Tesi sul tema "Bacteria research"
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1
McGinley, Susan. "Working Together on Nitrogen-Fixing Bacteria". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 1993. http://hdl.handle.net/10150/622335.
Testo completo
2
Han, Yeong-Hwan. "The microaerophilic nature of Wolinella recta, Wolinella curva, Bacteroides ureolyticus, and Bacteroides gracilis". Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39699.
Testo completoAbstract (sommario):
Broad relationships among bacteria can be identified by ribosomal RNA analysis, but the resulting groups may not be easily definable by phenotypic characteristics. This is exemplified by the genus Campylobacter, which consists of at least three separate groups that cannot be differentiated readily by phenotypic characteristics.
Examination of the type strains of all Campylobacter species (except Campylobacter pylori), Wolinella recta, Wolinella curva, Bacteroides ureolyticus, and Bacteroides gracilis revealed that sheathed flagella occur only in species of rRNA group II (except W.succinogenes). This is helpful in differentiating this group.
Campylobacters are microaerophilic: they can respire with oxygen but cannot grow at the full level of oxygen found in an air atmosphere (21% O₂). Although W. recta, W. curva, B. ureolyticus, and B. gracilis are closely related to the campylobacters of rRNA group I, they were thought to be anaerobes, incapable of oxygen-dependent growth and of respiring with O₂. However, the present study revealed that they are in fact microaerophiles. They exhibited oxygen-dependent growth but failed to grow at 21% O₂ and grew only very slightly under anaerobic conditions unless provided with electron acceptors such as fumarate and nitrate. They exhibited 0₂ uptake with H₂ or formate as electron donors (W. recta showed only a low O₂ uptake with H₂). Oxygen uptake was inhibited by KCN and 2-heptyl-4-hydroxyquinoline N-oxide. The organisms possessed membrane bound cytochromes (cytochromes b560 and C551-553, and a CO-binding cytochrome c), as well as soluble cytochrome C552 and CO-binding cytochrome c. The cytochromes were reduced by H₂ and formate as electron donors. Proton efflux from cells in anaerobic suspensions containing H₂ or formate occurred upon addition of a pulse of oxygen. With formate as the electron donor, H+/O ratios of W. curva, W. recta, B. ureolyticus, and B. gracilis were 0.75, 1.66,2.06, and 2.04, respectively. With H₂ as the electron donor, H⁺/O ratios of W.curva, B. ureoyticus, and B. gracilis were 1.25, 1.97, and 2.36, respectively; technical difficulties prevented measurement of the ratio in W. recta. Proton translocation was inhibited by the protonophore carbonylcyanide m-chlorophenylhydrazone. The results confirm the relationship of these organisms to campylobacters.Ph. D.
3
Mosteller, Tracy M. "Sanitizer efficacy towards attached bacteria". Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/45049.
Testo completoAbstract (sommario):
Pseudomonas fluorescens, Yersinia enterocolitica, and Listeria monocytogenes readily attach to both rubber and teflon surfaces. Once attached, a glycocalyx covering forms effectively protecting them from any sanitizer that passes over the surface. Therefore, sanitizers efficacy testing done in the laboratory with pure glycocalyx-free cultures could lead to false assumptions as to the sanitizer's true effectiveness under actual use conditions. Our objectives in this study were: (1) evaluate sanitizer efficacy of in use concentrations toward bacteria attached to gasket materials, (2) examine attachment on rubber versus teflon gaskets, (3) examine different methods of enumeration, (4) compare kill of attached bacteria to suspension tests, (5) determine the minimum inhibitory concentrations of Sanitizers. Iodophor, hypochlorite, acid anionic, peroxyacetic acid, fatty acid and QUAT sanitizers failed to provide an adequate log kill of bacteria attached in levels of 10⁴ to 10⁵. Most of the tests showed that the log kill falls well short of a 3 log reduction goal. Plate counts, impedance microbiology, and the direct epifluorescent filter technique were tested as methods of enumeration. Impedance microbiology was the best method of enumeration, since it allows the estimation of both reversibly and irreversibly attached bacteria. Minimum inhibitory concentration tests demonstrated the increased resistance of attached bacteria as compared to cell suspensions.Master of Science
4
Sislak, Christine Demko. "Novel Thermophilic Bacteria Isolated from Marine Hydrothermal Vents". PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1486.
Testo completoAbstract (sommario):
As part of a large study aimed at searching for patterns of diversity in the genus Persephonella along the north to south geochemical gradient of the ELSC, ten novel strains of Alphaproteobacteria were isolated unexpectedly. Using defined media under microaerophilic conditions to enrich for Persephonella from chimney samples collected at the seven vent fields on the ELSC and the dilution to extinction by serial dilution method to purify cultures, a total of ten strains belonging to the Alphaproteobacteria were isolated. Two of these isolates, designate MN-5 and TC-2 were chosen for further characterization and are proposed as two new species of a novel genus to be namedThermopetrobacter. Both strains are aerobic, capable of chemoautotrophic growth on hydrogen and grow best at 55°C, pH 6 and 3.0% NaCl. Strain MN-5 is capable of heterotrophic growth on pyruvate and malate and TC-2 is only able to grow heterotrophically with pyruvate. The GC content of MN-5 is 69.1 and TC-2 is 67 mol%. GenBank BLAST results from the 16S rRNA gene reveal the most closely related sequence to MN-5 is 90% similar and the most closely related sequence to strain TC-2 is 89% similar.
Sampling at a shallow marine vent on the coast of Vulcano Island, Italy in 2007 led to the isolation of a novel species of Hydrogenothermus, a genus within the Hydrogenothermaceae family. This isolate, designated NV1, represents the secondHydrogenothermusisolated from a shallow marine vent. NV1 cells are rod-shaped, approximately 1.5μm long and 0.7μm wide, motile by means of a polar flagellum and grow singularly or in short chains. Cells grow chemoautotrophically using hydrogen or thiosulfate as electron donors and oxygen as the sole electron acceptor. Growth was observed between 45 and 75°C with an optimum of 65°C (doubling time 140 min), pH 4.0-6.5 and requires NaCl (0.5-6.0% w/v). The G+C content of total DNA is 32 mol%.
5
Strobel, Philip Scott. "Inhibition of iron-oxidizing bacteria in wastes from coal and hard-rock mines using the anti-bacterial agent". Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42234.
Testo completoAbstract (sommario):
The production of acid mine drainage (AMD) is catalyzed by iron-oxidizing bacteria primarily of the species Thiobacillus ferrooxidans. By inhibiting these bacteria, the production of AMD can be greatly reduced. One compound found to be effective in the inhibition of T. ferrooxidans is nitrapyrine. N-Serve, a product of Dow Chemical, Inc., is the commercially available form of nitrapyrine. This compound has been widely used in agriculture for nitrification inhibition. The purpose of this study was to determine the effectiveness of N-Serve in reducing the production of AMD under simulated field conditions.
A column study was completed using a coal mine waste and a hard-rock mine waste. Eight columns containing 7kg of rock were established for each substrate. Three doses of NServe (22% nitrapyrine) were applied once at the beginning of this study: a high dose 2200 mg/kg, a medium dose 220 mg/kg, and a low dose 22 mg/kg. Duplicate columns were included for each N-Serve dose including two untreated columns to serve as a control for each substrate. Beginning the week after treatment, the columns were leached once a week for 29 weeks with deionized, distilled water (equivalent to 2.5 cm precipitation). Only the highest NServe dose produced a column leachate of significantly better quality than that of the controls. The acidity in the high-dose coal mine columns averaged less than 50 percent of the acidity in the control effluent from week 6 through the end of the study.
A monolithic controlled release system utilizing acrylonitrile rubber was successfully developed and tested for use with nitrapyrine. This formulation should withstand the rigors of the environment and with minor modification could produce a variety of release rates.Master of Science
6
McGinley, Susan. "Clostridium perfringens: New Ways to Type Strains of a Deadly Bacteria". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 1999. http://hdl.handle.net/10150/622290.
Testo completo
7
Klinke, Stefan. "Production of bioplastic in recombinant bacteria : from basic research to application /". [S.l.] : [s.n.], 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13448.
Testo completo
8
Gaspar-Rolle, Maria Nelma Pinto. "Attachment of bacteria to teflon and buna-n-rubber gasket materials". Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39818.
Testo completoAbstract (sommario):
Surface analysis of buna-N-rubber and teflon was performed. Scanning electron microscopy was used to analyze the topography of both materials and x-ray microanalysis identified the elemental chemical composition of the polymers.
Teflon was primarily a smooth surface with random irregular spots, while buna-N-rubber had a very rough topography with "caverns" and crevices spread over the surface. The x-ray microanalysis showed that there are no impurities on the surface of teflon; however, calcium, silicone and sulfur were present on the surface of buna-N-rubber. Water contact angle measurements indicated that buna-N-rubber was a more hydrophobic surface than teflon.
Qualitative analysis of the attachment of Pseudomonas fragi A TCC 4973, Listeria monocytogenes Scott A and Bacillus cereus ATCC 11778 to buna-N-rubber and teflon was assessed by scanning electron microscopy. These bacteria readily attached to both surfaces. Pseudomonas fragi attached after 2 hours in the presence of this microoorganism and Bacillus cereus and Listeria monocytogenes attached at 12 and 24 hours, respectively.
Quantitative analysis of the attachment of Pseudomonas fragi to both surfaces as affected by various milk fat concentrations and temperature, and the availability of nutrients (different dilutions of skim milk, casein, casein and lactose, and whey and lactose) was conducted. Attachment was assessed by impedance microbiology. Milk fat content did not play a significant role in the process of attachment of this organism to either type of surfaces; however, significantly greater numbers attached to buna-N-rubber than to teflon. Overall bacteria attached in higher numbers to both surfaces when grown at 21°C, compared to bacteria grown at 4°C. For buna-N-rubber, bacteria attached in significantly higher numbers when the concentration of nutrients was minimal, while for teflon, the results were, in most cases, opposite to these.Ph. D.
