Dissertations / Theses: 'Bacterial cell walls'

1

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

2

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

3

McMahon, Stephen Andrew. "Protein-carbohydrate recognition." Thesis, University of St Andrews, 1999. http://hdl.handle.net/10023/14045.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

4

Lou, Hubing. "Structural and functional studies of bacterial outer membrane proteins." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/995.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

5

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

6

SURANA, UTTAM CHAND. "BIOCHEMICAL CHARACTERIZATION OF THE BACILLUS SUBTILIS MACROFIBER CELL SURFACE." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184038.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

7

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/.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

8

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

9

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.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

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

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

11

Briehl, Margaret Marie. "Isolation of a set of mutations linked to the TAG-1 locus of Bacillus subtilis, which perturb cell surface properties." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184343.

Full text

Abstract:

The physiological role of the teichoic acid polymers found in Gram-positive bacterial cell walls is not known. Studies of Bacillus subtilis hybrid strains implicate a defined chromosomal region, which includes the tag-1 locus, as necessary for teichoic acid biosynthesis. A set of ten mutants carrying lesions in this region was identified from among forty-four temperature-sensitive (ts) mutants generated by nitrosoguanidine mutagenesis and bacteriophage 029 selection. This protocol gave a population enriched for ts, versus auxotrophic, mutants. For each of the ten mutants, the frequency of genetic reconstruction, or correction, of the ts phenotype indicated that it was due to change(s) in a single gene. Results of two-factor transformation crosses sorted the mutants into three complementation groups; all ten could complement tag-1. Mutants in two complementation groups were transformed to ts⁺ with cloned rodC DNA. The map order of the newly isolated ts markers was determined from the results of two factor crosses. Orientation with respect to the hisA marker was inferred from transduction experiments. The newly isolated strains were shown to be conditional rod⁻ mutants. Growth at 48°C resulted in reduced growth rates and spherically shaped cells. Additional phenotypes seen for some mutants, namely 029 phage resistance and ts spore outgrowth, appeared closely associated with the ts rod⁻ mutation. Wall phosphate content for two of the mutants, following growth at 48°C, was found to be reduced in comparison to the wild-type control. Taken together these results lend support to the argument that the tag-1 region of the chromosome, which most likely directs teichoic acid biosynthesis, is important for establishment and maintenance of the normal bacillary morphology seen for B. subtilis. The importance of other gene products to the organization of newly synthesized wall was examined using B. subtilis macrofibers. Left- and right-handed macrofibers were converted to spheroplasts and the multi-celled structures regenerated under the two sets of conditions conducive for production of the original, and inverse hand. The helix hands observed for the regenerated structures always corresponded to those expected on the basis of the parental genotype.

APA, Harvard, Vancouver, ISO, and other styles

12

Cole, Jason Nicklaus. "Characterisation of cell wall proteins, virulence factor maturation and invasive disease trigger of Group A streptococcus." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20070130.144214/index.html.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Morris, Terry Lynn. "Molecular characterization of the fepA-fes bidirectional promoter in escherichia coli." free to MU campus, to others for purchase, 2001. http://wwwlib.umi.com/cr/mo/fullcit?p3025640.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Somner, Elizabeth Ann. "Antibiotic inhibitors of bacterial cell wall synthesis." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359831.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Clarke, Jonathan H. "Molecular architecture of xylanases from two aerobic soil bacteria." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321447.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Gally, David Lawrence. "Cell wall assembly in gram positive bacteria." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287465.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Bjertsjö, Rennermalm Anna. "Staphylococcal cell wall associated proteins : characteristics and host interactions /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-542-9/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Markovski, Monica. "Bacterial Cell Wall Synthases Require Outer Membrane Lipoprotein Cofactors." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10146.

Full text

Abstract:

To fortify their cytoplasmic membrane and protect it from osmotic rupture, most bacteria surround themselves with a peptidoglycan (PG) exoskeleton. The PG synthases that build this structure are called penicillin-binding proteins (PBPs). Since they are the targets of penicillin and related antibiotics, the structures and in vitro biochemical functions of the PBPs have been extensively studied. However, the in vivo functions of the PBPs and the factors they work with to build the PG meshwork remain poorly understood. PBPs work in the context of multicomponent complexes organized by cytoskeletal elements. A major outstanding question has been whether or not these complexes contain factors required for PBP function. I addressed this using Escherichia coli as a model system by taking advantage of the synthetic lethal phenotype resulting from simultaneous inactivation of the major PG synthases: PBP1a and PBP1b. Using a screen for mutants synthetically lethal with the inactivation of PBP1b, I identified LpoA as a factor required for PBP1a function. A colleague in the lab performed the analogous screen for mutants synthetically lethal with the inactivation of PBP1a and identified LpoB as a factor required for PBP1b function. We showed that the Lpo factors are outer membrane lipoproteins that form specific trans-envelope complexes with their cognate PBPs in the inner membrane and that LpoB can stimulate the activity of PBP1b in vitro. Our results reveal unexpected complexity in the control of PBP activity and indicate that they likely receive regulatory input from the outer membrane in addition to cytoskeletal elements in the cytoplasm. To investigate the role of LpoB in morphogenesis further, I took a genetic approach that has identified PBP1b* variants capable of functioning in vivo in the absence of LpoB. Preliminary characterization of these variants indicates that LpoB has cellular functions in addition to PBP1b activation and that LpoB may be important for coordinating the two different catalytic activities of PBP1b. Future study of these mutants is likely to uncover important insights into PBP function and their control by the Lpo factors. These insights may open new avenues for the development of novel therapeutics that target the PBPs.

APA, Harvard, Vancouver, ISO, and other styles

19

Millward-Sadler, Sarah Jane. "The molecular biology of bacterial xylanases." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318256.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Poole, Deborah Marie. "Molecular analysis of plant cell wall hydrolases of bacterial origin." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238939.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Odoch, Martin. "Hydrolysis of cassava cell walls through alkaline treatment and fermentation with alkaliphilic bacteria." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/65933.

