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Morphological and functional variability of secretory glands in cercariae of chosen trematode groups
Krčmářová, Veronika ; Bulantová, Jana (advisor) ; Mikeš, Libor (referee)
Trematodes are characterized by their complex life cycles that include definitive hosts and variable number of intermediate hosts. Transfer of the parasite from the first intermediate host to the other is usually realized by larval stage called cercaria. After finishing of their development within the first intermediate host, morphology and fate of these larval stages vary according to the way of infection of the next host. Some cercariae actively penetrate directly to their definitive hosts trough their body surface, other encystate in the outer environment where they wait in a form of metacercariae to be ingested by definitive host. Both of these ways can be combinated and cercariae encystate inside second intermediate host after they actively penetrate them. Exceptionally, cercariae do not leave the sporocyst in which they were developing inside the first intermediate host. They encyst there waiting for ingestion by the definitive host. Various types of secretory glands have been developed in cercariae for successful direct infection of next hosts, survival of parasite in adverse conditions of outer environment or for transformation of one larval stage to subsequent one. Variability in morphology and function of these secretory glands in cercariae is closely connected with differences in life...
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Chrysophyte stomatocysts - encystation and excystation dynamics - bentic resting stages of chrysophytes
Mušálková, Petra ; Němcová, Yvonne (advisor) ; Juráň, Josef (referee)
The resting resistant stage has several important roles for phytoplankton microorganisms. It protects them from hostile conditions, allows them to spread to new locations and is often part of their life cycle. Chrysophytes form large populations for only a short part of the year, and therefore the formation of a resting stage is key for them to re-establish a vegetative population the following year. Chrysophyte resting stages are called stomatocysts, which are silicified and have a unique species-specific morphology. They can be form after both sexual and asexual reproduction. This is an understudied area. Most described stomatocysts are not assigned to species and much is not known about the triggers of encystation and excystation. It is thought that a combination of external (temperature, light, nutrients) and internal (cell age and cell concentration) factors are involved. So far, only sexual encystation in Dinobryon cyindricum and Synura petersenii has been studied in detail. My diploma thesis is based on laboratory experiments with Ochromonas tuberculata, Synura uvella and two strains of Synura petersenii. The aim of the study was to investigating whether external conditions such as temperature and lack of nitrogen or phosphorus have the effect on asexual encystation and whether it is...
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Encystation and life cycle of free living amoebae of the genus Acanthamoeba spp.
Bínová, Eva ; Nohýnková, Eva (advisor) ; Dyková, Iva (referee) ; Ondriska, František (referee)
Amoebae of the genus Acanthamoeba spp. are free-living unicellular organisms found in disparate ecosystems all over the world. Due to their ability to invade human body, evade its defensive mechanisms and cause extensive tissue damage, Acanthamoeba infection can lead to serious, if rare, diseases, affecting most commonly the eye and the central nervous system. Specific therapy for Acanthamoeba infections is not available. A major reason for therapeutic failure in ameobiasis is the ability of the protist to differentiate into resistant stages. These are cysts, known to be formed under prolonged unfavorable conditions, both in the environment and the infected tissues, and the pseudocysts, less durable but rapidly formed under acute stress. The present thesis focuses on as yet unexplored mechanisms of resistance of cysts and pseudocysts. Moreover, further characteristics distinguishing cysts and pseudocysts as well as the processes involved in their formation are investigated. One of the issues addressed is a presence of protective carbohydrate compounds mannitol and trehalose that participate in defensive reactions against abiotic stress in many organisms. Although putative genes for enzymes of the trehalose and mannitol synthetic pathways are present in the genome of Acanthamoeba, only one of the...
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Dynamics of Giardia intestinalis encystation.
Vinopalová, Martina ; Doležal, Pavel (advisor) ; Verner, Zdeněk (referee)
Giardia intestinalis is an anaerobic parasite, that colonizes the small intestine of humans and other vertebrate hosts. This cosmopolitan parasite, which causes diarrhoea, is transmitted by contaminated water or food via a resistant stage, the cyst. The encystation process involves a number of events that lead to a complete reconstruction of the cell into the form of infectious cyst. The aim of this work was to visualize these modifications in vivo by means of enzymatic labelling of proteins. For the purposes of this work, enzymatic tags Y-FAST and HaloTag were chosen, as they enable visualizing live cells under anaerobic conditions. Chimeric protein constructs were created to visualize the dynamics of the encystation vesicles, the structures of endoplasmic reticulum, the adhesive disc and mitosis. Using the developed constructs, we successfully followed the dynamics of the encystation vesicles and the adhesive disc in vivo. Finally, this work has provided novel molecular tools, which will be used to follow the overall redesign of the parasite cell during encystation.