9
Talwalkar, Akshat, University of Western Sydney, of Science Technology and Environment College e of Science Food and Horticulture School. "Studies on the oxygen toxicity of probiotic bacteria with reference to Lactobacillus acidophilus and Bifidobacterium spp". THESIS_CSTE_SFH_Talwalkar_A.xml, 2003. http://handle.uws.edu.au:8081/1959.7/629.
Testo completoAbstract (sommario):
Oxygen toxicity is considered significant in the poor survival of probiotic bacteria such as Lactobacillus acidophilus and Bifidobacterium spp. in yoghurts. This study investigated methods to protect these bacteria from oxygen exposure. To confirm the accuracy of the reported survival estimates of L. acidophilus or Bifidobacterium spp. in yoghurts, the reliability of several enumeration media was evaluated with different commercial yoghurts. None of the media however, was found reliable thereby casting doubts on the reported cell numbers of probiotic bacteria in yoghurts. After much research,it was found that although oxygen can be detrimental to L. acidophilus and Bifidobacterium spp.in culture broths, it may not be significant for their poor survival in yoghurts. Nevertheless, techniques such as oxidative stress stress adaption, alternative packaging materials and microencapsulation as investigated in this study, can serve as general protective techniques to help yoghurt manufacturers in maintaining the recommended numbers of probiotic bacteria in their products. This would eventually assist in the efficient delivery of probiotic health benefits to yoghurt consumers.Doctor of Philosphy (PhD)
10
Mathias, Elizabeth. "Exopolysaccharides of the Pseudomonas aeruginosa Biofilm Matrix". Ohio University Honors Tutorial College / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1400069245.
Testo completo
11
Bernhardt, Anne, Markus Wehrl, Birgit Paul, Thomas Hochmuth, Matthias Schumacher, Kathleen Schütz e Michael Gelinsky. "Improved Sterilization of Sensitive Biomaterials with Supercritical Carbon Dioxide at Low Temperature: Research Article". Public Library of Science, 2015. https://tud.qucosa.de/id/qucosa%3A29150.
Testo completoAbstract (sommario):
The development of bio-resorbable implant materials is rapidly going on. Sterilization of those materials is inevitable to assure the hygienic requirements for critical medical devices according to the medical device directive (MDD, 93/42/EG). Biopolymer-containing biomaterials are often highly sensitive towards classical sterilization procedures like steam, ethylene oxide treatment or gamma irradiation. Supercritical CO2 (scCO2) treatment is a promising strategy for the terminal sterilization of sensitive biomaterials at low temperature. In combination with low amounts of additives scCO2 treatment effectively inactivates microorganisms including bacterial spores. We established a scCO2 sterilization procedure under addition of 0.25% water, 0.15% hydrogen peroxide and 0.5% acetic anhydride. The procedure was successfully tested for the inactivation of a wide panel of microorganisms including endospores of different bacterial species, vegetative cells of gram positive and negative bacteria including mycobacteria, fungi including yeast, and bacteriophages. For robust testing of the sterilization effect with regard to later application of implant materials sterilization all microorganisms were embedded in alginate/agarose cylinders that were used as Process Challenge Devices (PCD). These PCD served as surrogate models for bioresorbable 3D scaffolds. Furthermore, the impact of scCO2 sterilization on mechanical properties of polysaccharide-based hydrogels and collagen-based scaffolds was analyzed. The procedure was shown to be less compromising on mechanical and rheological properties compared to established low-temperature sterilization methods like gamma irradiation and ethylene oxide exposure as well as conventional steam sterilization. Cytocompatibility of alginate gels and scaffolds from mineralized collagen was compared after sterilization with ethylene oxide, gamma irradiation, steam sterilization and scCO2 treatment. Human mesenchymal stem cell viability and proliferation were not compromised by scCO2 treatment of these materials and scaffolds. We conclude that scCO2 sterilization under addition of water, hydrogen peroxide and acetic anhydride is a very effective, gentle, non-cytotoxic and thus a promising alternative sterilization method especially for biomaterials.
12
Talwalkar, Akshat. "Studies on the oxygen toxicity of probiotic bacteria with reference to Lactobacillus acidophilus and Bifidobacterium spp". Thesis, View thesis, 2003. http://handle.uws.edu.au:8081/1959.7/629.
Testo completoAbstract (sommario):
Oxygen toxicity is considered significant in the poor survival of probiotic bacteria such as Lactobacillus acidophilus and Bifidobacterium spp. in yoghurts. This study investigated methods to protect these bacteria from oxygen exposure. To confirm the accuracy of the reported survival estimates of L. acidophilus or Bifidobacterium spp. in yoghurts, the reliability of several enumeration media was evaluated with different commercial yoghurts. None of the media however, was found reliable thereby casting doubts on the reported cell numbers of probiotic bacteria in yoghurts. After much research,it was found that although oxygen can be detrimental to L. acidophilus and Bifidobacterium spp.in culture broths, it may not be significant for their poor survival in yoghurts. Nevertheless, techniques such as oxidative stress stress adaption, alternative packaging materials and microencapsulation as investigated in this study, can serve as general protective techniques to help yoghurt manufacturers in maintaining the recommended numbers of probiotic bacteria in their products. This would eventually assist in the efficient delivery of probiotic health benefits to yoghurt consumers.
13
Phan, Due Thanh, e Thi Cuc Nguyen. "Study on culture conditions of several strains of toluene-degrading bacteria isolated from common ornamental houseplants: Research article". Technische Universität Dresden, 2014. https://tud.qucosa.de/id/qucosa%3A29097.
Testo completoAbstract (sommario):
This article studies the impact of some environmental conditions and the nutrition of culturing medium on the growth of bacteria and theirs capacity of toluene removal. The 5 bacterial strains isolated from leaf samples of three different common houseplants in Vietnam are Gram-negative, rod-shaped bacteria. The cells are single or arranged in chains. The cell size is relatively small and ranged from 0.7 to 2.5μm. These bacteria prefer the incubating temperature from 28°C to 32°C and a neutral pH 6.5 to 7.5. They are able to assimilate different nitrogen and carbon sources. In the liquid SH1 medium containing 200ppm toluene five selected strains have shown the ability to degrade toluene at a rate of 12.8 to 75.2% in comparison with the control at 30°C at a speed of 200rpm for over 120 hours. These 5 studied strains are potentially useful in bioremediation strategies to remove airborne toluene.5 chủng vi khuẩn có khả năng phân giải toluene được phân lập từ lá một số cây cảnh phổ biến ở Việt Nam là vi khuẩn G (-), dạng trực khuẩn và kích thước tế bào từ 0,7 – 2,5μm. Một số điều kiện môi trường nuôi cấy thích hợp cho 5 chủng vi khuẩn nghiên cứ gồm nhiệt độ 28°C-32°C, pH 6,5- 7,5, có khả năng đồng hoá nhiều nguồn nitơ và ba nguồn carbon khác nhau. Trong điều kiện môi trường dịch SH1 chứa 200ppm toluene, 5 chủng vi khuẩn này cho thấy khả năng phân giải toluene từ 12,8 – 75,2%. Đây là các chủng vi khuẩn có tiềm năng ứng dụng để loại bỏ toluene từ không khí ô nhiễm.
14
Lekganyane, Maleho Annastasia. "Isolation and characterization of antibacterial compounds from five selected plants used against bacteria which infects wounds". Thesis, University of Limpopo, 2015. http://hdl.handle.net/10386/1259.
Testo completoAbstract (sommario):
Thesis (M.Sc. (Microbiology)) --University of Limpopo, 2015Five plant species: Ziziphus mucronata, Senna italica, Lantana camara, Ricinus communis and Lippia javanica, were selected for this study based on their use in traditional medicine. In preliminary screening, crude extracts were prepared using hexane, dichloromethane (dcm), acetone and methanol. Phytochemical profiles on Thin Layer Chromatography plates of the extracts were obtained by developing the plates in mobile phases of varying polarity. Tests for compounds such as tannins, flavonoids, alkaloids, phlobatannins, terpenes, steroids, cardiac glycosides and saponins were carried out. Antibacterial activity of the extracts was carried out using microdilution assay for Minimum Inhibitory Concentration and bioautography against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Enterococcus faecalis. Antioxidant activity of the extracts was performed using the 2, 2, diphenyl-1-picrylhydrazyl (DPPH) assay. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay and Phagoburst test were used to investigate the toxic effects and anti-inflammatory activity of the extracts on mouse Raw 264.7 macrophage cells, respectively. The presence of phytochemicals was observed on the chromatograms after the plates were sprayed with vanillin sulphuric acid reagent. The dcm extracts of the plants showed antibacterial activity against the selected bacterial species on the bioautograms. Senna italica and Z. mucronata showed the most activity bands on the bioautograms. Lippia javanica had the lowest MIC average of 0.56 mg/ml. Antioxidant activity was observed in the extracts of L. javanica and R. communis. The extracts promoted proliferation of the mouse macrophage cells Raw 264.7 at concentrations ranging from 0.31 mg/ml and 0.08 mg/ml. Senna italica leaves were selected for isolation of antibacterial compounds. The isolated compound was analysed on 1H and 13C nuclear magnetic resonance (NMR) and Mass Spectrometry (MS) for structural analysis. The structure could not be elucidated due to impurities in the compound but the tentative structure is a branched chain alkane with at least one ether linkage per repeating unit. Therefore the study shows that there are plant components with biological activities against wound infecting bacteria and a single lead compound was identified.
the National Research Foundation
15
Klima, Cassidy L., e University of Lethbridge Faculty of Arts and Science. "Characterization of the genetic diversity and antimicrobial resistance in Mannheimia haemolytica from feedlot cattle". Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, c2009, 2009. http://hdl.handle.net/10133/2517.
