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No description available.

by Wynstan, H.K. Cheuk. / Thesis submitted in: Dec., 1997. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 57-65). / Abstract also in Chinese. / Chapter I. --- ABSTRACT --- p.i / Chapter II. --- ACKNOWLEDGMENTS --- p.iii / Chapter III. --- TABLE OF CONTENTS --- p.iv / Chapter IV. --- LIST OF TABLES --- p.viii / Chapter V. --- LIST OF FIGURES --- p.ix / Chapter VI. --- INTRODUCTION --- p.1 / Chapter VII. --- LITERATURE REVIEW --- p.3 / Chapter A. --- Cordyceps militaris infection --- p.3 / Chapter B. --- The diagnostic criteria for C. militaris infection --- p.3 / Chapter 1. --- Telemorphic stage of C. militaris --- p.4 / Chapter 2. --- Anamorphic stage of C. militaris --- p.4 / Chapter C. --- The natural occurrence of C. militaris infection --- p.5 / Chapter D. --- The epizootiology of C. militaris infection --- p.5 / Chapter E. --- The values of studying C. militaris infection --- p.6 / Chapter 1. --- Potential insect biocontrol agent --- p.6 / Chapter 2. --- Exploitation of medicinal values --- p.8 / Chapter (i) --- Chemical constituents --- p.8 / Chapter (ii) --- Pharmacological action --- p.9 / Chapter VIII. --- MATERIALS AND METHODS --- p.11 / Chapter A. --- Pathogen culture establishment --- p.11 / Chapter 1. --- Source of pathogen and strain maintenance --- p.11 / Chapter 2. --- Selection of the artificial medium for C. militaris --- p.11 / Chapter (i) --- Colony diameter --- p.11 / Chapter (ii) --- Enumeration of conidia --- p.12 / Chapter 3. --- Examination of the morphological features of C. militaris in selected agar medium of RF Agar --- p.13 / Chapter B. --- Host species establishment --- p.13 / Chapter 1. --- Source of host species and laboratory rearing --- p.13 / Chapter 2. --- Assessment of viable insect population --- p.13 / Chapter C. --- The Biological characteristics of C. militaris in RF broth --- p.14 / Chapter 1. --- Methods for the cultivation of C. militaris in RF broth --- p.14 / Chapter (i) --- Pathogen inoculum and culture medium --- p.14 / Chapter (ii) --- Culture conditions --- p.15 / Chapter 2. --- Techniques for harvesting --- p.15 / Chapter 3. --- Methodologies of various assessments --- p.15 / Chapter (i) --- Germination --- p.15 / Chapter (ii) --- Morphological developments --- p.16 / Chapter (iii) --- Biomass increase --- p.16 / Chapter (iv) --- Key enzymes profiles --- p.16 / Chapter a. --- Inocula preparation --- p.16 / Chapter 1. --- Extracellular enzymes --- p.16 / Chapter 2. --- Intracellular enzymes --- p.16 / Chapter b. --- Preliminary screening --- p.17 / Chapter c. --- Procedures for quantitative measure of selected enzymes --- p.17 / Chapter d. --- Eight selected key enzymes --- p.18 / Chapter 1. --- Esterase --- p.18 / Chapter 2. --- Lipase --- p.18 / Chapter 3. --- Peroxidase --- p.18 / Chapter 4. --- Acid phosphatase --- p.18 / Chapter 5. --- β- galactosidase --- p.19 / Chapter 6. --- N-acetyl-β-glucosaminidase --- p.19 / Chapter 7. --- Trypsin --- p.19 / Chapter 8. --- β-glucosidase --- p.20 / Chapter e. --- Total protein analysis --- p.20 / Chapter (v) --- Quantation of cordycepin --- p.20 / Chapter a. --- "Standard, mobile phase and reagents" --- p.20 / Chapter b. --- High Performance Liquid Chromatography (HPLC) apparatus --- p.20 / Chapter c. --- Assay procedures --- p.21 / Chapter D. --- C. militaris infection process --- p.22 / Chapter 1. --- "Sterilization of insect host, Antheraea pernyi" --- p.22 / Chapter 2. --- Criteria for eliminating unfit pupae for the infection experiments --- p.22 / Chapter 3 --- Techniques for inducing infection --- p.22 / Chapter (i) --- Cuticular contact --- p.22 / Chapter (ii) --- Injection --- p.23 / Chapter (iii) --- Dipping --- p.23 / Chapter 4. --- Assessment of gross infection and the percentage of parasitization --- p.24 / Chapter 5. --- Verification of Cordyceps infection --- p.24 / Chapter 6. --- Methodologies of histological and ultrastructural examinations --- p.24 / Chapter (i) --- Scanning Electron Microscopy (SEM) --- p.24 / Chapter a. --- "Sample preparation, fixation and dehydration" --- p.24 / Chapter b. --- Critical point drying --- p.25 / Chapter c. --- Mounting --- p.25 / Chapter d. --- SEM examination --- p.25 / Chapter (ii) --- Transmission Electron Microscopy (TEM) --- p.25 / Chapter a. --- "Sample preparation, fixation and dehydration" --- p.25 / Chapter b. --- Infiltration --- p.26 / Chapter c. --- "Semi-thin sectioning, ultra-thin sectioning and post-staining" --- p.26 / Chapter d. --- TEM examination --- p.27 / Chapter (iii) --- Light Microscopy (LM) --- p.27 / Chapter a. --- Sample preparation --- p.27 / Chapter b. --- Fixation and dehydration --- p.27 / Chapter c. --- Embedding --- p.28 / Chapter d. --- Sectioning and staining --- p.28 / Chapter e. --- LM examination --- p.28 / Chapter 7. --- Methodology of HPLC assay for cordycepin in infected host --- p.28 / Chapter 8. --- In vitro susceptibility testing of the microbes isolated from A. pernyi against cordycepin --- p.29 / Chapter (i) --- Isolation of microbes from the cuticle surface of the healthy A. pernyi --- p.29 / Chapter (ii) --- Isolation of microbes from the non-cuticle surface of the healthy A. pernyi --- p.29 / Chapter (iii) --- Isolation of microbes from the necrotic tissue of A pernyi --- p.29 / Chapter (iv) --- Conditions for incubation --- p.29 / Chapter (v) --- Identification of microbial isolates of A. pernyi --- p.30 / Chapter a. --- Fungal isolates --- p.30 / Chapter b. --- Bacterial isolates --- p.30 / Chapter (vi) --- Assay procedures of cordycepin susceptibility testing of isolated microbes --- p.31 / Chapter IX. --- RESULTS --- p.32 / Chapter A. --- Biological characteristics of C. militaris grown in vitro --- p.32 / Chapter 1. --- Selection of the artificial medium for C. militaris --- p.32 / Chapter 2. --- Morphological examinations of C. militaris in RF agar --- p.32 / Chapter (i) --- Appearance of C. militaris --- p.32 / Chapter (ii) --- Conidiogenesis --- p.33 / Chapter (iii) --- Morphological developments --- p.33 / Chapter 3. --- Physiological examinations of C. militaris in RF Broth --- p.34 / Chapter (i) --- Germination --- p.34 / Chapter (ii) --- Biomass and pH of the culture filtrate --- p.34 / Chapter 4. --- Biochemical examinations of C. militaris in RF Broth --- p.34 / Chapter (i) --- Key enzyme profiles --- p.34 / Chapter (ii) --- Quantitation of cordycepin --- p.35 / Chapter B. --- C. militaris infection of A pernyi --- p.35 / Chapter 1. --- Percentage of parasitization by cuticular contact methods --- p.35 / Chapter 2. --- Morphological examinations of C. militaris infection --- p.36 / Chapter (i) --- Gross infection of C. militaris --- p.36 / Chapter (ii) --- Site susceptibility of A.pernyi to C. militaris infection --- p.38 / Chapter (iii) --- Attachment of C. militaris --- p.38 / Chapter (iv) --- Penetration of A. pernyi by C. militaris hyphae --- p.38 / Chapter (v) --- Utilization of A. pernyi by C. militaris hyphae --- p.39 / Chapter 3. --- Biochemical examinations of C. militaris infection --- p.39 / Chapter (i) --- Cordycepin --- p.39 / Chapter 4. --- In vitro susceptibility testing of the microflora isolated from A. pernyi to cordycepin --- p.39 / Chapter (i) --- Isolation and identification of microflora associated with A. pernyi --- p.39 / Chapter (ii) --- Cordycepin susceptibility testing to microbes isolated from A. pernyi --- p.40 / Chapter X. --- DISCUSSION --- p.41 / Chapter A. --- Biological characteristics of C. militaris grown in vitro --- p.41 / Chapter 1. --- Medium selection --- p.42 / Chapter 2. --- Morphological characteristics of C. militaris in RF medium --- p.42 / Chapter 3. --- Biochemical characteristics of C. militaris in RF broth -enzymes production --- p.43 / Chapter 4. --- Biochemical characteristics of C. militaris in RF broth -cordycepin production --- p.45 / Chapter B. --- C. militaris infection of A. pernyi --- p.45 / Chapter 1. --- Induction method --- p.46 / Chapter 2. --- Host selection --- p.47 / Chapter 3. --- Site susceptibility --- p.48 / Chapter 4. --- Attachment --- p.48 / Chapter 5. --- Germination --- p.49 / Chapter 6. --- Penetration --- p.50 / Chapter 7. --- Tissue utilization by C. militaris --- p.52 / Chapter 8. --- Sexual reproduction --- p.53 / Chapter 9. --- Cordycepin --- p.54 / Chapter 10. --- Host susceptibility --- p.55 / Chapter XI. --- CONCLUSION --- p.56 / Chapter XII. --- LITERATURE CITED --- p.57 / Chapter XIII. --- TABLES --- p.66 / Chapter XIV. --- FIGURES --- p.74