Full text

Abstract:

Efficient processing of cassava roots by wet milling requires overcoming challenges associated with disaggregation of the starch-containing parenchyma cells. These cells entrap starch granules and hinder their release during wet milling. Steeping of ground cassava in 0.75% (w/v) NaOH in combination with wet milling was investigated to determine whether and how dilute NaOH modifies cassava cell walls. Gas chromatography (GC) data of cell wall constituent sugar composition and Fourier transform infrared (FTIR) data showed that NaOH steeping caused solubilisation of the cell wall pectin fraction. FTIR and wide-angle x-ray scattering (WAXS) spectroscopy indicated that NaOH steeping combined with fine (500 ?m opening screen size) wet milling reduced cellulose crystallinity. Dilute NaOH steeping also produced pits (micropores) through the cell wall structure as shown by scanning electron microscopy (SEM). The micropores seemed to have weakened the cell walls, as revealed by increased cellular disaggregation as viewed by light microscopy. Disaggregation of cassava root cells was associated with a reduction in large (diameter > 250 ?m) residue particle size in the bagasse and consequently more starch yield. Thus, it seems that mechanistically, dilute NaOH solubilisation of alkaline-soluble pectin weakens the cell walls of starch-containing cassava root parenchyma cells. Weakening of cassava cell walls with a combination of biological (14 day endogenous fermentation under microaerophilic conditions) and dilute alkaline pre-treatment (0.75% NaOH steeping) was investigated in an attempt to further increase starch yield by wet milling. However, the combined pre-treatment resulted in approx. 11.8% more starch yield, slightly less than the 12.3% increase obtained by using endogenous fermentation alone. The absence of an additive effect was probably because although endogenous fermentation (retting) and dilute NaOH steeping weakened cassava cell walls through different mechanisms (hydrolysis/solubilisation of pectin), the resultant loss in pectin cohesiveness was similar. Solid state fermentation of ground cassava using various alkaliphilic Bacillus spp. starter cultures separately and in combination was also investigated to determine their extracellular hydrolytic enzyme induced weakening effects on parenchyma cell walls. GC and FTIR data indicated that fermentation with Bacillus akibai + endogenous microflora (EM), B. cellulosilyticus + EM, B. hemicellulosilyticus + EM and B. spp. in combination + EM caused reduction in cell wall pectin, xyloglucan and cellulose contents. Cell wall solubilisation/hydrolysis seemed to have primarily involved the amorphous constituents, as indicated by an increase in cellulose crystallinity by WAXS spectroscopy. Enzyme assay and SEM indicated that Bacillus spp. extracellular cellulase and polygalacturonase weakened the cell walls through formation of micropores and possible rupturing of cellulose microfibril structures. These modifications seemed to have aided disaggregation of the cassava parenchyma cells and consequently liberation of more starch granules as indicated by light microscopy. Fermentation with B. akibai + EM, B. cellulosilyticus + EM, B. hemicellulosilyticus + EM and B. spp. in combination + EM also resulted in less large (diameter > 250 ?m) residue particle size in the bagasse and consequently higher starch yield. Thus, dilute NaOH steeping and fermentation with alkaliphilic Bacillus spp. starter cultures are techniques capable of improving the effectiveness of wet milling in disintegrating cassava cell walls. However, with regard to the demand for environmentally cleaner production, potential utilisation of alkaliphilic Bacillus spp. and more specifically Bacillus cellulosilyticus appears more promising.
Thesis (PhD)--University of Pretoria, 2017.
Food Science
PhD
Unrestricted

APA, Harvard, Vancouver, ISO, and other styles

22

Braithwaite, Kerynne Lindsay. "Novel plant cell wall hydrolases from Pseudomonas fluorescens subspecies cellulosa." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294928.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Choudhry, Anthony Ejaz. "Inhibition of bacterial cell wall biosynthesis by the affinity label N-bromoacetylglucosamine." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ40403.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Lancaster, M. J. "Studies on the export of extracellular proteins through the bacterial cell wall." Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356221.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Reynolds, Catherine B. "A lesson in bacterial variability : the C. difficile cell wall protein CwpV." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6993.

Full text

Abstract:

Clostridium difficile is the main cause of antibiotic-associated diarrhea, leading to significant morbidity and mortality, and putting considerable economic pressure on healthcare systems. Current knowledge of the molecular basis of pathogenesis is limited primarily to the activities and regulation of two major toxins. In contrast, little is known of the mechanisms used to colonise the enteric system. C. difficile expresses a proteinaceous array on its cell surface known as the S-layer, consisting primarily of SlpA and a family of homologues, the cell wall protein (CWP) family. CwpV is the largest member of this family. CwpV is expressed in a phase-variable manner controlled by an invertible DNA switch, the cwpV switch. The novel mechanism controlling this phase variation has been charaterised using enzymatic reporter assays. A site-specific recombinase (RecV) catalyzing the inversion of the cwpV switch has been identified. Knocking out this recombinase has enabled isolation of cwpV switch locked ON and locked OFF strains of C. difficile, indicating that cwpV switch orientation is the primary determinant of CwpV expression. CwpV is post-translationally cleaved and expressed on the cell surface as two proteins that form a stable complex, with one subunit responsible for the noncovalent cell wall anchoring of the other large repetitive subunit. Due to the significant heterogeneity of C. difficile strains the characteristics of CwpV across a panel of strains were investigated. The cwpV switch and recV are conserved across diverse strains and all strains tested express CwpV in a phase variable manner. The N-terminus of CwpV is well conserved, however the C-terminal repetitive domain of CwpV varies markedly. Five different types have been identified and shown to be antigenically distinct. All types of CwpV repeats promote aggregation of C. difficile cells, which may be an important function during infection. These findings suggest a complex evolutionary history for CwpV.

