Inhaltsverzeichnis
Auswahl der wissenschaftlichen Literatur zum Thema „Pili de type IVa“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit den Listen der aktuellen Artikel, Bücher, Dissertationen, Berichten und anderer wissenschaftlichen Quellen zum Thema "Pili de type IVa" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Zeitschriftenartikel zum Thema "Pili de type IVa"
1
Evans, Katy J., Carey Lambert und R. Elizabeth Sockett. „Predation by Bdellovibrio bacteriovorus HD100 Requires Type IV Pili“. Journal of Bacteriology 189, Nr. 13 (06.04.2007): 4850–59. http://dx.doi.org/10.1128/jb.01942-06.
Der volle Inhalt der QuelleAnnotation:
ABSTRACT Early electron microscopy and more recent studies in our laboratory of Bdellovibrio bacteriovorus cells indicated the presence of narrow fibers at the nonflagellar pole of this unusual predatory bacterium. Analysis of the B. bacteriovorus HD100 genome showed a complete set of genes potentially encoding type IV pili and an incomplete gene set for Flp pili; therefore, the role of type IV pili in the predatory life cycle of B. bacteriovorus HD100 was investigated. Alignment of the predicted PilA protein with known type IV pilins showed the characteristic conserved N terminus common to type IVa pilins. The pilA gene, encoding the type IV pilus fiber protein, was insertionally inactivated in multiple Bdellovibrio replicate cultures, and the effect upon the expression of other pilus genes was monitored by reverse transcriptase PCR. Interruption of pilA in replicate isolates abolished Bdellovibrio predatory capability in liquid prey cultures and on immobilized yellow fluorescent protein-labeled prey, but the mutants could be cultured prey independently. Expression patterns of pil genes involved in the formation of type IV pili were profiled across the predatory life cycle from attack phase predatory Bdellovibrio throughout the intraperiplasmic bdelloplast stages to prey lysis and in prey-independent growth. Taken together, the data show that type IV pili play a critical role in Bdellovibrio predation.
2
Harvey, Hanjeong, Marc Habash, Francisca Aidoo und Lori L. Burrows. „Single-Residue Changes in the C-Terminal Disulfide-Bonded Loop of the Pseudomonas aeruginosa Type IV Pilin Influence Pilus Assembly and Twitching Motility“. Journal of Bacteriology 191, Nr. 21 (28.08.2009): 6513–24. http://dx.doi.org/10.1128/jb.00943-09.
Der volle Inhalt der QuelleAnnotation:
ABSTRACT PilA, the major pilin subunit of Pseudomonas aeruginosa type IV pili (T4P), is a principal structural component. PilA has a conserved C-terminal disulfide-bonded loop (DSL) that has been implicated as the pilus adhesinotope. Structural studies have suggested that DSL is involved in intersubunit interactions within the pilus fiber. PilA mutants with single-residue substitutions, insertions, or deletions in the DSL were tested for pilin stability, pilus assembly, and T4P function. Mutation of either Cys residue of the DSL resulted in pilins that were unable to assemble into fibers. Ala replacements of the intervening residues had a range of effects on assembly or function, as measured by changes in surface pilus expression and twitching motility. Modification of the C-terminal P-X-X-C type II beta-turn motif, which is one of the few highly conserved features in pilins across various species, caused profound defects in assembly and twitching motility. Expression of pilins with suspected assembly defects in a pilA pilT double mutant unable to retract T4P allowed us to verify which subunits were physically unable to assemble. Use of two different PilA antibodies showed that the DSL may be an immunodominant epitope in intact pili compared with pilin monomers. Sequence diversity of the type IVa pilins likely reflects an evolutionary compromise between retention of function and antigenic variation. The consequences of DSL sequence changes should be evaluated in the intact protein since it is technically feasible to generate DSL-mimetic peptides with mutations that will not appear in the natural repertoire due to their deleterious effects on assembly.
3
de Bentzmann, Sophie, Marianne Aurouze, Geneviève Ball und Alain Filloux. „FppA, a Novel Pseudomonas aeruginosa Prepilin Peptidase Involved in Assembly of Type IVb Pili“. Journal of Bacteriology 188, Nr. 13 (01.07.2006): 4851–60. http://dx.doi.org/10.1128/jb.00345-06.
Der volle Inhalt der QuelleAnnotation:
ABSTRACT Several subclasses of type IV pili have been described according to the characteristics of the structural prepilin subunit. Whereas molecular mechanisms of type IVa pilus assembly have been well documented for Pseudomonas aeruginosa and involve the PilD prepilin peptidase, no type IVb pili have been described in this microorganism. One subclass of type IVb prepilins has been identified as the Flp prepilin subfamily. Long and bundled Flp pili involved in tight adherence have been identified in Actinobacillus actinomycetemcomitans, for which assembly was due to a dedicated machinery encoded by the tad-rcp locus. A similar flp-tad-rcp locus containing flp, tad, and rcp gene homologues was identified in the P. aeruginosa genome. The function of these genes has been investigated, which revealed their involvement in the formation of extracellular Flp appendages. We also identified a gene (designated by open reading frame PA4295) outside the flp-tad-rcp locus, that we named fppA, encoding a novel prepilin peptidase. This is the second enzyme of this kind found in P. aeruginosa; however, it appears to be truncated and is similar to the C-terminal domain of the previously characterized PilD peptidase. In this study, we show that FppA is responsible for the maturation of the Flp prepilin and belongs to the aspartic acid protease family. We also demonstrate that FppA is required for the assembly of cell surface appendages that we called Flp pili. Finally, we observed an Flp-dependent bacterial aggregation process on the epithelial cell surface and an increased biofilm phenotype linked to Flp pilus assembly.
4
Wairuri, Charles K., Jacquie E. van der Waals, Antoinette van Schalkwyk und Jacques Theron. „Ralstonia solanacearum Needs Flp Pili for Virulence on Potato“. Molecular Plant-Microbe Interactions® 25, Nr. 4 (April 2012): 546–56. http://dx.doi.org/10.1094/mpmi-06-11-0166.
Der volle Inhalt der QuelleAnnotation:
Type IV pili are virulence factors in various bacteria. Several subclasses of type IV pili have been described according to the characteristics of the structural prepilin subunit. Although type IVa pili have been implicated in the virulence of Ralstonia solanacearum, type IVb pili have not previously been described in this plant pathogen. Here, we report the characterization of two distinct tad loci in the R. solanacearum genome. The tad genes encode functions necessary for biogenesis of the Flp subfamily of type IVb pili initially described for the periodontal pathogen Aggregatibacter actinomycetemcomitans. To determine the role of the tad loci in R. solanacearum virulence, we mutated the tadA2 gene located in the megaplasmid that encodes a predicted NTPase previously reported to function as the energizer for Flp pilus biogenesis. Characterization of the tadA2 mutant revealed that it was not growth impaired in vitro or in planta, produced wild-type levels of exopolysaccharide galactosamine, and exhibited swimming and twitching motility comparable with the wild-type strain. However, the tadA2 mutant was impaired in its ability to cause wilting of potato plants. This is the first report where type IVb pili in a phytopathogenic bacterium contribute significantly to plant pathogenesis.
5
Chlebek, Jennifer L., Hannah Q. Hughes, Aleksandra S. Ratkiewicz, Rasman Rayyan, Joseph Che-Yen Wang, Brittany E. Herrin, Triana N. Dalia, Nicolas Biais und Ankur B. Dalia. „PilT and PilU are homohexameric ATPases that coordinate to retract type IVa pili“. PLOS Genetics 15, Nr. 10 (18.10.2019): e1008448. http://dx.doi.org/10.1371/journal.pgen.1008448.
Der volle Inhalt der Quelle
6
Hughes, Hannah Q., Nicholas D. Christman, Triana N. Dalia, Courtney K. Ellison und Ankur B. Dalia. „The PilT retraction ATPase promotes both extension and retraction of the MSHA type IVa pilus in Vibrio cholerae“. PLOS Genetics 18, Nr. 12 (21.12.2022): e1010561. http://dx.doi.org/10.1371/journal.pgen.1010561.
Der volle Inhalt der QuelleAnnotation:
Diverse bacterial species use type IVa pili (T4aP) to interact with their environments. The dynamic extension and retraction of T4aP is critical for their function, but the mechanisms that regulate this dynamic activity remain poorly understood. T4aP are typically extended via the activity of a dedicated extension motor ATPase and retracted via the action of an antagonistic retraction motor ATPase called PilT. These motors are generally functionally independent, and loss of PilT commonly results in T4aP hyperpiliation due to undeterred pilus extension. However, for the mannose-sensitive hemagglutinin (MSHA) T4aP of Vibrio cholerae, the loss of PilT unexpectedly results in a loss of surface piliation. Here, we employ a combination of genetic and cell biological approaches to dissect the underlying mechanism. Our results demonstrate that PilT is necessary for MSHA pilus extension in addition to its well-established role in promoting MSHA pilus retraction. Through a suppressor screen, we also provide genetic evidence that the MshA major pilin impacts pilus extension. Together, these findings contribute to our understanding of the factors that regulate pilus extension and describe a previously uncharacterized function for the PilT motor ATPase.