No description available.

Escherichia coli est le commensal aérobie le plus fréquent du tube digestif de l’homme et des animaux à sang chaud et le bacille à Gram négatif pathogène opportuniste le plus souvent impliqué dans les infections intestinales et extra intestinales de l’homme. C’est une espèce clonale chez laquelle 4 groupes phylogénétiques principaux, A, B1, B2 et D ont été décrits. L’objectif de cette thèse est d’étudier l’adaptation de E. coli et les rapports de cette adaptation avec la structure génétique de l’espèce caractérisée par les 4 groupes phylogénétiques dans deux circonstances : le commensalisme intestinal de l’homme et de plusieurs espèces animales sauvages et domestiques, herbivores et omnivores d’une part et la virulence extra-intestinale mesurée par l’expression des gènes codants pour un sidérophore, la yersiniabactine, dont les gènes sont situés au sein de l’ilot de pathogénicité HPI (PAI IV). La répartition dans les 4 groupes phylogénétiques des souches commensales du tube digestif de 100 hommes et de 137 animaux a été étudiée par une technique de PCR en temps réel originale. Trois principaux entérocolitypes, correspondant à des associations préférentielles de phylogroupes ont été ainsi décrits comme plus fréquents en fonction de la nature des hôtes.Chez l’homme, les souches du groupe B2 ont été retrouvés exclusives chez 15 % des individus et ont été clairement distinctes des souches B2 des animaux sauvages par la plus grande fréquence de leurs facteurs de virulences (sfa/foc et pks). L’effet du fond génétique des sous groupes II, III et IX du groupe B2 sur l’expression de la virulence liée au HPI a été étudié dans un modèle murin de virulence extra-intestinale et dans un modèle d’amibe sociale Dictyostelium discoideum, pouvant être assimilé à un macrophage. Le HPI chez E. coli interagît avec la clonalité de l’espèce qui s’exprime par l’existence des sous-groupes de B2. Dans les modèles de virulence que nous avons développés, les mêmes gènes ont, en fonction du fond génétique des différents isolats naturels, des effets différents. / Escherichia coli is the most abundant aerobic bacteria of the human microbiota, and a major opportunistic pathogen in humans. It is the clonal species for wich main phylogenetic groups have been described. The aim of this thesis is to study E. coli adaptation through the genetic structure of the specis in two circumstances : the intestinal comensalism, and the extra-intestinal virulence estimated via expression of genes encoding for yersiniabactin, a major siderophore, located on a high patogenicity island (HPI). The repartition of the 4 phylogroups has been studied in faecal microbiota of 100 humans and 137 animals thanks to an original quantitative PCR assay. Three main enterocolitypes, corresponding to associations of phylogroups, have been described. In humans, B2 phylogroup strains were exclusive in 15% of individuals and were shown to be clearly distinct from animal B2 strains on the base of the presence of two virulence factors (sfa/foc and pks). The impact of the genetic background of the B2 sub-groups II, III an IX on the virulence based on HPI was studied in a mice model and in an amoeba model Dictyostelium discoideum. The HPI interacts with the clonality of the species represented by the existence of the B2 subgroups.

No description available.

