to generate computational models of pilus filament assemblies, guided by biophysical parameters extracted from fiber diffraction data and electron microscopy image analysis, and by a dense literature of biological data. Most recently, cryo-electron microscopy has provided an intermediate resolution structure of a pilus filament. The pilin structures and filament models have been instrumental in advancing our understanding of the molecular mechanisms driving pilus assembly and the role of Type IV pili in key bacterial functions such as immune evasion, microcolony formation and DNA uptake. In very general terms the structural data point to a shared subunit structure and filament architecture for all Type IV pili, but a comprehensive, atomic-level understanding of these filaments and their biological processes will require additional higher resolution filament structures as well as new structural, genetic and biochemical data on the many components of the pilus assembly apparatus.
2. Type IV Pilus Biogenesis, Structure and Function: Lessons from Type IVa Pilin Systems
Type IV pili are unabashed celebrities of the world of prokaryotic appendages and their fame and attraction are well deserved. Not only are they expressed by a vast array of phlyogenetically distinct species, they are associated with a dazzling array of diverse processes and phenotypes that impact heavily on microbial biology. Here, I give an overview of where we are today with regard to understanding the biogenesis, dynamics, structure and function of the type IVa class of type IV pili. In particular, I highlight studies of organelle biology in two systems that have played prominent roles in the development of the field: Pseudomonas aeruginosa and Neisseria gonorrhoeae. New emerging systems and outstanding issues are also addressed.
3. The Bundle-forming Pilus and Other Type IVb Pili
Ekaterina Milgotina and Michael S. Donnenberg
Type IV pili are remarkable multifunctional organelles expressed by diverse pathogenic bacteria. Type IVb pili have proven highly amenable to study, in part because of the arrangement of the genes encoding their synthesis in contiguous clusters. In this chapter we review the biogenesis and function of type IVb pili, with an emphasis on the bundle-forming pilus produced by enteropathogenic Escherichia coli. In particular, we discuss the structure and function of the adhesive pilin protein and the cellular localization and known interactions among components of the biogenesis machinery.
4. Structure, Function and Biogenesis of Pili Formed by the Chaperone/Usher Pathway
Han Remaut and Gabriel Waksman
The chaperone/usher pathway is used by a wide range of gram-negative bacteria to expose adhesive filaments, called pili or fimbriae, on their outer surface. In pathogenic strains, pili constitute important virulence factors that allow host recognition and immune evasion via specific attachment, cell invasion and/or biofilm formation. Pilus biogenesis involves a periplasmic chaperone and an outer membrane protein called the usher. The periplasmic chaperone aids pilus subunit folding in the periplasm and maintains subunits in a polymerization-prone folding state. The usher recruits chaperone-subunit complexes to the outer membrane, facilitates their ordered polymerization and is responsible for pilus translocation to the outer surface. The tremendous advancements in the structural molecular characterization of pilus components and the chaperone/usher assembly machinery over the last two decades has brought the mechanistic understanding of this biosynthetic pathway to a point where strategies can now be developed for the targeted disarmament of bacteria of these virulence organelles.
5. Gram-positive Bacterial Pili and the Host-pathogen Interface
Anjali Mandlik, Andrew H. Gaspar, Anu Swaminathan, Arunima Mishra, Asis Das and Hung Ton-That
The cell wall of many gram-positive bacteria harbors covalently linked protein polymers, known as pili or fimbriae, which enable these bacteria to adhere to specific host tissues and initiate a pathogenic program. A typical pilus contains a major pilin forming the shaft and one or more minor pilin subunits. The heteromeric pilus is assembled by specific transpeptidase enzymes called sortases. While the joining of individual pilins into a polymer is catalyzed by a pilus-specific sortase, anchoring of the pilus to the cell wall peptidoglycan is carried out by the housekeeping sortase. This chapter reviews our current understanding of the mechanism of pilus assembly and the roles of pili in bacterial pathogenesis.
