Relevant bibliographies by topics / Bacterial cell walls

Academic literature on the topic 'Bacterial cell walls'

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Published: 4 June 2021
Last updated: 30 July 2024

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Journal articles on the topic "Bacterial cell walls"

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Singh, Adya P., Yoon Soo Kim, and Ramesh R. Chavan. "Relationship of wood cell wall ultrastructure to bacterial degradation of wood." IAWA Journal 40, no. 4 (November 16, 2019): 845–70. http://dx.doi.org/10.1163/22941932-40190250.

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ABSTRACT This review presents information on the relationship of ultrastructure and composition of wood cell walls, in order to understand how wood degrading bacteria utilise cell wall components for their nutrition. A brief outline of the structure and composition of plant cell walls and the degradation patterns associated with bacterial degradation of wood cell walls precedes the description of the relationship of cell wall micro- and ultrastructure to bacterial degradation of the cell wall. The main topics covered are cell wall structure and composition, patterns of cell wall degradation by erosion and tunnelling bacteria, and the relationship of cell wall ultrastructure and composition to wood degradation by erosion and tunnelling bacteria. Finally, pertinent information from select recent studies employing molecular approaches to identify bacteria which can degrade lignin and other wood cell wall components is presented, and prospects for future investigations on wood degrading bacteria are explored.
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Beveridge, T. J., and W. S. Fyfe. "Metal fixation by bacterial cell walls." Canadian Journal of Earth Sciences 22, no. 12 (December 1, 1985): 1893–98. http://dx.doi.org/10.1139/e85-204.

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All biomass contains a significant quantity of metallic constituents, and mineralization in living and dead biodebris may contribute to element transport from the hydrosphere into sediments. The anionic cell walls of bacteria are remarkable in their ability to fix metals and provide sites for nucleation and growth of minerals. Results presented show the types of cell wall polymers that are responsible for metal binding in walls of Gram-positive and Gram-negative bacteria.
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Beveridge, Terry J. "Visualizing Bacterial Cell Walls and Biofilms." Microbe Magazine 1, no. 6 (June 1, 2006): 279–84. http://dx.doi.org/10.1128/microbe.1.279.1.

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Egelman, Edward H. "Cell Walls, Cell Shape, and Bacterial Actin Homologs." Developmental Cell 5, no. 1 (July 2003): 4–5. http://dx.doi.org/10.1016/s1534-5807(03)00203-x.

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Errington, Jeff. "L-form bacteria, cell walls and the origins of life." Open Biology 3, no. 1 (January 2013): 120143. http://dx.doi.org/10.1098/rsob.120143.

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The peptidoglycan wall is a defining feature of bacterial cells and was probably already present in their last common ancestor. L-forms are bacterial variants that lack a cell wall and divide by a variety of processes involving membrane blebbing, tubulation, vesiculation and fission. Their unusual mode of proliferation provides a model for primitive cells and is reminiscent of recently developed in vitro vesicle reproduction processes. Invention of the cell wall may have underpinned the explosion of bacterial life on the Earth. Later innovations in cell envelope structure, particularly the emergence of the outer membrane of Gram-negative bacteria, possibly in an early endospore former, seem to have spurned further major evolutionary radiations. Comparative studies of bacterial cell envelope structure may help to resolve the early key steps in evolutionary development of the bacterial domain of life.
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Leclerc, Denis, and Alain Asselin. "Detection of bacterial cell wall hydrolases after denaturing polyacrylamide gel electrophoresis." Canadian Journal of Microbiology 35, no. 8 (August 1, 1989): 749–53. http://dx.doi.org/10.1139/m89-125.

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Cell walls from various Gram-positive bacteria were incorporated at a concentration of 0.2% (w/v) into polyacrylamide gels as a substrate for detection of cell wall hydrolases. Bacterial extracts from crude cell wall preparations were denatured with sodium dodecyl sulfate and 2-mercaptoethanol and subjected to denaturing polyacrylamide gel electrophoresis in gels containing bacterial cell walls. After renaturation in the presence of purified and buffered 1% (v/v) Triton X-100, cell wall hydrolases were visualized as clear lytic zones against the opaque cell wall background. One to fifteen bands with lytic activity could be detected, depending on bacterial extracts and on the nature of the cell walls incorporated into gels. Crude cell wall extracts were the best source of cell wall hydrolases from various Gram-positive bacteria such as Clostridium perfringens (15 bands), Micrococcus luteus (1 band), Bacillus megaterium (4 bands), Bacillus sp. (6 bands), B. cereus (3 bands), B. subtilis (7 bands), Staphylococcus aureus (13 bands), Streptococcus faecalis (3 bands), and Strep. pyogenes (5 bands). Molecular masses of cell wall hydrolases ranged from 17 to 114.6 kDa. Lytic activities against cell walls of Corynebacterium sepedonicum (Clavibacter michiganense pv. sepedonicum) could be shown with the cell wall extracts of Strep. pyogenes (45.7 kDa), Strep. faecalis (67 kDa), B. megaterium (67 kDa), and Staph. aureus (67 kDa).Key words: autolysins, electrophoresis, hydrolases, muramidases, peptidoglycan.
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Strominger, Jack L. "Bacterial cell walls, innate immunity and immunoadjuvants." Nature Immunology 8, no. 12 (December 2007): 1269–71. http://dx.doi.org/10.1038/ni1207-1269.

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Amir, A., and D. R. Nelson. "Dislocation-mediated growth of bacterial cell walls." Proceedings of the National Academy of Sciences 109, no. 25 (June 1, 2012): 9833–38. http://dx.doi.org/10.1073/pnas.1207105109.

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BUSH, K. "Antimicrobial agents targeting bacterial cell walls and cell membranes." Revue Scientifique et Technique de l'OIE 31, no. 1 (April 1, 2012): 43–56. http://dx.doi.org/10.20506/rst.31.1.2096.

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Singh, Adya P., Shruti Singh, and Ehsan Bari. "Bacterial Degradation of Wood by Tunnel Formation: Role of TEM in Understanding the Intricate Architecture of Tunnels and the Cell Wall Degradation Process." Microscopy Today 30, no. 5 (September 2022): 24–30. http://dx.doi.org/10.1017/s1551929522001080.

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Abstract:Certain bacteria degrade wood by creating tunnels in cell walls. Transmission electron microscopy (TEM) has played a key role in understanding the intricate architecture of the tunnels produced within the cell wall and the process of cell wall degradation. The most prominent feature of tunnels is the presence of periodic crescent-shaped slime bands, which is the single most important diagnostic characteristic of bacterial tunneling-type cell wall degradation. The review presented covers the aspects relevant to understanding bacterial tunneling of wood cell walls, emphasizing the importance of the application of TEM in this area of research.
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Dissertations / Theses on the topic "Bacterial cell walls"

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Haag, Andreas F. "Investigating the role of bacterial cell envelope components and host peptides in the Sinorhizobium meliloti-legume symbiosis." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=183674.

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Sinorhizobium meliloti forms a symbiosis with Medicago species of legumes. Within the legume root nodules, S. meliloti differentiates into a bacteroid, which fixes atmospheric nitrogen into ammonia for the legume. The legume produces hundreds of nodule-specific cysteine-rich (NCR) peptides, which mediate bacteroid differentiation. The S. meliloti BacA protein was the first bacterial factor identified to be essential for bacteroid development. BacA sensitises S. meliloti to certain antimicrobial peptides and influences the modification of the bacterial lipopolysaccharide (LPS) with a very-long-chain fatty acid (VLCFA). Therefore, it is thought that either the peptide uptake function or the role of BacA in LPS VLCFA decoration could be essential for survival of S. meliloti within the legume. In this PhD project, a role for BacA in the response of S. meliloti towards NCR peptides was investigated. It was determined that BacA protects S. meliloti from NCR-induced cell death. Furthermore, it was found that the structure and composition of the LPS plays a key role in the response of S. meliloti to NCR peptides. It was also shown that the peptide uptake function of BacA was conserved among different rhizobia. The role and biosynthesis of the LPS VLCFA in bacteroid development was also explored. It was determined that the acyltransferase but not the acyl-carrier-protein, was essential for the biosynthesis of VLCFA modified LPS in planta. Six genes, located in a gene cluster were proposed to be involved in the LPS VLCFA biosynthesis in rhizobia and my research found that this was the case. The outcome of this research has provided important insights into the mechanism of prolonged bacterial-host infections and the biosynthesis of unusual lipids.
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WOLFE, ALAN JEFFREY. "THE RELATIONSHIP OF BACILLUS SUBTILIS PHYSIOLOGY AND HELICAL STRUCTURE AND ORGANIZATION (MACROFIBER, CELL SURFACE, HELIX HAND INVERSION)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187939.