An epidemic increase in severity and incidence of asochyta blight, caused by Ascochyta rabiei (Pass) Labrousse (teleomorph: <i>Didymella rabiei</i> (Kovachevski) v. Arx. Syn. <i>Mycosphaerella rabiei </i>Kovachevski), has occurred on chickpea (<i>Cicer arietinum</i> L.) crops in Saskatchewan over the past 5 growing seasons. In order to explore the nature of the outbreak, studies assessing population differences in pathogenicity and genetic variability were employed. Isolates of <i>A. rabiei</i> collected in 1998, 2001 and 2002 were inoculated onto 7 differential chickpea genotypes for pathogenicity testing. <p> Significant isolate by differential interaction occurred, but accounted for a low proportion of the total variability suggesting no genotype specific relationship exists between <i>A. rabiei</i> and <i>C. arietinum</i>. Furthermore, it was found that when averaged over all differentials, the isolates from 2001 and 2002 caused significantly greater disease than isolates from 1998, suggesting that the disease epidemic is in part due to a shift in the population to overall greater aggressiveness. The largest increase in disease severity was observed on the cultivar Sanford, which was widely grown in commercial chickpea fields before 1999. To evaluate the genetic diversity of different <i>A. rabiei</i> populations, 30 isolates from 1998 and 30 isolates from 2002 were compared with random amplified polymorphic DNA fingerprinting. Several clusters of isolates collected from either 1998 or 2002 were approximately 60% genetic similar suggesting divergence of these populations of <i>A. rabiei</i>. However, analysis of molecular variance showed that over 90% of the variation occurred within populations. Pairwise differences and gene diversity over loci showed that genetic diversity of the 2 populations had the same amount of genetic variability. Analysis of mating type distributions revealed that the populations from 1998, 2001 and 2002 did not significantly depart from a 1:1 ratio suggesting random mating of each population. Further supporting the hypothesis of a randomly mating population, linkage disequilibrium for both 1998 and 2002 populations was very low.

An epidemic increase in severity and incidence of asochyta blight, caused by Ascochyta rabiei (Pass) Labrousse (teleomorph: <i>Didymella rabiei</i> (Kovachevski) v. Arx. Syn. <i>Mycosphaerella rabiei </i>Kovachevski), has occurred on chickpea (<i>Cicer arietinum</i> L.) crops in Saskatchewan over the past 5 growing seasons. In order to explore the nature of the outbreak, studies assessing population differences in pathogenicity and genetic variability were employed. Isolates of <i>A. rabiei</i> collected in 1998, 2001 and 2002 were inoculated onto 7 differential chickpea genotypes for pathogenicity testing. <p> Significant isolate by differential interaction occurred, but accounted for a low proportion of the total variability suggesting no genotype specific relationship exists between <i>A. rabiei</i> and <i>C. arietinum</i>. Furthermore, it was found that when averaged over all differentials, the isolates from 2001 and 2002 caused significantly greater disease than isolates from 1998, suggesting that the disease epidemic is in part due to a shift in the population to overall greater aggressiveness. The largest increase in disease severity was observed on the cultivar Sanford, which was widely grown in commercial chickpea fields before 1999. To evaluate the genetic diversity of different <i>A. rabiei</i> populations, 30 isolates from 1998 and 30 isolates from 2002 were compared with random amplified polymorphic DNA fingerprinting. Several clusters of isolates collected from either 1998 or 2002 were approximately 60% genetic similar suggesting divergence of these populations of <i>A. rabiei</i>. However, analysis of molecular variance showed that over 90% of the variation occurred within populations. Pairwise differences and gene diversity over loci showed that genetic diversity of the 2 populations had the same amount of genetic variability. Analysis of mating type distributions revealed that the populations from 1998, 2001 and 2002 did not significantly depart from a 1:1 ratio suggesting random mating of each population. Further supporting the hypothesis of a randomly mating population, linkage disequilibrium for both 1998 and 2002 populations was very low.

The species complex, Waitea circinata (WC) has been currently divided into five cultural types: var. circinata, var. oryzae, var. zeae, var. agrostis, and var. prodigus. These divisions are currently based on differences in their sclerotial morphology which have been supported by differences in their internal transcribed spacer region. Physiological differences such as optimal growth temperature, and morphological and pathogenic analyses as well as molecular biological techniques, were used to examine a broad WC collection coming from different geographic regions, and different susceptible hosts. The pathogenic examination showed that WC varieties are not host specific and can successfully infect both turfgrasses and cereals. Phylogenetic trees based on Neighbor-joining (NJ) and Maximum likelihood (ML) methods for three genomic regions (ITS, beta-tubulin, IGS1) showed support for only three of the five WC cultural types that have been described, namely Waitea circinata var. circinata, var. oryzae and var. zeae." / Waitea circinata varieties were characterized using molecular, morphological, physiological and pathological techniques. / Ontario Turfgrass Research Foundation, CONACYT (Ministry of Science from Mexico)

No description available.