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We report a new microsporidium Jirovecia sinensis sp. n. from a freshwater oligochaete, Branchiura sowerbyi collected in Hongze city, Jiangsu province, East China. Numerous whitish hypertrophied coelomocytes of 0.33-0.59 mm in diameter indicated infection. Transmission electron microscopy observations revealed that all developmental stages were diplokaryotic. The earliest life stages observed were meronts that were in direct contact with host cytoplasm, accumulated peripherally in the hypertrophied coelomocytes and connected with host cytoplasm through many pinocytotic canals. Mature spores are rod-shaped with a blunt end, measuring 17.0 ± 0.1 (14.9-18.5) µm long and 2.0 ± 0.2 (1.7-2.2) µm wide. The most conspicuous character of the novel microsporidian parasite is the tail-like posterior prolongations, with a length of 29.6-40.8 µm. Mature spores have a manubrium with a diameter of 447-485 nm which consist of six density-discontinuous concentric circles. Spores possess a collar-shaped anchoring disk and a bipartite polarplast with an anterior lamellar region and a posterior tubular section. SSU rDNA-based phylogenetic analysis indicated with high support values that the new species clustered with two Bacillidium species (B. vesiculoformis and Bacillidium sp.) infecting the freshwater oligochaetes and Janacekia debaisieuxi infecting the insect Simulium maculatum. Based on the ultrastructural features and molecular characteristics, a new species in the genus Jirovecia, Jirovecia sinensis sp. n., is designated.

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The ultrastructure of the fish-infecting microsporidium Spraguea gastrophysus found in the dorsal ganglia and kidney of the anglerfish, Lophius gastrophysus (family Lophiidae) collected on the Brazilian Atlantic coast is described. Each whitish xenoma (up to 3.1 × 1.8 mm) contains several groups of parasites. The host cells are hypertrophied and contain various parasite life stages including mature spores and several developmental stages with unpaired nuclei. Monomorphic spores are ellipsoidal, lightly curved and measure about 3.35 × 1.71 µm. The spore contains a gradually tapering isofilar polar filament with five to six coils arranged in a single row. The nucleus occupies a central zone of the sporoplasm where also several polyribosomes are presented. The posterior vacuole contains a voluminous spherical and granular posterosome measuring up to ~0.65 µm in diameter. The partial small subunit, intergenic spacer and partial large subunit rRNA gene were sequenced and the phylogenetic analysis places the microsporidian described here in the clade that includes all sequences of the Spraguea genus. The ultrastructural morphology of the xenoma and the spores of this microsporidian parasite, as well as the molecular and phylogenetic analysis, suggest the description of a new species. A redefining of the genus Spraguea is also done.

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Microsporidia, a large group of fungi-related intracellular parasites, are characterized by drastically reduced metabolism. They possess genes encoding glycolysis components, and the glycerol-phosphate shuttle, but lack mitochondria, Krebs cycle, respiratory chain and pyruvate-converting enzymes, except alpha and beta subunits of E(1) enzyme of pyruvate dehydrogenase (PDH) complex. Here, we have expressed PDH subunits from the microsporidum Paranosema (Antonospora) locustae in Escherichia coli. Western blot analysis with antibodies raised against recombinant proteins has revealed their specific accumulation in mature spores of P. locustae but not in the intracellular development stages. Two subunits were coprecipitated as a single heterooligomeric complex by anti-alpha or anti-beta PDH antibodies. Ultracentrifugation of spore homogenate has shown the presence of PDH in the soluble fraction. Relocalization of the mitochondrial protein in microsporidial spore cytoplasm was confirmed by immunoelectron microscopy of ultrathin cryosections with affinity-purified anti-alpha PDH antibodies. On cryosections, parasite enzyme was found partly associated with the cytoplasmic side of ER and other intraspore membranes, suggesting that electrons might be transferred to any membrane acceptor and finally to oxygen in the parasite cell.

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Two microsporidian genera, AnncaliiaIssi, Krylova, & Nicolaeva 1993 and BrachiolaCali et al. 1998, possess a Nosema-type life cycle and unique cell surface ornamentations, which include precocious electron-dense coating of the plasmalemma and a variety of secretory structures deposited on the parasite surface and scattered in the host cell cytoplasm. Comparative analysis of ultrastructure of Anncaliia meligethi (the type species of the genus Anncaliia) and of B. vesicularum and B. algerae (the best-studied members of the genus Brachiola) clearly demonstrated that these microsporidia share many distinctive morphological features. The comparison of small subunit ribosomal DNA sequences showed high sequence identity of A. meligethi and B. algerae. Phylogenetic analyses indicated that the rDNA sequences of A. meligethi clustered with those of B. algerae suggesting a close relatedness of these microsporidia. The combination of molecular and morphological data provided clear evidence that these microsporidia belong to the same genus and therefore, warranted emendation of the genus Anncaliia and establishments of the following new combinations: Anncaliia vesicularum nov. comb., Anncaliia algerae nov. comb., Anncaliia connori nov. comb., and Anncaliia gambiae nov. comb. The generic name Brachiola is submerged according to the rule of priority.

