The course of microsporidiosis caused by Encephalitozoon cuniculi in immunocompetent BALB/c mice and immunodeficient SCID mice was screened using molecular methods. The site of infection in organs was located using molecular and histology methods. The effectiveness of albendazole treatement and possibility of infection relapse after immunosuppresion (cyclosporine A, tacrolimus, mycofenolate mofetil) was also studied. Moreover, the course of excretion of microsporidial spores in feces was monitored during the whole time of experiment.

Among the most common endoparasites who infected small crustacean Daphnia pulex include microsporidia. These intracellular parasites appear to look like a simple single- celled organisms, but their cell structure and lifecycle prove the opposite. Microsporidia are species-specific. Although they infected most organisms of the animal kingdom, they are not yet sufficiently understood. This theses is inderectly followed up to the studies of waterflea Daphnia longispina and microsporidia Berwaldia schaefernai from the dam reservoirs The aim was to analyze closer microsporidian infection on host Daphnia pulex in a forest pool with simple enviroment, which included monitoring time dynamics of Daphnia population and identification infection caused by microsporidia Berwaldia singularis and yet unknown microsporidia labor-marked "HVH". Laboratory work included determination of zooplankton and parasites, calculation of prevalence, laboratory experiments with transmission of microsporidian infection between healthy and infected flea culture or by isolated spores. Genetic analysis of aquatic invertebrates from the forest pool, especially larvae of mite and mosquitos, helped make closer microsporidian life cycle and hypothesis about secondary hosts, for the presence of pathogen DNA using specific DNA...

Nosema bombycis est un parasite obligatoire intracellulaire et eukaryoitique microsporidia apparenté aux champignons. Cette microsporidie est l'agent responsable de la pébrine, maladie du ver à soie Bombyx mori qui inflige de sévères pertes économiques à la sériciculture mondiale. Nous avons étudié l'interactions N. bombycis-B. mori in vivo : l'infestation par N. bombycis démarre au niveau de l'épithélium intestinal antérieur, puis s'étend aux muscles et trachées adjacents. Les tissus plus distants sont ensuite infectés. Cependant, les réponses immune mélanisation et phagocytose, l'hémolymphe et les hémocytes sont les vecteurs de la dissémination de N. bombycis dans son hôte. Nous avons développé une approche protéomique pour identifier des protéines de tube polaire (PTP). Trois PTPs ont été caracterisés par immunocytochimie MET et MS/MS. Des motifs de séquence peptidique ont pu en être déduits par les programmes Peaks Online et DeNovoX, puis évalués par algorithmes Mascot et Sequest

No description available.

The original aim of my diploma thesis was examination of fixed samples of cladocerans from the Daphnia longispina species complex from reservoirs Vír and Vranov for the presence of 4 groups of microparasites: microsporidia, oomycetes, the protozoan Caullerya mesnili, and the yeast Metschnikowia bicuspidata. The next aim was to determine the effect of parasites on Daphnia fecundity, and determination of their spatial and temporal distribution within reservoirs. From the total number 4452 of examined Daphnia females, however, only 56 individuals were infected. This number was not sufficient for the planned analyses. As I recorded for all examined individuals the clutch size, I thus dealt to a large extent with an alternative issue: the temporal and spatial variation of, and the influence of environmental factors on Daphnia fecundity. Both studied reservoirs are characteristic by canyon-shaped profile that allows formation of environmental gradients on the horizontal as well as vertical axis. The results confirm that reservoir identity, season, and location within the reservoir (or gradient of food supply) have all significant effects on fecundity. During my work I have encountered difficulties associated with determining microparazites from fixed zooplankton samples. The appendix section of my thesis...