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Helix hand inversion exhibited by Bacillus subtilis macrofibers is induced by changes in culture medium composition. The kinetics of this inversion are compared to those of temperature-induced inversions. D-alanine evokes a similar inversion process. The role of left-twist proteins(s), the existence of "memory", and the asymmetry of left to right versus right to left kinetics are confirmed within the context of these inversion regimes. Initiation time of right to left inversions is correlated to degree of pre-shift twist. Evidence is presented suggesting effective twist of the wall is defined by (1) the average of that twist conformation inserted prior to a shift in culture conditions and that of wall inserted following the shift and (2) the location of left-handed material within the wall. A constant 50 minute delay is observed before initiation of left to right inversions, irregardless of twist. Evidence is presented for a protein in the left to right inversion process. A classification system of macrofiber phenotypes based upon hand and degree of structural organization has been established. Three major classes are identified. Subclasses are shown to be distinguishable. Isotwist phenotypes of seven strains are defined upon a matrix of temperature and medium composition. These plots reveal a fundamental pattern of hand and organization that is present in each of the strains studied. The polarity of the four axes, the range of attainable twist conformations, and the existence of a right-hand maximum in the 12.5% SPl domain remain virtually constant. Major variations include extent of a disorganized band and/or the shifting of conformational range either left or right. Several mutants were transformed into A734, a strain that produces the tightest structures at all four matrix corners. Multiple mutations are responsible for the phenotypes of several strains. Evidence is presented for single genes that express as extreme left-handedness and stress at high temperature, swelling and stress in TB at high temperature, and reduction in structural organization produced in high TB content at low temperature.
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McMahon, Stephen Andrew. "Protein-carbohydrate recognition." Thesis, University of St Andrews, 1999. http://hdl.handle.net/10023/14045.

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Protein-carbohydrate recognition is an important target for inhibitor development. Improved inhibitor design requires a fundamental molecular basis of these interactions. This thesis describes the preliminary structural studies on three carbohydrate processing enzymes, UDP-galactopyranose mutase, alpha-D-glucose-1-phosphate thymidylyltransferase and TDP-glucose 4,6-dehydratase. These enzymes are found in important human pathogens such as Mycobacterium tuberculosis and Salmonella typhimurium. The major focus of the thesis has been on UDP-galactopyranose mutase, the enzyme responsible for catalysing synthesis of the thermodynamically unfavourable 5 membered ring form of galactose, UDP-galactofuranose from the thermodynamically favoured 6 membered ring form, UDP-galactopyranose. UDP-galactofuranose plays a key role in mycobacterial cell walls. This thesis also describes work with concanavalin A. This legume lectin is an invaluable model for the study of protein-carbohydrate interactions. Two concanavalin A complexes are discussed. Both structures clear up misunderstandings in the literature and provide an insight into designing enzyme inhibitors.
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Lou, Hubing. "Structural and functional studies of bacterial outer membrane proteins." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/995.

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This thesis studies two particular bacterial outer membrane proteins called OmpC and Wzi, focusing on their expression, purification, crystallization and X-ray structure determination. A series of four naturally occurring OmpC mutants were isolated from a single patient with an E. coli infection of liver cysts. The isolated E. coli strains progressively exhibited increasing breadth of antibiotic resistance in which OmpC was predicted to take a partial role. We carried out an assay in which a strain of E. coli lacking OmpC was used to express the first (antibiotic sensitive) and the last (antibiotic resistant) of the clinical OmpC mutants and drug permeation assessed. Single channel conductance measurements were carried out and the X-ray structures for all the isolates were determined. Protein stability was assessed. With these data we propose that changes in the transverse electric field, not the pore size, underlie the clinically observed resistance to the antibiotics. This is the first demonstration of this strategy for antibiotic resistance. Wzi is a novel outer membrane protein involved in the biosynthesis and translocation mechanism of the K30 antigen from E. coli. The mechanism is a complicated process that requires several proteins including outer and inner membrane proteins. The protein Wzi was expressed, purified and crystallized. Initial crystals were tested and diffracted to 15Å. After optimization, a crystal diffracting to 2.4Å has been obtained.
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Ainge, Gary D., and n/a. "The synthesis of phosphatidylinositol mannans and their analogues." University of Otago. Department of Chemistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20090113.101325.

