National Repository of Grey Literature 14 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Bacteria in the lichen symbiosis
Moťková, Eliška ; Steinová, Jana (advisor) ; Peksa, Ondřej (referee)
This thesis summarizes the most recent research on bacteria in lichen symbiosis. Lichen symbiosis and the partners participating in it are described in the first part of the thesis. The emphasis is mainly on the different functions that bacteria can have in lichen symbiosis. These functions include, for example, the fixation of atmospheric nitrogen, the production of cobalamin, essential for the growth of some algae, the secretion of antimicrobial substances and the recycling of nutrients contained in old parts of the litter. The main groups of bacteria that occur in the lichen symbiosis are also discussed, along with the factors that influence their occurrence. The most abundant group of bacteria in lichens are the Alphaproteobacteria. Their abundance in lichens is probably influenced by the frequent occurrence of these bacteria in the substrate on which the lichen grows. Other abundant groups of bacteria in lichens are representatives of Firmicutes, actinobacteria or acidobacteria. All important groups of bacteria are acquired by lichens through both vertical transfer and horizontal transfer. Key words: Alphaproteobacteria, nitrogen fixation, antagonistic activity, microbiota, biofilm
Role of basidiomycete yeasts in the lichen symbiosis
Jerhot, Štěpán ; Steinová, Jana (advisor) ; Černajová, Ivana (referee)
Lichens are, according to the latest definition considered ecosystems, which consist of a fungus, one or more photosynthesizing partners and an undefined number of additional microorganisms. The role of basidiomycete yeasts, which were shown to appear in many lichen species, has been discussed in the latest lichenological scientific papers. This bachelor thesis summarizes the knowledge about the distribution of lichen-associated yeasts and their importance in these symbioses. It also presents some of the methods newly used to study yeasts in lichen symbioses and compares the often inconsistent results based on the methods used in the papers. The topic is not sufficiently covered to draw sufficiently robust conclusions about the role of yeasts in lichen symbiosis. However, the results to date suggest that lichen yeasts do not have any significant specificity of association with mycobiont species, and there has been no support that yeasts directly enhance host fitness. A more detailed depiction of the structures that yeasts form at sites of contact with the host and a description of the mechanisms by which the participating partners communicate with each other could help to definitively determine their role in the lichen symbiosis.
Photobiont plurality in lichen thalli
Dědková, Kamila ; Steinová, Jana (advisor) ; Vančurová, Lucie (referee)
Photobiont plurality refers to the presence of multiple photobionts within a single lichen thallus. This phenomenon was described at the end of the last century but has received deeper attention in the last decade. The available literature on this topic is limited. This bachelor thesis summarizes all the important findings published on plurality to date. The most common photobionts coexisting in a thallus are algae of the genus Trebouxia, but other algae and cyanobacteria more or less phylogenetically related may also coexist together. Thallus with multiple photobionts is formed either at the beginning by the association of hyphae with several photobionts at once (horizontal transport) or by the acquisition of additional photobionts during life (vertical transport). The most important factors affecting the cooccurrence of multiple photobionts in a single thallus are probably the specificity and selectivity of mycobionts and local environmental conditions. The plurality of photobionts has been found in more than fifty lichen species. Many important findings have been described in a model lichen Ramalina farinacea. Its coexisting photobionts differ in responses to several environmental, mostly stress conditions, suggesting that the presence of multiple photobionts in a thallus may provide an...
Methanogenic symbionts of Psalteriomonadidae (Heterolobosea: Tetramitia)
Foučková, Martina ; Čepička, Ivan (advisor) ; Steinová, Jana (referee)
Psalteriomonadidae is a small family of anaerobic amoeboflagellates belonging to Heterolobosea. So far, 16 species have been described and there are also at least another 17 putative species which are yet to be formally described. Their anaerobic lifestyle is associated with a modification of the mitochondria into hydrogen-producing hydrogenosomes. The main focus of this thesis is on methanogenic symbionts of this family. The presence of prokaryotic symbionts has been observed in three species of Psalteriomonas, namely P. lanterna, P. vulgaris and P. magna. In P. lanterna, and P. vulgaris the symbionts were identified as Methanobacterium formicicum on the basis of their morphology and biochemical properties. For this thesis, 37 new freshwater isolates of psalteriomonadids were collected, identified, sequenced, and together with older isolates in culture, were investigated for the presence of prokaryotic symbionts. The UV autofluorescence of the symbionts of P. lanterna P. magna and Psalteriomonadidae sp. 5 indicates that they are methanogenic Archaea. No traces of methanogens were found in three isolates of Sawyeria marylandensis and three isolates of different Harpagon species. The symbionts were identified as Methanoregula sp. based on the 16S rRNA gene sequence. The symbionts were divided into...
Diversity and phylogeny of symbiotic partners in zeorin-containing red-fruited Cladonia species.
Steinová, Jana ; Škaloud, Pavel (advisor) ; Pérez-Ortega, Sergio (referee) ; Vondrák, Jan (referee)
Lichens are a classic example of mutualistic symbiotic associations, yet the views on lichen symbiosis have changed considerably during the last fifty years. Nowadays, lichens are generally understood to be microecosystems consisting of several symbiotic partners which contribute in different ways to the prosperity of the whole system and which differ by the strength of their bond to other symbiotic partners. The level of knowledge of the individual partners (mycobionts vs. photobionts vs. bacteria) varies greatly in terms of their specificity, diversity and in the forces that shape this diversity. The main aim of this work was to reveal the diversity of organisms participating in lichen symbiosis and to better understand the biological forces which shape this diversity. We worked with a relatively common lichen group, zeorin-containing red-fruited Cladonia species, and specifically, we focused on the mycobionts, photobionts and bacteria that participate in this association. During the course of the study, it became apparent that species delimitation, which is a fundamental requirement for accurate diversity estimates, is another topic that requires further research. Our analyses revealed that species circumscription of most of recently recognized Cladonia mycobionts cannot by supported by...
Interaction of lichens and invertebrates with emphasis on mites
Vtípilová, Věra ; Steinová, Jana (advisor) ; Černajová, Ivana (referee)
Lichens interact with many groups of invertebrates. Acari (mites), Gastropoda (gastropods), Rotifera (rotifers), Nematoda (nematodes), Tardigrada (tardigrades), Protozoa (protists), Collembola (springtails) and Insecta (insects), especially Psocoptera (book and bark lice), Lepidoptera (butterflies and moths) and Coleoptera (beetles) represent the most common groups. These animals use lichens as a shelter and food. Lichens have different defence mechanisms, for example, secondary metabolites. On the other hand, invertebrates often mediate the dispersal of lichens. Some lichens can grow on shells or a body surface of living invertebrates. In my thesis, I describe individual groups of invertebrates that interact with lichens, and I mention specific examples of these interactions. A special emphasis is given on mites because they are one of the most important consumers of lichens, and I will pay attention to them in my diploma thesis.
Lichens on metal-rich substrates with emphasis on serpentinites
Ghlimová, Heda ; Steinová, Jana (advisor) ; Peksa, Ondřej (referee)
Serpentinite is an ultramafic rock covering about 1 % of the Earth's surface. Serpentinite contains a high content of heavy metals such as Ni, Cr, Co and, conversely, low content of major nutrients N, P, K. The high concentration of Mg reduces the availability of Ca to plants. Serpentinites are not distinguished only by their chemistry - they are also, for example, poorly thermally conductive and soils that form on the serpentine subsoil are considered infertile. This complex of properties causes the formation of so- called serpentinomorphoses in vascular plants and also promotes the development of endemism. However, these adaptations do not occur in fungi and in lichens and bryophytes they occur only partially. This bachelor thesis summarizes the basic physiological mechanisms by which myco- and photobionts ensure the survival of lichens on substrates with high content of heavy metals - it is above all extracellular absorption of metals (binding to cell wall ligands), intracellular absorption (and subsequent detoxification with metallothionein and phytochelatins), and exclusion of metals on the surface of mycobiont hyphae or on the surface of the thallus (binding to oxalates and secondary metabolites). The bachelor thesis also summarizes the morphological adaptations that occur in lichens in...
Genetic variability in the Physconia muscigena group (Physciaceae, Ascomycota) in the Northern Hemisphere
Starosta, Jakub ; Koukol, Ondřej (advisor) ; Steinová, Jana (referee)
The principal goal of our study was to test whether ecologically and chemically different populations of lichens in the Physconia muscigena (Ach.) Poelt group belong to multiple species or one. We used sequence data from three markers (ITS rDNA, mtSSU rDNA and TEF1-α) for the reconstruction of phylogenetic trees based on a sampling of mostly European and Canadian populations of P. muscigena (Ach.) Poelt, P. muscigena var. bayeri (Nádv.) Poelt, and P. isidiomuscigena Essl. Further, we sought any possible geographical or ecological trends among chemotypes and haplotypes. Results show that: 1) Sequence data of ITS rDNA and TEF1-α shows large genetic variation in the Physconia muscigena group. This genetic variability does not correlate with geographical distribution or thallus chemistry; 2) Physconia muscigena var. bayeri and P. isidiomuscigena appear undifferentiated in our phylogenetic trees with P. muscigena. These three species cannot be distinguished on the basis of ITS rDNA, mtSSU rDNA and TEF1-α sequences. 3) We synonymized Physconia muscigena var. bayeri with P. muscigena and we recombine P. isidiomuscigena as a variety of P. muscigena.
A comparison of metabarcoding and morphology-based identification of protist communities
Tučková, Kateřina ; Škaloud, Pavel (advisor) ; Steinová, Jana (referee)
This thesis is focusing on metabarcoding; its history, principles and current use in science. Metabarcoding brings us a new way to observe a diversity of protists. Although the protists are ubiquitous on the Earth and play a key role in the majority of biological processes, our knowledge of their diversity is still very poor. Traditional microscopy techniques are mostly based on morphology-based identification of taxa. However, they are not so suitable for investigating protist diversity due to their small size, low concentration in the environment, and the convergent morphological evolution of many groups. Similarly, the metabarcoding has its pros and cons, as well. This thesis summarizes pros and cons of both techniques, trying to emphasize the need to both of them to gain a more complete insight into the diversity of protists on the Earth.

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