Testo completoAbstract (sommario):
Mannheimia haemolytica is an opportunistic pathogen in cattle and the main bacterial agent in bovine respiratory disease. Despite its economic importance, few studies have characterized the genetic diversity of M. haemolytica, particularly from feedlots. Three genotyping techniques (BOX-PCR, (GTG)5-PCR and PFGE) were compared to discriminate M. haemolytica and strains from the family Pasteurellaceae. PFGE was the most discriminating and repeatable, although BOX-PCR was most accurate in clustering isolates together according to species.
Mannheimia haemolytica was isolated from nasal swab samples collected from cattle upon entry and exit from two feedlots in southern Alberta. These were characterized by PFGE and antimicrobial susceptibility using a disk-diffusion assay. Select gene determinants were screened for using PCR. PFGE analysis revealed the isolates to be highly diverse. Ten percent of the isolates exhibited resistance. At present, the development and spread of antimicrobial resistance in M. haemolytica observed within the feedlots examined appears to be low.xi, 116 leaves : ill. ; 29 cm
16
Walz, Paul S. "Influence of pathogenic bacterial determinants on genome stability of exposed intestinal cells and of distal liver and spleen cells". Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biology, c2011, 2011. http://hdl.handle.net/10133/3405.
Testo completoAbstract (sommario):
Most bacterial infections can be correlated to contamination of consumables such as food and water. Upon contamination, boil water advisories have been ordered to ensure water is safe to consume, despite the evidence that heat-killed bacteria can induce genomic instability of exposed (intestine) and distal cells (liver and spleen). We hypothesize that exposure to components of heat-killed Escherichia coli O157:H7 will induce genomic instability within animal cells directly and indirectly exposed to these determinants. Mice were exposed to various components of dead bacteria such as DNA, RNA, protein or LPS as well as to whole heat-killed bacteria via drinking water. Here, we report that exposure to whole heat-killed bacteria and LPS resulted in significant alterations in the steady state RNA levels and in the levels of proteins involved in proliferation, DNA repair and DNA methylation. Exposure to whole heat-killed bacteria and their LPS components also leads to increased levels of DNA damage.xiv, 132 leaves : ill. (chiefly col.) ; 29 cm
17
Milbrandt, Eric Charles. "Microbial ecology of South Slough sediments : community composition of bacteria and patterns of occurrence". Thesis, Thesis (Ph. D.)--University of Oregon, 2003, 2003. http://hdl.handle.net/1794/9965.
Testo completo
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OCAÑA, DE JESUS ROSA LAURA 543020, e DE JESUS ROSA LAURA OCAÑA. "Penetración y permanencia de Escherichia coli y Salmonella en plantas y frutos de tomate (Licopersicum sculentum Mill)". Tesis de doctorado, Universidad Autónoma del Estado de México, 2018. http://hdl.handle.net/20.500.11799/68749.
Testo completoAbstract (sommario):
Se evaluó la capacidad de E. coli y Salmonella serovar Enteritidis de penetrar, permanecer y moverse en plantas y frutos de tomate.La presencia de bacterias patógenas, como Escherichia coli y Salmonella, afecta la calidad e inocuidad de las hortalizas que se consumen en fresco y se relaciona con graves problemas de salud. El tomate procedente de México es una de las hortalizas que ha presentado alertas sanitarias por la presencia de enteropatógenos. El objetivo del presente estudio fue detectar la presencia de Escherichia coli y Salmonella en cinco localidades del Estado de México, así como evaluar la capacidad de E. coli y Salmonella serovar Enteritidis de penetrar, permanecer y moverse en plantas y frutos de tomate. El estudio comprendió dos etapas (E): EI. Para detectar la presencia de enteropatógenos se determinó la calidad microbiológica de frutos de tomate producidos bajo condiciones de invernaderos en cinco Municipios del Estado de México. Se realizó un análisis microbiológico de muestras de agua de riego, suelo y de 100 frutos de tomate de la variedad Cid para determinar Mesófilos Aerobios, Coliformes Totales y Coliformes Fecales. Se utilizo la metodología establecida por las Normas Oficiales Mexicanas y se compararon los recuentos con los límites máximos permisibles. E II. Para evaluar la capacidad de E. coli y Salmonella serovar Enteritidis de penetrar, permanecer y moverse en plantas y frutos de tomate, se siguió un diseño experimental completamente al azar, para lo cual se estableció un cultivo de tomate (variedad “Cid”) en condiciones de invernadero y se evaluaron cuatro tratamientos, T1 (E. coli O157:H7), T2 (EcT O157:H16), T3 (EcH O105ab), T4 (Salmonella Enteritidis) y el grupo testigo. Los tratamientos costaron con 100 plantas cada uno y cuatro formas de inoculación: en el sustrato, en el tallo, en el pecíolo y en el pedúnculo. Se realizaron muestreos en etapa vegetativa, floración, fructificación y madurez fisiológica para cuantificar en placa las xii UFC/g y así identificar la movilidad en los órganos de la planta separados al punto de inoculación. Los resultados de la EI en agua para Coliformes Totales y Fecales se encontraron dentro de los parámetros permitidos por la norma NOM-127-SSA1-1999. El análisis realizado en suelo demostró la ausencia de estos microorganismos. Para los frutos, el nivel de microorganismos de Mesófilos Aerobios se encontró dentro de los límites máximos permitidos por la norma NOM- 093-SSA1-1994. Para Coliformes Fecales, los municipios de Coatepec Harinas y Texcaltitlán sobrepasaron el límite permitido por la misma norma. En la EII a los 120 días, la recuperación de bacterias en la planta fue del 23 % (E. coli O157:H7), 28 % (EcT O157:H16), 55 % (EcH O105ab) y 35 % (Salmonella Enteritidis) con la inoculación al sustrato, mientras que con la inoculación por punción, la recuperación fue (en igual orden) del 5 %, 3 % , 4 % y 8 % a los 30 días; del 42 %, 39 %, 13 % y 36 % a los 65 días y del 37 %, 35 %, 30 % y 20 % a los 90 días. Las cepas utilizadas mostraron la capacidad de entrar a la planta de tomate y de permanecer en ella y transportarse hasta llegar al fruto, sin producir síntomas que indiquen su presencia, por lo que el consumo de sus frutos implica riesgos a la salud.
FE057/2012 Financiado por PROMEP
19
Kim, Jeffrey. "Antimicrobial Use and Resistance in Zoonotic Bacteria Recovered from Nonhuman Primates". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460912847.
Testo completo
20
Miller, Craig William, University of Western Sydney, of Science Technology and Environment College e of Science Food and Horticulture School. "A study of packaging methods to reduce the dissolved oxygen content in probiotic yoghurt". THESIS_CSTE_SFH_Miller_C.xml, 2003. http://handle.uws.edu.au:8081/1959.7/633.
Testo completoAbstract (sommario):
Probiotic bacteria are added to commercial yoghurts as adjunct cultures, to impart health benefits to consumers. To gain maximum therapeutic benefit, the bacteria must remain viable over the shelf life of the yoghurt. Studies have shown, however, that the viability of these bacteria decreases significantly over this period and in some products, is negligible prior to the expiry date. Some strains of probiotic bacteria are oxygen sensitive. Yoghurt has been found to contain a significant concentration of dissolved oxygen and it has been proposed that this has a negative effect on probiotic viability. In this research, several tests were conducted and observations made. Experiments were conducted with non-commercial probiotic cultures to observe the effect of low oxygen environment on probiotic viability. No significant difference existed in viability between probiotic bacteria stored in oxygen reduced yoghurt and regular yoghurt. All yoghurt stored in oxygen barrier packaging material displayed enhanced shelf-life properties, this was observed in replicated experiments. Oxygen barrier packaging combined with an oxygen scavenging material was found to be the most effective oxygen removal system, particularly when used with set type yoghurt.Doctor of Philosophy (PhD)
21
Matlola, Nthane Martha. "The in vitro anti-mycobacterial activities of the novel tetramethylpiperidyl-substituted phenazines, B4121 and B4128". Thesis, University of Pretoria, 1999. http://hdl.handle.net/2263/24462.