Les microsporidies sont des pathogènes intracellulaires obligatoires apparentés aux champignons. Elles infectent de nombreux animaux, dont le nématode Caenorhabditis elegans. La première microsporidie isolée d’une souche de C. elegans sauvage a été nommée Nematocida parisii. L’interaction entre N. parisii et C. elegans est devenue un puisant modèle pour l'étude des interactions hôte-pathogène. Cependant, ce modèle a été récemment découvert et de nombreux détails sur son écologie et sa biologie restaient inconnus. Notamment, nous ignorions l’incidence et la diversité des infections microsporidiennes chez C. elegans et autres nématodes dans la nature.A partir d’une collection de nématodes, de la famille des Rhabditidae, échantillonnés dans le monde entier, j’ai recensé un panel de 47 nématodes présentant des symptômes d’infection par des microsporidies. J’ai caractérisé moléculairement la diversité de ce parasite infectant ces nématodes et déterminé que N. parisii est la microsporidie la plus souvent responsable des infections chez C. elegans dans la nature. J’ai également décrit et nommé six nouvelles espèces de Nematocida. Au cours de mes travaux, j’ai aussi défini deux nouveaux genres de microsporidies génétiquement distincts de Nematocida, appelés Enteropsectra et Pancytospora. Mes travaux ont de plus détaillé la diversité qui existe chez les microsporidies parasites de nématodes. Ces microsporidies présentent des différences en terme de taille et forme de leurs spores, de leur tropismes tissulaire et intracellulaire chez l’hôte, de leur voie de sortie des cellules hôtes mais aussi de spectre d’hôtes. Mes résultats ont démontré que, dans la nature, les infections de C. elegans et autres nématodes par les microsporidies sont répandues et diverses.De plus, j’ai estimé la variation naturelle pour la sensibilité de C. elegans à l'infection par N. ausubeli. J’ai notamment comparé 10 souches naturelles de C. elegans en utilisant des tests de consommation alimentaire. Deux souches de C. elegans, JU1249 et JU2825, présentaient des niveaux contrastés de sensibilité, ce que j’ai interprété comme étant une différence de niveau de tolérance aux infections. Ces deux souches se sont révélées être de bons candidats pour une future caractérisation des loci génétiques associés à la variation de sensibilité de C. elegans aux infections microsporidiennes. Enfin, j’ai observé un effet surprenant de l'infection de C. elegans par les microsporidies. En effet, la présence du pathogène est capable de supprimer le déclin progressif de la fécondité à haute température chez certaines lignées de C. elegans. / Microsporidia are fungi-related intracellular pathogens that infect a great variety of animals, including the nematode Caenorhabditis elegans. The first microsporidia isolated from wild C. elegans was named Nematocida parisii in 2008. C. elegans and N. parisii have been used as a powerful model for the study of host-pathogen interactions. However, it was unclear how widespread and diverse microsporidia infections are in C. elegans or other related nematodes in the wild.By sampling rhabditid nematodes worldwide, we established a collection of 47 nematodes that displayed putative microsporidia infections. We characterized molecularly these infections and determined that N. parisii (or N. ironsii) is the most common microsporidia infecting C. elegans in the wild. We further described and named six new Nematocida species. In addition, we defined two new genera of nematode-infecting microsporidia, named Enteropsectra and Pancytospora, which are genetically distinct from Nematocida. Further investigations showed that these microsporidia are diverse in terms of spore size and shape, host tissue tropism, host cell intracellular localization, cellular exit route, host specificity pattern, etc. Overall, these findings illustrate the widespread and diverse microsporidia infections in C. elegans and related nematodes in the wild.We further assayed the natural variation of C. elegans in sensitivity to N. ausubeli infection, by comparing 10 C. elegans strains using food consumption tests. Two C. elegans strains, JU1249 and JU2825, displayed the largest sensitivity differences, which were suggested to be a result of the different tolerance between the two strains. These two strains are proven to be good candidates for future studies on the genetic loci associated with C. elegans sensitivity variation to microsporidian infections. Furthermore, I observed an exciting effect of host-pathogen interaction. Microsporidia infection is able to suppress the progressive decline in fertility in some C. elegans with the mortal germline phenotype (Mrt).

No description available.

Phylogenetic models generally assume a homogeneous, time reversible, stationary process. These assumptions are often violated by the real, far more complex, evolutionary process. This thesis is centered on non-homogeneous, lineage-specific, properties of molecular sequences. It consist several related but independent studies. LineageSpecificSeqgen, an extension to the Seq-Gen program, which allows generation of sequences with changes in the proportion of variable sites, is introduced. This program is then used in a simulation study showing that changes in the proportion of variable sites can hinder tree estimation accuracy, and that tree reconstruction under the best-fit model chosen using a relative test can result in a wrong tree. In this case, the less commonly used absolute model-fit was a better predictor of tree estimation accuracy. This study found that increased taxon sampling of lineages that have undergone a change in the proportion of variable sites was critical for accurate tree reconstruction and that, in contrast to some earlier findings, the accuracy of maximum parsimony is adversely affected by such changes. This thesis also addresses the well-known long-branch attraction artifact. A nonparametric bootstrap test to identify changes in the substitution process is introduced, validated, and applied to the case of Microsporidia, a highly reduced intracellular parasite. Microsporidia was first thought to be an early branching eukaryote, but is now believed to be sister to, or included within, fungi. Its apparent basal eukaryote position is considered a result of long-branch attraction due to an elevated evolutionary rate in the microsporidian lineage. This study shows that long-branch estimates and basal positioning of Microsporidia both correlate with increased proportions of radical substitutions in the microsporidian lineage. In simulated data, such increased proportions of radical substitutions leads to erroneous long-branch estimates. These results suggest that the long microsporidian branch is likely to be a result of an increased proportion of radical substitutions on that branch, rather than increased evolutionary rate per se. The focus of the last study is the intriguing case of Mesostigma, a fresh water green alga for which contradicting phylogenetic relationships were inferred. While some studies placed Mesostigma within the Streptophyta lineage (which includes land plants), others placed it as the deepest green algae divergence. This basal positioning is regarded as a result of long-branch attraction due to poor taxon sampling. Reinvestigation of a 13- taxon mitochondrial amino acid dataset and a sub-dataset of 8 taxa reveals that site sampling, and in particular the treatment of missing data, is just as important a factor for accurate tree reconstruction as taxon sampling. This study identifies a difficulty in recreating the long-branch attraction observed for the 8-taxon dataset in simulated data. The cause is likely to be the smaller number of amino acid characters per site in simulated data compared to real data, highlighting the fact that there are properties of the evolutionary process that are yet to be accurately modeled.