6. What is Essential for Flagellar Assembly?
The flagellum is a motile organelle for most swimming bacteria. In Salmonella enterica, flagellar assembly and function requires about 50 genes, among which 21 gene products are incorporated in the complete flagellar structure as component proteins. In other eubacterial species including gram-positive bacteria and spirochetes, the number of genes and component proteins required for flagellar assembly is more or less the same, suggesting that the assembly mechanism for the flagellar structure is universal and that the flagellar machine is essentially the same in all species.
7. The Coordination of Flagellar Gene Expression and the Flagellar Assembly Pathway
Jonathon Brown, Alexandra Faulds-Pain and Phillip Aldridge
The assembly of a bacterial flagellum requires the coordinated synthesis of over 60 gene products. These genes encode structural and regulatory proteins. A key feature of all flagellar systems is the ability to sense the progression of assembly and the assimilation of this information to allow for the coordination of flagellar gene expression. Our understanding of the regulation of flagellar gene expression encompasses flagellar systems from all corners of the bacterial kingdom. All flagellar systems coordinate flagellar gene expression through a transcriptional hierarchy central to an integrated regulatory network of multiple regulatory components. These networks exhibit a number of conserved circuit architectures reflective of the strong conservation found within the structural components of the flagellum. However, a fascinating level of diversity is evident amongst flagellar systems in how assembly intermediates are sensed and how the perception of these intermediates modulates the activity of the associated transcriptional hierarchy. This chapter explores the conservation and divergence exhibited amongst flagellar system regulatory networks.
8. Structure and Mechanism of the Flagellar Rotary Motor
David F. Blair
The flagellar motor is a biochemical machine that transforms energy stored in the membrane ion gradient into the mechanical work of rotation, at a high rate of speed and with great efficiency. Discrete steps in rotation have recently been detected, attaining a long-sought goal of biophysical measurement and opening a path to detailed physiological dissection of the mechano-chemical cycle of the motor. Structural and biochemical studies of the elements that function in torque generation have provided a fairly detailed picture of the rotor and have begun to reveal crucial features of the stator. A molecular-level understanding of the mechanism appears almost within reach.
9. Flagella Structure
Fadel A. Samatey
Since its discovery, the flagellum has fascinated researchers. The scientific community had been wondering about the composition, the construction and the function, at the molecular level, of such an organelle. All available techniques in genetics, molecular biology, electron microscopy, X-ray diffraction, electron cryotomography and molecular dynamics simulation have been used, quite successfully, independently or in a combined manner to answer many of the questions. It is now well established that the flagellum is a complex multi-component organelle that spans from the cell membrane to outside of the cell, with the exception of the spirochete flagellum that stays in the periplasmic space. The flagellum self-assembles to form a helical propeller that enables prokaryotic cells to swim in its living environment. Diverse structural studies are done to understand the molecular interactions relative to its function. The nature of the flagellum makes it suitable for structural studies using electron microscopy and three-dimensional image reconstruction techniques. Therefore, electron microscopy has given many structural models of flagella from different species of Archaea and Bacteria. Structural investigations of flagellar systems have been more successful by combining X-ray diffraction and electron microscopy. The combination of these techniques produced high-resolution models of the filament from S. typhimurium.
10. Glycosylation of Flagellins
Susan M. Logan
In recent years it has become clearly established that a number of bacteria produce flagellins which are posttranslationally modified with novel glycan structures via O-linkage. In contrast, the flagella of Aarchaea, which closely resemble bacterial type IV pili in structure, can also have glycosylated flagellin monomers, although the glycan moiety in this system is attached in N-linkage. The unique mechanisms of assembly of these distinct flagellar structures plays an integral role in the respective glycosylation processes. The glycosylation of flagellin has been shown to affect flagellar assembly or play a role in virulence of a number of pathogenic species. This chapter will focus on reviewing the current knowledge of structural diversity of flagellar glycans and mechanisms of glycosylation, and in addition describe the unique biological roles of some of these flagellar glycans.