Testo completoAbstract (sommario):
The intra- and extracellular activities of 2 novel tetramethylpiperidine (TMP)-substituted phenazines, B4121 and B4128 against Mycobacterium tuberculosis H37R (ATCC 27294) were determined and compared with those of clofazimine (B663). Clofazimine, together with B4121 and B4128, were also tested for their activities against drug-resistant strains of M.tuberculosis. Both B4121 and B4128 were significantly more active than clofazimine against M.tuberculosis, including multidrug-resistant clinical strains of this microbial pathogen, demonstrating a lack of cross resistance between the riminophenazines and standard anti-tuberculous drugs. Using M.tuberculosis-infected monocyte-derived macrophages both B4121 and B4128 were found to possess intracellular activity, which was superior to that of both clofazimine and rifampicin. The relationship between anti mycobacterial action of the TMP-subsitituted phenazines and clofazimine and the effects of these agents on microbial PLA2 activity, cation (K+, Ca2+) fluxes and energy metabolism (ATP) was also investigated. PLA2 and cation fluxes were measured by radiometric procedures, while microbial ATP was assayed using a luciferin/luciferase chemiluminescence method. All 3 riminophenazines, particularly B4128 caused dose-related enhancement of microbial PLA2 activity, which was associated with inhibition of K+-influx and enhancement of uptake of Ca2+. The results of kinetics studies demonstrated that riminophenazine-mediated enhancement of PLA2 activity and inhibition of K+ uptake in mycobacteria are rapidly-occurring and probably related events that precede, by several minutes, any detectable effects on microbial ATP concentrations and uptake of Ca2+. Inclusion of the extracellular and intracellular Ca2+-chelating agents EGTA and BAPTA, respectively, individually or in combination, did not prevent the effects of the riminophenazines on mycobacterial PLA2 (enhancement) or K+ transport (inhibition), whereas α-tocopherol, which neutralizes PLA2 primary hydrolysis products, antagonized the inhibitory effects of the riminophenazines on microbial K+ uptake. These results demonstrated that the riminophenazine-mediated enhancement of PLA2 is a Ca2+-independent event. The involvement of PLA2 in the antimicrobial activity of the riminophenazines was supported by the observation that added, exogenous Iysophosphotidylcholine (a primary hydrolysis product of PLA2 action on membrane phospholipids) also inhibited K+ transport and growth of mycobacteria. Enhancement of endogenous PLA2 as a mechanism of riminophenazine-mediated disruption of cation transport and antimycobacterial activity was further investigated using the conventional calcium-mobilizing stimuli, calcium ionophore A23187 and thapsigargin. Both agents, but A23187 in particular caused in dose-related enhancement of microbial PLA2 activity, which was associated with inhibition of K+ influx and growth. Influx of Ca2+ into A23187- and thapsigargin-treated mycobacteria was observed using both radiometric and FURA-2-based spectrofluorimetric procedures. Exposure of the mycobacteria to these agents resulted in an immediate increase in uptake of Ca2+, which implies that enhancement of PLA2 activity in calcium-mobilizing stimuli-treated mycobacteria is Ca2+ dependent. In conclusion, the TMP-substituted phenazines possess anti mycobacterial properties which are superior to those of clofazimine, particularly against intraphagocytic M.tuberculosis. The superior anti mycobacterial properties of these agents is paralleled by their potentiating effects on microbial PLA2 and consequent inhibitory action on uptake of K+, particularly in the case of B4128. Mycobacterial PLA2 and K+ transporters may therefore represent novel targets for antimicrobial chemotherapy.Thesis (DPhil (Medical Immunology))--University of Pretoria, 2007.
Immunology
unrestricted
22
Hardison, Rachael Lake. "Haemophilus pathogenesis during otitis media: Influence of nutritional immunity on bacterial persistence and intracellular lifestyles". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1540483623343597.
Testo completo
23
Jankovic, Dragana. "Direct selection and phage display of the Lactobacillus rhamnosus HN001 secretome : a thesis presented to Massey University in partial fulfillment of the requirements for the degree of Doctor of Philosophy". Massey University, 2008. http://hdl.handle.net/10179/869.
Testo completoAbstract (sommario):
Bacteria communicate with their hosts in part via surface, secreted and transmembrane proteins (collectively the secretome) resulting in probiotic (beneficial) or pathogenic (harmful) outcomes to the host. Therapeutic benefits of probiotic bacteria have been shown previously, but the molecular mechanisms and the health-promoting effector components involved are still being elucidated. Some evidence suggests that probiotic bacteria can competitively adhere to intestinal mucus and displace pathogens. The adherence of probiotic bacteria to human intestinal mucus and cells appears to be mediated, at least in part, by secretome proteins. Secretome proteins-encoding open reading frames can be identified in bacterial genome sequences using bioinformatics. However, functional analysis of the translated secretome is possible only if many secretome proteins are expressed and purified individually. Phage display technology offers a very efficient way to purify and functionally characterise proteins by displaying them on the surface of the bacteriophage. While a phage display system for cloning secretome proteins has been previously reported it is not efficient for enrichment and display of Gram-positive secretome proteins. In this study a new phage display system has been developed and applied in direct selection, identification, expression and purification of Gram-positive Lactobacillus rhamnosus strain HN001 secretome proteins. The new phage display system is based on the requirement of a signal sequence for assembly of sarcosyl-resistant filamentous phage virions. Using this system 89 secretome open reading frames were identified from a library of only 106 clones, performing at least 20-fold more efficiently than the previously reported enrichment method. Seven of the identified secretome proteins are unique for L. rhamnosus HN001. A L. rhamnosus HN001 shot-gun phage display library was also constructed to capture proteins that mediate adhesion or aggregation, initial steps in establishing host-microbe contact or forming multicellular aggregates, both of which may lead to beneficial effects – colonisation of the gastro-intestinal tract and exclusion of pathogens. In search for proteins involved in adhesion, a L. rhamnosus HN001 shot-gun phage display library was screened against the human extracellular matrix component fibronectin commonly used as binding target by bacteria that colonise diverse tissues. This screen selected, instead of a fibronectin-binding protein, a protein that binds to avidin, used to immobilise biotinylated fibronectin. Affinity screening of the shot-gun library for binding to L. rhamnosus HN001 cells identified a secretome protein, Lrh33, as an HN001-cell surface binding protein. This protein contains two bacterial immunoglobulin-like domains type 3. Analysis of phage-displayed nested deletions of Lrh33 determined that the proximal (N-terminal) immunoglobulin-like domain is not sufficient for binding; only the constructs displaying both domains demonstrated binding to HN001. Lrh33 does not have any similarity to previously identified Lactobacillus-binding proteins and no match in the NCBI database (at a cutoff value of > e-13), hence it represents potentially a new type of bacterial auto-aggregation protein.
24
Nguyen, Thi Thanh Tra, e Van Duy Nguyen. "Biodiversity of major bacterial groups in association with agarwood (Aquilaria crassna) in Khanh Hoa province, Vietnam: Research article". Technische Universität Dresden, 2014. https://tud.qucosa.de/id/qucosa%3A29083.
Testo completoAbstract (sommario):
Agarwood mainly formed by Aquilaria species is an economically and pharmaceutically important natural product used for the production of incense, perfumes and traditional medicines in Asia. Endophytic bacteria are potentially important in producing pharmaceutical compounds found in the plants. The aim of this research is to isolate, classify and identify major endophytic bacteria groups associated with agarwood of Aquilaria crassna species in Khanh Hoa province, Vietnam. Agarwood samples were collected and surface-sterilized, and total endophytic bacteria were isolated on Tryptic Soy Agar by the spread plate method. Major bacterial groups were classified according to the Bergey’s system. The 16S rRNA gene fragments were amplified using PCR method, and bacterial isolates were identified using this gene sequence similarity based method. The results showed that from 0.121 g of agarwood, total 26 bacterial isolates were purified and divided into 7 separated groups, in which the group II of Gram-positive spore-forming bacteria was the most dominant. Especially, two dominant strains, T14 of group II, and T15 of group VII, were identified as Bacillus pumilus and Alcaligenes faecalis, respectively.!To our knowledge, it is the first time that biodiversity of bacterial endophytes associated with agarwood from Aquilaria crassna in Vietnam has been reported, which requires of further study to understand the relationship of endophytic bacteria to agarwood-producing Aquilaria crassna species as well as explore their potential applications towards the development of valuable bioactive compounds.Trầm hương, chủ yếu được tạo ra từ các loài cây Dó (Aquilaria), là một sản phẩm tự nhiên có giá trị kinh tế và y học đã được sử dụng để sản xuất hương, nước hoa và các dược phẩm truyền thống ở châu Á. Vi khuẩn nội cộng sinh thực vật được cho là một nguồn quan trọng cho các dược phẩm có nguồn gốc thực vật. Mục tiêu của nghiên cứu này là nhằm phân lập, phân loại và định danh các nhóm vi khuẩn chính trên Trầm hương Khánh Hòa, Việt Nam. Các mẫu Trầm hương được thu nhận và vô trùng bề mặt dùng để phân lập vi khuẩn tổng số trên môi trường TSA bằng phương pháp trải đĩa. Các nhóm vi khuẩn chính được phân loại dựa theo hệ thống chuẩn Bergey. Đoạn gen mã hóa 16S rRNA được khuếch đại bằng phương pháp PCR, và các chủng vi khuẩn được định danh bằng phép so sánh độ tương đồng trình tự của đoạn gen này. Kết quả cho thấy từ 0,121 g mẫu trầm hương, chúng tôi đã phân lập được 26 chủng vi khuẩn và phân chúng vào 7 nhóm chính, trong đó nhóm II bao gồm các vi khuẩn Gram dương sinh bào tử là nhóm chiếm ưu thế nhất. Đặc biệt, có 2 chủng ưu thế là chủng T14 thuộc nhóm II và chủng T15 thuộc nhóm VII đã được định danh tương ứng là Bacillus pumilus và Alcaligenes faecalis.!Đây là nghiên cứu đầu tiên về đa dạng sinh học của các nhóm vi khuẩn chính trên Trầm hương Khánh Hòa. Vì vậy, cần có những nghiên cứu tiếp theo nhằm tìm hiểu mối quan hệ giữa các vi khuẩn nội cộng sinh với cây Dó bầu (Aquilaria crassna) tạo trầm cũng như khai thác những ứng dụng tiềm năng của các vi khuẩn này theo hướng phát triển các hoạt chất sinh học có giá trị.
25
Miller, Craig William. "A study of packaging methods to reduce the dissolved oxygen content in probiotic yoghurt". Thesis, View thesis, 2003. http://handle.uws.edu.au:8081/1959.7/633.
Testo completoAbstract (sommario):
Probiotic bacteria are added to commercial yoghurts as adjunct cultures, to impart health benefits to consumers. To gain maximum therapeutic benefit, the bacteria must remain viable over the shelf life of the yoghurt. Studies have shown, however, that the viability of these bacteria decreases significantly over this period and in some products, is negligible prior to the expiry date. Some strains of probiotic bacteria are oxygen sensitive. Yoghurt has been found to contain a significant concentration of dissolved oxygen and it has been proposed that this has a negative effect on probiotic viability. In this research, several tests were conducted and observations made. Experiments were conducted with non-commercial probiotic cultures to observe the effect of low oxygen environment on probiotic viability. No significant difference existed in viability between probiotic bacteria stored in oxygen reduced yoghurt and regular yoghurt. All yoghurt stored in oxygen barrier packaging material displayed enhanced shelf-life properties, this was observed in replicated experiments. Oxygen barrier packaging combined with an oxygen scavenging material was found to be the most effective oxygen removal system, particularly when used with set type yoghurt.