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Adaptive functions of algal resting stages with emphasis on the chrysophyte stomatocysts
Mušálková, Petra ; Němcová, Yvonne (advisor) ; Pusztai, Martin (referee)
Formation of resting stages is a very common feature occurring in most algae classes. Primarily this stage is considered as a resistant form that helps the organism to survive adverse conditions and rapidly changing environment. However, it may also serve to spread as a seed bank to recolonize habitat or can be a source of genetic variation if it follows sexual reproduction. The importance of this dormant benthic stage grows with algae whose population growth is seasonal and the formation of cysts or spores is crucial for them, for instance dinoflagellates and golden algae. Resting stages of Chrysophyceae are called stomatocysts they are produced endogenously and are composed of polymerized silica. Stomatocysts have species-specific morphology. For most described species of Chrysophyceae morphology of the stomatocyst is unknown. Determining the species is difficult especially because of rapid alternation of chrysophyte dominant species in natural waterbodies. So far, it has not been elucidated what factors cause encystation and excystation. Several laboratory experiments has been conducted on this subject. The process of encystation and excystation is assumed to be induced by combination of external and internal factors. Stomatocysts may developed after sexual reproduction or from vegetative cells....
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Morphological and functional variability of secretory glands in cercariae of chosen trematode groups
Krčmářová, Veronika ; Bulantová, Jana (advisor) ; Mikeš, Libor (referee)
Trematodes are characterized by their complex life cycles that include definitive hosts and variable number of intermediate hosts. Transfer of the parasite from the first intermediate host to the other is usually realized by larval stage called cercaria. After finishing of their development within the first intermediate host, morphology and fate of these larval stages vary according to the way of infection of the next host. Some cercariae actively penetrate directly to their definitive hosts trough their body surface, other encystate in the outer environment where they wait in a form of metacercariae to be ingested by definitive host. Both of these ways can be combinated and cercariae encystate inside second intermediate host after they actively penetrate them. Exceptionally, cercariae do not leave the sporocyst in which they were developing inside the first intermediate host. They encyst there waiting for ingestion by the definitive host. Various types of secretory glands have been developed in cercariae for successful direct infection of next hosts, survival of parasite in adverse conditions of outer environment or for transformation of one larval stage to subsequent one. Variability in morphology and function of these secretory glands in cercariae is closely connected with differences in life...
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Live cycle of the free-living amoeba. Differentiation of amoebae of the genera Acanthamoeba and Balamuthia
Klieščiková, Jarmila ; Nohýnková, Eva (advisor) ; Ondriska, František (referee) ; Walochnik, Julia (referee)
Free-living pathogenic amoebae Acanthamoeba spp. and Balamuthia mandrillaris are causative agents of important diseases of human: rarely occurring but highly fatal granulomatous amoebic encephalitis (both) and keratitis (Acanthamoeba). One of the reasons for the problematic therapy is differentiation into highly resistant cysts often found in affected tissues. In our study we have found that correct encystation in Acanthamoeba requires apart from others, the presence of functioning Golgi apparatus transporting the cyst wall material to the cell surface; glycogen phosphorylase degrading glycogen into glucose which seems to be further used for cellulose synthesis and two non-constitutive cellulose synthases. Acanthamoeba cellulose synthases seem not to be inhibited by known herbicides. In the cyst wall of acanthamoebae we detected cellulose, -mannan, and -1, 3-1, 4-linked glucan [lichenin or mixed-linkage glucan (MLG)]. Cellulose is present in the inner (endocyst) and the outer (exocyst) layers of the cyst wall, whereas-mannan and MLG are found in the endocyst. In a protozoan organism, MLG was detected for the first time. The MLG of Acanthamoeba has a similar composition to that found in barley with high amount of cellobiosyl and cellotriosyl followed by cellotetraosyl units. In contrast, with...
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