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Medical Microbiology and Immunology Jun 2020Type IV pili are versatile and highly flexible fibers formed on the surface of many Gram-negative and Gram-positive bacteria. Virulence and infection rate of several... (Review)
Review
Type IV pili are versatile and highly flexible fibers formed on the surface of many Gram-negative and Gram-positive bacteria. Virulence and infection rate of several pathogenic bacteria, such as Neisseria meningitidis and Pseudomonas aeruginosa, are strongly dependent on the presence of pili as they facilitate the adhesion of the bacteria to the host cell. Disruption of the interactions between the pili and the host cells by targeting proteins involved in this interaction could, therefore, be a treatment strategy. A type IV pilus is primarily composed of multiple copies of protein subunits called major pilins. Additional proteins, called minor pilins, are present in lower abundance, but are essential for the assembly of the pilus or for its specific functions. One class of minor pilins is required to initiate the formation of pili, and may form a complex similar to that identified in the related type II secretion system. Other, species-specific minor pilins in the type IV pilus system have been shown to promote additional functions such as DNA binding, aggregation and adherence. Here, we will review the structure and the function of the minor pilins from type IV pili.
Topics: Bacterial Adhesion; Fimbriae Proteins; Fimbriae, Bacterial; Host Microbial Interactions; Models, Molecular; Protein Conformation; Protein Multimerization; Virulence
PubMed: 31784891
DOI: 10.1007/s00430-019-00642-5 -
MBio Jun 2022
Topics: Electron Transport; Fimbriae Proteins; Fimbriae, Bacterial; Geobacter; Nanowires; Oxidation-Reduction
PubMed: 35642973
DOI: 10.1128/mbio.00850-22 -
Microbiology Spectrum Jan 2019Type IV pili (T4P) are remarkable bacterial surface appendages that carry out a range of functions. Various types of T4P have been identified in bacteria and archaea,...
Type IV pili (T4P) are remarkable bacterial surface appendages that carry out a range of functions. Various types of T4P have been identified in bacteria and archaea, making them almost universal structures in prokaryotes. T4P are best characterized in Gram-negative bacteria, in which pilus biogenesis and T4P-mediated functions have been studied for decades. Recent advances in microbial whole-genome sequencing have provided ample evidence for the existence of T4P also in many Gram-positive species. However, comparatively little is known, and T4P in Gram-positive bacteria are just beginning to be dissected. So far, they have mainly been studied in and spp. and are involved in diverse cellular processes such as adhesion, motility, and horizontal gene transfer. Here we summarize the current understanding of T4P in Gram-positive species and their functions, with particular focus on the type IV competence pilus produced by the human pathogen and its role in natural transformation.
Topics: Bacterial Adhesion; DNA Transformation Competence; DNA, Bacterial; Fimbriae Proteins; Fimbriae, Bacterial; Gene Transfer, Horizontal; Streptococcus pneumoniae
PubMed: 30737914
DOI: 10.1128/microbiolspec.PSIB-0011-2018 -
EMBO Reports Feb 2019Conjugation is the process by which bacteria exchange genetic materials in a unidirectional manner from a donor cell to a recipient cell. The discovery of conjugation... (Review)
Review
Conjugation is the process by which bacteria exchange genetic materials in a unidirectional manner from a donor cell to a recipient cell. The discovery of conjugation signalled the dawn of genetics and molecular biology. In Gram-negative bacteria, the process of conjugation is mediated by a large membrane-embedded machinery termed "conjugative type IV secretion (T4S) system", a large injection nanomachine, which together with a DNA-processing machinery termed "the relaxosome" and a large extracellular tube termed "pilus" orchestrates directional DNA transfer. Here, the focus is on past and latest research in the field of conjugation and T4S systems in Gram-negative bacteria, with an emphasis on the various questions and debates that permeate the field from a mechanistic perspective.
Topics: Bacterial Outer Membrane Proteins; Bacterial Proteins; Biological Transport; Conjugation, Genetic; Fimbriae, Bacterial; Gram-Negative Bacteria; Gram-Negative Bacterial Infections; Humans; Models, Biological; Models, Molecular; Multiprotein Complexes; Protein Conformation; Structure-Activity Relationship; Type IV Secretion Systems
PubMed: 30602585
DOI: 10.15252/embr.201847012 -
Microbiology and Molecular Biology... Sep 2022Type IV pili (T4P) are retractable multifunctional nanofibers present on the surface of numerous bacterial and archaeal species. Their importance to microbiology is... (Review)
Review
Type IV pili (T4P) are retractable multifunctional nanofibers present on the surface of numerous bacterial and archaeal species. Their importance to microbiology is difficult to overstate. The scientific journey leading to our current understanding of T4P structure and function has included many innovative research milestones. Although multiple T4P reviews over the years have emphasized recent advances, we find that current reports often omit many of the landmark discoveries in this field. Here, we attempt to highlight chronologically the most important work on T4P, from the discovery of pili to the application of sophisticated contemporary methods, which has brought us to our current state of knowledge. As there remains much to learn about the complex machine that assembles and retracts T4P, we hope that this review will increase the interest of current researchers and inspire innovative progress.
Topics: Archaea; Bacteria; Fimbriae, Bacterial
PubMed: 35612326
DOI: 10.1128/mmbr.00076-22 -
Proceedings of the National Academy of... Nov 2023Horizontal transfer of F-like plasmids by bacterial conjugation is responsible for disseminating antibiotic resistance and virulence determinants among pathogenic...
Horizontal transfer of F-like plasmids by bacterial conjugation is responsible for disseminating antibiotic resistance and virulence determinants among pathogenic Enterobacteriaceae species, a growing health concern worldwide. Central to this process is the conjugative F pilus, a long extracellular filamentous polymer that extends from the surface of plasmid donor cells, allowing it to probe the environment and make contact with the recipient cell. It is well established that the F pilus can retract to bring mating pair cells in tight contact before DNA transfer. However, whether DNA transfer can occur through the extended pilus has been a subject of active debate. In this study, we use live-cell microscopy to show that while most transfer events occur between cells in direct contact, the F pilus can indeed serve as a conduit for the DNA during transfer between physically distant cells. Our findings enable us to propose a unique model for conjugation that revises our understanding of the DNA transfer mechanism and the dissemination of drug resistance and virulence genes within complex bacterial communities.
Topics: Escherichia coli; Genes, Bacterial; Plasmids; Fimbriae, Bacterial; DNA, Bacterial; Conjugation, Genetic; DNA; Gene Transfer, Horizontal
PubMed: 37963249
DOI: 10.1073/pnas.2310842120 -
PloS One 2021Axenically cultured Liberibacter crescens (Lcr) is a closely related surrogate for uncultured plant pathogenic species of the genus Liberibacter, including 'Candidatus...
Axenically cultured Liberibacter crescens (Lcr) is a closely related surrogate for uncultured plant pathogenic species of the genus Liberibacter, including 'Candidatus L. asiaticus' (CLas) and 'Ca. L. solanacearum' (CLso). All Liberibacters encode a completely conserved gene repertoire for both flagella and Tad (Tight Adherence) pili and all are missing genes critical for nucleotide biosynthesis. Both flagellar swimming and Tad pilus-mediated twitching motility in Lcr were demonstrated for the first time. A role for Tad pili in the uptake of extracellular dsDNA for food in Liberibacters was suspected because both twitching and DNA uptake are impossible without repetitive pilus extension and retraction, and no genes encoding other pilus assemblages or mechanisms for DNA uptake were predicted to be even partially present in any of the 35 fully sequenced Liberibacter genomes. Insertional mutations of the Lcr Tad pilus genes cpaA, cpaB, cpaE, cpaF and tadC all displayed such severely reduced growth and viability that none could be complemented. A mutation affecting cpaF (motor ATPase) was further characterized and the strain displayed concomitant loss of twitching, viability and reduced periplasmic uptake of extracellular dsDNA. Mutations of comEC, encoding the inner membrane competence channel, had no effect on either motility or growth but completely abolished natural transformation in Lcr. The comEC mutation was restored by complementation using comEC from Lcr but not from CLas strain psy62 or CLso strain RS100, indicating that unlike Lcr, these pathogens were not naturally competent for transformation. This report provides the first evidence that the Liberibacter Tad pili are dynamic and essential for both motility and DNA uptake, thus extending their role beyond surface adherence.
Topics: Adenosine Triphosphatases; Amino Acid Sequence; Bacterial Proteins; Citrus; DNA, Bacterial; Fimbriae, Bacterial; Liberibacter; Mutagenesis, Site-Directed; Plant Diseases; Sequence Alignment
PubMed: 34644346
DOI: 10.1371/journal.pone.0258583 -
Structure (London, England : 1993) May 2023Bacterial adhesion pili are key virulence factors that mediate host-pathogen interactions in diverse epithelial environments. Deploying a multimodal approach, we probed...
Bacterial adhesion pili are key virulence factors that mediate host-pathogen interactions in diverse epithelial environments. Deploying a multimodal approach, we probed the structural basis underpinning the biophysical properties of pili originating from enterotoxigenic (ETEC) and uropathogenic bacteria. Using cryo-electron microscopy we solved the structures of three vaccine target pili from ETEC bacteria, CFA/I, CS17, and CS20. Pairing these and previous pilus structures with force spectroscopy and steered molecular dynamics simulations, we find a strong correlation between subunit-subunit interaction energies and the force required for pilus unwinding, irrespective of genetic similarity. Pili integrate three structural solutions for stabilizing their assemblies: layer-to-layer interactions, N-terminal interactions to distant subunits, and extended loop interactions from adjacent subunits. Tuning of these structural solutions alters the biophysical properties of pili and promotes the superelastic behavior that is essential for sustained bacterial attachment.
Topics: Fimbriae Proteins; Bacterial Adhesion; Cryoelectron Microscopy; Fimbriae, Bacterial
PubMed: 37001523
DOI: 10.1016/j.str.2023.03.005 -
Current Topics in Microbiology and... 2018Agrobacterium tumefaciens attaches stably to plant host tissues and abiotic surfaces. During pathogenesis, physical attachment to the site of infection is a prerequisite... (Review)
Review
Agrobacterium tumefaciens attaches stably to plant host tissues and abiotic surfaces. During pathogenesis, physical attachment to the site of infection is a prerequisite to infection and horizontal gene transfer to the plant. Virulent and avirulent strains may also attach to plant tissue in more benign plant associations, and as with other soil microbes, to soil surfaces in the terrestrial environment. Although most A. tumefaciens virulence functions are encoded on the tumor-inducing plasmid, genes that direct general surface attachment are chromosomally encoded, and thus this process is not obligatorily tied to virulence, but is a more fundamental capacity. Several different cellular structures are known or suspected to contribute to the attachment process. The flagella influence surface attachment primarily via their propulsive activity, but control of their rotation during the transition to the attached state may be quite complex. A. tumefaciens produces several pili, including the Tad-type Ctp pili, and several plasmid-borne conjugal pili encoded by the Ti and At plasmids, as well as the so-called T-pilus, involved in interkingdom horizontal gene transfer. The Ctp pili promote reversible interactions with surfaces, whereas the conjugal and T-pili drive horizontal gene transfer (HGT) interactions with other cells and tissues. The T-pilus is likely to contribute to physical association with plant tissues during DNA transfer to plants. A. tumefaciens can synthesize a variety of polysaccharides including cellulose, curdlan (β-1,3 glucan), β-1,2 glucan (cyclic and linear), succinoglycan, and a localized polysaccharide(s) that is confined to a single cellular pole and is called the unipolar polysaccharide (UPP). Lipopolysaccharides are also in the outer leaflet of the outer membrane. Cellulose and curdlan production can influence attachment under certain conditions. The UPP is required for stable attachment under a range of conditions and on abiotic and biotic surfaces. Other factors that have been reported to play a role in attachment include the elusive protein called rhicadhesin. The process of surface attachment is under extensive regulatory control and can be modulated by environmental conditions, as well as by direct responses to surface contact. Complex transcriptional and post-transcriptional control circuitry underlies much of the production and deployment of these attachment functions.
Topics: Agrobacterium tumefaciens; Bacterial Adhesion; Bacterial Proteins; Fimbriae, Bacterial; Flagella; Virulence
PubMed: 29998422
DOI: 10.1007/82_2018_96 -
Advances in Microbial Physiology 2019The family Geobacteraceae, with its only valid genus Geobacter, comprises deltaproteobacteria ubiquitous in soil, sediments, and subsurface environments where metal... (Review)
Review
The family Geobacteraceae, with its only valid genus Geobacter, comprises deltaproteobacteria ubiquitous in soil, sediments, and subsurface environments where metal reduction is an active process. Research for almost three decades has provided novel insights into environmental processes and biogeochemical reactions not previously known to be carried out by microorganisms. At the heart of the environmental roles played by Geobacter bacteria is their ability to integrate redox pathways and regulatory checkpoints that maximize growth efficiency with electron donors derived from the decomposition of organic matter while respiring metal oxides, particularly the often abundant oxides of ferric iron. This metabolic specialization is complemented by versatile metabolic reactions, respiratory chains, and sensory networks that allow specific members to adaptively respond to environmental cues to integrate organic and inorganic contaminants in their oxidative and reductive metabolism, respectively. Thus, Geobacteraceae are important members of the microbial communities that degrade hydrocarbon contaminants under iron-reducing conditions and that contribute, directly or indirectly, to the reduction of radionuclides, toxic metals, and oxidized species of nitrogen. Their ability to produce conductive pili as nanowires for discharging respiratory electrons to solid-phase electron acceptors and radionuclides, or for wiring cells in current-harvesting biofilms highlights the unique physiological traits that make these organisms attractive biological platforms for bioremediation, bioenergy, and bioelectronics application. Here we review some of the most notable physiological features described in Geobacter species since the first model representatives were recovered in pure culture. We provide a historical account of the environmental research that has set the foundation for numerous physiological studies and the laboratory tools that had provided novel insights into the role of Geobacter in the functioning of microbial communities from pristine and contaminated environments. We pay particular attention to latest research, both basic and applied, that has served to expand the field into new directions and to advance interdisciplinary knowledge. The electrifying physiology of Geobacter, it seems, is alive and well 30 years on.
Topics: Biodegradation, Environmental; Biofilms; Biotechnology; Cytochrome c Group; Electric Conductivity; Electron Transport; Fimbriae, Bacterial; Geobacter; Metals; Oxidation-Reduction
PubMed: 31126529
DOI: 10.1016/bs.ampbs.2019.02.007