26
Liu, Yunhao. "Structural and biochemical analysis of HutD from Pseudomonas fluorescens SBW25 : a thesis submitted in fulfilment of the requirements for the degree of Master of Science in Molecular Biosciences at Massey University, Auckland, New Zealand". Massey University, 2009. http://hdl.handle.net/10179/1074.
Testo completoAbstract (sommario):
Pseudomonas fluorescens SBW25 is a gram-negative soil bacterium capable of growing on histidine as the sole source of carbon and nitrogen. Expression of histidine utilization (hut) genes is controlled by the HutC repressor with urocanate, the first intermediate of the histidine degradation pathway, as the direct inducer. Recent genome sequencing of P. fluorescens SBW25 revealed the presence of hutD in the hut locus, which encodes a highly conserved hypothetical protein. Previous genetic analysis showed that hutD is involved in hut regulation, in such a way that it prevents overproduction of the hut enzymes. Deletion of hutD resulted in a slow growth phenotype in minimal medium with histidine as the sole carbon and nitrogen source. While the genetic evidence supporting a role of hutD in hut regulation is strong, nothing is known of the mechanism of HutD action. Here I have cloned and expressed the P. fluorescens SBW25 hutD in E. coli. Purified HutD was subjected to chemical and structural analysis. Analytic size-exclusion chromatography indicated that HutD forms a dimer in the elution buffer. The crystal structure of HutD was solved at 1.80 Å (R = 19.3% and Rfree = 22.3%) by using molecular replacement based on HutD from P. aeruginosa PAO1. P. fluorescens SBW25 HutD has two molecules in an asymmetric unit and each monomer consists of one subdomain and two ß-barrel domains. Comparative structural analysis revealed a conserved binding pocket. The interaction of formate with a highly conserved residue Arg61 via salt-bridges in the pocket suggests HutD binds to small molecules with carboxylic group(s) such as histidine, urocanate or formyl-glutamate. The hypothesis that HutD functions via binding to urocanate, the hut inducer, was tested. Experiments using a thermal shift assay and isothermal titration calorimetry (ITC) analysis suggested that HutD binds to urocanate but not to histidine. However, the signal of HutD-urocanate binding was very weak and detected only at high urocanate concentration (53.23 mM), which is not physiologically relevant. The current data thus does not support the hypothesis of HutD-urocanate binding in vivo. Although the HutD-urocanate binding was not confirmed, this work has laid a solid foundation for further testing of the many alternative hypotheses regarding HutD function.
27
Dore, Dalin Shelley. "Grapevine rhizosphere bacteria : influence of diversity and function on two root diseases : a thesis submitted in fulfilment of the requirements for the degree of Master of Science at Lincoln University /". Diss., Lincoln University, 2009. http://hdl.handle.net/10182/1305.
Testo completoAbstract (sommario):
The overall goal of this research was to determine what, if any, role grapevine rhizosphere bacteria play in the differing susceptibilities of New Zealand grown rootstocks to Cylindrocarpon black foot disease. The size and diversity of bacterial populations associated with the rhizospheres of grapevine rootstocks: 101-14, 5C, Schwarzmann and Riparia Gloire were evaluated. Dilution plating showed that total bacterial (P=0.012, P=0.005 for NA and KB, respectively) and fluorescent Pseudomonad (P=0.035) rhizosphere counts differed between rhizosphere and bulk soils but did not correlate with the differing susceptibilities of the rootstock varieties to black foot. No varietal differences were found for spore forming bacteria (P=0.201). SSCP banding patterns showed that species diversity was similar for most rootstocks, but that there were some differences in the composition of bacterial populations, probably attributable to vigour. Some functional characteristics of the bacteria isolated from the rhizospheres of the most and least susceptible rootstock varieties were assessed to investigate their potential to suppress the pathogen. In dual culture, bacteria from Riparia Gloire, 101-14 and the control soil all had little ability to antagonise Cylindrocarpon destructans. However, they differed in their degrees of activity for glucanase (P=0.000), protease (P=0.001) and siderophores (P=0.000). In all tests, bacterial isolates from the rhizosphere of 101-14 had the largest number of active isolates (P≤0.002); however, those from Riparia Gloire had the greatest degree of positive responses for the glucanase and siderophore assays. Bacterial isolates from the control soil produced few glucanases and no siderophores, but had the highest degree of protease activity. Bands excised and sequenced from SSCP gels frequently matched to other ‘uncultured bacteria’ in GenBank, as well as to other bacterial phyla, classes and genera commonly isolated from soil and sediment samples. These included members of the Firmicutes, Proteobacteria (α, δ, γ), Verrucomicrobia, Acidobacteria and Chromatiales. The pathogenicity of C. destructans and Fusarium oxysporum was investigated by inoculating soil containing wounded ungrafted rootstocks of 101-14, 5C, Schwarzmann and Riparia Gloire. Results indicated that F. oxysporum might be a more aggressive pathogen than C. destructans. Inoculation with F. oxysporum or C. destructans increased disease severity, P=0.018 and P=0.056, respectively at 0 cm. Rootstock variety influenced disease severity caused by C. destructans (P<0.001) and F. oxysporum (P=0.090), with rootstocks 101-14 and 5C being most susceptible to C. destructans, and Riparia Gloire and Schwarzmann most susceptible to F. oxysporum. There was also an indication that inoculation with one pathogen increased plant susceptibility to the other, with increased F. oxysporum infection in the C. destructans inoculated treatments of Riparia Gloire and Schwarzmann (P<0.05). The effect of carbohydrate stress (leaf trimming) and inoculation on C. destructans disease severity, incidence, and rootstock rhizosphere bacterial populations was evaluated by inoculating the soil containing one year old plants of Sauvignon Blanc scion wood grafted to rootstocks 101-14 and Schwarzmann. Disease severity and incidence was similar for both Schwarzmann (8.4% and 29.3%, respectively) and 101-14 (14.9% and 31.0%, respectively). When data for the moderate and no stress treatments were combined, because their effects were similar, the disease severity was significantly higher for the highly stressed plants(P=0.043). Stress did not influence disease incidence (P=0.551). Infection occurred in the non-inoculated plants, but disease severity was higher in the plants inoculated with C. destructans than those that were not. Root dry weight of highly stressed plants was lower than in both the moderately stressed (P=0.000) and unstressed plants (P=0.003). An interaction between inoculation and stress (P=0.031) showed that inoculated and highly stressed plants had the lowest root dry weight but there was no effect of rootstocks (P=0.062). There was no significant effect of carbohydrate stress (P=0.259) or inoculation (P=0.885) on shoot dry weight. SSCP banding patterns showed that bacterial diversity was generally similar between rootstocks, but stress and inoculation altered rhizosphere bacterial communities. This study has demonstrated that functionality of grapevine rhizosphere bacteria do differ between grapevine rootstock varieties that have different susceptibilities to black foot disease, but that this role needs to be further investigated if more accurate and practically relevant conclusions are to be drawn.
28
Paquette, Nicholas Paul. "Caspase Mediated Cleavage, IAP Binding, Ubiquitination and Kinase Activation : Defining the Molecular Mechanisms Required for Drosophila NF-кB Signaling: A Dissertation". eScholarship@UMMS, 2009. https://escholarship.umassmed.edu/gsbs_diss/444.
Testo completoAbstract (sommario):
Innate immunity is the first line of defense against invading pathogens. Vertebrate innate immunity provides both initial protection, and activates adaptive immune responses, including memory. As a result, the study of innate immune signaling is crucial for understanding the interactions between host and pathogen. Unlike mammals, the insect Drosophila melanogasterlack classical adaptive immunity, relying on innate immune signaling via the Toll and IMD pathways to detect and respond to invading pathogens. Once activated these pathways lead to the rapid and robust production of a variety of antimicrobial peptides. These peptides are secreted directly into the hemolymph and assist in clearance of the infection.
The genetic and molecular tools available in the Drosophila system make it an excellent model system for studying immunity. Furthermore, the innate immune signaling pathways used by Drosophilashow strong homology to those of vertebrates making them ideal for the study of activation, regulation and mechanism. Currently a number of questions remain regarding the activation and regulation of both vertebrate and insect innate immune signaling. Over the past years many proteins have been implicated in mammalian and insect innate immune signaling pathways, however the mechanisms by which these proteins function remain largely undetermined.
My work has focused on understanding the molecular mechanisms of innate immune activation in Drosophila. In these studies I have identified a number of novel protein/protein interactions which are vital for the activation and regulation of innate immune induction. This work shows that upon stimulation the Drosophila protein IMD is cleaved by the caspase-8 homologue DREDD. Cleaved IMD then binds the E3 ligase DIAP2 and promotes the K63-polyubiquitination of IMD and activation of downstream signaling. Furthermore the Yersinia pestis effector protein YopJ is able to inhibit the critical IMD pathway MAP3 kinase TAK1 by serine/threonine-acetylation of its activation loop. Lastly TAK1 signaling to the downstream Relish/NF-κB and JNK signaling pathways can be regulated by two isoforms of the TAB2 protein. This work elucidates the molecular mechanism of the IMD signaling pathway and suggests possible mechanisms of homologous mammalian systems, of which the molecular details remain unclear.
29
Noyes, Marcus Blaine. "An Omega-Based Bacterial One-Hybrid System for the Determination of Transcription Factor Specificity". eScholarship@UMMS, 2009. https://escholarship.umassmed.edu/gsbs_diss/407.