APA, Harvard, Vancouver, ISO, and other styles

26

Rayner, Joanna Clare. "The role of the bacterial cell wall in biofilm formation and antibiotic susceptibility." Thesis, University of Exeter, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388624.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Al-Bar, Omar Abdulrahman Mostafa. "Modified amino acids and peptides as potential inhibitors of bacterial cell wall biosynthesis." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303364.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Torres, Marco Tulio Rincon. "Cellulosome organisation of plant cell wall degrading enzymes in Ruminococcus flavefaciens 17." Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327013.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Renner-Schneck, Michaela Gabriele [Verfasser], and Thilo [Akademischer Betreuer] Stehle. "Bacterial cell wall recycling in molecular detail / Michaela Gabriele Renner-Schneck ; Betreuer: Thilo Stehle." Tübingen : Universitätsbibliothek Tübingen, 2015. http://d-nb.info/1163397458/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Chu, Michele, Michael J. G. Mallozzi, Bryan P. Roxas, Lisa Bertolo, Mario A. Monteiro, Al Agellon, V. K. Viswanathan, and Gayatri Vedantam. "A Clostridium difficile Cell Wall Glycopolymer Locus Influences Bacterial Shape, Polysaccharide Production and Virulence." PUBLIC LIBRARY SCIENCE, 2016. http://hdl.handle.net/10150/622410.

Full text

Abstract:

Clostridium difficile is a diarrheagenic pathogen associated with significant mortality and morbidity. While its glucosylating toxins are primary virulence determinants, there is increasing appreciation of important roles for non-toxin factors in C. difficile pathogenesis. Cell wall glycopolymers (CWGs) influence the virulence of various pathogens. Five C. difficile CWGs, including PSII, have been structurally characterized, but their biosynthesis and significance in C. difficile infection is unknown. We explored the contribution of a conserved CWG locus to C. difficile cell-surface integrity and virulence. Attempts at disrupting multiple genes in the locus, including one encoding a predicted CWG exporter mviN, were unsuccessful, suggesting essentiality of the respective gene products. However, antisense RNA-mediated mviN downregulation resulted in slight morphology defects, retarded growth, and decreased surface PSII deposition. Two other genes, lcpA and lcpB, with putative roles in CWG anchoring, could be disrupted by insertional inactivation. lcpA(-) and lcpB(-) mutants had distinct phenotypes, implying non-redundant roles for the respective proteins. The lcpB mutant was defective in surface PSII deposition and shedding, and exhibited a remodeled cell surface characterized by elongated and helical morphology, aberrantly-localized cell septae, and an altered surface-anchored protein profile. Both lcpA(-) and lcpB(-) strains also displayed heightened virulence in a hamster model of C. difficile disease. We propose that gene products of the C. difficile CWG locus are essential, that they direct the production/assembly of key antigenic surface polysaccharides, and thereby have complex roles in virulence.

APA, Harvard, Vancouver, ISO, and other styles

31

Renner-Schneck, Michaela [Verfasser], and Thilo [Akademischer Betreuer] Stehle. "Bacterial cell wall recycling in molecular detail / Michaela Gabriele Renner-Schneck ; Betreuer: Thilo Stehle." Tübingen : Universitätsbibliothek Tübingen, 2015. http://d-nb.info/1163397458/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Xayarath, Bobbi. "Effects of specific alterations in capsule structure on Streptococcus pneumoniae capsule assembly and virulence." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2008r/xayarath.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

May, Terry J. "Synthesis and evaluation of inhibitors of cell wall biosynthesis in Mycobacterium tuberculosis." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/35769/.

Full text

Abstract:

The emergence of drug-resistant strains of tuberculosis has led to a demand for the development of new antibiotics. One new target is the cell wall biosynthesis enzyme UDP-Galp mutase (UGM), which aids the formation of the bacteria’s characteristic mycolic acid cell wall. LQ10 and LQ6 were discovered through a library screen. The synthesis of LQ10 was achieved along with 4 analogues. Another class of compounds, 2-aminothiazoles, were produced. Thirteen of these compounds were produced and along with the LQ10 analogues, initially gave encouraging results in silico. To test their biological activity, a fluorescent probe was synthesised for use in a high-throughput fluorescence polarization (FP) assay against UDP-Galp Mutase which was expressed from E. coli. The compounds were screened using the fluorescence polarisation assay initially at a concentration of 50 µM, 9 of which demonstrated >70 % inhibition of UGM. Two of which had inhibition greater than 90 %. These preliminary results suggest that some of these compounds are, and can be developed into potent UGM inhibitors. However, it should be noted that these are only single-point results due to limitations in the quantity of UGM available, and that these will need be repeated in triplicate to determine any errors and give more reliable values.

APA, Harvard, Vancouver, ISO, and other styles

34

Finney, Simon Jonathan. "Leukocyte recruitment in vivo : diverse effects of gram positive and gram negative bacterial cell wall components." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413481.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Vasala, A. (Antti). "Characterization of Lactobacillus bacteriophage LL-H genes and proteins having biotechnological interest." Doctoral thesis, University of Oulu, 1998. http://urn.fi/urn:isbn:9514250826.

Full text

Abstract:

Abstract Two regions of the genome of the Lactobacillus delbrueckii subsp. lactis bacteriophage LL-H were characterized, representing 14 % of the phage genome. The first region of 2497 bp contained genes encoding phage structural proteins and the second region of 2498 bp genes involved in lytic functions. The nucleotide sequences of the major capsid protein gene g34, a putative capsid morphogenesis gene (ORF178A), the gene mur encoding phage cell wall hydrolase (lysin), the gene hol (ORF107) encoding the cell membrane permeabilizing phage holin, and six other genes with unknown function were found. Identification of these genes was performed by amino acid sequencing of their encoded proteins (genes g34 and mur), by their physiological effect on E. coli (genes hol and mur), by sequence comparison (genes mur, hol, ORF178A), and by biochemical analysis of their encoded purified protein (gene mur). A promoter for the capsid protein encoding gene cluster was determined by primer extension method. A purification method suitable for large scale processing (cation exchange chromatography by expanded bed adsorption method) was developed for the phage LL-H lysin protein Mur. Purified Mur was biochemically determined as a N-acetylmuramidase, which was effective on cell walls of Lb. delbrueckii, Lb. helveticus, Lb. acidophilus and Pediococcus damnosus. Some biotechnological applications for the lysis genes hol and mur or the purified protein Mur are suggested. Mur digests E. coli cell walls inefficiently, but could still be used for lysis of E. coli. Coexpression of the phage LL-H lysin and holin genes yielded to lysis of the E. coli host only at low culture densities. Therefore, some chemicals were tested for their ability to trigger lysis of E. coli cells overexpressing the phage LL-H gene mur. Thymol was found to mimic the physiological effects of the phage holin in a bacterial growth state independent manner. An efficient lysis method utilizing intracellular production of Mur and triggering the lysis with thymol was developed.