7
Iruegas, Ruben, Katharina Pfefferle, Stephan Göttig, Beate Averhoff und Ingo Ebersberger. „Feature architecture aware phylogenetic profiling indicates a functional diversification of type IVa pili in the nosocomial pathogen Acinetobacter baumannii“. PLOS Genetics 19, Nr. 7 (27.07.2023): e1010646. http://dx.doi.org/10.1371/journal.pgen.1010646.
Der volle Inhalt der QuelleAnnotation:
The Gram-negative bacterial pathogen Acinetobacter baumannii is a major cause of hospital-acquired opportunistic infections. The increasing spread of pan-drug resistant strains makes A. baumannii top-ranking among the ESKAPE pathogens for which novel routes of treatment are urgently needed. Comparative genomics approaches have successfully identified genetic changes coinciding with the emergence of pathogenicity in Acinetobacter. Genes that are prevalent both in pathogenic and a-pathogenic Acinetobacter species were not considered ignoring that virulence factors may emerge by the modification of evolutionarily old and widespread proteins. Here, we increased the resolution of comparative genomics analyses to also include lineage-specific changes in protein feature architectures. Using type IVa pili (T4aP) as an example, we show that three pilus components, among them the pilus tip adhesin ComC, vary in their Pfam domain annotation within the genus Acinetobacter. In most pathogenic Acinetobacter isolates, ComC displays a von Willebrand Factor type A domain harboring a finger-like protrusion, and we provide experimental evidence that this finger conveys virulence-related functions in A. baumannii. All three genes are part of an evolutionary cassette, which has been replaced at least twice during A. baumannii diversification. The resulting strain-specific differences in T4aP layout suggests differences in the way how individual strains interact with their host. Our study underpins the hypothesis that A. baumannii uses T4aP for host infection as it was shown previously for other pathogens. It also indicates that many more functional complexes may exist whose precise functions have been adjusted by modifying individual components on the domain level.
8
Orndorff, Paul E., Aditya Devapali, Sarah Palestrant, Aaron Wyse, Mary Lou Everett, R. Randal Bollinger und William Parker. „Immunoglobulin-Mediated Agglutination of and Biofilm Formation by Escherichia coli K-12 Require the Type 1 Pilus Fiber“. Infection and Immunity 72, Nr. 4 (April 2004): 1929–38. http://dx.doi.org/10.1128/iai.72.4.1929-1938.2004.
Der volle Inhalt der QuelleAnnotation:
ABSTRACT The binding of human secretory immunoglobulin A (SIgA), the primary immunoglobulin in the gut, to Escherichia coli is thought to be dependent on type 1 pili. Type 1 pili are filamentous bacterial surface attachment organelles comprised principally of a single protein, the product of the fimA gene. A minor component of the pilus fiber (the product of the fimH gene, termed the adhesin) mediates attachment to a variety of host cell molecules in a mannose inhibitable interaction that has been extensively described. We found that the aggregation of E. coli K-12 by human secretory IgA (SIgA) was dependent on the presence of the pilus fiber, even in the absence of the mannose specific adhesin or in the presence of 25 mM α-CH3Man. The presence of pilus without adhesin also facilitated SIgA-mediated biofilm formation on polystyrene, although biofilm formation was stronger in the presence of the adhesin. IgM also mediated aggregation and biofilm formation in a manner dependent on pili with or without adhesin. These findings indicate that the pilus fiber, even in the absence of the adhesin, may play a role in biologically important processes. Under conditions in which E. coli was agglutinated by SIgA, the binding of SIgA to E. coli was not increased by the presence of the pili, with or without adhesin. This observation suggests that the pili, with or without adhesin, affect factors such as cell surface rigidity or electrostatic repulsion, which can affect agglutination but which do not necessarily determine the level of bound immunoglobulin.
9
Dahlgren, U. I., S. Ahlstedt und L. A. Hanson. „The localization of the antibody response in milk or bile depends on the nature of the antigen.“ Journal of Immunology 138, Nr. 5 (01.03.1987): 1397–402. http://dx.doi.org/10.4049/jimmunol.138.5.1397.
Der volle Inhalt der QuelleAnnotation:
Abstract Immunization in the Peyer's patches of rats with horse spleen ferritin or Escherichia coli 06 carrying type 1 pili resulted in an IgA antibody response detected in milk and bile and an IgG and IgM antibody response in serum, milk, and bile. The IgA antibody response to type 1 pili was as a mean 5.0-fold higher in milk than in bile. In contrast IgA antibody activity to 06 LPS was as a mean 6.3-fold higher in bile than in milk. The IgA antibodies to ferritin were randomly distributed between milk and bile. The IgG and IgM antibody activity to all three antigens studied were higher in the milk than in the bile. The secretory antibody response could be transferred from immunized rats to unimmunized rats with mesenteric lymph node cells (MLN) taken from donor rats 4 days after immunization in the Peyer's patches. IgA antibodies to pili and ferritin appeared solely in the milk of the recipients, whereas IgA antibodies to the 06 LPS only appeared in the bile. The ratios serum:milk and serum:bile for the IgG and IgM antibodies indicated an antigen-specific direction of homing with local production of these two isotypes primarily in the mammary gland. Antibody-forming cells of the IgA class could not be detected in the MLN on the day the cells were transferred. It is concluded that the difference seen in antibody distribution between milk and bile is not due to dissemination of antigen, but instead a result of different homing or expansion at the mucosal-glandular site dependent on the antigen specificity of the migrating cells.
10
Quigley, Bernard R., Matthew Hatkoff, David G. Thanassi, Mahamoudou Ouattara, Zehava Eichenbaum und June R. Scott. „A Foreign Protein Incorporated on the Tip of T3 Pili in Lactococcus lactis Elicits Systemic and Mucosal Immunity“. Infection and Immunity 78, Nr. 3 (22.12.2009): 1294–303. http://dx.doi.org/10.1128/iai.01037-09.
Der volle Inhalt der QuelleAnnotation:
ABSTRACT The use of Lactococcus lactis to deliver a chosen antigen to the mucosal surface has been shown to elicit an immune response in mice and is a possible method of vaccination in humans. The recent discovery on Gram-positive bacteria of pili that are covalently attached to the bacterial surface and the elucidation of the residues linking the major and minor subunits of such pili suggests that the presentation of an antigen on the tip of pili external to the surface of L. lactis might constitute a successful vaccine strategy. As a proof of principle, we have fused a foreign protein (the Escherichia coli maltose-binding protein) to the C-terminal region of the native tip protein (Cpa) of the T3 pilus derived from Streptococcus pyogenes and expressed this fusion protein (MBP*) in L. lactis. We find that MBP* is incorporated into pili in this foreign host, as shown by Western blot analyses of cell wall proteins and by immunogold electron microscopy. Furthermore, since the MBP* on these pili retains its native biological activity, it appears to retain its native structure. Mucosal immunization of mice with this L. lactis strain expressing pilus-linked MBP* results in production of both a systemic and a mucosal response (IgG and IgA antibodies) against the MBP antigen. We suggest that this type of mucosal vaccine delivery system, which we term UPTOP (for unhindered presentation on tips of pili), may provide an inexpensive and stable alternative to current mechanisms of immunization for many serious human pathogens.
Dissertationen zum Thema "Pili de type IVa"
1
Zatakia, Hardik M. „Characterization of symbiotically important processes in Sinorhizobium meliloti“. Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/56652.
Der volle Inhalt der QuelleAnnotation:
Bacteria perform biological nitrogen fixation (BNF) which leads to conversion of N2 to ammonia. One of the best studied models of BNF is the symbiotic association of Sinorhizobium meliloti - Medicago sativa (alfalfa). Since alfalfa is a major source of animal feed and the fourth largest crop grown in the USA, enhanced understanding of this symbiosis can have implications for increasing crop yields, reducing environmental contamination and food costs. Studies discussed here focus on two symbiotically important bacterial traits, type IVb pili and chemotaxis.
Chapter 2 characterizes S. meliloti type IVb pili encoded by flp-1 and establishes their role in nodulation. Bundle-forming pili were visualized in wild-type cells, while cells lacking pilA1, the pilin-encoding gene, showed an absence of pili. Competitive nodulation assays with alfalfa concluded that cells lacking pili had a significant nodulation defect. Regulation of pilA1 expression via a quorum sensing regulator, ExpR, was confirmed.
Chapter 3 describes the role of the flp-2 cluster in establishing symbiosis. PilA2 is a pilin subunit encoded from flp-2. The pilA2 deletion strain was defective in nodulation by 31% as compared to the wild type. A non-significant change in nodulation was seen in pilA1pilA2 strain. Thus, both flp-1 and flp-2 have a significant role in establishing symbiosis.
Chapter 4 focuses on the deviations of S. meliloti chemotaxis from the enterobacterial paradigm. Transcriptional fusions showed that S. meliloti chemoreceptors (MCPs) are class III genes and regulated by FlbT. Quantitative immunoblots determined the cellular amounts of chemoreceptors. Chemoreceptors were grouped in three classes; high, low, and extremely-low
abundance, similar to the high and low abundance chemoreceptors of Escherichia coli. Importantly, the MCP:CheA ratio in an S. meliloti cell was observed to be 37:1, similar to that in Bacillus subtilis of 24:1, but quite different from that in E. coli of 3.4:1. In conclusion, our data indicates that soil bacteria may have optimized their chemotaxis system based on their milieu, which is different from enteric bacteria.