11. Lateral Flagella Systems
Susana Merino and Juan M. Tomás
Flagella-dependent locomotion is usually attributed to only one flagella system, but some bacteria are able to produce dual flagella systems responsible for different types of motility. These bacteria are able to express constitutively polar or subpolar flagella, required for swimming motility, and an inducible, second (lateral) flagella system in viscous environment or on surfaces, essential for swarming motility. Lateral flagella also contribute to the virulence of pathogenic bacteria through adhesion and biofilm formation to host surfaces. Since flagella synthesis and motility have a high metabolic cost for the bacterium, lateral flagella expression is highly regulated by a number of environmental factors and regulators. Although inducible lateral flagella systems were considered uncommon, comparative bioinformatics analysis indicate the presence of homologous non-functional lateral systems in different bacteria that only express one flagella system. These findings show that the presence of dual flagella systems within the same species is more common than was previously thought.
12. The Bacterial Flagellum as a Surface Display and Expression Tool
Katariina Majander, Lena Anton, Riikka Kylväjä, and Benita Westerlund-Wikström
The complex and self-assembling bacterial flagellum was earlier considered solely as a motility organelle used by bacteria and archaea for swimming towards attractants. In recent years, additional functions for the flagellum have been reported, such as adhesive properties, involvement in biofilm formation, sensor of environmental wetness, and importantly, a molecule recognized by components of the innate immune system of eukaryotic cells. This review will summarize the basis and use of the flagellum in bacterial surface display, as an apparatus for extracellular secretion, as a vaccine component, and in expression techniques. Targeting of foreign polypeptides to the bacterial surface is based on fusion by genetic methods of the heterologous polypeptide to a surface-localized carrier protein. Subunits of the flagellum, i.e. the major subunit FliC and the tip-localized FliD, can be used for surface display of foreign polypeptides in e.g. basic research, construction of random peptide libraries, vaccinology, and for diagnostic purposes. Surface-localized flagellar subunits are translocated to the extracellular milieu by the flagellar secretion apparatus, which can be utilized for high-yield export of foreign polypeptides into the bacterial growth medium. The flagellar subunit is, due to its potency as an immunomodulator, being explored as a carrier of antigens in vaccine design.
13. Origin and Evolution of the Bacterial Flagellar System
Elucidating the origin and evolution of complex systems such as the bacterial flagellum is one of the major challenges of evolutionary studies. Taking advantages of whole genome sequences from hundreds of bacterial genomes, recent studies have shown that the bacterial flagellum evolved from a simple secretion system to a well-honed structure, and various evolutionary forces have contributed to the stepwise formation process, including gene duplication, horizontal gene transfer, and gene loss. Whereas structural genes arose before the divergence of major bacterial lineages, auxiliary and regulatory genes are recruited in a lineage-specific fashion. Although the physical structure of the flagellum is conserved across bacterial phyla, the composition, organization, and operon structure of flagellar genes are under constant modification. Additional genome sequences and better functional characterization of genetic components will help illustrate details of the evolutionary process in the future.
14. Archaeal Flagella and Pili
Ken F. Jarrell, David J. VanDyke and John Wu
Archaeal flagella and pili are unique cellular appendages that are distinct from their bacterial namesakes. The better studied of the two structures is the archaeal flagellum. While it resembles the bacterial flagellum in terms of being a reversible rotating organelle responsible for swimming motility, its composition, structure and likely mode of assembly are all very different. Archaeal flagella have a unique structure which lacks a central channel. Similar to bacterial type IV pilins, the component flagellins are made with class 3 signal peptides and they are processed by a type IV prepilin peptidase-like enzyme. The flagellins are typically modified by the addition of N-linked glycans which are necessary for proper assembly and/or function. The study of archaeal pili is extremely limited. In Methanococcus maripaludis, the structures are formed from type IV pilin-like proteins, again possessing class 3 signal peptides processed by a type IV prepilin peptidase-like enzyme. However, the structure of the assembled pilus does not resemble any known bacterial pilus type and, unlike type IV pili, has a central channel of a diameter similar to that observed in bacterial flagella.
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(EAN: 9781904455486 9781912530922 Subjects: [bacteriology] [microbiology] [medical microbiology] [molecular microbiology] )