APA, Harvard, Vancouver, ISO, and other styles

36

Yao, Zhizhong. "Using Live Cell Imaging to Probe Biogenesis of the Gram-Negative Cell Envelope." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10230.

Full text

Abstract:

In Gram-negative bacteria, the three-layered cell envelope, including the cell wall, outer and inner membranes, is essential for cell survival in the changing, and often hostile environments. Conserved in all prokaryotes, the cell wall is incredibly thin, yet it functions to prevent osmotic lysis in diluted conditions. Based on observations obtained by genetic and chemical perturbations, time-lapse live cell imaging, quantitative imaging and statistical analysis, Part I of this dissertation explores the molecular and physical events leading to cell lysis induced by division-specific beta-lactams. We found that such lysis requires the complete assembly of all essential components of the cell division apparatus and the subsequent recruitment of hydrolytic amidases. We propose that division-specific beta-lactams lyze cells by inhibiting FtsI (PBP3) without perturbing the normal assembly of the cell division machinery and the consequent activation of cell wall hydrolases. On the other hand, we demonstrated that cell lysis by beta-lactams proceeds through four physical phases: elongation, bulge formation, bulge stagnation and lysis. Bulge formation dynamics is determined by the specific perturbation of the cell wall and outer membrane plays an independent role in stabilizing the bulge once it is formed. The stabilized bulge delays lysis, and allows escape and recovery upon drug removal. Asymmetrical in structure and unique to Gram-negative bacteria, outer membrane prevents the passage of many hydrophobic, toxic compounds. Together with inner membrane and the cell wall, three layers of the Gram-negative cell envelope must be well coordinated throughout the cell cycle to allow elongation and division. Part II of this dissertation explores the essentiality of the LPS layer, the outer leaflet of the outer membrane. Using a conditional mutant severely defective in LPS transport, we found that mutations in the initiation phase of fatty acid synthesis suppress cells defective in LPS transport. The suppressor cells are remarkably small with a 70% reduction in cell volume and a 50 % reduction in growth rate. They are also blind to nutrient excess with respect to cell size control. We propose a model where fatty acid synthesis regulates cell size in response to nutrient availability, thereby influencing growth rate.
Chemistry and Chemical Biology

APA, Harvard, Vancouver, ISO, and other styles

37

Pinheiro, Benedita Andrade. "Novel insight into the mechanism of cellulosome assembly and plant cell wall hydrolysis in anaerobic bacteria." Doctoral thesis, Universidade Técnica de Lisboa. Faculdade de Medicina Veterinária, 2010. http://hdl.handle.net/10400.5/1742.

Full text

Abstract:

Tese de Doutoramento em Ciência e Tecnologia Animal
Cellulosomes are one of nature’s most elaborate and highly efficient nanomachines. These cell bound multi-enzyme complexes orchestrate the deconstruction of cellulose and hemicellulose, two of the most abundant polymers on earth, thus playing a major role in carbon turnover. Integration of cellulosomal components occurs via highly ordered protein:protein interactions between cohesins and dockerins, whose specificities allow the precise incorporation of cellulases and hemicellulases onto a molecular scaffold. Clostridium thermocellum and C. cellulolyticum cellulosomes have been extensively characterized and constitute the paradigm for the organization of cellulases and hemicellulases in multi-enzyme complexes by thermophilic and mesophilic anaerobic bacteria, respectively. The recent sequencing of C. thermocellum and C. cellulolyticum genomes allowed the identification of the complete set of cohesins, dockerins and cellulosomal domains encoded by these bacteria. Here, several unresolved issues concerning cohesin-dockerin specificity, cellulosome assembly and the role of cellulosomal catalytic components in plant cell wall hydrolysis will be explored. The ligand specificities of some newly identified C. thermocellum cohesin and dockerin domains were described (Chapter 2). A novel cell-bound protein, termed OlpC, which contains a type I cohesin domain was discovered in C. thermocellum. A restricted set of dockerins were shown to interact, primarily, with OlpC. All the remaining dockerin containing polypeptides expressed by C. thermocellum are directed to cellulosomes. Significantly, the structure of two C. cellulolyticum cohesin-dockerin complexes revealed that, as it was previously reported for C. thermocellum, mesophilic dockerins also express a dual binding mode for cohesins (Chapter 3). Initial crystallization studies with the two N-terminal domains of C. thermocellum cellulosomal xylanase Xyn10B anticipate the elucidation of its 3D structure, which may provide insightful data concerning the function of this enzyme in plant cell wall hydrolysis (Chapter 4). Finally, a cellulosomal family 2 CE (CtCE2), which grafts a second discrete non-catalytic binding functionality into its active site, was characterized (Chapter 5). CtCE2 provides a rare example of “gene sharing” where the introduction of a second functionality into the active site of an enzyme does not compromise the original activity of the biocatalyst.
RESUMO - Nova perspectiva no mecanismo de integração do celulossoma e na degradação da parede celular vegetal por bactérias anaeróbias - Os celulossomas são um dos mais intricados e eficientes complexos multi-enzimáticos existentes na Natureza. Estes complexos, que se encontram ligados à parede celular bacteriana, desempenham um papel importante na degradação da celulose e da hemicelulose, dois dos mais abundantes polímeros na terra. A integração dos componentes celulossomais ocorre através de interacções proteína-proteína, muito ordenadas, estabelecidas entre coesinas e doquerinas, cuja especificidade permite a incorporação precisa de celulases e hemicelulases numa proteína de integração celulossomal. Os celulossomas dos organismos Clostridium thermocellum e C. cellulolyticum têm sido extensivamente caracterizados e constituem o paradigma para a organização de celulases e hemicelulases em complexos multienzimáticos de bactérias anaeróbias, tanto termófilas como mesófilas, respectivamente. A recente sequenciação dos genomas do C. thermocellum e do C. cellulolyticum permitiu a identificação de um conjunto completo de coesinas, doquerinas e domínios celulossomais codificados por estas bactérias. Neste trabalho, várias questões relativas à especificidade coesina-doquerina, à formação do celulossoma e ao papel dos componentes celulossomais catalíticos serão investigadas. A especificidade de doquerinas e coesinas do C. thermocellum recentemente identificados foi descrita (Capítulo 2). Uma nova proteína da parede celular, designada como OlpC, que contém um domínio doquerina, foi descoberta no C. thermocellum. Demonstrou-se que um conjunto restrito de doquerinas reage preferencialmente com a OlpC. Os restantes polipéptidos expressos pela bactéria C. thermocellum, contendo também doquerinas, ligam-se ao celulossoma. A estrutura de dois complexos coesina-doquerina do C. cellulolyticum revelou, como previamente comunicado para a bactéria C.thermocellum, que as doquerinas de organismos mesófilos também apresentam uma dupla ligação para com as coesinas (Capítulo 3). Estudos preliminares de cristalização dos dois domínios Nterminais da xilanase celulossomal Xyn10B antecipam a futura elucidação da sua estrutura 3D, o que poderá esclarecer a função deste enzima na hidrólise da parede celular vegetal (Capítulo 4). Finalmente, foi descrita uma esterase de hidratos de carbono da família 2 (CtCE2), que apresenta uma funcionalidade discreta, não-catalítica de ligação a glúcidos no seu centro catalítico. A CtCE2 fornece um raro exemplo de “gene sharing”, onde a introdução de uma segunda funcionalidade no centro catalítico de uma enzima não compromete a actividade original do biocatalisador.
This work was funded by Fundação para a Ciência e a Tecnologia, grant SFRH/BD/25439/2005 Co-funded by POCTI/BIA-PRO/59118/2004 and PPCDT/BIA-PRO/59118/2004 from Ministério da Ciência, Tecnologia e Ensino Superior