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A microsporidian infection was discovered in laboratory cultures of Drosophila species. Ultrastructural examination suggested it belonged to the poorly characterized species Tubulinosema kingi, and morphological and sequence data are presented. We explored how T. kingi affected the fitness of Drosophila melanogaster and D. subobscura, as well as the fitness of 2 of their parasitoids, Asobara tabida and Pachycrepoideus vindemiae. In Drosophila, infections caused changes in most of the traits we looked at that were associated with fitness, in particular causing a 34-55% reduction in early-life fecundity. Parasitoid fitness was affected more severely by infection than that of their hosts, with pupal mortality in particular increasing by 75-89%. We investigated the most important routes of transmission for T. kingi in a laboratory setting. Letting Drosophila larvae feed on medium contaminated with spores from infected dead flies resulted in 100% infection. Low levels of transmission (<10%) were found between larvae, and vertically between mothers and their offspring. Parasitoids developing in infected hosts all became infected, but infected adults were neither able to transmit the pathogen to their offspring nor to their offspring's Drosophila host, either directly, or via contamination of the ovipositor or other body parts. A field survey of Drosophila and their parasitoids in southern England revealed no natural infections. We discuss the potential importance of Microsporidia in parasitoid-host interactions, and for those working with Drosophila in the laboratory.

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A xenoma-inducing microsporidian species was found to infect the liver of the teleost fish, peacock wrasse Symphodus (Crenilabrus) tinca. Minimal estimates of the prevalence of the parasite in fishes caught along Tunisian coasts were as high as 43 % for Bizerte samples (over 2 yr) and 72% for Monastir samples (over 3 yr). Developmental stages were dispersed within a xenoma structure that was bounded only by the plasma membrane of the hypertrophic host cell. Ultrastructural features support allocation to the genus Microgemma Ralphs and Matthews, 1986. Meronts were multinucleate plasmodia and were surrounded by rough endoplasmic reticulum (RER) of the host cell. Merogonic plasmodia developed into sporogonic plasmodia, with loss of the RER interface. Sporogony was polysporoblastic. Ovocylindrical spores (3.6 x 1.2 microm) harbored a lamellar polaroplast and a polar tube that was coiled 9 times. Spore features and host specificity led us to propose a new species, Microgemma tincae. The conversion of M. tincae xenomas into well-visible cyst structures or granulomas reflected an efficient host response involving the infiltration of phagocytic cells, degradation of various parasite stages and formation of a thick fibrous wall. The small subunit rDNA gene of M. tincae was partially sequenced. Phylogenetic analysis confirms the placement within the family Tetramicriidae represented by the genera Tetramicra and Microgemma.

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Xenomas caused by Microgemma vivaresi Canning, Feist, Longshaw, Okamura, Anderson, Tsuey Tse et Curry, 2005 were found in liver and skeletal muscle of sea scorpions, Taurulus bubalis (Euphrasen). All muscle xenomas examined were in an advanced stage of destruction. In developing xenomas found in liver, parasites were restricted to the centre of the cell, separated from a parasite-free zone by a nuclear network formed by branching of the host cell nucleus. Although xenomas were able to reach a size of several hundred microns, the surface remained a simple plasma membrane. Host reactions took the form of penetration by phagocytes and isolation by fibroblasts. Once the xenoma had been attacked, the nuclear profiles became pycnotic and the barrier between parasitized and parasite-free zones was lost. Parasite antigens cannot be exposed at the surface of intact xenomas, as the host does not recognise the enlarging cell as foreign. Breaches in the plasma membrane of the xenoma and leakage of parasite antigens are thought to be the stimuli for phagocyte entry into the cell, its isolation by fibroblasts and eventual granuloma formation.

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The genus Brachiola is the newest microsporidian genus established for a human infection with the type species being B. vesicularum in skeletal muscle. Subsequently, the microsporidium, Nosema algerae, identified from mosquitoes, was added to this genus because of morphological and physiological similarities. The present report illustrates a confirmed case of Brachiola algerae infecting skeletal muscle in a 56-year-old woman who was being treated for rheumatoid arthritis with immunosuppressive drugs. In the following study, these two human-infecting microsporidian species are ultrastructurally compared from human biopsy tissue. Additionally, Brachiola algerae from mosquitoes as reference B. algerae, was grown in athymic mice and compared to the human isolate in vivo, and in culture. B. algerae is morphologically identical in the host situations presented and different from B. vesicularum in human skeletal muscle. B. algerae has a consistently, slightly longer spore that typically contains one row of polar filament coils, while B. vesicularum typically contains two rows of polar filament coils and occasionally, one or three rows. In proliferative development, B. vesicularum forms protoplasmic extensions which do not occur on B. algerae, nor have they been reported on any other microsporidium. This report demonstrates that B. vesicularum and B. algerae are two different species of Brachiola that infect human skeletal muscle.

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