Testo completoAbstract (sommario):
From the yeast genome completed in 1996 to the 12 Drosophilagenomes published earlier this year; little more than a decade has provided an incredible amount of genomic data. Yet even with this mountain of genetic information the regulatory networks that control gene expression remain relatively undefined. In part, this is due to the enormous amount of non-coding DNA, over 98% of the human genome, which needs to be made sense of. It is also due to the large number of transcription factors, potentially 2,000 such factors in the human genome, which may contribute to any given network directly or indirectly. Certainly, one of the central limitations has been the paucity of transcription factor (TF) specificity data that would aid in the prediction of regulatory targets throughout a genome.
The general lack of specificity data has hindered the prediction of regulatory targets for individual TFs as well as groups of factors that function within a common regulatory pathway. A large collection of factor specificities would allow for the combinatorial prediction of regulatory targets that considers all factors actively expressed in a given cell, under a given condition. Herein we describe substantial improvements to a previous bacterial one-hybrid system with increased sensitivity and dynamic range that make it amenable for the high-throughput analysis of sequence-specific TFs. Currently we have characterized 108 (14.3%) of the predicted TFs in Drosophilathat fall into a broad range of DNA-binding domain families, demonstrating the feasibility of characterizing a large number of TFs using this technology.
To fully exploit our large database of binding specificities, we have created a GBrowse-based search tool that allows an end-user to examine the overrepresentation of binding sites for any number of individual factors as well as combinations of these factors in up to six Drosophila genomes (veda.cs.uiuc.edu/cgi-bin/gbrowse/gbrowse/Dmel4). We have used this tool to demonstrate that a collection of factor specificities within a common pathway will successfully predict previously validated cis-regulatory modules within a genome. Furthermore, within our database we provide a complete catalog of DNA-binding specificities for all 84 homeodomains in Drosophila. This catalog enabled us to propose and test a detailed set of recognition rules for homeodomains and use this information to predict the specificities of the majority of homeodomains in the human genome.
30
Babatunde, Oluwaseun Oyeniyi. "Exploring the potential of Rhodobacter sphaeroides in photodynamic therapy of tumors". Bowling Green State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1624793446693196.
Testo completo
31
Babatunde, Oluwaseun Oyeniyi. "Exploring the potential of Rhodobacter sphaeroides in photodynamic therapy of tumors". Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1624793446693196.
Testo completo
32
Gammack, Graham F. "Bacterial attachment and activity in oligotrophic environments". Thesis, Heriot-Watt University, 1988. http://hdl.handle.net/10399/991.
Testo completo
33
Gavanescu, Irina Catrinel. "Autoantibodies to Centrosomes are Diagnostic for Human Scleroderma and Can Be Induced by Experimental Mycoplasma Infection in Mice: A Dissertation". eScholarship@UMMS, 2002. https://escholarship.umassmed.edu/gsbs_diss/76.
Testo completoAbstract (sommario):
The overall objective of this thesis work was to develop new insights into the etiology of scleroderma, a human systemic autoimmune disease, by analyzing the autoantibodies to centrosome antigens that develop during the disease. Centrosomes are perinuclear organelles that form microtubule arrays, including mitotic spindles that ensure the faithful segregation of chromosomes during mitosis.
These studies used a novel methodology to determine the prevalence of anti-centrosome autoantibodies in patients with scleroderma. Recombinant centrosome antigens were used to determine the antigenic specificity of anti-centrosome antibody subsets by immunoblotting. Centrosome marker antibodies were used in indirect immunofluorescence assays to distinguish centrosomes within the polymorphic staining pattern frequently given by scleroderma sera. We found that 43% of patients are autoreactive to centrosomes, a prevalence higher than has been reported for any other scleroderma autoantigen. Half of the centrosome-positive patients also had autoantibodies against other antigens used in scleroderma diagnosis. However, in the remaining half of these patients, anti-centrosome antibodies represented the sole class of autoantibodies that was detectable. Anti-centrosome antibodies were detected in only a small percentage of normal individuals and patients with other connective tissue diseases. These data suggest that anti-centrosome autoantibodies may represent a new diagnostic tool in scleroderma. Upon examination of anti-centrosome autoantibody development in an animal model, it appeared that this autoantibody specificity may develop in mice as a consequence of an infection.
An infectious agent was isolated by plaque-formation from carrier mice. Further characterization of the infectious agent was undertaken to obtain information on its physical, morphological and cytopathological properties. The infectious agent was identified by sequence and unique antigenic properties to be homologous to the pig pathogen Mycoplasma hyorhinis. When reintroduced into naive mice, the murine mycoplasma triggered anti-centrosome autoantibody development. While anti-centrosome autoantibodies of IgM isotype are part of the repertoire of naive unimmunized mice, mycoplasma infection specifically triggered the development of anti-centrosome IgG. Moreover, centrosome autoreactivity was prevented by antibiotic treatment. The autoantibody response evolved to recruit additional specificities, having IgM isotypes, reactive to endoplasmic reticulum-associated autoantigens.
34
McGinley, Susan. "Detecting Bacterial Pathogens in Oysters: Program Targets Campylobacter and Salmonella". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/622254.
Testo completo
35
McGinley, Susan. "Better Parasitic Wasps for Biological Control: Bacterial Symbionts Make a Difference". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/622173.
Testo completo
36
Li, Dan. "Novel Protein Materials based on Bacterial Efflux Pumps". University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1304692634.
Testo completo
37
Kim, Yeojung. "The Role of Hyaluronan in Innate Host Defense against Bacterial Infection". Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1499340461710323.
Testo completo
38
Mallick, Emily M. "A New Murine Model For Enterohemorrhagic Escherichia coli Infection Reveals That Actin Pedestal Formation Facilitates Mucosal Colonization and Lethal Disease: A Dissertation". eScholarship@UMMS, 2012. https://escholarship.umassmed.edu/gsbs_diss/601.
Testo completoAbstract (sommario):
Enterohemorrhagic Escherichia coli (EHEC) colonizes the intestine and produces the phage-encoded Shiga toxin (Stx) which is absorbed systemically and can lead to hemolytic uremic syndrome (HUS) characterized by hemolytic anemia, thrombocytopenia, and renal failure. EHEC, and two related pathogens, Enteropathogenic E. coli (EPEC), and the murine pathogen, Citrobacter rodentium, are attaching and effacing (AE) pathogens that intimately adhere to enterocytes and form actin “pedestals” beneath bound bacteria. The actin pedestal, because it is a unique characteristic of AE pathogens, has been the subject of intense study for over 20 years. Investigations into the mechanism of pedestal formation have revealed that to generate AE lesions, EHEC injects the type III effector, Tir, into mammalian cells, which functions as a receptor for the bacterial adhesin intimin. Tir-intimin binding then triggers a signaling cascade leading to pedestal formation. In spite of these mechanistic insights, the role of intimin and pedestal formation in EHEC disease remains unclear, in part because of the paucity of murine models for EHEC infection. We found that the pathogenic significance of EHEC Stx, Tir, and intimin, as well as the actin assembly triggered by the interaction of the latter two factors, could be productively assessed during murine infection by recombinant C. rodentium expressing EHEC virulence factors. Here we show that EHEC intimin was able to promote colonization of C. rodentium in conventional mice. Additionally, previous in vitro data indicates that intimin may have also function in a Tir-independent manner, and we revealed this function using streptomycin pre-treated mice. Lastly, using a toxigenic C. rodentium strain, we assessed the function of pedestal formation mediated by Tir-intimin interaction and found that Tir-mediated actin polymerization promoted mucosal colonization and a systemic Stx-mediated disease that shares several key features with human HUS.
39
Scott, B. B. "Identification and functional evaluation of cross-reactive antibodies to Gram-negative bacterial endotoxin in a blood donor population". Thesis, Open University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383285.
Testo completo
40
Kapadia, Jaimin Maheshbhai. "DNA transfer in the soil bacterium Rhodococcus". Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/565.
Testo completoAbstract (sommario):
Gene transfer plays an important role in bacterial evolution. Especially in an under explored species like Rhodococcus, a type of bacteria found in the soil. Rhodococcus has several applications in the pharmaceutical industry and in the production of antibiotics. Rhodococcus possess several unique sets of properties which makes it beneficial to have a reliable method of producing mutants of Rhodococcus. The goal of the experiment was to find an efficient way of forming Rhodococcus colonies with kanamycin resistant genes. The project began from an unexpected observation from an earlier experiment with Rhodococcus strain MTM3W5.2. where I attempted to transform this strain with a transposon via electro-transformation. The colonies that grew/ appeared transformants were screened to confirm the presence of kanamycin gene, however there was no amplified DNA seen on the PCR gel (i.e. absence of the kanamycin gene). The electro-transformant colonies were selected on LB plates containing different higher concentrations of kanamycin. Then the appeared transformants were again screened via disk diffusion assay and were classified into 3 different kanamycin resistant phenotypes. Majority of the “C” phenotypic colonies (i.e., high level resistance to kanamycin) appear to contain the kanamycin gene, but these colonies were less in numbers. This led us to try another method of gene transfer which is conjugation. Conjugation was carried on a double selection antibiotic plate containing both chloramphenicol (30 µg) and kanamycin (100 µg). The transconjugate colonies that appeared on the double selection plates were also screened by PCR, but none of the colonies had amplified DNA suggesting absence of the kanamycin gene. The colonies seen on the double selection plate were possibly due to spontaneous mutation or some type of unknown phenotypic variation. However, in the future, double selection plates with higher concentrations of antibiotics can possibly give us transconjugants with kanamycin genes.