APA, Harvard, Vancouver, ISO, and other styles

38

Büttner, Felix Michael [Verfasser], and Thilo [Akademischer Betreuer] Stehle. "Modulation of the bacterial cell wall by N‐acetylmuramoyl‐L‐alanine amidases / Felix Michael Büttner ; Betreuer: Thilo Stehle." Tübingen : Universitätsbibliothek Tübingen, 2016. http://d-nb.info/1164169521/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Laddomada, Federica. "Structure et assemblage de complexes des enzymes Mur, essentielles pour la synthèse de la paroi bactérienne." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV090.

Full text

Abstract:

Les enzymes de la famille Mur (MurA-MurG) sont essentielles pour la survie bactérienne, car elles catalysent les étapes cytoplasmiques de la biosynthèse du peptidoglycane, la principale composante de la paroi cellulaire. En outre, les Murs métabolisent des molécules qui sont absentes chez les eucaryotes, et ces enzymes sont structurellement et biochimiquement tractables. Cependant, malgré le fait que nombreux inhibiteurs anti-Mur ont été développés, un nombre tres réduit de ces molécules ont montré une activité antibactérienne prometteuse, ce qui a incité l'hypothèse selon laquelle, dans le cytoplasme bactérien, les enzymes Mur peuvent exister dans un complexe où les sites actifs sont à proximité, bloquant donc l'accès de petites molécules venant de l'extérieur. Cette hypothèse est soutenue par l'observation selon laquelle, dans de nombreux organismes, les gènes codant pour les enzymes Mur sont présents dans un seul opéron, souvent dans le même ordre; en outre, souvent des paires de gènes sont fusionnées pour générer un seul polypeptide, préconisant la possibilité que des complexes entre ces enzymes pourraient être formés dès qu'ils sont synthétisés. Nous avons obtenu les premières informations structurales et fonctionnelles sur la forme fusionnée MurE-MurF, présente dans le pathogène humain Bordetella pertussis, et nous avons montré qu'elle interagit avec la glycosyltransférase périphérique MurG, ce qui suggère la présence d'un complexe enzymatique ternaire. De façon intéressante, nous avons constaté que MurG de B. pertussis est capable de s'associer avec elle-même et de former différentes espèces oligomériques. Cette découverte pourrait renforcer le rôle de MurG en tant que protéine agissant comme une plateform capable d'ancrer d'autres enzymes Mur à la face interne de la membrane cytoplasmique bactérienne. Nos resultats pourront également être explorés pour comprendre le rôle potentiel de MurG en tant que régulateur de l'activité des enzymes de synthèse du PG. Ces résultats passionnants ouvriront le chemin vers la compréhension du mecanisme d’interaction des enzymes Mur dans le cytoplasme bactérien et pourraient permettre l'emploi éventuel des Murs comme cibles de facto pour développer de nouveaux antibiotiques
Enzymes of the Mur family (MurA-MurG) are essential for bacteria, since they catalyse the cytoplasmic steps of peptidoglycan biosynthesis, the major component of bacterial cell wall; they metabolize molecules that do not exist in eukaryotes, and are structurally and biochemically tractable. However, despite the fact that many anti-Mur inhibitors have been developed, few of these molecules have shown promising antibacterial activity, which has prompted the hypothesis that within the bacterial cytoplasm Mur enzymes may exist in a complex where the active sites are in closed proximity, blocking small molecule access from the outside. This suggestion is supported by the observation that in many organisms, genes encoding Mur enzymes are present in a single operon, often in the same order, and often pairs of genes are fused to generate a single polypeptide, advocating the possibility that complexes between these enzymes could be formed as soon as they are synthesized. We have obtained the first structural and functional information on the MurE-MurF fused form, present in the human pathogen Bordetella pertussis, and shown that it interacts with the peripheral glycosyltransferase MurG, suggesting the presence of a ternary enzymatic complex. Interestingly, we have found that B. pertussis MurG is able to self-associate and form different oligomeric species. This finding could strengthen the hypothesis of MurG as a scaffold protein capable of anchoring other Murs to the inner face of bacterial inner membrane, but could be also further explored to understand its potential role as a regulator of the activity of PG synthesis enzymes. These exciting results will open the path towards the understanding of how Mur enzymes interact within the bacterial cytoplasm, and could permit the eventual employment of Mur enzymes as de facto targets for novel antibiotic development

APA, Harvard, Vancouver, ISO, and other styles

40

Megrian, Nuñez Daniela. "Phylogenomic approaches to uncover the diversity and evolution of the bacterial cell envelope." Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS349.