These studies have enhanced our understanding of two symbiotically important processes in S. meliloti, and pave the way for future manipulations of the system to increase symbiosis and reduce our dependence on synthetic fertilizers.Ph. D.
2
Berry, Jamie. „Structural characterization of type IV pilus biogenesis proteins“. Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/structural-characterization-of-type-iv-pilus-biogenesis-proteins(1e0d7119-58d5-4e5d-839d-daef8deb76ab).html.
Der volle Inhalt der QuelleAnnotation:
Type IV pili, or fimbriae, are long, thin proteinaceous appendages found on the surface of many well-known pathogens. They mediate a variety of important virulence functions for the organism, such as twitching motility, biofilm formation, uptake of genetic material and host cell recognition and adhesion. Pili are formed by the rapid polymerization and de-polymerization of the pilin subunit, and this is orchestrated by a complex macromolecular machine which spans the bacterial cell envelope, requiring a variety of gene products. The type IV pilus biogenesis system is closely related to the bacterial type II secretion system, one of six designated multi-protein cell envelope complexes which are dedicated to the specific secretion of exotoxins and virulence factors. Many of these secretion systems also produce fimbrial structures to facilitate the extrusion of their substrates or to communicate with the host. As they form crucial virulence factors, the secretion systems and the type IV pilus biogenesis system have become attractive potential antimicrobial targets and obtaining structural and functional information for the components of these systems is an important first step towards achieving this.Type IV pili appear on the surface of bacteria through an outer membrane pore, PilQ, which is a member of the secretin family. Secretins are also found in the type II and III secretion systems, but the way in which they are regulated remains unclear. PilQ forms a dodecameric chamber in the outer membrane with a large vestibule which reaches into the periplasm, composed of its N-terminal domains. In this project, N-terminal domains from PilQ were produced in recombinant form and their structures determined by NMR. One of these domains revealed an eight-stranded beta-sandwich structure which appears to be unique to type IV pilus secretins and has not been structurally characterized before. Another revealed an alpha/beta type fold which is common to secretins of other systems. In the second part of this project, the interaction formed between the N-terminal alpha/beta domains of PilQ and an essential inner membrane-anchored lipoprotein, PilP, was probed by NMR chemical shift perturbation. Based on changes to the 15N-HSQC spectra the binding site was mapped onto each protein to produce a computational model for the complex formed between the two. Using a recent cryo-EM structure for the Neisseria PilQ dodecamer determined by colleagues, it was possible to model the PilQ N-terminal domains in complex with PilP into the electron density map. This produced a model for the trans-periplasmic assembly formed by PilQ and PilP in the type IV pilus biogenesis system, and led to the conclusion that the PilQ dodecamer needs to disassemble considerably at the base to accommodate a pilus fibre. The novel beta-domains might therefore function to gate or open the secretin, and PilP may play a role in stabilizing the secretin during this and serve to connect the outer and inner membrane system components.
3
Jacobsen, Theis. „Structure and assembly of bacterial type IV filaments unravelled by an integrative approach“. Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS146.
Der volle Inhalt der QuelleAnnotation:
La superfamille des filaments de type IV (TFF) est un groupe de machines moléculaires localisées dans la membrane des bactéries et des archées. Ces machines associent des polymères protéiques de manière non-covalente appelés des pili, qui s’étendent depuis la cellule pour réaliser plusieurs fonctions qui ont évolué spécifiquement pour s’adapter à des organismes hôtes différents. La superfamille TFF comprend le système de sécrétion de type II (T2SS) et les pili de type IVa (T4aP). Le T2SS induit la sécrétion de substrats chez les bactéries Gram-négatives. Ces substrats sont en général des enzymes qui dégradent les complexes carbohydrates, le peptidoglycane, les lipides, ce qui à terme entraîne la libération de nutriments. Les T4aP sont de longues fibres flexibles qui sont ancrées dans la membrane et permettent de nombreuses fonctions. Le mécanisme par lequel le T2SS et les T4aP remplissent ces différentes fonctions n’est toujours pas entièrement compris. Pour comprendre le mécanisme de sécrétion du T2SS, nous avons étudié par RMN la structure de la pseudopiline OutG, le composant majeur du pseudopilus chez Dickeya dadantii. Dans une seconde partie, nous avions pour objectif d’aborder la structure et l’assemblage des pilines mineures, des protéines qui composent le T4P d’Escherichia coli entérohémorragique. Nous avons optimisé la surexpression, la purification et le marquage de les pilines mineures pour leur étude par RMN. De plus, la modélisation des pilines et le cross-linking ont été réalisés sur les échantillons de pseudopili T4P et T2SS purifiés en tant que méthodologie pour déterminer la structure et les interactions des pilines et pseudopilines au sein du pilus natifThe type IV filament (TFF) superfamily is a group of molecular machineries located in the membrane of bacteria and archaea. These machineries assemble non-covalent protein polymers called pili extending away from the cell to perform multiple functions which have evolved specifically to adapt to different host organisms. The TFF superfamily includes the type II secretion system (T2SS) and the type IVa pili (T4aP). The T2SS promotes the secretion of substrates in Gram-negative bacteria. These substrates are in general enzymes degrading complex carbohydrates, peptidoglycan, and lipids, resulting in the release of nutrients. The T4aP are long flexible fibres anchored in the membrane and enable various functions such as twitching motility, DNA uptake and biofilm formation. The mechanism by which the T2SS and T4aP pilus fulfil their different functions is still not completely understood. To understand the mechanism of secretion by T2SS, we studied the structure of the pseudopilin OutG, the major component of the pseudopilus in Dickeya dadantii by Nuclear Magnetic Resonance (NMR). In a second part, we aimed to address the structure and the assembly of minor pilins, protein components of Enterohemorrhagic Escherichia coli T4aP. We optimised the overexpression, purification and labelling of the minor pilins for their structural study by NMR. Furthermore, molecular modelling of the minor pilins and crosslinking mass spectrometry were performed on whole T4aP and T2SS pseudopili purified samples as a methodology to determine the structure and the interactions of pilins and pseudopilins within the native pilus
4
Luna-Rico, Areli-Noemi. „Enterobacterial type IV pili : structure, assembly and molecular function“. Thesis, Sorbonne Paris Cité, 2018. https://theses.md.univ-paris-diderot.fr/LUNARICO_Areli_4_va_20180629.pdf.
Der volle Inhalt der QuelleAnnotation:
Nombreuses espèces bactériennes présentent des fibres à leur surface qui leur permettent d’interagir avec leur environnement. Les pili de type 4 (PT4) sont des fibres longues, fines et flexibles, impliquées dans des fonctions multiples telles que l'adhérence, la motilité, la sécrétion, l'import d'ADN et la formation des biofilms. Ils sont composés de milliers de copies de sous-unité majeure de piline et sont assemblés par un complexe protéique localisé dans l'enveloppe bactérienne. Dans cette étude, nous nous sommes intéressés aux PT4 chez Escherichia coli entérohémorragique (EHEC) de sérotype O157: H7. EHEC est un agent pathogène humain d'origine alimentaire qui provoque des épidémies de diarrhées hémorragiques et/ou des atteintes rénales sévères appelées syndrome hémolytique et urémique (SHU), qui peuvent être mortelles. Les PT4 chez EHEC sont composés de la sous-unité majeure PpdD et probablement des pilines mineures PpdA, PpdB, YgdB et PpdC en plus faible abondance.Dans cette étude notre objectif était de décrire la structure des PT4 chez EHEC, en tant que modèle de la famille des pili conservés chez les entérobactéries. La structure est indispensable pour décrire le mode d'action de ces organites. Dans cette étude, nous avons abordé la structure de l'EHEC T4P ainsi que les bases moléculaires de leur assemblage. En raison de la nature flexible et non covalente des fibres T4P, nous avons utilisé une approche intégrative incluant des données obtenues par cryo-microscopie électronique (cryo-ME), spectroscopie RMN, modélisation moléculaire et analyses biochimiques pour déterminer la structure des pili PpdD. Les interactions entre les sous-unités de pilines présentes dans la fibre ont été étudiées par mutagenèse dirigée et analyses fonctionnelles. Ces expériences nous ont permis d’identifier les résidus de PpdD essentiels pour l’assemblage des pili.Les T4aP ont été peu étudiés chez les entérobactéries. Bien que tous les gènes nécessaires soient présents chez E. coli, les conditions induisant leur expression restent inconnues. Cependant, les gènes codant pour les PT4 chez E. coli sont co-régulés avec des gènes codant pour la machinerie impliquée dans l’import d'ADN, ce qui suggère leur rôle dans la compétence naturelle. Afin de faciliter l'étude de PT4, nous avons réalisé une reconstitution fonctionnelle de l'EHEC T4PS chez E. coli K-12 non pathogène par l'expression contrôlée des gènes de PT4 clonés dans un opéron artificiel. Cette construction nous a permis de réaliser des analyses comparatives d'assemblage des pili par le système hétérologue (système de sécrétion de type 2 provenant d'une autre entérobactérie, Klebsiella oxytoca) et le système d'assemblage propre aux PT4 chez EHEC. Leur analyse par cryo-ME a montré que les pili assemblés sont identiques, indiquant ainsi que ce sont les pilines majeures qui déterminent la structure et la symétrie des fibres. Les résultats des études comparatives ont également apporté des informations importantes sur l'assemblage des pili. Nous avons identifié des composants de la machinerie d'assemblage qui interagissent avec la piline majeure PpdD. La formation des dimères de PpdD et ses interactions spécifiques avec les facteurs d’assemblage semblent importantes pour la stabilité de la piline avant l'assemblage en pilus. L’ensemble de nos résultats consitutent des bases pour de futures analyses structurales et fonctionnelles des pili chez les entérobactériesMany bacterial species display surface fibers to interact with the surrounding environment. Type 4 pili (T4P) are long and thin, flexible fibers involved in a variety of functions including adherence, motility, secretion, DNA uptake and biofilm formation. They are composed of thousands of copies of major pilin subunits and are assembled by a protein complex localized in the bacterial envelope. In this study we focused on the T4P from Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7. EHEC is a human foodborne pathogen that causes outbreaks of bloody diarrhea and hemolytic uremic syndrome (HUS), which can lead to a lethal outcome. EHEC T4P is composed of the major subunit PpdD and presumably in lower abundance by minor pilins PpdA, PpdB, YgdB and PpdC.This study has aimed to describe the structure of the T4P from EHEC, a representative of pili conserved in enterobacteria. Structural information provides insights that can relate to the mode of action of these organelles. In this project we addressed the structure of the EHEC T4P and the molecular basis of their assembly. Due to the flexible and non-covalent nature of T4P fibers we used an integrative approach to combine information obtained by cryo-electron microscopy, NMR spectroscopy, molecular modeling and biochemical analyses to obtain a high quality structure of the EHEC T4P. In addition, from functional, interaction and mutational analysis we gained insights into the molecular interactions between the pilin subunits present in the fiber. The T4P are poorly studied in enterobacterial systems; despite the presence of all the necessary genes, the conditions that trigger their expression in E. coli are unknown. In addition, in E. coli the T4P-related genes are coregulated with genes encoding the DNA uptake machinery, suggesting their role in natural competence. In order to facilitate the study of T4P, we achieved a functional reconstitution of the EHEC T4PS in the non-pathogenic E. coli K-12 through the controlled expression of the T4P genes cloned together as a single artificial operon. With this accomplishment we were able to perform comparative analyses between pili assembled by a heterologous system (the Type 2 secretion system from another enterobacterium, Klebsiella oxytoca) and by the cognate EHEC T4P assembly system. CryoEM analysis showed that these pili are identical, indicating that major pilins are the key determinants of fiber structure and symmetry. The results also led us to obtain important insights into pilus assembly and to characterize PpdD interactions with the assembly machinery. These interactions and PpdD dimerization were required for pilin stability prior to pilus assembly, highlighting important early steps involving targeting of subunits to the assembly machinery. Together, these results lay the foundations for future structural and functional studies of enterobacterial T4P
5
Seow, Vui Yin. „DNA Transformation and Type IV Pili in Neisseria gonorrhoeae“. Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS049.
Der volle Inhalt der QuelleAnnotation:
La résistance aux antibiotiques, évidente chez des souches telles que Neisseria gonorrhoeae, est une crise sanitaire mondiale. Il est vital de comprendre son mécanisme, en particulier la transformation naturelle par les Pili de type IV de ces bactéries. Bien qu'elle ait été découverte en 1928, la transformation naturelle n'a toujours pas été élucidée. La dépendance de Neisseria gonorrhoeae à l'égard des Pili de type IV en fait un modèle idéal pour l'étude de ce processus.Cette thèse se lance dans une exploration intensive des processus complexes de transformation de l'ADN au sein de Neisseria gonorrhoeae, répondant ainsi à l'urgence de ce problème critique. Le rôle central de cette étude approfondie est attribué aux pili de type IV, un acteur multifonctionnel et essentiel dans l'orchestration de la transformation de l'ADN.Cette recherche pose méticuleusement les bases, en introduisant des techniques de biologie moléculaire essentielles pour le génie génétique chez N. gonorrhoeae. Nous explorons le développement d'outils, en particulier l'optimisation des milieux et les outils de microscopie adaptés à l'étude de l'absorption et de la transformation de l'ADN. En outre, nos recherches ont mis en évidence une corrélation intrigante entre l'amidon et les acides gras, qui a un impact significatif sur la croissance des gonocoques. Pour comprendre la dynamique des pili de type IV pendant l'absorption de l'ADN, nous avons mis au point des outils et un flux de travail rationalisé capables de visualiser et de quantifier à la fois les pili et les molécules d'ADN. En outre, nous avons automatisé l'analyse des micropiliers d'hydrogel afin d'étudier les propriétés mécaniques des rétractions des pili. En outre, des adaptations des revêtements des micropiliers nous ont permis d'étudier les rétractions des pili en interaction avec l'ADN.Cette étude approfondie comprend également l'examen du comportement des mutants ΔPilV, ΔPilC, et ΔPilD, dévoilant ainsi de profondes connaissances sur les mécanismes de régulation des pili de type IV et leur impact sur la dynamique de l'absorption de l'ADN. Il est particulièrement intéressant de noter que les mutations ΔPilV induisent des altérations dans la translocation de PilE, ce qui entraîne l'émergence de pili plus courts mais efficaces. Cette découverte souligne la nature adaptative de N. gonorrhoeae dans la manipulation de la diversité des pili de type IV pour optimiser les processus d'absorption de l'ADN, une révélation qui revêt une importance considérable dans la lutte contre la résistance aux antibiotiques.En outre, nos études sur d'autres pilines mineures mettent en lumière les altérations du phénotype sans entraver le mécanisme de rétraction des pili. Nos études sur les mutants PilV et PilD mettent en évidence l'influence des modifications post-traductionnelles sur PilE, accentuant ainsi la composition hétérogène des pili de type IV et leur fonctionnalité robuste en tant que polymère.Nous incluons également une courte étude examinant l'interaction entre les espèces de Neisseria commensales et pathogènes dans le contexte de l'absorption de l'ADN, ce qui élargit le champ des implications, invitant à une enquête plus approfondie et élargissant les horizons de ce domaine captivant.Bien que cette expédition laisse certaines questions sans réponse, sa profondeur et son ampleur permettent de mieux comprendre les mécanismes complexes de transformation de l'ADN et le rôle dynamique joué par les pili de type IV dans la remarquable adaptabilité de Neisseria gonorrhoeae. Non seulement cette thèse apporte des solutions aux questions existantes, mais elle ouvre également de nouvelles voies pour la recherche future, suscitant la curiosité et la fascination pour l'élucidation des complexités fonctionnelles des structures pili et leurs implications profondes dans la transformation de l'ADNAntibiotic resistance, evident in strains like Neisseria gonorrhoeae, is a global health crisis. Understanding its mechanism, particularly natural transformation through Type IV Pili in these bacteria, remains vital. Despite discovery in 1928, the specifics of natural transformation remain elusive. Neisseria gonorrhoeae's dependence on Type IV Pili makes it an ideal model for studying this process.This thesis embarks on an intensive exploration into the intricate processes of DNA transformation within Neisseria gonorrhoeae, responding to the urgency of this critical concern. Central to this comprehensive study is the pivotal role attributed to Type IV Pili, a multifunctional and essential player in orchestrating DNA transformation.This research meticulously lays the groundwork, introducing molecular biology techniques essential for genetic engineering within N. gonorrhoeae. We explores tool development, particularly in medium optimization and microscopy tools tailored to study DNA uptake and transformation. Moreover, our investigations uncovered an intriguing correlation between starch and fatty acid, significantly impacting gonococcal growth. To understand Type IV pili dynamics during DNA uptake, we engineered tools and a streamlined workflow capable of visualizing and quantifying both pili and DNA molecules. Additionally, we automated the analysis of hydrogel micropillars to delve into the mechanical properties of pili retractions. Furthermore, adaptations to the micropillar coatings enabled us to study pili retractions interacting with DNA.This in-depth investigation also involves scrutinizing the behaviour of ΔPilV, ΔPilC, and ΔPilD mutants, unveiling profound insights into the regulatory mechanisms of Type IV Pili and their consequential impact on the dynamics of DNA uptake. Particularly noteworthy is the revelation that ΔPilV mutations induce alterations in PilE translocation, resulting in the emergence of shorter yet efficient pili. This discovery underscores the adaptive nature of N. gonorrhoeae in manipulating the diversity of Type IV Pili to optimize DNA uptake processes, a revelation that holds immense significance in combating antibiotic resistance.Furthermore, our studies on other minor pilins sheds light on phenotype alterations without impeding the mechanics of pili retraction. Our studies on PilV and PilD mutants, highlight the influence of posttranslational modifications on PilE, thereby accentuating the heterogeneous composition of Type IV Pili and their robust functionality as a polymer.We also include a short study examining the interplay between commensal and pathogenic Neisseria species within the context of DNA uptake broadens the scope of implications, inviting further inquiry and expanding the horizons of this captivating field.While this expedition leaves certain questions unanswered, its depth and breadth offer extensive insights into the intricate mechanisms of DNA transformation and the dynamic role played by Type IV Pili in the remarkable adaptability of Neisseria gonorrhoeae. Not only does this thesis provide solutions to existing queries, but it also illuminates novel pathways for future research, sparking curiosity and fascination in unravelling the functional intricacies of pili structures and their profound implications in DNA transformation
6
Alteri, Christopher. „Novel Pili of Mycobacterium tuberculosis“. Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1276%5F1%5Fm.pdf&type=application/pdf.
Der volle Inhalt der Quelle
7
Couchman, Edward. „Investigating the Type IV pili of Clostridium difficile and Clostridium sordellii“. Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/48055.
Der volle Inhalt der QuelleAnnotation:
Type IV pili (T4P) are the only type of bacterial pili known to be produced by both Gram-negative and Gram-positive organisms. Though the main pilus shaft consists primarily of only one protein (the major pilin), T4P are unusual in their complexity, requiring multiple (10 or more) different protein components for assembly. Like most types of pili, T4P often function as virulence factors. In particular, T4P frequently operate as adhesins, enabling bacteria on which they are present to stick to each other (to form a biofilm or suchlike) or to adhere directly to host cells. Many T4P systems are able to retract, in which case the T4P may mediate flagella-independent motility. Most research into T4P has historically been performed on Gram-negative organisms, with T4P-encoding genes only being identified in Gram-positive organisms more recently. In particular, all sequenced species of the genus Clostridium are known to encode T4P, but only minimal investigation of these systems has been performed to date. In this study, the T4P of Clostridium difficile were investigated. C. difficile is an important pathogen, being the leading cause of antibiotic-associated diarrhoea in the developed world and thus a considerable burden on Western healthcare systems. By investigating the T4P of this species it was hoped to further elucidate its mechanisms of pathogenicity. Data is presented demonstrating the control of T4P expression by cyclic-di-GMP, and identifying which genes are essential for T4P production in C. difficile. Additionally, a genomic analysis of the related pathogen Clostridium sordellii was performed, using the first high quality genome sequence produced for this species. Genes encoding T4P were identified, analysed and investigated. Furthermore, plasmids carrying the genes encoding the species’ key virulence factors (Lethal Toxin, TcsL, and in some cases haemorrhagic toxin, TcsH) were identified. These plasmids appear to be unstable, a fact with significant implications for diagnosis of C. sordellii disease.
8
Hendrick, William Anthony. „Molecular Analysis of Type IV Pilus Assembly in Clostridium perfringens“. Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81696.
Der volle Inhalt der QuelleAnnotation:
Clostridium perfringens is a Gram-positive anaerobe capable of causing disease in humans and many animals. C. perfringens is able to move across surfaces in a manner that is dependent on growth and type IV pili.
Type IV pili are filaments that can be extended away from the cell by rapid polymerization, and retracted by depolymerization. Furthering the understanding of the initial and final energetic states of the pilins will reveal insights into possible mechanisms of type IV pilus assembly. Toward that end, a pilin was purified from the Gram-negative pathogen Pseudomonas aeruginosa and incorporated into an artificial membrane. The pilin was probed by a solid state nuclear magnetic resonance (ssNMR) technique that can determine the angle and depth of insertion of a helical peptide, as well as fluorescent and electron microscopy.
All type IV pilus systems involve the action of an assembly ATPase to provide energy to polymerize the pilus. One proposed mechanism involves two primary proteins: an ATPase and an integral membrane core protein (IMCP). Other type IV pilus proteins are thought to play supportive roles in aiding the traversal of the cell envelope. In order to evaluate this model, the assembly ATPase PilB2 and IMCP PilC2 from C. perfringens were purified and examined for interactions. The evidence presented here suggest that PilB2 and PilC2 do not interact directly, and cannot function as a core assembly apparatus.
The carbonic anhydrase (Cpb) from C. perfringens strain 13 was characterized both biochemically and physiologically. Cpb belongs to the type I subclass of the β class and is the first β class enzyme investigated from a strictly anaerobic bacteria. Kinetic analyses revealed a two-step, pingpong, zinc-hydroxide mechanism of catalysis. Analyses of a cpb deletion mutant of C. perfringens strain HN13 showed that Cpb is strictly required for growth when cultured in semi-defined medium and an atmosphere without CO₂. The grew well in nutrient-rich media with or without CO₂ in the atmosphere, although elimination of glucose resulted in decreased production of acetate, propionate, and butyrate. The results suggest a role for Cpb in anaplerotic CO₂ fixation reactions by supplying bicarbonate to carboxylases.Ph. D.
9
Amerighi, Fulvia. „Impact of S.pneumoniae type-I pilus and its subunits on bacterial adherence to human epithelial cells“. Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3422591.
Der volle Inhalt der QuelleAnnotation:
S. pneumoniae is a human pathogen able to cause both invasive and non-invasive diseases as well as to colonize the nasopharyngeal tract of children and adults. Despite pneumococcus is a leading cause of morbidity and mortality worldwide, the pathogenic mechanisms exploited by S. pneumoniae are not yet clear. A critical step is colonization of the nasopharynx and the initial interaction of pneumococci with host cells. Recently, pili were discovered in gram-positive bacteria, mediating critical host-bacterial interactions, such as adherence to the epithelium, biofilm formation and translocation of host mucosal barriers. Thirty to 50% S. pneumoniae strains harbor pilus islet-1 (PI-1) coding for a surface exposed pilus reported to be important both for colonization and virulence. In particular it has been clearly demonstrated that pilus component RrgA is the major determinant for adhesion to epithelial cells in vitro whereas RrgB is important to allow the formation of the polymeric structure into which the adhesin is incorporated.
The data reported in this work contribute to better define the involvement of S. pneumoniae pili in adhesion to human epithelial cells and providing evidence that anti-pilus antibodies are able to prevent bacterial adherence.
In order to test the adhesive attitude of S.pneumoniae strains, we selected a panel of epithelial cell lines differing for their anatomical origin and the capacity to constitute polarized monolayers. Me180 cervical epithelial cells, characterized to form weak adherence junctions and thus expose basolateral surface, result the best model to study pneumococcal adhesiveness. This evidence led us to hypothesize that the pilus ligands may reside in some of the extracellular matrix components rather than in cell associated receptors. Once identified the most appropriate cellular model we started the characterization of pilus dependent adhesion by using TIGR4 mutants lacking pilus components or subpopulations derived from the wild type strain and differing only in pilus expression (highly or poorly piliated). The results reveal that piliated bacteria were drastically more adherent to cells compared to non piliated strains. However, both the lack of the pilus adhesion moiety (RrgA) or of the pilus backbone (RrgB) determined a dramatic reduction of adhesion, suggesting that both the presence of the adhesin and its correct spacing from the bacterial cell were equally important. In addiction we tested the pilus mediated adhesiveness of different pneumococcal strains that could be successfully divided into sub-populations highly (H) or poorly (L) expressing pili. By comparing the H sub-populations we noticed striking difference in their capacity to adhere to host cells. Conventional and immune electron microscopy studies reveal that the capsule thickness is inversely related with the bacterial ability to adhere to host cells likely due to the different exposure of pili on the bacterial surface. Moreover the deletion of the capsular locus in the poorly adherent strain 19FTaiwan14 results in a considerable increase in the adhesion to epithelial cells, at levels comparable to that of poorly capsulated TIGR4 strain. Additionally, in this study, we demonstrate that anti-pilus antibodies were able to significantly impair pneumoccal adhesion to human epithelial cells in strains prominently extruding pili from the capsule. Of interest, we found a monoclonal antibody against RrgA that was able to compete with adhesion in a similar manner with respect to the polyclonal serum against the whole protein. Epitope mapping experiments resulted in the identification of the possible binding region on the RrgA molecule, located in the c-terminal domain. At the moment we are trying to confirm this result by producing point-mutated forms of RrgA with the scope to select mutants that are not recognized by the functional monoclonal antibody and finally complement rrga ko strain with these sequences to confirm the importance of the epitope in the adhesion to human epithelial cells.Streptococcus pneumoniae è un batterio Gram-positivo che fa parte della normale flora microbica che colonizza in modo asintomatico le vie respiratorie. Tuttavia questo microorganismo è anche uno dei principali patogeni umani, può, infatti, causare gravi infezioni del tratto respiratorio sia in forma non invasiva quali otite media, sinusite e polmonite che in casi più gravi forme invasive quali setticemia e meningite. Sebbene S. pneumoniae sia una delle principali cause di mortalità e morbilità nel mondo, i meccanismi patogenetici di questo batterio non sono ancora stati completamente chiariti. Un punto chiave è la colonizzazione del tratto nasofaringeo e l’interazione dei batteri con le cellule ospiti. A questo proposito, recentemente, sono state identificate nei batteri Gram-positivi delle strutture, note come pili, che svolgono un ruolo cruciale nell’interazione ospite-patogeno, sono infatti coinvolti in processi quali: adesione alle cellule epiteliali, formazione di biofilm e traslocazione degli epiteli. Una percentuale variabile tra il 30% e il 50% dei ceppi di S.pneumoniae contiene nel proprio DNA genomico un elemento genetico noto come pilus islet-1 (PI-1) che codifica per una struttura fibrillare, il pilo di tipo1, coinvolto nei processi di colonizzazione e virulenza. In dettaglio, è stato dimostrato che la sub-unità RrgA è coinvolta nell’adesione in vitro dei batteri alle cellule epiteliali mentre la sub-unità RrgB è il principale costituente della struttura del pilo, all’interno della quale è incorporata l’adesina. I dati riportati in questo lavoro contribuiscono a chiarire il ruolo svolto dal pilo nel meccanismo di adesione di Streptococcus pneumoniae alle cellule epiteliali e forniscono evidenze dell’attività degli anticorpi contro le componenti del pilo di inibire l’adesione dei batteri alle cellule ospiti. Al fine di valutare le capacità di adesione di Streptococcus pneumoniae, abbiamo selezionato una serie di linee cellulari provenienti da diversi distretti anatomici e con diversa capacità di formare un monostrato di cellule polarizzate in vitro. Tra le linee cellulari testate, il miglior modello per lo studio dell’adesione sono le ME180 (cellule epiteliali di cervice uterina) caratterizzate dal formare giunzioni lasse e quindi consentire l’esposizione di componenti della superficie basolaterale. Questo risultato ci fa ipotizzare che il ligando dei pili possa essere un elemento della matrice extracellulare o un recettore posto sulla superficie basolaterale delle cellule. Una volta identificato il modello cellulare ideale, abbiamo analizzato le capacità di adesione pilo-dipendenti di mutanti che mancano delle componenti del pilo e di sottopopolazioni isolate dal ceppo wild type che differiscono tra loro unicamente per una diversa espressione del pilo, una popolazione è altamente piliata, l’altra scarsamente piliata. I risultati mostrano che la popolazione piliata ha una capacità di aderire alle cellule molto più elevata rispetto alla popolazione non piliata. Inoltre abbiamo osservato che sia l’assenza dell’adesina (RrgA) che del backbone (RrgB) determinano una drastica riduzione dell’adesione sottolineando l’importanza per un corretto funzionamento del pilo sia della presenza dell’adesina che della sua localizzazione nella struttura del pilo. Successivamente abbiamo analizzato il contributo del pilo nell’adesione in diversi ceppi di Streptococcus pneumoniae selezionati sulla base della possibilità di poter isolare le due sottopopolazioni con diversa espressione del pilo (popolazione piliata e non piliata). Prendendo in esame le sottopopolazioni pilate dei ceppi selezionati abbiamo osservato notevoli differenze nella capacità di aderire alle cellule epiteliali. Per spiegare questo fenomeno abbiamo condotto studi di microscopia elettronica convenzionale e immuno-elettro microscopia che hanno evidenziato la presenza di una correlazione inversa tra lo spessore della capsula e le capacità adesive pilo-dipendenti, molto probabilmente dovuta alla diversa esposizione dei pili sulla superficie del batterio. Infatti, la delezione dell’intero locus capsulare in un ceppo che mostra scarsa capacità di adesione alle cellule epiteliali come il ceppo 19FTaiwan14, comporta un notevole aumento dell’adesione a livelli paragonabili al ceppo TIGR4 che è scarsamente capsulato. In questo lavoro abbiamo anche dimostrato che anticorpi prodotti contro le componenti del pilo sono in grado di inibire l’adesione dei batteri alle cellule epiteliali in ceppi in cui il pilo è molto esposto al di fuori della capsula e abbiamo identificato un anticorpo monoclonale anti-RrgA in grado di bloccare l’adesione dei batteri alle cellule ospiti in modo comparabile al siero policlonale prodotto contro l’intera proteina. Studi di epitope mapping hanno portato all’identificazione della regione di RrgA probabilmente coinvolta nel binding con l’anticorpo monoclonale, localizzata nel dominio c-terminale della proteina. Attualmente stiamo cercando di confermare questi risultati inserendo nella regione di RrgA che abbiamo identificato delle mutazioni puntiformi per ottenere forme mutate dell’epitopo che non vengano più riconosciute dal monoclonale e infine complementare il ceppo mutante rrga con queste sequenze per confermare l’importanza di questo epitopo nell’adesione alle cellule epiteliali umane.
10
Hartman, Andrea H. „Use of an Inducible Promoter to Characterize Type IV Pili Homologues in Clostridium perfringens“. Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/76874.
Der volle Inhalt der QuelleAnnotation:
Researchers of Clostridium perfringens, a Gram-positive anaerobic pathogen, were lacking a tightlyregulated, inducible promoter system in their genetic toolbox. We constructed a lactose-inducible plasmid-based system utilizing the transcriptional regulator, BgaR. Using the E. coli reporter GusA, we characterized its induction in three different strains of C. perfringens. We then used a newly-developed mutation system to create in-frame deletion mutants in three genes with homology to Type IV pilins, and we used the promoter system described above to complement the mutants. We analyzed each pilin for localization and expression, as well as tested each of the mutants for various phenotypes frequently associated with type IV pili (TFP) and type II secretion systems. PilA2, PilA3, and PilA4 localized to the poles of the cells. PilA2 was expressed in the wildtype when C. perfringens was grown on agar plates, and the PilA3 mutant lacked a von Willebrand factor A domain-containing protein in its secretome. We used our promoter system to express GFP-tagged versions of the TFP ATPase homologues and view them in cells growing on surfaces. We saw that PilB1 and PilB2 co-localized nearly all of the time, while a portion of PilT was independent of the PilB proteins. PilT appeared necessary for the localization of PilB, and it localized independently of TFP proteins in Bacillus subtilis. PilT's typical localization in Bacillus subtilis was disrupted when the GTPase and polymerization activity of cell division protein FtsZ was blocked, suggesting that PilT associates with cell division proteins.Master of Science
Bücher zum Thema "Pili de type IVa"
1
Chiang, Poney Che. Molecular investigation of the role of type 4 pili ATPases involved in twitching motility of Pseudomonas aeruginosa. 2005.
Den vollen Inhalt der Quelle finden
2
Sybert, Virginia P. Disorders of Epidermal Appendages. Oxford University Press, 2012. http://dx.doi.org/10.1093/med/9780195397666.003.0003.
Der volle Inhalt der QuelleAnnotation:
Hair – Alopecias – Loose Anagen Hair – Male Pattern Baldness – Marie Unna Syndrome – Hirsutism – Gingival Fibromatosis and Hypertrichosis – Hypertrichosis Lanuginosa Congenita – Leprechaunism – Localized Hypertrichosis – Polycystic Ovarian Disease – Hair Shaft Abnormalities, Isolated – Monilethrix – Pili Annulati – Pili Torti – Pili Trianguli Et Canaliculi – Trichorrhexis Invaginata – Trichorrhexis Nodosa – Woolly Hair – Hair Shaft Abnormalities, Syndromic – Menkes Disease – Trichodentoosseous Syndrome – Trichorhinophalangeal Syndrome – Trichothiodystrophy – Nails – Nail Disorders, Isolated – Congenital Malalignment of the Great Toenails – Familial Dystrophic Shedding of the Nails – Leukonychia – Twenty-Nail Dystrophy – Nail Disorders, Syndromic – Nail-Patella Syndrome – Onychotrichodysplasia and Neutropenia – Pachyonychia Congenita – Sweat Glands – Hidradenitis Suppurativa – Hyperhidrosis – Multiple Syringomas – Sebaceous Glands – Eruptive Vellus Hair Cysts – Familial Dyskeratotic Comedones – Oral-Facial-Digital Syndrome Type I – Steatocystoma Multiplex – Ectodermal Dysplasia Syndromes – AEC Syndrome – Clouston Syndrome – EEC Syndrome – Focal Facial Ectodermal Dysplasia – GAPO Syndrome – Hypohidrotic Ectodermal Dysplasia – Tooth and Nail Syndrome
3
Sybert, Virginia P. Disorders of Epidermal Appendages. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190276478.003.0003.
Der volle Inhalt der QuelleAnnotation:
Chapter 3 starts by covering conditions of the hair, including Alopecias (Loose Anagen Hair, Male Pattern Baldness, and Marie Unna Syndrome), Hirsutism (Gingival Fibromatosis and Hypertrichosis, Hypertrichosis Lanuginosa Congenita, Leprechaunism, and Localized Hypertrichosis), and Hair Shaft Abnormalities (including Monilethrix, Pili Annulati, Pili Torti, Pili Trianguli Et Canaliculi, Trichorrhexis Invaginata, Trichorrhexis Nodosa, Woolly Hair, Menkes Disease, Trichodentoosseous Syndrome, Trichorhinophalangeal Syndrome, and Trichothiodystrophy). It then covers conditions of the nails, including Congenital Malalignment of the Great Toenails, Familial Dystrophic Shedding of the Nails, Leukonychia, Twenty-Nail Dystrophy, Nail-Patella Syndrome, Onychotrichodysplasia and Neutropenia, and Pachyonychia Congenita). Conditions of the Sweat Glands (Hidradenitis Suppurativa, Hyperhidrosis, and Multiple Syringomas), Sebaceous Glands (Eruptive Vellus Hair Cysts, Familial Dyskeratotic Comedones, Oral-Facial-Digital Syndrome Type I, and Steatocystoma Multiplex), and Ectodermal Dysplasia Syndromes (AEC Syndrome, Clouston Syndrome, EEC Syndrome, Focal Facial Ectodermal Dysplasia, GAPO Syndrome, Hypohidrotic Ectodermal Dysplasia, and Tooth and Nail Syndrome) are also covered. Each condition is discussed in detail, including dermatologic features, associated anomalies, histopathology, basic defect, treatment, mode of inheritance, prenatal diagnosis, and differential diagnosis.
Buchteile zum Thema "Pili de type IVa"
1
Orndorff, Paul E. „Escherichia coli Type 1 Pili“. In Molecular Genetics of Bacterial Pathogenesis, 91–111. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555818340.ch7.
Der volle Inhalt der Quelle
2
Muschiol, Sandra, Marie-Stephanie Aschtgen, Priyanka Nannapaneni und Birgitta Henriques-Normark. „Gram-Positive Type IV Pili and Competence“. In Protein Secretion in Bacteria, 129–35. Washington, DC, USA: ASM Press, 2019. http://dx.doi.org/10.1128/9781683670285.ch11.
Der volle Inhalt der Quelle
3
Craig, Lisa, und Tuba Altindal. „Purification of Type IV Pili and Pilin Subunits“. In Neisseria gonorrhoeae, 97–110. New York, NY: Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9496-0_7.
Der volle Inhalt der Quelle
4
Gonzalez Rivera, Alba Katiria, und Katrina T. Forest. „Shearing and Enrichment of Extracellular Type IV Pili“. In Methods in Molecular Biology, 311–20. New York, NY: Springer New York, 2017. http://dx.doi.org/10.1007/978-1-4939-7033-9_25.
Der volle Inhalt der Quelle
5
Robert O’Neill, J., und Rowan W. Parks. „Surgical Resection of a Type IVa Choledochal Cyst“. In Case-Based Lessons in the Management of Complex Hepato-Pancreato-Biliary Surgery, 215–25. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-50868-9_16.
Der volle Inhalt der Quelle
6
Shoji, Mikio, Satoshi Shibata, Mariko Naito und Koji Nakayama. „Transport and Polymerization of Porphyromonas gingivalis Type V Pili“. In Periodontal Pathogens, 61–73. New York, NY: Springer US, 2020. http://dx.doi.org/10.1007/978-1-0716-0939-2_7.
Der volle Inhalt der Quelle
7
Marrs, Carl F. „Type 4 Pili in the Families Moraxellaceae and Neisseriaceae“. In Molecular Genetics of Bacterial Pathogenesis, 127–43. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555818340.ch9.
Der volle Inhalt der Quelle
8
Pooley, Linda, und Miles D. Houslay. „A Novel Form of Type-IVA cAMP Phosphodiesterase found in rat brain“. In Signalling Mechanisms — from Transcription Factors to Oxidative Stress, 65–76. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79675-3_7.
Der volle Inhalt der Quelle
9
Skotnicka, Dorota, und Lotte Søgaard-Andersen. „Type IV Pili-Dependent Motility as a Tool to Determine the Activity of c-di-GMP Modulating Enzymes in Myxococcus xanthus“. In c-di-GMP Signaling, 157–65. New York, NY: Springer New York, 2017. http://dx.doi.org/10.1007/978-1-4939-7240-1_13.
Der volle Inhalt der Quelle
10
Schreiber, W., und Michael S. Donnenberg. „Type IV Pili“. In Escherichia Coli, 307–36. Elsevier, 2002. http://dx.doi.org/10.1016/b978-012220751-8/50012-4.
Der volle Inhalt der QuelleKonferenzberichte zum Thema "Pili de type IVa"
1
GLOCKSHUBER, RUDOLF. „ASSEMBLY OF FILAMENTOUS TYPE 1 PILI FROM UROPATHOGENIC ESCHERICHIA COLI STRAINS“. In 23rd International Solvay Conference on Chemistry. WORLD SCIENTIFIC, 2014. http://dx.doi.org/10.1142/9789814603836_0040.
Der volle Inhalt der Quelle
2
Chen, Feng-Jung, Chia-Han Chan, Kuo-Liang Liu, Ying-Jung Huang, Hwei-Ling Peng, Hwan-You Chang, Tri-Rung Yew, Ken Y. Hsu und Long Hsu. „Uncoiling mechanism of Klebsiella pneumoniae type 3 pili measured by using optical tweezers“. In NanoScience + Engineering, herausgegeben von Kishan Dholakia und Gabriel C. Spalding. SPIE, 2007. http://dx.doi.org/10.1117/12.733097.
Der volle Inhalt der Quelle
3
Asgarian, Behrouz, Alireza Fiouz und Ali Shakeri Talarposhti. „Incremental Dynamic Analysis Considering Pile-Soil-Structure Interaction for the Jacket Type Offshore Platforms“. In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57273.
Der volle Inhalt der QuelleAnnotation:
Nonlinear response of piles is the most important source of potentially nonlinear behavior of offshore platforms due to earthquake excitations. It is often necessary to perform dynamic analysis of offshore platforms that accounts for soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural nonlinear behaviors of the piles. Incremental dynamic analysis is an analysis method that has recently emerged as a promising tool for thoroughly evaluating the seismic performance of structures. It involves subjecting a structural model to a suite of ground motion records, each scaled to several intensities and recording the responses at each level to form IDA curves of response versus intensity. In this paper, jacket and soil-pile system is modeled and the effects of Soil-Pile-Structure Interaction (SPSI) are considered, and the Incremental Dynamic Analysis (IDA) is used to investigate nonlinear behavior of offshore platforms. An attempt is made to introduce a practical BNWF (Beam on Nonlinear Winkler Foundation) model for estimating the lateral response of flexible piles embedded in layered soil deposits subjected to seismic loading. This model was incorporated into a Finite Element program (OpenSees). All the analyses are performed in two directions and the results are compared with each others. A computer program for Nonlinear Earthquake site Response Analyses of layered soil deposits (NERA) is used for analysis nonlinear response of soil layers. Limit state of the jacket is calculated from incremental dynamic analysis of the jacket using fiber elements for the nonlinear modeling of the system.
4
Asgarian, Behrouz, Mohammad Amin Assareh und Pejman Alanjari. „Nonlinear Behavior of Single Piles in Jacket Type Offshore Platforms Using Incremental Dynamic Analysis“. In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57148.
Der volle Inhalt der QuelleAnnotation:
Offshore platforms are some of those structures which are built to withstand environmental and accidental loads during oil exploitation operation. One of the most usual types of these platforms is the Jacket Type Offshore Platform (JTOP) which can be divided into three important parts, which are Deck, Jacket, and piles. In order to increase the safety, particular attention should be paid to earthquake excitations which are directly applied to the piles of these structures. Nonlinearity in piles and buckling of the struts are important issues which have to be considered by the designers of offshore platforms. Incremental Dynamic Analysis (IDA) is a powerful tool to assess the capacity of a structure upon seismic loads. In this paper incremental dynamic analysis has been implemented on single piles considering soil-pile interactions and free field site response. The use of nonlinear materials and lateral load resisting elements in the incremental dynamic analysis done in this paper has made it possible to get promising insights for incorporation of appropriate limit states and applications of performance based engineering. Special Engineering Demand Parameters (EDP) and Intensity Measures (IM) have been introduced for the single pile dynamic analysis in jacket type offshore platforms.
5
Facchina, Giulia, Alessandro Amaddeo, Sonia Khirani, Genevieve Baujat, Syril James, Sylvain Breton und Brigitte Fauroux. „Retrospective analysis of sleep breathing disorders in mucopolysaccharidosis type IVA“. In ERS International Congress 2018 abstracts. European Respiratory Society, 2018. http://dx.doi.org/10.1183/13993003.congress-2018.pa4590.
Der volle Inhalt der Quelle
6
Morikawa, Akira, Ryo Ishii, Hajime Noto, Atsushi Fukayama und Takao Nakamura. „Determining most suitable listener backchannel type for speaker's utterance“. In IVA '22: ACM International Conference on Intelligent Virtual Agents. New York, NY, USA: ACM, 2022. http://dx.doi.org/10.1145/3514197.3549619.
Der volle Inhalt der Quelle
7
Sulaiman, R. A. R., R. P. Aji, N. M. Prakoso, R. Priambodo, Y. A. Aswin, C. N. Hafifah und D. R. Sjarif. „Variant identification of exon 11 of galactosamine (N-acetyl)-6-sulfatase (GALNS) gene in mucopolysaccharidosis type IVA patients in Indonesia“. In THE 2ND SCIENCE AND MATHEMATICS INTERNATIONAL CONFERENCE (SMIC 2020): Transforming Research and Education of Science and Mathematics in the Digital Age. AIP Publishing, 2021. http://dx.doi.org/10.1063/5.0042042.
Der volle Inhalt der Quelle
8
Barreiro, Jose A., John S. Knowles, Carl R. Johnson, Iain D. Gordon und Lene K. Gjerde. „Successful Application of a Reinforced Composite Mat Pill Technology for Lost Circulation Control in the Norwegian Continental Shelf“. In SPE/IADC International Drilling Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/204062-ms.