41
Echeverría, Medina Mayra Fernanda. "Anti-staphylococcal properties of four plant extracts against sensitive and multi-resistant bacterial strains isolated from cattle and rabbits". Tesis de Licenciatura, Universidad Autonoma del Estado de México, 2018. http://hdl.handle.net/20.500.11799/95124.
Testo completoAbstract (sommario):
The aim of this study is to investigate the biopotency of methanolic extracts of Vitex mollis, Psidium guajava,
Dalbergia retusa, and Crescential alata leaves against various staphylococcal strains isolated from cattle and
rabbits. Methicillin-resistant S. aureus strains were isolated from cattle, while other strains were isolated from
rabbits using standard methodology. The total phytochemical phenolic and saponins contents were obtained
being the main groups of the antinutritional factors. The antimicrobial activity of the extracts against the
standard culture of S. aureus (control) and S. aureus isolated from cattle and rabbits were investigated comparatively
relative to that of oxacillin. It was found that both the control S. aureus and the isolated S. aureus are
susceptible to all the four plant extracts, and sensitive to oxacillin. Of all the S. aureus including the control,
MRSA2 is the most susceptible to all the extracts at 1000 μg/mL, except that of V. mollis where it is the least
susceptible. Among all the plant extracts, P. guajava is the most active against MRSA2 and SOSA2. Therefore, the
isolates from cattle (MRSA1 and MRSA2) are more susceptible to all the plant extracts than the isolates from
rabbits. Among all the rabbit isolates, CoNS3 is the least susceptible to the extracts. Since all the plant extracts
exhibit remarkable inhibitory activities against all the S. aureus strains, they are promising towards the production
of therapeutic drugs.
42
Toporski, Jan. "The preservation and detection of morphological and molecular bacterial biomarkers and their implications for astrobiological research". Thesis, University of Portsmouth, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369436.
Testo completo
43
Selenska-Pobell, Sonja, e Heino Nitsche. "Bacterial-Metal/Radionuclide Interaction: Basic Research and Bioremediation-Extendet Abstracts, Eurokonference, Forschungszentrum Rossendorf, December 2-4, 1998: Bacterial-Metal/Radionuclide Interaction: Basic Research and Bioremediation-Extendet Abstracts, Eurokonference, Forschungszentrum Rossendorf, December 2-4, 1998". Forschungszentrum Rossendorf, 1999. https://hzdr.qucosa.de/id/qucosa%3A21880.
Testo completo
44
Múfalo, Bruno Corrêa. "Avaliação da resposta imune de anticorpos contra proteínas recombinantes derivadas do Antígeno 1 de Membrana Aplical (AMA-1) de Plasmodium vivax em indivíduos de áreas endêmicas de malária do Brasil". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/9/9136/tde-26112013-100904/.
Testo completoAbstract (sommario):
O Antígeno 1 de Membrana Apical (AMA-1) de Plasmodium sp tem sido sugerido como candidato a compor uma vacina contra a malária. No presente estudo geramos cinco proteínas recombinantes baseadas em diferentes regiões do ectodomínio de AMA-1 de Plasmodium vivax, o qual compreende os domínios I a III, com intuito de mapear regiões particularmente imunogênicas da proteína. Cada uma das cinco proteínas recombinantes foi expressa em Eschericha coli a partir do vetor pET-28a em fusão com a cauda de histidina e purificadas por cromatografia de afinidade. As diferentes proteínas recombinantes foram comparadas, por ELISA, quanto ao reconhecimento por anticorpos IgM, IgG e subclasses de IgG de 100 indivíduos infectados por P. vivax procedentes de áreas endêmicas do Estado do Pará e 32 indivíduos não infectados que relataram terem sido acometidos de mais de 10 episódios prévios de malária procedentes do município de Terra Nova do Norte (MT). As freqüências de indivíduos que apresentaram anticorpos IgM foram mais baixas e variaram de 4% (DIII) a 36% (DII-III). Por outro lado, as freqüências de indivíduos que apresentaram anticorpos IgG para DI, DII, DIII, DI-II e DII-III foram 13%, 65%, 12%, 59% e 58%, respectivamente. Podemos observar que as proteínas recombinantes contendo o DII foram particularmente imunogênicas durante a infecção natural. Com o objetivo de avaliar se os epítopos reconhecidos nas cinco proteínas baseadas nos diferentes domínios estão expostos na proteína recombinante correspondente ao ectodomínio (DI-III) gerada previamente, realizamos ensaios de inibição por ELISA utilizando placas sensibilizadas com a proteína DI-III. Nossos resultados sugerem a presença de um maior número de epítopos comuns entre as proteínas recombinantes baseadas nos domínios I-II e ectodomínio de AMA-1. Além disso, observamos que a proporção de indivíduos que apresentaram anticorpos contra DII, DI-II e DII-III aumentou de acordo com o maior número de exposições prévias ao P. vivax. As subclasses de IgG que predominaram contra todas as proteínas foram IgG1, IgG3 e IgG4. Em conjunto, nossos resultados sugerem que as proteínas recombinantes contendo o DII podem ser exploradas em futuros estudos de indução de imunidade protetora contra malária vivax em primatas não-humanos.The Apical Membrane Antigen 1 (AMA-1) of Plasmodium sp has been suggested as a vaccine candidate against malaria. Herein, to identify novel antigenic epitopes on the Plasmodium vivax AMA-1 ectodomain, we have generated five recombinant proteins, comprising domains I to III. All recombinant proteins were expressed in Escherichia coli using the pET-28a vector system fused to hexahistidine tag for purification by affinity chromatography. Recognition of recombinant proteins by antibodies was evaluated using a panel of sera collected from onehundred P. vivax -infected patients resident in the State of Pará and from thirty-two non-infected individuals, living in the State of Mato Grosso and who have faced a minimum of ten malaria episodes. ELISA analyses demonstrated that protein recognition was highly dependent on IgG antibodies, raging from 13%, 65%, 12%, 59% up to 58%, respectively for DI, DII, DIII, DI-II and DII-III domains. Indeed, we have noticed a lower frequency of recognition, ranging from 4% (DIII) to 36% (DII-III), by sera from those individuals that presented IgM antibodies. Collectively, these data suggest that the DII domain is particularly immunogenic during natural infections. Next, to verify whether the epitopes recognized in these five different recombinant proteins were also expressed in a recombinant protein spanning domains I through III (DI-III), we carried out ELISA inhibition assays using plates coated with the DI-III recombinant protein. Our findings revealed the presence of a higher number of common epitopes among recombinant proteins based on domains I-II and the AMA-1 ectodomain. Moreover, we observed that the proportion of individuals who had presented antibodies against DII, DI-II and DII-III domains increased according to the previous number of P. vivax episodes. Overall, IgG1, IgG3 and IgG4 antibodies were prevalent to all proteins. Taken together, our results demonstrated that DII domain is highly recognized, mainly by IgG antibodies; and open promising perspectives to use this region as an experimental vaccine in non-human primates capable to induce protective immunity against vivax malaria.
45
Surujon, Defne. "Computational approaches in infectious disease research: Towards improved diagnostic methods". Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:109089.
Testo completoAbstract (sommario):
Thesis advisor: Kenneth WilliamsDue to overuse and misuse of antibiotics, the global threat of antibiotic resistance is a growing crisis. Three critical issues surrounding antibiotic resistance are the lack of rapid testing, treatment failure, and evolution of resistance. However, with new technology facilitating data collection and powerful statistical learning advances, our understanding of the bacterial stress response to antibiotics is rapidly expanding. With a recent influx of omics data, it has become possible to develop powerful computational methods that make the best use of growing systems-level datasets. In this work, I present several such approaches that address the three challenges around resistance. While this body of work was motivated by the antibiotic resistance crisis, the approaches presented here favor generalization, that is, applicability beyond just one context. First, I present ShinyOmics, a web-based application that allow visualization, sharing, exploration and comparison of systems-level data. An overview of transcriptomics data in the bacterial pathogen Streptococcus pneumoniae led to the hypothesis that stress-susceptible strains have more chaotic gene expression patterns than stress-resistant ones. This hypothesis was supported by data from multiple strains, species, antibiotics and non-antibiotic stress factors, leading to the development of a transcriptomic entropy based, general predictor for bacterial fitness. I show the potential utility of this predictor in predicting antibiotic susceptibility phenotype, and drug minimum inhibitory concentrations, which can be applied to bacterial isolates from patients in the near future. Predictors for antibiotic susceptibility are of great value when there is large phenotypic variability across isolates from the same species. Phenotypic variability is accompanied by genomic diversity harbored within a species. I address the genomic diversity by developing BFClust, a software package that for the first time enables pan-genome analysis with confidence scores. Using pan-genome level information, I then develop predictors of essential genes unique to certain strains and predictors for genes that acquire adaptive mutations under prolonged stress exposure. Genes that are essential offer attractive drug targets, and those that are essential only in certain strains would make great targets for very narrow-spectrum antibiotics, potentially leading the way to personalized therapies in infectious disease. Finally, the prediction of adaptive outcome can lead to predictions of future cross-resistance or collateral sensitivities. Overall, this body of work exemplifies how computational methods can complement the increasingly rapid data generation in the lab, and pave the way to the development of more effective antibiotic stewardship practices
Thesis (PhD) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology
46
Conesa, Agustín. "Detección de enterotoxinas en especies Staphylococcus coagulasa negativos aislados de muestras de leche bovina". Master's thesis, Conesa A. Detección de enterotoxinas en especies Staphylococcus coagulasa negativos aislados de muestras de leche bovina [Internet]. Universidad Nacional de Córdoba, 2018 [citado el 10 de marzo de 2020]. Disponible en: https://rdu.unc.edu.ar/handle/11086/15019, 2018. http://hdl.handle.net/11086/15019.
Testo completoAbstract (sommario):
Tesis - Maestría en Salud Pública - Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Escuela de Salud Pública, 2018Due to the potential danger to the public health posed by staphylococcal thermostable enterotoxins in dairy products, the need arose to investigate the potential ability to produce these toxins by different coagulase negative Staphylococcus species (CNS) isolated in bovine milk. These bacteria, which are becoming increasingly involved in herd infections, produce several virulence factors, including enterotoxins, and biofilm forming, which contributes to their permanence in the dairy sector by hindering the action of sanitizing agents and disinfectants. Given that the correct identification of staphylococcal species is essential for effective diagnosis and treatment, this work had among its objectives the genotypic identification of the isolates by PCR-RFLP analysis of the gap gene. The comparison of this method and the technique considered as definitive proof of species identification based on protein profiles, MALDI-TOF MS, allowed the former to be considered reliable for the identification of species of CNS isolates with a 93.9% coincidence. Regarding the virulence factors of SCN, the presence of enterotoxin genes and the phenotypic capacity to form biofilm were investigated, in order to later determine the association between both. An important number of enterotoxin-producing strains was obtained (78.1%). Among the genes found, the gene was the most prevalent, present in forty-seven of the 96 strains (48.9%). Regarding the phenotypic capacity of biofilm formation, the majority (92.7%), eighty nine of the 96 isolates analyzed, showed this ability. It is interesting to note that 60.4% (58/96) were strong formers. The ability to produce biofilm by different species of SCN with the presence of enterotoxins genes, highlights the potential risk of persistence of these bacteria in the food processing environment. Since the staphylococcal toxins remain in the products even after the thermal process, the results obtained in this study value the importance of having strict hygiene programs that ensure milking practices and animal health, and in this way help preserve consumer's health.
Ante el potencial peligro que representa para la salud pública la presencia de enterotoxinas estafilocócicas termoestables en productos lácteos, surgió la necesidad de investigar la potencial habilidad de producir estas toxinas por diferentes especies de Staphylococcus coagulasa negativos (SCN) aislados en leche bovina. Estas bacterias, que están adquiriendo cada vez mayor participación en las infecciones de los rebaños, producen varios factores de virulencia, entre ellos, enterotoxinas, y crecimiento en biofilm, lo cual contribuye a su permanencia en el sector productivo por dificultar la acción de agentes sanitizantes y desinfectantes. Dado que es esencial la correcta identificación de las especies estafilocócicas para un diagnóstico y tratamiento eficaz, este trabajo tuvo entre sus objetivos, la identificación genotípica de los aislamientos por análisis de PCR-RFLP del gen gap. La comparación de este método y la técnica considerada como prueba definitiva de identificación de especie basada en perfiles proteicos, MALDI-TOF MS, permitieron considerar al primero como confiable para la identificación de especie de los aislamientos de SCN con un 93,9% de coincidencia Sobre los factores de virulencia de SCN, se investigó, presencia de genes de enterotoxinas y capacidad fenotípica de formar biofilm, para luego determinar el grado de asociación entre ambas. Se obtuvo un importante número de cepas productoras de enterotoxinas (78,1%). Entre los genes encontrados, el gen sea fue el más prevalente, presente en cuarenta y siete de las 96 cepas (48,9%). En cuanto a la capacidad fenotípica de formación de biofilm, la mayoría (92,7%), ochenta y nueve de los 96 aislamientos analizados, presentaron esta habilidad. Es interesante destacar que el 60,4%, (58/96), resultaron fuertes formadores. La habilidad de producir biofilm por diferentes especies de SCN con presencia de genes para enterotoxinas remarca el riesgo potencial de la persistencia de estas bacterias en el ambiente de procesamiento de alimentos. Dado que las toxinas estafilocócicas permanecen en los productos aun luego del proceso térmico, los resultados obtenidos en este estudio valorizan la importancia de contar con estrictos programas de higiene que aseguren las prácticas de ordeño y la salud animal, y de este modo se ayude a preservar la salud del consumidor.
2020-11-19
Fil: Conesa, Agustín.Universidad Nacional de Villa María; Argentina
Fil: Conesa, Agustín. Consejo Nacional De Investigaciones Científicas y Técnicas. Centro Científico Tecnológico. Centro de Investigaciones y transferencia de Villa María; Argentina
47
Rho, Jung-hyun. "A novel mucin-desulfating sulfate-6-N-acetylglucosaminidase (sulfoglycosidase) from the anaerobic colonic bacterium Prevotella strain RS2". Thesis, University of Auckland, 2004. http://hdl.handle.net/2292/2275.
Testo completoAbstract (sommario):
Sulfate removal from sulfomucin is believed to be a rate-limiting step in sulfomucin degradation by bacteria from the digestive tract. A novel sulfomucin-desulfating enzyme has been discovered in the anaerobic bacterium, Prevotella strain RS2, which can grow on colonic mucin as its sole energy source. The enzyme, located in the periplasm, was assayed by measuring p-nitrophenol removal from the model substrate sulfate-6-N-acetylglucosamine-1-p-nitrophenol, sulfate-6-N-acetylglucosamine being the other product. This activity differs from that of sulfatases which remove the sulfate ester group from sulfate-6-N-acetylglucosamine and its analogues substituted at the Cl position. The enzyme has been termed a sulfate-6-N-acetylglucosaminidase or sulfoglycosidase (SGL). The SGL was purified to a single protein band of 100 kDa as analyzed by SDS-PAGE. The purified SGL protein was trypsin-digested and peptide fragments were sequenced. PCR and inverse PCR were then used to amplify the entire sg/ gene from Prevotella strain RS2 genomic DNA. After inserting the gene into a suitable plasmid, active recombinant SGL was expressed using an Escherichia coli expression system. The SGL was characterized using a selection of model substrates, and shown to be an exo-enzyme that removes non-reducing terminal sulfate-6-N-acetylglucosamine residues by glycosidic bond cleavage. When tested against its putative physiological substrate, sulfomucin, the only small molecular size product detected corresponded to a sulfate-6-N-acetylglucosamine residue. Thus the SGL can catalyze a reaction, formerly thought to be performed in bacteria by the combined actions of a N-acetylglucosamine-6-sulfatase and a N-acetylglucosaminidase. Inhibition studies on the SGL were carried out. Inhibitors of the SGL and those of the sulfatases were used to confirm the presence or absence of SGL-like activity in other bacteria that inhabit environments containing sulfomucin. Four isolates, including Prevotella strain RS2, of the thirteen strains tested, appeared to have SGL-like activity. This research on the SGL with its novel catalytic activity, suggests a new mechanism by which sulfomucin desulfation can occur. The physiological importance of the enzyme is postulated to be (i) to provide energy in the form of sulfate-6-N-acetylglucosamine, for the bacterium, (ii) to remove sulfate-6-N-acetylglucosamine groups present on mucin chains, thus creating or removing sites for different adhesins, and (iii) removal of inhibitory sulfate-6-N-acetylglucosamine groups from mucin chains that limit degradation of the chain by exoglycosidases and neuraminidases.
48
Selenska-Pobell, Sonja, e Heino Nitsche. "Bacterial-Metal/Radionuclide Interaction: Basic Research and Bioremediation-Extendet Abstracts, Eurokonference, Forschungszentrum Rossendorf, December 2-4, 1998". Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-30535.
Testo completo
49
Campbell, Regenia Beth Phillips. "Arrested and Aberrant: Effects of Amoxicillin in a Murine Model of Chlamydial Infection". Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etd/2269.
Testo completoAbstract (sommario):
Chlamydia trachomatis is the most common sexually transmitted bacterial disease agent worldwide, and, though frequently asymptomatic, can cause extreme pathology including infertility. Chlamydial species exhibit a unique biphasic developmental cycle. Once attached to a cell surface, infectious elementary bodies (EB) are internalized within an inclusion, the membrane-bound structure in which EB transform to noninfectious, replicable reticulate bodies (RB). After multiple rounds of division, RB condense to form EB, which are released and can infect new host cells. In culture, exposure to stressors, such as beta-lactam antibiotics, induce chlamydiae to reversibly detour from normal development into a noninfectious, viable state termed persistence. Cell culture data suggest that persistent forms are resistant to azithromycin (AZM), a front-line antibiotic, and are able to alter the host transcriptome. Though persistence has been described in culture for over 50 years, whether or not it: i) occurs in vivo; and ii) influences chlamydial pathogenesis, transmission and therapy has remained unresolved. To address these questions, we developed an animal model of persistent chlamydial infection using amoxicillin (AMX) treatment. AMX exposure decreased shedding of infectious chlamydiae in C. muridarum-infected mice without affecting chlamydial viability, demonstrating the presence of persistent chlamydiae. Shedding of infectious EB resumed following AMX cessation. Shedding data and microarray analyses suggested that host immunity might limit chlamydia’s exit from persistence in our model. Thus, we hypothesized that cyclophosphamide (CTX) treatment would increase the magnitude of chlamydial shedding observed after AMX-treatment cessation. CTX treatment increased post-AMX shedding by more than 10-fold compared to AMX-only controls. To determine whether persistent chlamydiae are resistant to antibiotic eradication in vivo, we induced persistence by administering AMX and treated mice with various AZM dosing regimes. Persistently infected mice demonstrated increased treatment failure following AZM therapy compared to productively infected controls. These data suggest that persistent chlamydiae are refractory to treatment in vivo and provide an explanation for the observation that treatment fails in some patients. In addition to creating the first fully characterized, experimentally tractable, in vivo model of chlamydial persistence, these experiments provide evidence that persistent/stressed chlamydial forms may serve as a long-term reservoir of infectious organisms in vivo.
50
Yuan, Lihui. "Quorum sensing regulated gene expression in Porphyromonas gingivalis". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010043.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--University of Florida, 2005.Typescript. Title from title page of source document. Document formatted into pages; contains 134 pages. Includes Vita. Includes bibliographical references.