Full text

Abstract:

L’enveloppe bactérienne est l’une des structures cellulaires les plus anciennes et les plus fondamentales. Toutefois, de nombreux aspects concernant sa diversité et son histoire évolutive sont encore inconnus. Dans cette thèse, j’ai profité du nombre croissant de génomes disponibles dans les bases de données publiques, afin de mener une analyse de phylogénomique et de génomique comparative à une large échelle évolutive. Les deux objectifs de ce travail doctoral étaient (i) d’identifier de nouvelles lignées didermes au sein des Firmicutes pour éclairer la transition monoderme/diderme, et (ii) d’élucider l’histoire évolutive de l’enveloppe cellulaire chez les bactéries et d’en déduire la nature chez le LBCA.En résumé, les résultats que j'ai obtenus au cours de cette thèse fournissent une avancée significative dans notre compréhension de la diversité et de l'évolution de l'enveloppe cellulaire, et sur l'une des transitions majeures de l'histoire des bactéries, celle entre les monodermes et les didermes
The bacterial envelope is one of the oldest and most fundamental cellular structures. Yet, many aspects of its diversity and evolutionary history are unknown. In this thesis I have taken advantage of the large available genomic data to investigate the issue through a large-scale phylogenomic and comparative genomic analyses at the level of Bacteria. The two goals of this doctoral work were (i) to identify putative new diderm lineages in the Firmicutes to illuminate the monoderm/diderm transition, and (ii) to elucidate the evolutionary history of the cell envelope in Bacteria and infer its nature in the LBCA. To sum up, the results I obtained during this thesis provide a timely and significant advancement to our understanding of the diversity and evolution of the cell envelope, and on one of the major transitions in the history of Bacteria, that between monoderms and diderms

APA, Harvard, Vancouver, ISO, and other styles

41

Sehmsdorf, Ute-Stephani. "Einfluss von "Calcitonin Gene-Related Peptide" und "Substance P" auf die mRNA-Expression und Freisetzung von Zytokinen aus zerebralen Endothelzellen bei Kostimulation mit Pneumokokkenzellwänden." Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 2001. http://dx.doi.org/10.18452/14660.

Full text

Abstract:

Die bakterielle Meningitis (BM) ist trotz antibiotischer Therapie eine Erkrankung mit einer hohen Mortalität und Morbidität. Kopfschmerzen und Meningismus sind Hauptsymtome und ein klinischer Hinweis für die Aktivierung trigeminaler Fasern. Ziel dieser Arbeit war es zu prüfen ob die freigesetzten Neuropeptide einen proinflammatorischen Effekt auf zerebrale Endothelzellen, einen wesentlichem Bestandteil der Blut-Hirn-Schranke haben. Wir verwendeten primär kultivierte zerebrale Kapillarendothelzellen (BMEC) der Ratte und als Stimulus Neuropeptide und/oder Pneumokokkenzellwände (PCW). Beide Neuropeptide, CGRP mehr als SP, verstärken den Effekt von PCW auf die mRNA Expression und Freisetzung von TNF-alpha, IL-1beta, IL-6, IL-10 und MIP-2 aus den BMEC. CGRP und SP haben nur eine geringe Wirkung. PCW regulieren die Dichte der CRLR (CGRP1-R) bzw. NK-1 Rezeptoren und erklären damit die kostimulatorische Wirkung. Zudem untersuchten wir den Effekt von PCW und/oder CGRP auf die Adrenomedullin (AM)- Synthese. AM ist ein vasodilatorisch wirkendes Peptid, dass vorwiegend in Endothelzellen konstitutiv gebildet wird und am CRLR Rezeptor wirkt. PCW und CGRP verstärken die Synthese von AM. Mit dieser Arbeit konnte gezeigt werden, dass PCW zur Hochregulation von Neuropeptidrezeptoren führt und CGRP und SP über diese Rezeptoren einen modulatorischen Effekt auf die Zytokinproduktion in BMEC haben. Ein genaues Verständnis dieser Interaktionen könnte die Entwicklung immunmodulatorischer Interventionen und damit eine Verbesserung der Prognose der bakteriellen Meningitis bewirken.
Despite antibiotic treatment bacterial meningitis is still associated with a high mortality and morbidity. Headache and meningismus as key symptoms, provide clear evidence for the activation of trigeminal nerve fibers. Aim of the study was to test whether the released neuropeptides have a proinflammatory effect in cerebral endothelial cells the major compartment of the blood brain barrier. We used primary brain microvascular endothelial cells of the rat (BMEC) which were stimulated with CGRP, SP and/or pneumococcal cell walls (PCW). Both neuropeptides CGRP more than SP enhanced PCW-induced mRNA expression and the release of TNF-alpha, IL-1-beta, IL-6, IL-10 and MIP-2. Neuropeptides alone were not able to induce these cytokines. PCW upregulate the density of CRLR receptor and regulate the NK-1 receptor and therefore may explain the costimulatory effect. Furthermore the effect of PCW and/or CGRP on adrenomedullin synthesis in BMEC was investigated. Adrenomedullin is a vasodilatatory peptide, which is constitutivly produced by endothelial cells and act on the CRLR receptor. PCW as well as CGRP enhance the synthesis of AM. Our data suggest that PCW upregulate neuropeptide receptors and modulate via these specific receptors the cytokine production. A detailed understanding of these interactions may open new immunmodulatory interventions and therefore may contribute to a better prognosis of bacterial meningitis.

APA, Harvard, Vancouver, ISO, and other styles

42

Ochiai, Akihito. "Physiological and X-ray crystallographic studies on plant cell wall polysaccharides-degrading lyases from plant pathogenic and saprophytic bacteria." Kyoto University, 2008. http://hdl.handle.net/2433/136591.

Full text

Abstract:

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第13864号
農博第1679号
新制||農||952(附属図書館)
学位論文||H20||N4331(農学部図書室)
UT51-2008-C780
京都大学大学院農学研究科食品生物科学専攻
(主査)教授村田幸作, 教授清水昌, 教授井上國世
学位規則第4条第1項該当

APA, Harvard, Vancouver, ISO, and other styles

43

Wei, Yuping. "Characterization of two Bacillus subtilis penicillin-binding protein-coding genes, ykuA (pbpH) and yrrR (pbpI)." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34900.

