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Infection Experiments (infection + experiment)
Selected AbstractsGenetics of the relationship between the ciliate Paramecium bursaria and its symbiotic algaeINVERTEBRATE BIOLOGY, Issue 4 2007Yuki Tonooka Abstract. Paramecium bursaria, a freshwater protozoan, typically harbors hundreds of symbiotic algae (Chlorella sp.) in its cytoplasm. The relationship between host paramecia and symbiotic algae is stable and mutually beneficial in natural environments. We recently collected an aposymbiotic strain of P. bursaria. Infection experiments revealed that the natural aposymbiotic strain (Ysa2) showed unstable symbiosis with Chlorella sp. The algae aggregated at the posterior region of the host, resulting in aposymbiotic cell production after cell division. Cross-breeding analyses were performed to determine the heritability of the aposymbiotic condition. In crosses of Ysa2 with symbiotic strains of P. bursaria, F1 progeny were able to form stable symbioses with Chlorella sp. However, unstable symbiosis, resembling Ysa2 infection, occurred in some F2 progeny of sibling crosses between symbiotic F1 clones. Infection experiments using aposymbiotic F2 cells showed that these F2 subclones have limited ability to reestablish the symbiosis. These results indicate that the maintenance of stable symbiosis is genetically controlled and heritable, and that Ysa2 is a mutant lacking the mechanisms to establish stable symbiosis with Chlorella sp. [source] Experimental evidence for costs of parasitism for a threatened species, White Sands pupfish (Cyprinodon tularosa)JOURNAL OF ANIMAL ECOLOGY, Issue 5 2004MICHAEL L. COLLYER Summary 1We used field and experimental data to test if white grub parasites (Diplostomatidae) are costly to White Sands pupfish (Cyprinodon tularosa), a threatened species restricted to four sites in the Chihuahuan desert, New Mexico. 2Of the four populations of C. tularosa, two are native and two are introduced. The two native populations (Malpais Spring and Salt Creek) are genetically distinct and have been isolated historically in dissimilar aquatic habitats (brackish spring and saline river, respectively). Two populations were established c. 1970 from translocation of Salt Creek fish to another saline river (Lost River) and another brackish spring (Mound Spring). 3Physid snails (Physidae) occur in the two brackish spring habitats but not the saline river habitats. These snails are first intermediate hosts for white grubs (Diplostomatidae). Therefore, the two freshwater populations are infected by diplostomatids. For the Mound Spring population, the ecological relationship of C. tularosa and diplostomatids has only recently occurred. 4In 1995, a population crash occurred for C. tularosa at Mound Spring, associated with a parasite outbreak. Diplostomatids were the presumptive cause of this crash, but this was inferred from observation of infection in collected fish. 5Two years of seasonal sampling of the two populations revealed that all collected fish were infected. Parasite intensities were significantly lower in winter compared to summer, suggesting that heavily infected fish were lost from the population on a seasonal basis. 6We conducted an artificial infection experiment to assess the costs of parasitism for previously uninfected C. tularosa females for various life-history traits. Under experimental conditions, diplostomatid infection caused increases in C. tularosa mortality and decreases in growth and fat storage. Individual-level costs of parasitism may translate to population-level patterns of parasitism for C. tularosa populations. Results from this study suggest that parasites may impact host overwinter survival, which is consistent with lower parasite intensities found during winters in wild populations. [source] An experimental test of the symbiosis specificity between the ciliate Paramecium bursaria and strains of the unicellular green alga ChlorellaENVIRONMENTAL MICROBIOLOGY, Issue 8 2007Monika Summerer Summary The ciliate Paramecium bursaria living in mutualistic relationship with the unicellular green alga Chlorella is known to be easily infected by various potential symbionts/parasites such as bacteria, yeasts and other algae. Permanent symbiosis, however, seems to be restricted to Chlorella taxa. To test the specificity of this association, we designed infection experiments with two aposymbiotic P. bursaria strains and Chlorella symbionts isolated from four Paramecium strains, seven other ciliate hosts and two Hydra strains, as well as three free-living Chlorella species. Paramecium bursaria established stable symbioses with all tested Chlorella symbionts of ciliates, but never with symbiotic Chlorella of Hydra viridissima or with free-living Chlorella. Furthermore, we tested the infection specificity of P. bursaria with a 1:1:1 mixture of three compatible Chlorella strains, including the native symbiont, and then identified the strain of the newly established symbiosis by sequencing the internal transcribed spacer region 1 of the 18S rRNA gene. The results indicated that P. bursaria established symbiosis with its native symbiont. We conclude that despite clear preferences for their native Chlorella, the host,symbiont relationship in P. bursaria is flexible. [source] Histopathological studies on viral nervous necrosis of sevenband grouper, Epinephelus septemfasciatus Thunberg, at the grow-out stageJOURNAL OF FISH DISEASES, Issue 7 2004S Tanaka Abstract Viral nervous necrosis caused by sevenband grouper nervous necrosis virus (SGNNV) has occurred in grow-out stages (0,3 years old) of sevenband grouper, Epinephelus septemfasciatus, since the 1980s. In the present study, based on histopathological features of the central nervous system (CNS) in naturally diseased fish, pernasal infection experiments using grow-out fish were performed and pernasal infection was established as a putative invasion route of SGNNV. The definite SGNNV-targeted cells were determined by histopathological studies including indirect fluorescent antibody test and electron microscopy. Nerve cells in the olfactory lobe were most extensively necrotized with vacuolation followed by infiltration of microglia and macrophages. Purkinje cells and Golgi cells were extensively infected in the cerebellum. Megalocells and small nerve cell nuclei were also infected in the preoptic area, thalamus, medulla oblongata and spinal cord. Only a few small nerve cells were infected in the olfactory bulb and optic tectum. The retina of some diseased fish displayed vacuolated bipolar cells of the inner nuclear layer and in the ganglion cell layer. These SGNNV-infected nerve cells displayed viroplasmic inclusions containing virions, vacuoles and myelin-like structures. Based on observed histopathological changes, the lesion of the CNS was characterized by encephalitis but not encephalopathy. [source] Dynamics of experimental production of Thelohanellus hovorkai (Myxozoa: Myxosporea) in fish and oligochaete alternate hostsJOURNAL OF FISH DISEASES, Issue 10 2003Y S Liyanage Abstract The dynamics of development and production of Thelohanellus hovorkai (Myxozoa) were examined to investigate factors inducing haemorrhagic thelohanellosis in carp, Cyprinus carpio L. Fresh actinospores of T. hovorkai were harvested from the oligochaete alternate host, Branchiura sowerbyi, and used for infection experiments with myxosporean-free carp. Visualization of actinospores by fluorescent labelling revealed that sporoplasms penetrated the gill filaments of carp immersed in an actinospore suspension as early as 30 min post-exposure (PE). Plasmodia of T. hovorkai developed in the connective tissues of various organs and matured 3,5 weeks PE; dispersion of myxospores from degenerate plasmodia occurred 5,7 weeks PE. Challenges with a high dose of actinospores (4.5 × 106 spores per fish) resulted in the onset of disease, which was more easily achieved by the oral intubation of actinospores than by immersion in an actinospore suspension. Actinosporean-free B. sowerbyi were exposed to different densities of myxospores (104,106 spores per oligochaete) and subsequently reared at different temperatures (15, 20, 25 °C). At 20 and 25 °C, actinospore releases were first detected 40,43 days PE, with multiple peaks of release (max. 7 × 105 actinospores day,1) during the next 60 days. We concluded that the developmental cycle of T. hovorkai was completed within 3,5 months at 20,25 °C, and that the ingestion of large numbers of actinospores orally, possibly by feeding on infected oligochaetes, resulted in a disease condition in carp. [source] Differential expression of Bordetella pertussis iron transport system genes during infectionMOLECULAR MICROBIOLOGY, Issue 1 2008Timothy J. Brickman Summary Temporal expression patterns of the Bordetella pertussis alcaligin, enterobactin and haem iron acquisition systems were examined using alcA,, bfeA, and bhuR,tnpR recombinase fusion strains in a mouse respiratory infection model. The iron systems were differentially expressed in vivo, showing early induction of the alcaligin and enterobactin siderophore systems, and delayed induction of the haem system in a manner consistent with predicted changes in host iron source availability during infection. Previous mixed infection competition studies established the importance of alcaligin and haem utilization for B. pertussis in vivo growth and survival. In this study, the contribution of the enterobactin system to the fitness of B. pertussis was confirmed using wild-type and enterobactin receptor mutant strains in similar competition infection experiments. As a correlate to the in vivo expression studies of B. pertussis iron systems in mice, sera from uninfected and B. pertussis -infected human donors were screened for antibody reactivity with Bordetella iron-repressible cell envelope proteins. Pertussis patient sera recognized multiple iron-repressible proteins including the known outer membrane receptors for alcaligin, enterobactin and haem, supporting the hypothesis that B. pertussis is iron-starved and responds to the presence of diverse iron sources during natural infection. [source] | ||||||||||