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Phosphatidylinositol mannosides (PIMs) isolated from mycobacteria have been identified as an important class of glycolipids that possess significant immune modulating properties. To provide discrete synthetic compounds for biological assay, this thesis describes the syntheses of three PIM molecules, namely dipalmitoyl PIM2 (12), PIM4 (84), and PIM6 (108), and two PIM2 analogues designed for increased stability, PIM2ME (147) and PIM2MA (148). The synthesis of all of these molecules involved mannosylation of 1-O-allyl-3,4,5-tri-O-benzyl-D-myo-inositol (22), which was prepared from methyl α-D-glucopyranoside in 8% yield over 8 steps, using a Ferrier reaction strategy. A common intermediate, 3,4,5-tri-O-benzyl-2,6-di-O-(2,3,4,6-tetra-O-benzyl-α-D-mannopyranosyl)-D-myo-inositol (9), was used for the syntheses of 12, 147, and 148. This compound was prepared by bis-mannosylation of the C-1 and C-6 hydroxyl groups of 22 with 2-O-acetyl-3,4,6-tri-O-benzyl-α-D-mannopyranosyl trichloroacetimidate (63) to give, after protecting group manipulations, the α,α-pseudo-trisaccharide 9 in 37% over 4 steps. The selectivity of the desired α,α-product was found to be increased by the selection of Et₂O as the solvent for the glycosylation reaction. The C-1 hydroxyl group of 9 was coupled to benzyl (1,2-di-O-palmitoyl-sn-glycero)-diisopropylphosphoramidite (28) using 1H-tetrazole. Global debenzylation of the resulting product gave PIM2 (12) in 23% yield over 6 steps from 22. In a similar fashion 9 was coupled to 1-O-hexadeconyl-2-O-hexadecyl-sn-glycero-3-O-benzyl-(N,N-diisopropyl)-phosphoramidite (156), and subsequent deprotection gave PIM2ME (147) in 30% yield over 2 steps from 9. Coupling of 9 with 2-deoxy-1-O-hexadeconyl-2-O-hexadeconylamino-sn-glycero-3-O-benzyl-(N,N-diisopropyl)-phosphoramidite (172) and subsequent deprotection gave PIM2MA (148) in 47% yield over 2 steps from 9. A modified approach was required for the syntheses of PIM4 (84) and PIM6 (108). A selective glycosylation of the C-6 hydroxyl of 22 with an orthogonally protected mannose donor would allow extension of the manno-oligosaccharide in a 2+3 or 4+3 glycosylation strategy required to build the pseudo-pentasaccharide or pseudo-heptasaccharide core of 84 or 108 respectively. Sequential mannosylation of 22, firstly at the more reactive C-6 hydroxyl, with 2-O-acetyl-3,4-di-O-benzyl-6-O-tert-butyldiphenylsilyl-α-D-mannopyranosyl trichloroacetimidate (85), was followed by mannosylation at the C-2 hydroxyl with 63. Removal of the silyl protecting group followed by a 2+3 coupling with the dimannoside donor, 2-O-acetyl-6-O-(2-O-acetyl-3,4,6-tri-O-benzyl-α-D-mannopyranosyl)-3,4-di-O-benzyl-α-D-mannopyranosyl trichloroacetimidate (95), gave a pseudo-pentasaccharide intermediate. Protecting group manipulations followed by coupling of the of the C-1 hydroxyl group of the inositol ring to phosphoramidite 28, and a global debenzylation, gave PIM4 (84) in 6% yield over 9 steps from 22. During the synthesis of PIM6 (108), thioglycosylation chemistry was explored and found to be comparable to reactions with trichloroacetimidate donors. Similar methodology was used for the synthesis of PIM6 (108) as had previously been carried out for the synthesis of PIM4 (84). Mannosylation at the more reactive C-6 hydroxyl of 22 with either phenyl 2-O-benzoyl-3,4-di-O-benzyl-6-O-triisopropylsilyl-1-thio-α-D-mannopyranoside (112) or 2-O-benzoyl-3,4-di-O-benzyl-6-O-triisopropylsilyl-α-D-mannopyranosyl trichloroacetimidate (113), was followed by mannosylation at the C-2 hydroxyl with 63. Removal of the silyl group followed by a 4+3 coupling with either of the tetramannoside donors, phenyl (2-O-benzoyl-3,4,6-tri-O-benzyl-α-D-mannopyranosyl)-(1[to]2)-(3,4,6-tri-O-benzyl-α-D-mannopyranosyl)-(1[to]2)-(3,4,6-tri-O-benzyl-α-D-mannopyranosyl)-(1[to]6)-2-O-benzoyl-3,4-di-O-benzyl-1-thio-α-D-mannopyranoside (109) or (2-O-benzoyl-3,4,6-tri-O-benzyl-α-D-mannopyranosyl)-(1[to]2)- (3,4,6-tri-O-benzyl-α-D-mannopyranosyl)-(1[to]2)-(3,4,6-tri-O-benzyl-α-D-mannopyranosyl-(1[to]6)-2-O-benzoyl-3,4-di-O-benzyl-α-D-marmopyranosyl trichloroacetimidate (131) gave a gave a pseudo-heptasaccharide intermediate. Protecting group manipulations followed by coupling of the of the C-1 hydroxyl group of the inositol ring to phosphoramidite 28, and a global debenzylation, gave PIM6 (108) in 9% yield over 9 steps from 22. To aid characterisation of 108, a sample was deacylated to afford dPIM6 (144) which gave the same spectral data as a sample from a natural source. The compounds PIM2 (12), PIM4 (84), PIM2ME (147), and PIM2MA (148) were assayed for adjuvant activity and were found to have comparable activity to fractions isolated from natural sources. The analogue PIM2ME (147) gave the best results and is currently undergoing further development.
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SURANA, UTTAM CHAND. "BIOCHEMICAL CHARACTERIZATION OF THE BACILLUS SUBTILIS MACROFIBER CELL SURFACE." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184038.

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Cell walls of Bacillus subtilis macrofibers have been biochemically analyzed to determine the contribution of various surface polymers in the twist regulation. Helix hand inversion was induced by a variation in either the growth temperature or the nutritional composition of the culture medium. Initial experiments had demonstrated a fivefold difference in the sensitivity of right- and left-handed forms to muramidases indicating modifications of peptidoglycan as a possible mechanism underlaying inversion. An examination of lysozyme susceptibility of purified cell walls and whole cells derived from the two structural forms, however, exhibited no significant difference suggesting loss of the relevant component(s), perhaps biomechanical in nature, during disintegration of macrofibers. The effect of various twist modulators such as trypsin, ammonium sulfate and D-alanine on the development of helical twist in both switchable and "fixed" mutants were studied. The interaction matrices have established D-alanine as the most potent of right-factors. Intestinal alkaline phosphatase is reported as a newly discovered antagonist to the development of leftward twist. Heat inactivation and protein purification experiments strongly indicated that twist modulation was due to the phosphatase activity rather than minor protease contaminants. The chemical composition of cell walls purified from right- and left-handed structures was determined. No twist correlated differences in the overall content of peptidoglycan, teichoic acid and teichuronic acid were detected. Evidence is presented for the absence of correlation between the extent of ester-linked alanine substitution and twist state. These findings suggest that gross changes in wall composition is perhaps not the mechanism for hand inversion. From the profiles of the wall associated proteins, a 200 Kdal band has been identified whose presence is strongly correlated with the development of leftward twist. This polypeptide was found to be highly sensitive to trypsin; a property it shares with a previously proposed left-twist protein. Preliminary evidence for isolation of left-hand specific polyclonal antibodies is also presented. FJ7, a switchable mutant, was successfully transformed with a plasmid containing the Streptococcus transposon Tn917. A small bank of insertional mutants has been constructed for the isolation of mutants impaired in helix hand inversion.
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Chang, Po-Hsun. "Characterization of the Outer Membrane of Treponema Pallidum Subsp. Pallidum by Binding Studies Using Antibodies, Complement, and Host Serum Proteins." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc798468/.

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The major goal of this study was to achieve sustained cultivation of virulent T. pallidum in vitro. The putatuive binding of host proteins to the outer membrane (OM) of intact, virulent T. pallidum subsp. pallidum has been investigated. A major breakthrough was the development of a filtration assay, usinglow protein-binding membrane filters, for the measurement of substances bound to or incorporated into th eOM of T. pallidum. This avoided the conventional manipulations which can damage the fragile OM of T. pallidum. Using this filtration assay, studies on the binding of host serum proteins demonstrated that intact treponemes did not bind host proteins as previously reported. It also indicated that previous studies were probably performed with damaged by this research. The studies on the binding of polyclonal and monoclonal antibodies to intact and detergent treated treponemes provided evidence of the low level binding of antibody to intact treponemes which was greatly enhanced but the removal of the outer membrane with 0.1% Triton X. This research research corroborated that of others which suggests that the outer membrane of T. pallidum contains very little protein or surface exposed antigen.
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Dyer, Blake S., and n/a. "The synthesis and characterisation of phosphatidylinositol mannans." University of Otago. Department of Chemistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080415.142001.

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Mycobacterial cell wall components have been shown to elicit a range of immunological responses in mammalian hosts. A family of cell wall antigens, the phosphatidylinositol mannans (PIMs), have been shown to reduce allergic response in a murine model of allergic airway disease and have been suggested as potential therapeutic agents. Isolation and characterisation of these compounds is not facile. To confirm the structure of PIMs a number of phosphatidylinositols (PIs), 1a-c, PIM1s 2a, 2d and 2e, and AcPIM1s, 2g and 2f, were prepared to allow assignment of the acylation pattern of natural products and for evaluation in immunological assays. As the natural products include 19:0 acylation in the form of (R)-tuberculostearoyl residues, a source of (R)-tuberculostearic acid was needed. To this end, an efficient synthesis of (R)-tuberculostearic acid from (S)-citronellol, utilising a copper-catalysed cross-coupling reaction and a modified Julia olefination, was developed. This material was incorporated into diacylglycerols prepared from (R)-benzyl glycidol. A protected myo-inositol derivative, 188, and two protected pseudo-disaccharides, 10 and 241, were prepared from myo-inositol via desymmetrisation utilising a camphylidene acetal. These were coupled with diacylglycerols via a phosphate ester and deprotected to give PIs, PIM1s and AcPIM1s. Mass spectrometry studies were undertaken on the PIs, 1a-c, PIM1s 2a, 2d and 2e, and AcPIM1s, 2g and 2f which structures that have been established by chemical synthesis. Comparison of these data with those reported for natural PIs and PIMs containing 19:0 ((R)-tuberculostearoyl) and 16:0 (palmitoyl) acyl groups unequivocally established that the 19:0 residue was located at the sn-1 and the 16:0 at the sn-2 position of the glycerol moiety in nature.
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Kilelee, Erin M. "Modeling the interaction of the platelet microbicidal protein tPMP-1 with the cell membrane." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-3/r3/kileleee/erinkilelee.pdf.

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Huang, Hexian. "Regulations of export and chain length of extracellular bacterial polysaccharides." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/4441.

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Many Gram-positive and Gram-negative bacteria produce an additional thick layer of carbohydrate polymers on the cell wall surface. These capsules (capsular polysaccharides; CPS) play critical roles in interactions between bacteria and their environments (Whitfield, 2006). This is especially important in infection processes since for both Gram-negative and Gram-positive pathogens CPS is the point of first contact with the host immune system (Whitfield, 2006). However, the details of CPS biosynthesis and assembly mechanisms are still unclear. Therefore, we embarked on structural and kinetic studies of the proteins Wzc, Wza and Wzb/ Cps4B from the Wzy-dependent pathway, as well as the protein WbdD from the ATP-binding cassette (ABC) transporter dependent system. Full-length Wzc failed to crystallise due to the presence of large disordered regions and the overall difficulty of membrane protein crystallisation. A truncated version of Wzc (1-480) without the C-terminal tyrosine kinase domain was crystallised and diffracted to 15 Å in house. A previous study suggested Wza and Wzc form a functional complex (Whitfield, 2006), so Wza was also studied. Since the full-length Wza structure is available (C. Dong et al., 2006), Pulsed electron–electron double resonance spectroscopy (PELDOR) was used to study the conformational change. The PELDOR spectroscopy distance fingerprint of Wza was determined. These data also confirmed that PELDOR is a powerful tool to study large, highly symmetrical membrane proteins and can be used to study other complex membrane protein systems, such as ion channels or transporters. The crystal structure of Wzb the cognate phosphatase of Wzc was determined to 2.2 Å. Also Cps4B, which is a functional homologue of Wzb but has a completely unrelated sequence, was crystallised in two crystal forms. Form I and II Cps4B crystals diffracted to 2.8 Å and 1.9 Å resolution in house, respectively. The full-length WbdD failed to crystallise due to the presence of large disordered regions. Therefore, a shorter construct, WbdD₅₅₆ (1-556) was cloned and crystallised. The structure was determined to 2.2 Å. WbdD is a bifunctional enzyme consisting of a methyltransferase (MTase) and a kinase domain. In order to better understand the function of this protein, a variety of techniques were used, such as the ADP-Glo kinase assay, Nuclear magnetic resonance (NMR) spectroscopy, small angle X-ray scattering (SAXS) and X-ray crystallography. The various findings in the current projects provide meaningful insights towards a better understanding of the CPS biosynthesis and assembly mechanisms, which may contribute to a more intensive study identifying inhibitors and beginning to unravel the mechanism of chain length regulation.
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Books on the topic "Bacterial cell walls"

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M, Ghuysen J., and Hackenbeck R. 1948-, eds. Bacterial cell wall. Amsterdam: Elsevier, 1994.

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Ian, Hancock, and Poxton Ian, eds. Bacterial cell surface techniques. Chichester [West Sussex]: Wiley, 1988.

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Kuhn, Andreas, ed. Bacterial Cell Walls and Membranes. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18768-2.

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B, Sleytr Uwe, ed. Crystalline bacterial cell surface proteins. Austin, TX: R.G. Landes Co., 1996.

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Remaut, Han, and Rémi Fronzes. Bacterial membranes: Structural and molecular biology. Norfolk: Caister Academic Press, 2014.

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Nava, Mozes, ed. Microbial cell surface analysis: Structural and physicochemical methods. New York: VCH, 1991.

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Alakomi, Hanna-Leena. Weakening of the Gram-negative bacterial outer membrane: A tool for increasing microbiological safety. [Espoo, Finland]: VTT Technical Research Centre of Finland, 2007.

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Brass, J. M. The cell envelope of gram-negative bacteria: New aspects of its function in transport and chemotaxis. Berlin: Springer-Verlag, 1986.

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1935-, Tipper Donald J., ed. Antibiotic inhibitorsof bacterial cell wall biosynthesis. Oxford: Pergamon, 1987.

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1933-, Quesnel Louis B., Gilbert P, and Handley Pauline S, eds. Microbial cell envelopes: Interactions and biofilms. Oxford: Blackwell Scientific Publications, 1993.

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Book chapters on the topic "Bacterial cell walls"

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Wicken, Anthony J. "Bacterial Cell Walls and Surfaces." In Bacterial Adhesion, 45–70. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4615-6514-7_2.

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Santos-Beneit, Fernando, Juan F. Martín, and Carlos Barreiro. "Glycopeptides and Bacterial Cell Walls." In Antimicrobial Compounds, 285–311. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-40444-3_11.

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Nilsson, Thomas, and Geoffrey Daniel. "Bacterial Attack of Wood Cell Walls." In Biodeterioration 7, 739–42. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-1363-9_96.

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König, Helmut, and Evamarie Hartmann. "Biosynthesis of Pseudomurein and Other Methanobacterial Cell Walls." In Bacterial Growth and Lysis, 205–12. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4757-9359-8_24.

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Weidel, W., and H. Pelzer. "Bagshaped Macromolecules-A New Outlook on Bacterial Cell Walls." In Advances in Enzymology - and Related Areas of Molecular Biology, 193–232. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2006. http://dx.doi.org/10.1002/9780470122716.ch5.

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Cocking, Edward C. "Signals Between Plant and Bacterial Cells: Specific Domains in Cell Walls, a New Insight." In Cell Separation in Plants, 301–5. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-74161-6_28.

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Cosgrove, Daniel J., Nathan K. Hepler, Edward R. Wagner, and Daniel M. Durachko. "Biomechanical Weakening of Paper and Plant Cell Walls by Bacterial Expansins." In Methods in Molecular Biology, 79–88. New York, NY: Springer US, 2023. http://dx.doi.org/10.1007/978-1-0716-3151-5_5.

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Schaefer, J. "REDOR NMR of Biological Solids: From Protein Binding Sites to Bacterial Cell Walls." In Recent Trends in Molecular Recognition, 25–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03574-0_2.

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Salton, M. R. J. "Interaction of Phages with Bacterial Cell Walls and the Development of Phage in the Wall-Less Protoplast." In Ciba Foundation Symposium - The Nature of Viruses, 263–76. Chichester, UK: John Wiley & Sons, Ltd., 2008. http://dx.doi.org/10.1002/9780470715239.ch17.

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Cosgrove, Daniel J., Nathan K. Hepler, Edward R. Wagner, and Daniel M. Durachko. "Measuring the Biomechanical Loosening Action of Bacterial Expansins on Paper and Plant Cell Walls." In Methods in Molecular Biology, 157–65. New York, NY: Springer New York, 2017. http://dx.doi.org/10.1007/978-1-4939-6899-2_12.

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Conference papers on the topic "Bacterial cell walls"

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Zheng, Zhouyuan, Parth Bansal, and Yumeng Li. "Numerical Study on Antibacterial Effects of Bio-Inspired Nanostructured Surface." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23594.

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Abstract Natural bactericidal surfaces are found on the wings of cicada and dragonfly that compose of nanopatterns such as nanopillar arrays. Experimental studies have unveiled that the nanopillars can penetrate the bacterial walls or stretch them, resulting in the cell death. This offers an attractive “chemical-free” and wide-spectrum strategy to fight against bacteria-related infections and fouling, especially for implant-associated infections (IAIs). However, what is the fundamental mechanism and key factors governing the bactericidal performance of the nanostructured surface is the critical research questions need to be answered to realize its full potential. In this work, we developed mechanical single cell model of bacteria based on finite element analysis (FEA) to simulate the interactions between different strains of bacteria and the nanostructured surface. The nanostructured surface contains nanopillar arrays, which are made of polymer materials. Different strains of bacteria are simulated by adopting the corresponding geometry and material properties from experimental values. The mechanical responses of the bacteria cell on the nanopillar arrays with various configurations are studied based on estimated stress and strain distributions within the cell.
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Ravel, B., S. D. Kelly, D. Gorman-Lewis, M. I. Boyanov, J. B. Fein, and K. M. Kemner. "A pH-Dependent X-Ray Absorption Spectroscopy Study of U Adsorption to Bacterial Cell Walls." In X-RAY ABSORPTION FINE STRUCTURE - XAFS13: 13th International Conference. AIP, 2007. http://dx.doi.org/10.1063/1.2644474.

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Salek, M., and R. J. Martinuzzi. "Numerical Simulation of Fluid Flow and Oxygen Transport in the Tube Flow Cells Containing Biofilms." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37063.

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The hydrodynamics in flow systems is known to induce phenotypic changes associated with bacterial biofilms, including increased tolerance to antimicrobial agents and biocides. Results obtained in flow cells commonly used in biological and medical studies on the influence of flow on biofilm behavior and antimicrobial susceptibility are sometimes contradictory. It is thus hypothesized that discrepancies in the results may be related to the flow cell geometry. In this study, the shear stress distribution and substrate concentration were numerically simulated inside long rectangular and square tubes. The fluid was Newtonian and a uniform distribution of biofilms, which consume the substrate from the medium, was assumed on the walls. The consumption of oxygen by biofilms was assumed to follow the Monod kinetics. The effects of flow velocity, flow cell geometry, and substrate diffusivity on wall shear stress and substrate concentration distributions were investigated. Based on simulation results, differences observed in the morphology and response of biofilms can be directly related to hydrodynamic changes caused by the flow cell configuration.
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Mautner, Andreas, Kathrin Weiland, and Alexander Bismarck. "Invited Perspective: Strong or Fluffy Nanopapers: How to Utilise Cellulose Nanofibrils Effectively?" In Advances in Pulp and Paper Research. Pulp & Paper Fundamental Research Committee (FRC), Manchester, 2022. http://dx.doi.org/10.15376/frc.2022.1.141.

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Apart from its wide application in the paper, textile and biomedical industry, cellulose is now an emerging alternative reinforcement to improve the properties of polymers. Numerous research focuses on the development of renewable nanocomposites. In this context, nanocellulose liberated from plant cell walls or produced by bacterial serves as excellent candidate due to its inherently nano-sized nature, high crystallinity and high Young’s modulus. However, numerous cellulose-reinforced polymer nanocomposites reported in literature often failed to fully exploit the fibril tensile stiffness and strength, estimated to be 114 GPa and >2000 MPa, respectively. Nanofibrils can be compounded directly into polymers as reinforcement or used in paper form to produce laminated paperbased composites.
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Sadamoto, Reiko, Kenichi Niikura, Akarat Suksomcheep, Fusao Tomita, and Shin-Ichiro Nishimura. "CELL WALL MODIFICATION OF LIVING BACTERIA THROUGH THE BIOSYNTHESIS." In XXIst International Carbohydrate Symposium 2002. TheScientificWorld Ltd, 2002. http://dx.doi.org/10.1100/tsw.2002.439.

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Kuliabin, V. A., A. V. Skorynina, and A. M. Shadrin. "PRODUCTION OF RECOMBINANT FUSION PROTEINS BASED ON ENDOLYSIN PLY57 AND POLY-GAMMA-D-GLUTAMATE DEPOLYMERASE ENVD." In X Международная конференция молодых ученых: биоинформатиков, биотехнологов, биофизиков, вирусологов и молекулярных биологов — 2023. Novosibirsk State University, 2023. http://dx.doi.org/10.25205/978-5-4437-1526-1-95.

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Endolysins that destroy the cell wall of gram-positive bacteria, and depolymerases that hydrolyze the polysaccharide capsule act as potential antimicrobial agents. Creation of a fusion protein combining two functions is a promising way to combat dangerous multi-resistant strains of bacteria.
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Even-Tzur, Nurit, Uri Zaretsky, Michael Wolf, and David Elad. "Respose of Cultured Nasal Epithelial Cells to Wall Shear Stress." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176374.

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The nasal cavity lining is rich with mucus secreting goblet cells. Nasal defense is based on the mucociliary clearance mechanism, in which the secreted mucus layer traps inhaled particles and is constantly driven towards the nasopharynx for removal of the particles from the body. The mucus layer is also important for the exchange of temperature and water vapor with the inspired air. Airway goblet cells discharge mucus in response to a wide variety of biological stimuli, including cytokines, bacterial products, proteinases, oxidants, irritant gases, and inflammatory mediators [1], as well as biophysical changes, such as osmolarity alterations [2].
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Zyubin, Andrey Y., Anna A. Kundalevich, and Ilia Samusev. "IR and Raman spectra modeling for pathogenic bacteria cell-wall components using DFT." In Optics in Health Care and Biomedical Optics XII, edited by Qingming Luo, Xingde Li, Ying Gu, and Dan Zhu. SPIE, 2023. http://dx.doi.org/10.1117/12.2637422.

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Pratama, Mohammad, and Isna Aziz. "Molecular Docking of Bawang Dayak (Eleutherine bulbosa) Secondary Metabolites as Bacterial Cell Wall Synthesis Inhibitor." In 1st International Conference on Science and Technology, ICOST 2019, 2-3 May, Makassar, Indonesia. EAI, 2019. http://dx.doi.org/10.4108/eai.2-5-2019.2284686.

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Alomari, Anaam. "High Resolution Imaging and Nanomechanical Properties of Gram-Positive Bacterial Cell Wall Using Atomic Force Microscopy." In Microscience Microscopy Congress 2021 incorporating EMAG 2021. Royal Microscopical Society, 2021. http://dx.doi.org/10.22443/rms.mmc2021.277.

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Reports on the topic "Bacterial cell walls"

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Myneni, Satish C., Bhoopesh Mishra, and Jeremy Fein. Role of Sulfhydryl Sites on Bacterial Cell Walls in the Biosorption, Mobility and Bioavailability of Mercury and Uranium. Office of Scientific and Technical Information (OSTI), April 2009. http://dx.doi.org/10.2172/1111104.

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Myneni, Satish C. B., Jeremy Fein, and Bhoopesh Mishra. Role of Sulfhydryl Sites on Bacterial Cell Walls in the Biosorption, Mobility and Bioavailability of Mercury and Uranium. Office of Scientific and Technical Information (OSTI), September 2016. http://dx.doi.org/10.2172/1325258.

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Manulis, Shulamit, Christine D. Smart, Isaac Barash, Guido Sessa, and Harvey C. Hoch. Molecular Interactions of Clavibacter michiganensis subsp. michiganensis with Tomato. United States Department of Agriculture, January 2011. http://dx.doi.org/10.32747/2011.7697113.bard.

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Clavibacter michiganensis subsp. michiganensis (Cmm), the causal agent of bacterial wilt and canker of tomato, is the most destructive bacterial disease of tomato causing substantial economic losses in Israel, the U.S.A. and worldwide. The molecular strategies that allow Cmm, a Gram-positive bacterium, to develop a successful infection in tomato plants are largely unknown. The goal of the project was to elucidate the molecular interactions between Cmmand tomato. The first objective was to analyze gene expression profiles of susceptible tomato plants infected with pathogenic and endophytic Cmmstrains. Microarray analysis identified 122 genes that were differentially expressed during early stages of infection. Cmm activated typical basal defense responses in the host including induction of defense-related genes, production of scavenging of free oxygen radicals, enhanced protein turnover and hormone synthesis. Proteomic investigation of the Cmm-tomato interaction was performed with Multi-Dimensional Protein Identification Technology (MudPIT) and mass spectroscopy. A wide range of enzymes secreted by Cmm382, including cell-wall degrading enzymes and a large group of serine proteases from different families were identified in the xylem sap of infected tomato. Based on proteomic results, the expression pattern of selected bacterial virulence genes and plant defense genes were examined by qRT-PCR. Expression of the plasmid-borne cellulase (celA), serine protease (pat-1) and serine proteases residing on the chp/tomA pathogenicity island (chpCandppaA), were significantly induced within 96 hr after inoculation. Transcription of chromosomal genes involved in cell wall degradation (i.e., pelA1, celB, xysA and xysB) was also induced in early infection stages. The second objective was to identify by VIGS technology host genes affecting Cmm multiplication and appearance of disease symptoms in plant. VIGS screening showed that out of 160 tomato genes, which could be involved in defense-related signaling, suppression of 14 genes led to increase host susceptibility. Noteworthy are the genes Snakin-2 (inhibitor of Cmm growth) and extensin-like protein (ELP) involved in cell wall fortification. To further test the significance of Snakin -2 and ELP in resistance towards Cmm, transgenic tomato plants over-expressing the two genes were generated. These plants showed partial resistance to Cmm resulting in a significant delay of the wilt symptoms and reduction in size of canker lesion compared to control. Furthermore, colonization of the transgenic plants was significantly lower. The third objective was to assess the involvement of ethylene (ET), jasmonate (JA) and salicylic acid (SA) in Cmm infection. Microarray and proteomic studies showed the induction of enzymes involved in ET and JA biosynthesis. Cmm promoted ET production 8 days after inoculation and SIACO, a key enzyme of ET biosynthesis, was upregulated. Inoculation of the tomato mutants Never ripe (Nr) impaired in ET perception and transgenic plants with reduced ET synthesis significantly delayed wilt symptoms as compared to the wild-type plants. The retarded wilting in Nr plants was shown to be a specific effect of ET insensitivity and was not due to altered expression of defense related genes, reduced bacterial population or decrease in ethylene biosynthesis . In contrast, infection of various tomato mutants impaired in JA biosynthesis (e.g., def1, acx1) and JA insensitive mutant (jai1) yielded unequivocal results. The fourth objective was to determine the role of cell wall degrading enzymes produced by Cmm in xylem colonization and symptoms development. A significance increase (2 to 7 fold) in expression of cellulases (CelA, CelB), pectate lyases (PelA1, PelA2), polygalacturonase and xylanases (XylA, XylB) was detected by qRT-PCR and by proteomic analysis of the xylem sap. However, with the exception of CelA, whose inactivation led to reduced wilt symptoms, inactivation of any of the other cell wall degrading enzymes did not lead to reduced virulence. Results achieved emphasized the complexity involved in Cmm-tomato interactions. Nevertheless they provide the basis for additional research which will unravel the mechanism of Cmm pathogenicity and formulating disease control measures.
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Splitter, Gary A., Menachem Banai, and Jerome S. Harms. Brucella second messenger coordinates stages of infection. United States Department of Agriculture, January 2011. http://dx.doi.org/10.32747/2011.7699864.bard.

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Aim 1: To determine levels of this second messenger in: a) B. melitensiscyclic-dimericguanosinemonophosphate-regulating mutants (BMEI1448, BMEI1453, and BMEI1520), and b) B. melitensis16M (wild type) and mutant infections of macrophages and immune competent mice. (US lab primary) Aim 2: To determine proteomic differences between Brucelladeletion mutants BMEI1453 (high cyclic-dimericguanosinemonophosphate, chronic persistent state) and BMEI1520 (low cyclicdimericguanosinemonophosphate, acute virulent state) compared to wild type B. melitensisto identify the role of this second messenger in establishing the two polar states of brucellosis. (US lab primary with synergistic assistance from the Israel lab Aim 3: Determine the level of Brucellacyclic-dimericguanosinemonophosphate and transcriptional expression from naturally infected placenta. (Israel lab primary with synergistic assistance from the US lab). B. Background Brucellaspecies are Gram-negative, facultative intracellular bacterial pathogens that cause brucellosis, the most prevalent zoonosis worldwide. Brucellosis is characterized by increased abortion, weak offspring, and decreased milk production in animals. Humans are infected with Brucellaby consuming contaminated milk products or via inhalation of aerosolized bacteria from occupational hazards. Chronic human infections can result in complications such as liver damage, orchitis, endocarditis, and arthritis. Brucellaspp. have the ability to infect both professional and non-professional phagocytes. Because of this, Brucellaencounter varied environments both throughout the body and within a cell and must adapt accordingly. To date, few virulence factors have been identified in B. melitensisand even less is known about how these virulence factors are regulated. Subsequently, little is known about how Brucellaadapt to its rapidly changing environments, and how it alternates between acute and chronic virulence. Our studies suggest that decreased concentrations of cyclic dimericguanosinemonophosphate (c-di-GMP) lead to an acute virulent state and increased concentrations of c-di-GMP lead to persistent, chronic state of B. melitensisin a mouse model of infection. We hypothesize that B. melitensisuses c-di-GMP to transition from the chronic state of an infected host to the acute, virulent stage of infection in the placenta where the bacteria prepare to infect a new host. Studies on environmental pathogens such as Vibrio choleraeand Pseudomonas aeruginosasupport a mechanism where changes in c-di-GMP levels cause the bacterium to alternate between virulent and chronic states. Little work exists on understanding the role of c-di-GMP in dangerous intracellular pathogens, like Brucellathat is a frequent pathogen in Israeli domestic animals and U.S. elk and bison. Brucellamust carefully regulate virulence factors during infection of a host to ensure proper expression at appropriate times in response to host cues. Recently, the novel secondary signaling molecule c-di-GMP has been identified as a major component of bacterial regulation and we have identified c-di-GMP as an important signaling factor in B. melitensishost adaptation. C. Major conclusions, solutions, achievements 1. The B. melitensis1453 deletion mutant has increased c-di-GMP, while the 1520 deletion mutant has decreased c-di-GMP. 2. Both mutants grow similarly in in vitro cultures; however, the 1453 mutant has a microcolony phenotype both in vitro and in vivo 3. The 1453 mutant has increased crystal violet staining suggesting biofilm formation. 4. Scanning electron microscopy revealed an abnormal coccus appearance with in increased cell area. 5. Proteomic analysis revealed the 1453 mutant possessed increased production of proteins involved in cell wall processes, cell division, and the Type IV secretion system, and a decrease in proteins involved in amino acid transport/metabolism, carbohydrate metabolism, fatty acid production, and iron acquisition suggesting less preparedness for intracellular survival. 6. RNAseq analysis of bone marrow derived macrophages infected with the mutants revealed the host immune response is greatly reduced with the 1453 mutant infection. These findings support that microlocalization of proteins involved in c-di-GMP homeostasis serve a second messenger to B. melitensisregulating functions of the bacteria during infection of the host.
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Manulis-Sasson, Shulamit, Christine D. Smart, Isaac Barash, Laura Chalupowicz, Guido Sessa, and Thomas J. Burr. Clavibacter michiganensis subsp. michiganensis-tomato interactions: expression and function of virulence factors, plant defense responses and pathogen movement. United States Department of Agriculture, February 2015. http://dx.doi.org/10.32747/2015.7594405.bard.

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Clavibactermichiganensissubsp. michiganensis(Cmm), the causal agent of bacterial wilt and canker of tomato, is the most destructive bacterial disease of tomato causing substantial economic losses in Israel, the U.S.A. and worldwide. The goal of the project was to unravel the molecular strategies that allow Cmm, a Gram-positive bacterium, to develop a successful infection in tomato. The genome of Cmm contains numerous genes encoding for extracellular serine proteases and cell wall degrading enzymes. The first objective was to elucidate the role of secreted serine proteases in Cmm virulence. Mutants of nine genes encoding serine proteases of 3 different families were tested for their ability to induce wilting, when tomato stems were puncture-inoculated, as compared to blisters formation on leaves, when plants were spray-inoculated. All the mutants showed reduction in wilting and blister formation as compared to the wild type. The chpCmutant displayed the highest reduction, implicating its major role in symptom development. Five mutants of cell wall degrading enzymes and additional genes (i.e. perforin and sortase) caused wilting but were impaired in their ability to form blisters on leaves. These results suggest that Cmm differentially expressed virulence genes according to the site of penetration. Furthermore, we isolated and characterized two Cmmtranscriptional activators, Vatr1 and Vatr2 that regulate the expression of virulence factors, membrane and secreted proteins. The second objective was to determine the effect of bacterial virulence genes on movement of Cmm in tomato plants and identify the routes by which the pathogen contaminates seeds. Using a GFP-labeledCmm we could demonstrate that Cmm extensively colonizes the lumen of xylem vessels and preferentially attaches to spiral secondary wall thickening of the protoxylem and formed biofilm-like structures composed of large bacterial aggregates. Our findings suggest that virulence factors located on the chp/tomAPAI or the plasmids are required for effective movement of the pathogen in tomato and for the formation of cellular aggregates. We constructed a transposon plasmid that can be stably integrated into Cmm chromosome and express GFP, in order to follow movement to the seeds. Field strains from New York that were stably transformed with this construct, could not only access seeds systemically through the xylem, but also externally through tomato fruit lesions, which harbored high intra-and intercellular populations. Active movement and expansion of bacteria into the fruit mesocarp and nearby xylem vessels followed, once the fruit began to ripen. These results highlight the ability of Cmm to invade tomato fruit and seed through multiple entry routes. The third objective was to assess correlation between disease severity and expression levels of Cmm virulence genes and tomato defense genes. The effect of plant age on expression of tomato defense related proteins during Cmm infection was analyzed by qRT-PCR. Five genes out of eleven showed high induction at early stages of infection of plants with 19/20 leaves compared to young plants bearing 7/8 leaves. Previous results showed that Cmm virulence genes were expressed at early stages of infection in young plants compared to older plants. Results of this study suggest that Cmm virulence genes may suppress expression of tomato defense-related genes in young plants allowing effective disease development. The possibility that chpCis involved in suppression of tomato defense genes is currently under investigation by measuring the transcript level of several PR proteins, detected previously in our proteomics study. The fourth objective was to define genome location and stability of virulence genes in Cmm strains. New York isolates were compared to Israeli, Serbian, and NCPPB382 strains. The plasmid profiles of New York isolates were diverse and differed from both Israeli and Serbian strains. PCR analysis indicated that the presence of putative pathogenicity genes varied between isolates and highlighted the ephemeral nature of pathogenicity genes in field populations of Cmm. Results of this project significantly contributed to the understanding of Cmm virulence, its movement within tomato xylem or externally into the seeds, the role of serine proteases in disease development and initiated research on global regulation of Cmm virulence. These results form a basis for developing new strategies to combat wilt and canker disease of tomato.
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Sessa, Guido, and Gregory Martin. MAP kinase cascades activated by SlMAPKKKε and their involvement in tomato resistance to bacterial pathogens. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7699834.bard.

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The research problem: Pseudomonas syringae pv. tomato (Pst) and Xanthomonas campestrispv. vesicatoria (Xcv) are the causal agents of tomato bacterial speck and spot diseases, respectively. These pathogens colonize the aerial parts of the plant and cause economically important losses to tomato yield worldwide. Control of speck and spot diseases by cultural practices or chemicals is not effective and genetic sources of resistance are very limited. In previous research supported by BARD, by gene expression profiling we identified signaling components involved in resistance to Xcvstrains. Follow up experiments revealed that a tomato gene encoding a MAP kinase kinase kinase (MAPKKKe) is required for resistance to Xcvand Pststrains. Goals: Central goal of this research was to investigate the molecular mechanisms by which MAPKKKεand associated MAP kinase cascades regulate host resistance. Specific objectives were to: 1. Determine whether MAPKKKεplays a broad role in defense signaling in plants; 2. Identify components of MAP kinase cascades acting downstream of MAPKKKε; 3. Determine the role of phosphorylation-related events in the function of MAPKKKε; 4. Isolate proteins directly activated by MAPKKKε-associatedMAPK modules. Our main achievements during this research program are in the following major areas: 1. Characterization of MAPKKKεas a positive regulator of cell death and dissection of downstream MAP kinase cascades (Melech-Bonfil et al., 2010; Melech-Bonfil and Sessa, 2011). The MAPKKKεgene was found to be required for tomato resistance to Xcvand Pstbacterial strains and for hypersensitive response cell death triggered by different R gene/effector gene pairs. In addition, overexpression analysis demonstrated that MAPKKKεis a positive regulator of cell death, whose activity depends on an intact kinase catalytic domain. Epistatic experiments delineated a signaling cascade downstream of MAPKKKεand identified SIPKK as a negative regulator of MAPKKKε-mediated cell death. Finally, genes encoding MAP kinase components downstream of MAPKKKεwere shown to contribute to tomato resistance to Xcv. 2. Identification of tomato proteins that interact with MAPKKKεand play a role in plant immunity (Oh et al., 2011). We identified proteins that interact with MAPKKKε. Among them, the 14-3-3 protein TFT7 was required for cell death mediated by several R proteins. In addition, TFT7 interacted with the MAPKK SlMKK2 and formed homodimersin vivo. Thus, TFT7 is proposed to recruit SlMKK2 and MAPKKK client proteins for efficient signal transfer. 3. Development of a chemical genetic approach to identify substrates of MAPKKKε-activated MAP kinase cascades (Salomon et al., 2009, 2011). This approach is based on engineering the kinase of interest to accept unnatural ATP analogs. For its implementation to identify substrates of MAPKKKε-activated MAP kinase modules, we sensitized the tomato MAP kinase SlMPK3 to ATP analogs and verified its ability to use them as phosphodonors. By using the sensitized SlMPK3 and radiolabeled N6(benzyl)ATP it should be possible to tag direct substrates of this kinase. 4. Development of methods to study immunity triggered by pathogen-associated molecular patterns (PAMPs) in tomato and N. benthamiana plants (Kim et al., 2009; Nguyen et al. 2010). We developed protocols for measuring various PTI-associatedphenotypes, including bacterial populations after pretreatment of leaves with PAMPs, induction of reporter genes, callose deposition at the cell wall, activation of MAP kinases, and a luciferase-based reporter system for use in protoplasts. Scientific and agricultural significance: Our research activities discovered and characterized a signal transduction pathway mediating plant immunity to bacterial pathogens. Increased understanding of molecular mechanisms of immunity will allow them to be manipulated by both molecular breeding and genetic engineering to produce plants with enhanced natural defense against disease. In addition, we successfully developed new biochemical and molecular methods that can be implemented in the study of plant immunity and other aspects of plant biology.
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Harman, Gary E., and Ilan Chet. Discovery and Use of Genes and Gene Combinations Coding for Proteins Useful in Biological Control. United States Department of Agriculture, September 1994. http://dx.doi.org/10.32747/1994.7568787.bard.

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The objectives of the research in this proposal were to (A) identify synergy among proteins that provide enhanced activity over single proteins for control of plant pathogenic fungi, (B) clone and characterize genetic sequences coding for proteins with ability to control pathogenic fungi, (C) produce transgenic organisms with enhanced biocontrol ability using genes and gene combinations and determine their efficiency in protecting plants against plant pathogenic fungi. A related objective was to produce disease-resistant plants. Fungal cell wall degrading enzymes from any source are strongly synergistic with any membrane active compound and, further, different classes of cell wall degrading enzymes are also strongly synergistic. We have cloned and sequenced a number of genes from bacterial and fungal sources including five that are structurally unrelated. We have prepared transgenic fungi that are deficient in production of enzymes and useful in mechanistic studies. Others are hyperproducers of specific enzymes that permit us, for the first time, to produce enzymes from T. harzianum in sufficient quantity to conduct tests of their potential use in commercial agriculture. Finally, genes from these studies have been inserted into several species of crop plants were they produce a high level of resistance to several plant pathogenic fungi.
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Morrison, Mark, Joshuah Miron, Edward A. Bayer, and Raphael Lamed. Molecular Analysis of Cellulosome Organization in Ruminococcus Albus and Fibrobacter Intestinalis for Optimization of Fiber Digestibility in Ruminants. United States Department of Agriculture, March 2004. http://dx.doi.org/10.32747/2004.7586475.bard.

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Improving plant cell wall (fiber) degradation remains one of the highest priority research goals for all ruminant enterprises dependent on forages, hay, silage, or other fibrous byproducts as energy sources, because it governs the provision of energy-yielding nutrients to the host animal. Although the predominant species of microbes responsible for ruminal fiber degradation are culturable, the enzymology and genetics underpinning the process are poorly defined. In that context, there were two broad objectives for this proposal. The first objective was to identify the key cellulosomal components in Ruminococcus albus and to characterize their structural features as well as regulation of their expression, in response to polysaccharides and (or) P AA/PPA. The second objective was to evaluate the similarities in the structure and architecture of cellulosomal components between R. albus and other ruminal and non-ruminal cellulolytic bacteria. The cooperation among the investigators resulted in the identification of two glycoside hydrolases rate-limiting to cellulose degradation by Ruminococcus albus (Cel48A and CeI9B) and our demonstration that these enzymes possess a novel modular architecture specific to this bacterium (Devillard et al. 2004). We have now shown that the novel X-domains in Cel48A and Cel9B represent a new type of carbohydrate binding module, and the enzymes are not part of a ceiluiosome-like complex (CBM37, Xu et al. 2004). Both Cel48A and Cel9B are conditionally expressed in response to P AA/PPA, explaining why cellulose degradation in this bacterium is affected by the availability of these compounds, but additional studies have shown for the first time that neither PAA nor PPA influence xylan degradation by R. albus (Reveneau et al. 2003). Additionally, the R. albus genome sequencing project, led by the PI. Morrison, has supported our identification of many dockerin containing proteins. However, the identification of gene(s) encoding a scaffoldin has been more elusive, and recombinant proteins encoding candidate cohesin modules are now being used in Israel to verify the existence of dockerin-cohesin interactions and cellulosome production by R. albus. The Israeli partners have also conducted virtually all of the studies specific to the second Objective of the proposal. Comparative blotting studies have been conducted using specific antibodies prepare against purified recombinant cohesins and X-domains, derived from cellulosomal scaffoldins of R. flavefaciens 17, a Clostridium thermocellum mutant-preabsorbed antibody preparation, or against CbpC (fimbrial protein) of R. albus 8. The data also suggest that additional cellulolytic bacteria including Fibrobacter succinogenes S85, F. intestinalis DR7 and Butyrivibrio fibrisolvens Dl may also employ cellulosomal modules similar to those of R. flavefaciens 17. Collectively, our work during the grant period has shown that R. albus and other ruminal bacteria employ several novel mechanisms for their adhesion to plant surfaces, and produce both cellulosomal and non-cellulosomal forms of glycoside hydrolases underpinning plant fiber degradation. These improvements in our mechanistic understanding of bacterial adhesion and enzyme regulation now offers the potential to: i) optimize ruminal and hindgut conditions by dietary additives to maximize fiber degradation (e.g. by the addition of select enzymes or PAA/PPA); ii) identify plant-borne influences on adhesion and fiber-degradation, which might be overcome (or improved) by conventional breeding or transgenic plant technologies and; iii) engineer or select microbes with improved adhesion capabilities, cellulosome assembly and fiber degradation. The potential benefits associated with this research proposal are likely to be realized in the medium term (5-10 years).
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Bart, Rebecca. Optimizing tradeoffs implicit during bioenergy crop improvement: Understanding the effect of altered cell wall and sugar content on sorghum-associated pathogenic bacteria. Office of Scientific and Technical Information (OSTI), March 2024. http://dx.doi.org/10.2172/2318644.

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Thomashow, Linda, Leonid Chernin, Ilan Chet, David M. Weller, and Dmitri Mavrodi. Genetically Engineered Microbial Agents for Biocontrol of Plant Fungal Diseases. United States Department of Agriculture, 2005. http://dx.doi.org/10.32747/2005.7696521.bard.

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The objectives of the project were: a) to construct the site-specific integrative expression cassettes carrying: (i) the chiA gene for a 58-kDa endochitinase, (ii) the pyrrolnitrin biosynthesis operon, and (iii) the acdS gene encoding ACC deaminase; b) to employ these constructs to engineer stable recombinant strains with an expanded repertoire of beneficial activities; c) to evaluate the rhizosphere competence and antifungal activity of the WT and modified strains against pathogenic fungi under laboratory and greenhouse conditions; and d) to monitor the persistence and impact of the introduced strains on culturable and nonculturable rhizosphere microbial populations in the greenhouse and the field. The research generally support our concepts that combining strategically selected genes conferring diverse modes of action against plant pathogens into one organism can improve the efficacy of biological control agents. We hypothesized that biocontrol agents (BCAs) engineered to expand their repertoire of beneficial activities will more effectively control soilborne plant pathogens. In this work, we demonstrated that biocontrol activity of Pseudomonas fluorescens Q8r1-96 and Q2-87, both producing the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) effective against the plant pathogenic fungus Rhizoctonia solani, can be improved significantly by introducing and expressing either the 1.6-kb gene chiA, encoding the 58-kDa endochitinase ChiA from the rhizosphere strain SerratiaplymuthicaIC1270, or the 5.8-kb prnABCDoperon encoding the broad-range antibiotic pyrrolnitrin (Prn) from another rhizosphere strain, P. fluorescens Pf-5. The PₜₐcchiAandPₜₐcprnABCDcassettes were cloned into the integrative pBK-miniTn7-ΩGm plasmid, and inserted into the genomic DNA of the recipient bacteria. Recombinant derivatives of strains Q8r1-96 and Q2-87 expressing the PₜₐcchiA or PₜₐcprnABCD cassettes produced endochitinase ChiA, or Prn, respectively, in addition to 2,4-DAPG, and the recombinants gave significantly better biocontrol of R. solani on beans under greenhouse conditions. The disease reduction index increased in comparison to the parental strains Q8r1-96 and Q2-87 to 17.5 and 39.0% from 3.2 and 12.4%, respectively, in the case of derivatives carrying the PₜₐcchiAcassette and to 63.1 and 70% vs. 2.8 and 12,4%, respectively, in the case of derivatives carrying the PₜₐcprnABCDcassette. The genetically modified strains exhibited persistence and non-target effects comparable to those of the parental strains in greenhouse soil. Three integrative cassettes carrying the acdS gene encoding ACC deaminase cloned under the control of different promoters were constructed and tested for enhancement of plant growth promotion by biocontrol strains of P. fluorescens and S. plymuthica. The integrative cassettes constructed in this work are already being used as a simple and efficient tool to improve biocontrol activity of various PGPR bacteria against fungi containing chitin in the cell walls or highly sensitive to Prn. Some parts of the work (e. g., construction of integrative cassettes) was collaborative while other parts e.g., (enzyme and antibiotic activity analyses) were fully synergistic. The US partners isolated and provided to the Israeli collaborators the original biocontrol strains P. fluorescens strains Q8r1-96 and Q2-87 and their mutants deficient in 2,4-DAPG production, which were used to evaluate the relative importance of introduction of Prn, chitinase or ACC deaminase genes for improvement of the biocontrol activity of the parental strains. The recombinant strains obtained at HUJI were supplied to the US collaborators for further analysis.
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