Full text

Abstract:

Penicillin-binding proteins (PBPs) are required in the synthesis of the cell wall of bacteria. In Bacillus subtilis, PBPs play important roles in the life cycle, including both vegetative growth and sporulation, and contribute to the formation of the different structures of vegetative cell wall and spore cortex. The B. subtilis genome sequencing project revealed there were two uncharacterized genes, ykuA and yrrR, with extensive sequence similarity to class B PBPs. These two genes are renamed and referred to henceforth as pbpH and pbpI, respectively.

A sequence alignment of the predicted product of pbpH against the microbial protein database demonstrated that the most similar protein in B. subtilis is PBP2A and in E. coli is PBP2. This suggested that PbpH belongs to a group of the genes required for maintaining the rod shape of the cell. Study of a pbpH-lacZ fusion showed that pbpH was expressed weakly during vegetative growth and the expression reached the highest level at the transition from exponential phase to stationary phase. The combination of a pbpA deletion and the pbpH deletion was lethal and double mutant strains lacking pbpH and pbpC or pbpI (also named yrrR) were viable. The viable mutants were indistinguishable from the wild-type except that the vegetative PG of the pbpC pbpH strain had a slightly slightly lower amount of disaccharide tetrapeptide with 1 amidation and higher amount of disaccharide tripeptide tetrapeptide with 2 amidations when compared to others strains. This suggests that PbpC (PBP3) is involved in vegetative PG synthesis but only affects the PG structure with a very low efficiency.

A pbpA pbpH double mutant containing a xylose-regulated pbpH gene inserted into the chromosome at the amyE locus was constructed. Depletion of PbpH resulted in an arrest in cell growth and a dramatic morphological change in both vegetative cells and outgrowing spores. Vegetative cells lacking pbpA and pbpH expression swelled and cell elongation was arrested, leading to the formation of pleiomorphic spherical cells and eventual lysis. In these cells, cell septations were randomly localized, cell walls and septa were thicker than those seen in wild type cells, and the average cell width and volume were larger than those of cells expressing pbpA or pbpH. The vegetative PG had an increased abundance of one unidentified muropeptide. Spores produced by the pbpA pbpH double mutant were able to initiate germination but the transition of the oval-shaped spores to rod-shape cells was blocked. The outgrowing cells were spherical, gradually enlarged, and eventually lysed. Outgrowth of these spores in the presence of xylose led to the formation of helical cells. Thus, PbpH is apparently required for maintenance of cell shape, specifically for cell elongation. PbpH and PBP2a play a redundant role homologous to that of PBP2 in E. coli.

A sequence alignment of the predicted product of pbpI against the microbial protein database demonstrated that the most similar protein in B. subtilis is SpoVD and in E. coli is PBP3. This suggested that PbpI belongs to the group of the genes required for synthesis of the spore or septum PG. PbpI was identified using radio-labeled penicillin and found to run underneath PBP4 on SDS-PAGE. PbpI is therefore renamed PBP4b. Study of a pbpI-lacZ fusion showed that pbpI was expressed predominantly during early sporulation. A putative sigma F recognition site is present in the region upstream of pbpI and studies using mutant strains lacking sporulation-specific sigma factors demonstrated that the expression of pbpI is mainly dependent on sigma factor F. A pbpI single mutant, a pbpI pbpG double mutant, and a pbpI pbpF double mutant were indistinguishable from the wild-type. The sporulation defect of a pbpI pbpF pbpG triple mutant was indistinguishable from that of a pbpF pbpG double mutant. Structure parameters of the forespore PG in a pbpI spoVD strain are similar to that of a spoVD strain. These results indicate that PBP4b plays a unknown redundant role.

Master of Science

APA, Harvard, Vancouver, ISO, and other styles

44

Huff, Jason. "Functional determinants of the porin MspA and its role in permeabilizing mycobacterial outer membranes." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2010. https://www.mhsl.uab.edu/dt/2010p/huff.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

LEPORI, IRENE. "Optimization of attenuated Listeria monocytogenes cell wall chemical engineering to increase its anticancer vaccine activity and to use it as metastasis tracer." Doctoral thesis, Università di Siena, 2019. http://hdl.handle.net/11365/1072153.

Full text

Abstract:

Attenuated Listeria monocytogenes (Lmat) is widely investigated as anticancer vaccine thanks to its capability to activate host immune-response against the tumour tissues. Lots of genetic engineering strategies have been used to improve its power, such as increasing its immune-stimulation against the cancer tissues by the expression of tumour associated antigens. Since Lmat is capable to selectively accumulate in primary tumours and metastasis, compared with the healthy tissues, we started exploring the possibility of using Lmat as drug carrier and metastasis tracer, by using chemical cell wall modifications that allow us to attach little chemicals onto the bacterial cell wall. In this work we optimized the chemical engineering of Lmat cell wall to let it expose reporter chemical groups, such as alkyne or azido group, that can selectively react with the respective chemical partner (azido and alkyne) by bioorthogonal and bio-compatible “click-reaction”. After comparison of different probes for the functionalization of Lmat cell wall, we optimized the protocol for efficient and totally bio-compatible labelling by using azido-D-alanine probe and both the strain-promoted alkyne-azide cycloaddition (SPAAC) and the copper(I)-catalysed azide-alkyne cycloaddition (CuAAC) reactions. We tested the in vitro features of labelled Lmat and demonstrated that it maintains unaltered proliferative activity, infectivity and intrinsic toxicity effect on 501-mel cell line. We started exploring the chemical conjugation between Lmat and doxorubicin for the drug-carrier strategy, and with Cy7.5 Photoacoustic Dye (PAI) for the metastasis imaging strategy.

APA, Harvard, Vancouver, ISO, and other styles

46

Gwozdzinski, Konrad [Verfasser]. "Macromolecular modification of the cell wall of Gram-negative bacteria leading to antibiotic resistance and formation of outer membrane vesicles / Konrad Gwozdzinski." Gießen : Universitätsbibliothek, 2018. http://d-nb.info/1158494696/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Banzato, Ticyana Carone. "Ocorrência e identificação molecular de fitoplasmas em pessegueiro, nectarineira e mostarda-do-campo." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/11/11135/tde-17072018-144836/.