Der volle Inhalt der QuelleAnnotation:
Abstract An operator in the Norwegian continental shelf (NCS) required sufficient zonal isolation around a casing shoe to accommodate subsequent targeted injection operations. Located in the Ivar Aasen field, and classified as critical, the well had a 9 ⅝-in. casing shoe set in the depleted Skagerrak 2 reservoir. The lost circulation risk was high during cementing because the Hugin formation, located above the reservoir, contained 40 m [~ 131.2 ft] of highly porous and permeable sandstone. During previous operations in the field, lost circulation was observed before and during the casing running and cementing operations. After unsuccessful attempts to cure the losses with various lost circulation materials, a new solution was proposed to target the specific lost circulation problem by combining two types of reinforced composite mat pill (RCMP) technology. Specifically, the first type of RCMP technology was engineered for use in the viscous preflush spacer, and the second was applied to the cement slurry itself. Working in synergy, the RCMP systems mitigated the risk of incomplete zonal isolation. With no losses observed upon reaching total depth (TD) for the 12 ¼-in. hole, the 9 ⅝-in. casing was run with a reamer shoe and 15 rigid centralizers. Between 2700 and 2728 m [~ 8,858 and 8,950 ft] measured depth (MD), the rig observed constant drag of 30 to 40 MT whilst working the casing down, and circulation was completely lost before partial returns were eventually observed. The rig continued to work the string down to the planned landing depth at 3897 m [~ 12,785 ft] MD. Precementing circulation ensued with staged pump rates increasing at 100-L/min [~ 0.6-bbl/min] intervals up to 1400 L/min [~ 8.8 bbl/min], which induced losses at a rate of 6.5 m3/hour [~ 40 bbl/hour]). Subsequently, the flow rate was reduced to 1300 L/min [~ 8.1 bbl/min], and the annular volume was circulated 2.6 times with full returns. Attempts to reduce equivalent circulating density (ECD) ahead of the cementing operation were implemented at 1300 L/min [~ 8.1 bbl/min] using a low-density, low-rheology oil-based drilling fluid pill. However, a significant loss rate of 18.0 m3/hour [~113 bbl/hour] was observed. The flow rate was reduced to 950 L/min [~ 6.0 bbl/min], and partial circulation was recovered. After the spacer and cement had reached the annulus, full returns were immediately observed and continued until the top plug was successfully bumped. Acoustic logging determined that the operation had achieved the primary job objective of establishing the required length of hydraulically isolating cement in the annulus. Lost circulation is a costly problem that can be difficult to solve, even with the wide variety of technologies available (Vidick, B., Yearwood, J. A., and Perthuis, H. 1988. How To Solve Lost Circulation Problems. SPE-17811-MS). This case study demonstrates a successful solution. The operator will be able to incorporate lessons learned and best practices into future operations, and these lessons and practices will be useful to other operators with similar circumstances.
9
Cao Bayout, Lucile, François Migeon und Florian Sarrasin. „Assessment of New Materials in Unbonded Flexible Pipes“. In Offshore Technology Conference. OTC, 2022. http://dx.doi.org/10.4043/31811-ms.
Der volle Inhalt der QuelleAnnotation:
Abstract The present paper is related to the assessment of new materials for use in unbonded flexibles pipes designed and manufactured as per API 17J. Unbonded flexible pipes are a key solution in the oil and gas industry and are used as subsea static flowlines and dynamic risers to convey various types of fluids at high pressure, high temperature and in deep-water environment. In view of the increasingly challenging applications it shall withstand, the unbonded flexible pipe is complex in terms of design, fabrication and installation aspects and leads to a generally tailor-made design. Consequently, it drives flexible pipe manufacturers to constantly develop, optimize and qualify new solutions, including new materials for the different layers and components of the flexible pipe. This paper focuses on the process followed for the incorporation of new materials in the flexible pipe TAC (Type Approval Certificate) upon verification of conformity versus API 17J. Firstly, development / assessment of a new material, or an existing material in a new environment, is generally made with the help of methods to qualify a new technology, through functional analysis and Qualification-FMECA (Q-FMECA), allowing to establish the qualification program. In a second part, API 17J requirements to qualify a new material are outlined, including procurement, manufacturing process, quality assurance, small scale, medium and full-scale tests and design rules aspects. Involvement of the IVA and IVA deliverables will be finally described.
10
Cao Bayout, Lucile, François Migeon und Florian Sarrasin. „Assessment of New Materials in Unbonded Flexible Pipes“. In Offshore Technology Conference. OTC, 2022. http://dx.doi.org/10.4043/31811-ms.
Der volle Inhalt der QuelleAnnotation:
Abstract The present paper is related to the assessment of new materials for use in unbonded flexibles pipes designed and manufactured as per API 17J. Unbonded flexible pipes are a key solution in the oil and gas industry and are used as subsea static flowlines and dynamic risers to convey various types of fluids at high pressure, high temperature and in deep-water environment. In view of the increasingly challenging applications it shall withstand, the unbonded flexible pipe is complex in terms of design, fabrication and installation aspects and leads to a generally tailor-made design. Consequently, it drives flexible pipe manufacturers to constantly develop, optimize and qualify new solutions, including new materials for the different layers and components of the flexible pipe. This paper focuses on the process followed for the incorporation of new materials in the flexible pipe TAC (Type Approval Certificate) upon verification of conformity versus API 17J. Firstly, development / assessment of a new material, or an existing material in a new environment, is generally made with the help of methods to qualify a new technology, through functional analysis and Qualification-FMECA (Q-FMECA), allowing to establish the qualification program. In a second part, API 17J requirements to qualify a new material are outlined, including procurement, manufacturing process, quality assurance, small scale, medium and full-scale tests and design rules aspects. Involvement of the IVA and IVA deliverables will be finally described.
Berichte der Organisationen zum Thema "Pili de type IVa"
1
Morrison, Mark, und Joshuah Miron. Molecular-Based Analysis of Cellulose Binding Proteins Involved with Adherence to Cellulose by Ruminococcus albus. United States Department of Agriculture, November 2000. http://dx.doi.org/10.32747/2000.7695844.bard.
Der volle Inhalt der QuelleAnnotation:
At the beginning of this project, it was clear that R. albus adhered tightly to cellulose and its efficient degradation of this polysaccharide was dependent on micromolar concentrations of phenylacetic acid (PAA) and phenylpropionic acid (PPA). The objectives for our research were: i) to identify how many different kinds of cellulose binding proteins are produced by Ruminococcus albus; ii) to isolate and clone the genes encoding some of these proteins from the same bacterium; iii) to determine where these various proteins were located and; iv) quantify the relative importance of these proteins in affecting the rate and extent to which the bacterium becomes attached to cellulose. BARD support has facilitated a number of breakthroughs relevant to our fundamental understanding of the adhesion process. First, R. albus possesses multiple mechanisms for adhesion to cellulose. The P.I.'s laboratory has discovered a novel cellulose-binding protein (CbpC) that belongs to the Pil-protein family, and in particular, the type 4 fimbrial proteins. We have also obtained genetic and biochemical evidence demonstrating that, in addition to CbpC-mediated adhesion, R. albus also produces a cellulosome-like complex for adhesion. These breakthroughs resulted from the isolation (in Israel and the US) of spontaneously arising mutants of R. albus strains SY3 and 8, which were completely or partially defective in adhesion to cellulose, respectively. While the SY3 mutant strain was incapable of growth with cellulose as the sole carbon source, the strain 8 mutants showed varying abilities to degrade and grow with cellulose. Biochemical and gene cloning experiments have been used in Israel and the US, respectively, to identify what are believed to be key components of a cellulosome. This combination of cellulose adhesion mechanisms has not been identified previously in any bacterium. Second, differential display, reverse transcription polymerase chain reaction (DD RT-PCR) has been developed for use with R. albus. A major limitation to cellulose research has been the intractability of cellulolytic bacteria to genetic manipulation by techniques such as transposon mutagenesis and gene displacement. The P.I.'s successfully developed DD RT- PCR, which expanded the scope of our research beyond the original objectives of the project, and a subset of the transcripts conditionally expressed in response to PAA and PPA have been identified and characterized. Third, proteins immunochemically related to the CbpC protein of R. albus 8 are present in other R. albus strains and F. intestinalis, Western immunoblots have been used to examine additional strains of R. albus, as well as other cellulolytic bacteria of ruminant origin, for production of proteins immunochemically related to the CbpC protein. The results of these experiments showed that R. albus strains SY3, 7 and B199 all possess a protein of ~25 kDa which cross-reacts with polyclonal anti-CbpC antiserum. Several strains of Butyrivibrio fibrisolvens, Ruminococcus flavefaciens strains C- 94 and FD-1, and Fibrobacter succinogenes S85 produced no proteins that cross-react with the same antiserum. Surprisingly though, F. intestinalis strain DR7 does possess a protein(s) of relatively large molecular mass (~200 kDa) that was strongly cross-reactive with the anti- CbpC antiserum. Scientifically, our studies have helped expand the scope of our fundamental understanding of adhesion mechanisms in cellulose-degrading bacteria, and validated the use of RNA-based techniques to examine physiological responses in bacteria that are nor amenable to genetic manipulations. Because efficient fiber hydrolysis by many anaerobic bacteria requires both tight adhesion to substrate and a stable cellulosome, we believe our findings are also the first step in providing the resources needed to achieve our long-term goal of increasing fiber digestibility in animals.