Phylogenetic models generally assume a homogeneous, time reversible, stationary process. These assumptions are often violated by the real, far more complex, evolutionary process. This thesis is centered on non-homogeneous, lineage-specific, properties of molecular sequences. It consist several related but independent studies. LineageSpecificSeqgen, an extension to the Seq-Gen program, which allows generation of sequences with changes in the proportion of variable sites, is introduced. This program is then used in a simulation study showing that changes in the proportion of variable sites can hinder tree estimation accuracy, and that tree reconstruction under the best-fit model chosen using a relative test can result in a wrong tree. In this case, the less commonly used absolute model-fit was a better predictor of tree estimation accuracy. This study found that increased taxon sampling of lineages that have undergone a change in the proportion of variable sites was critical for accurate tree reconstruction and that, in contrast to some earlier findings, the accuracy of maximum parsimony is adversely affected by such changes. This thesis also addresses the well-known long-branch attraction artifact. A nonparametric bootstrap test to identify changes in the substitution process is introduced, validated, and applied to the case of Microsporidia, a highly reduced intracellular parasite. Microsporidia was first thought to be an early branching eukaryote, but is now believed to be sister to, or included within, fungi. Its apparent basal eukaryote position is considered a result of long-branch attraction due to an elevated evolutionary rate in the microsporidian lineage. This study shows that long-branch estimates and basal positioning of Microsporidia both correlate with increased proportions of radical substitutions in the microsporidian lineage. In simulated data, such increased proportions of radical substitutions leads to erroneous long-branch estimates. These results suggest that the long microsporidian branch is likely to be a result of an increased proportion of radical substitutions on that branch, rather than increased evolutionary rate per se. The focus of the last study is the intriguing case of Mesostigma, a fresh water green alga for which contradicting phylogenetic relationships were inferred. While some studies placed Mesostigma within the Streptophyta lineage (which includes land plants), others placed it as the deepest green algae divergence. This basal positioning is regarded as a result of long-branch attraction due to poor taxon sampling. Reinvestigation of a 13- taxon mitochondrial amino acid dataset and a sub-dataset of 8 taxa reveals that site sampling, and in particular the treatment of missing data, is just as important a factor for accurate tree reconstruction as taxon sampling. This study identifies a difficulty in recreating the long-branch attraction observed for the 8-taxon dataset in simulated data. The cause is likely to be the smaller number of amino acid characters per site in simulated data compared to real data, highlighting the fact that there are properties of the evolutionary process that are yet to be accurately modeled.

Phylogenetic models generally assume a homogeneous, time reversible, stationary process. These assumptions are often violated by the real, far more complex, evolutionary process. This thesis is centered on non-homogeneous, lineage-specific, properties of molecular sequences. It consist several related but independent studies. LineageSpecificSeqgen, an extension to the Seq-Gen program, which allows generation of sequences with changes in the proportion of variable sites, is introduced. This program is then used in a simulation study showing that changes in the proportion of variable sites can hinder tree estimation accuracy, and that tree reconstruction under the best-fit model chosen using a relative test can result in a wrong tree. In this case, the less commonly used absolute model-fit was a better predictor of tree estimation accuracy. This study found that increased taxon sampling of lineages that have undergone a change in the proportion of variable sites was critical for accurate tree reconstruction and that, in contrast to some earlier findings, the accuracy of maximum parsimony is adversely affected by such changes. This thesis also addresses the well-known long-branch attraction artifact. A nonparametric bootstrap test to identify changes in the substitution process is introduced, validated, and applied to the case of Microsporidia, a highly reduced intracellular parasite. Microsporidia was first thought to be an early branching eukaryote, but is now believed to be sister to, or included within, fungi. Its apparent basal eukaryote position is considered a result of long-branch attraction due to an elevated evolutionary rate in the microsporidian lineage. This study shows that long-branch estimates and basal positioning of Microsporidia both correlate with increased proportions of radical substitutions in the microsporidian lineage. In simulated data, such increased proportions of radical substitutions leads to erroneous long-branch estimates. These results suggest that the long microsporidian branch is likely to be a result of an increased proportion of radical substitutions on that branch, rather than increased evolutionary rate per se. The focus of the last study is the intriguing case of Mesostigma, a fresh water green alga for which contradicting phylogenetic relationships were inferred. While some studies placed Mesostigma within the Streptophyta lineage (which includes land plants), others placed it as the deepest green algae divergence. This basal positioning is regarded as a result of long-branch attraction due to poor taxon sampling. Reinvestigation of a 13- taxon mitochondrial amino acid dataset and a sub-dataset of 8 taxa reveals that site sampling, and in particular the treatment of missing data, is just as important a factor for accurate tree reconstruction as taxon sampling. This study identifies a difficulty in recreating the long-branch attraction observed for the 8-taxon dataset in simulated data. The cause is likely to be the smaller number of amino acid characters per site in simulated data compared to real data, highlighting the fact that there are properties of the evolutionary process that are yet to be accurately modeled.