Full text

Abstract:

Fitoplasmas são organismos procarióticos desprovidos de parede celular, parasitas intracelulares obrigatórios de floema e patogênicos às plantas. Numerosas doenças associadas a este tipo de agentes patogênicos têm sido frequentemente relatadas em espécies cultivadas e plantas daninhas. No presente estudo, sintomas tipicamente induzidos por fitoplasmas, tais como clorose e avermelhamento foliar, redução no tamanho das folhas, diminuição dos órgãos florais, superbrotamento de ramos e declínio da planta, foram observados em pomares de fruteiras de caroço como pessegueiro e nectarineira. Além disto, em campos de couve-flor, plantas daninhas conhecidas como mostarda-do-campo também manifestaram sintomas que pareciam ter sido provocados por fitoplamas, expressados por superbrotamento de ramos finos e redução no tamanho de folhas e flores. Assim, o presente trabalho teve por objetivos detectar, identificar e classificar a nível molecular os possíveis fitoplasmas associados às plantas sintomáticas citadas anteriormente, utilizando as técnicas de PCR, análise de RFLP virtual e o método de classificação on-line denominado de iPhyclassifier. Para tanto, o DNA das amostras das fruteiras de caroço e da erva daninha foi extraído com o auxílio de um kit comercial ou através do protocolo 2X CTAB. A detecção dos fitoplasmas foi conduzida por duplo PCR com os primers universais R16mF2/mR1 e SN910601/SN011119 na primeira reação e com o par R16F2n/R2 na segunda reação. Para a mostarda, a identificação dos fitoplasmas também foi realizada através de duplo PCR com os primers e R16(III)F2/R16(III)R1 específicos para fitoplasmas do grupo 16SrIII. A aplicação de PCR com primers universais permitiu a detecção consistente desses agentes nos tecidos das plantas sintomáticas de pessegueiro, nectarineira e mostarda-do-campo pela amplificação de um fragmento genômico de 1250 pb, correspondente ao gene 16S rRNA. Para todos os hospedeiros analisados, os produtos amplificados por duplo PCR com os primers universais foram purificados, clonados em Escherichia coli e submetidos ao sequenciamento. A análise de RFLP virtual e iPhyclassifier permitiram classificar os fitoplasmas encontrados em mostarda nos grupos 16SrIII e 16SrVII. Os fitoplasmas detectados na mostarda-do-campo, foram definitivamente classificados como representantes dos subgrupos 16SrIII-B, 16SrIII-J e 16SrIII-U e 16SrVII-B. Em relação aos fitoplasmas encontrados no pessegueiro e nectarineira, foi possível classificar os fitoplasmas nos grupos 16SrI e 16SrIII, sendo definitivamente classificados como representantes dos subgrupos 16SrI-B em pessegueiro, e em nectarineira, classificados em 16SrI-B e 16SrIII-J.
Phytoplasmas are prokaryotic organisms devoid of cell wall, obligate intracellular phloem parasites and pathogenic to plants. Numerous diseases associated with this type of pathogen have been frequently reported in cultivated species of plants and weeds. In this present study, symptoms typically induced by phytoplasmas, such a yellowing an reddeling leaves, small leaves and flowers, \"witches\' broom\" appearance on terminal new bud growth, and death in plants, were observed in orchards of stone fruit trees such as peach and nectarines. In addition, in fields of cauliflower, weeds known as mustard-field also exhibited symptoms that appeared to have been caused by phytoplasmas, expressed by thin branches and reduced leaf and flower size. The objective of this present study was to detect, identify and classify at molecular level the phytoplasmas possibly associated with the symptomatic plants. PCR techniques, virtual RFLP analysis and the online method known as iPhyclassifier were used. Total DNA was extracted using a commercial kit or through the CTAB protocol. The detection of phytoplasmas was conducted by nested PCR with the universal primers R16mF2/mR1 and SN910601/SN011119 in the first reaction and R16F2n/R2 pair in the second reaction. For mustard-field, the identification of the phytoplasmas was also performed through nested PCR with the primers R16(III) F2/R16(III) R1, which are specific to detection of 16SrIII group phytoplasmas. The application of PCR with universal primers allowed the consistent detection of these agents in the tissues in symptomatic plants of peach, nectarine and mustard-field by the amplification of a 1250 bp genomic fragment, corresponding to the 16S rRNA gene. For all hosts analyzed, the products amplified by nested PCR with the universal primers were purified, cloned in Escherichia coli and sequenced. The analysis of virtual RFLP and iPhyclassifier allowed to classify the phytoplasmas found in mustard in the 16SrIII and 16SrVII groups. The phytoplasmas detected in mustard-field were definitively classified as representatives of the subgroups 16SrIII-B, 16SrIII-J and 16SrIII-U and 16SrVII-B. The phytoplasmas found in the peach and nectarine were classified within the 16SrI and 16SrIII groups, as representatives of the subgroups 16SrI-B for peach and 16SrI-B and 16SrIII-J for nectarine.

APA, Harvard, Vancouver, ISO, and other styles

48

Beri, Hina. "Chemical and molecular analysis of the cell wall composition of tomato (Lycopersicon esculentum) in relation to resistance to Ralstonia solanacearum, causal agent of bacterial wilt." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976699133.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Merget, Benjamin [Verfasser], and Christoph [Gutachter] Sotriffer. "Computational methods for assessing drug-target residence times in bacterial enoyl-ACP reductases and predicting small-molecule permeability for the \(Mycobacterium\) \(tuberculosis\) cell wall / Benjamin Merget ; Gutachter: Christoph Sotriffer." Würzburg : Universität Würzburg, 2016. http://d-nb.info/1125884541/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Robinson, Margaret Reybold. "I: Enhanced specificity for aromatics using 2E mass spectrometry II: Evaluation of the proteolytic activity of cathepsin G and elastase upon bacterial cell wall III: Hydrolysis studies of an isocoumar." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/30968.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Bacterial cell walls'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles