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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.
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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...
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Photobiont dynamics of Stereocaulon lichens
Vančurová, Lucie ; Škaloud, Pavel (advisor) ; Bérešová, Anna (referee) ; Dal Grande, Francesco (referee)
7 Abstract Lichens are an iconic example of symbiosis. They are widespread throughout the world. In some ecosystems, lichens are dominant autotrophs, sometimes one of the few living organisms capable of surviving local conditions. They grow on a variety of substrata, including artificial surfaces. Great diversity of their life strategies is related to the diversity of symbiotic partners forming the lichen thalli, which remains largely unresearched. Lichens as sessile organisms often have to face a changing environment or adapt to conditions at new localities where their propagules can spread. We have chosen the widespread genus Stereocaulon as a model system for studying symbiotic relationships in lichens and the connection of this relationships with environmental conditions. The main goals of this thesis were (1) to uncover the diversity of phycobionts (i.e., green algal photobionts) associated with Stereocaulon within the whole genus and particular species-level lineages; (2) to identify environmental factors affecting the distribution of phycobionts and their relationships with mycobionts on a global and local scale; and (3) to inspect the possibility of sharing phycobiont pool with other lichens and soil. For this purpose, we used phylogenetic analyses (ITS rDNA, 18S rDNA, rbcL, and actin type I gene),...
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Functions of secondary metabolites of lichens
Zvěřinová, Gabriela ; Svoboda, David (advisor) ; Bouda, František (referee)
This bachelor thesis is a review of available literature about lichen secondary metabolites and their functions. Lichens produce a great variety of these compounds; most of them are unique to the lichen symbiosis and are not found in higher plants. Besides the role of these compounds in chemotaxonomy and systematics, lichen secondary metabolites exhibit various biological functions and can affect biotic and abiotic interactions of lichens with their environment. Well-known and often described functions of lichen substances include especially antimicrobial, antiherbivory and antioxidant activity, allelopathy, metal homeostasis and photoprotection. This thesis is focused on these functions and summarizes current knowledge in this area. Key words: lichen, secondary metabolites, allelopathy, antimicrobial activity, herbivory, antioxidant activity, photoprotection, metal homeostasis, pollution tolerance, literary review
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Diversity of green algae identified as lichen photobionts
Vaiglová, Zuzana ; Škaloud, Pavel (advisor) ; Štifterová, Anna (referee)
This thesis is focused on green algae, which have been recorded as lichen photobionts. The thesis consists of description of genera from the green algal from classes Ulvophyceae, Trebouxiophyceae and Chlorophyceae. I focused on phylogenetics position of genera, I define their morphology and I summarize their participation in lichen symbiotic relationships. I compare evidences based on the traditional morphological methods and modern molecular data. The following genera can be stated to uncertainly represent lichen photobionts: Trentepohlia, Cephaleuros, Phycopeltis and Dilabifilum from the class Ulvophyceae, and Dictyochloropsis, Chloroidium, Elliptochloris, Coccomyxa, Diplosphaera, Auxenochlorella, Myrmecia, Asterochloris, Trebouxia, Coccobotrys and Leptosira from the class Trebouxiophyceae. The genera Chlorella and Stichococcus are morphologically poorly defined, but they are commonly reported as lichen photobionts. Prasiola associates with the mycobiont, but the identity of their partnership is not certainly defined. The lichen symbiosis of genera Parachloroidium, Pseudochlorella and Gloeocystis has not been confirmed by molecular methods, so far. Key words photobiont, lichen, green algae, Chlorophyta, diversity, phylogeny, Trebouxiophyceae
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Comparing the diversity of free-living and symbiotic algae in lichen symbioses
Veselá, Veronika ; Škaloud, Pavel (advisor) ; Vančurová, Lucie (referee)
This work discusses the diversity of free-living lichen photobionts belonging to the class Trebouxiophyceae (Chlorophyta). The introduction summarises the change in perspective on the possibility of existence of free-living photobionts. The main part of this work contains a list of lichen photobiont genera with their description and taxonomical classification. In addition, I summarize published records and of these organisms in studies focusing on diversity of aerophytic and soil algae. The work also contains a list of known lichen photobionts species of the class Trebouxiophyceae. Keywords: Trebouxiophyceae, Trebouxia, green algae, photobiont, lichen, diversity
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Diversity of symbiotic partners within the lichen family Verrucariaceae
Schmidtová, Jana ; Škaloud, Pavel (advisor) ; Steinová, Jana (referee)
This thesis summarizes the current knowledge of photobionts of the lichen family Verrucariaceae. It classifies the free-living photobionts systematically, mentions their main morphological features, distribution, and ecology, and notices their participation in the symbiosis. Subsequently, it also describes and characterizes the fungal component of mycobionts, their phylogenetic position, the main morphological features, distribution, and the most common habitats. Finally, it studies the influence of the environment, mycobiont, and other factors in the occurrence of particular photobionts in lichens. Keywords: Verrucariaceae, photobiont, mycobiont, lichen, diversity, symbiosis, characterization
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Dynamics of a lichen symbiosis
Vaiglová, Zuzana ; Škaloud, Pavel (advisor) ; Vondrák, Jan (referee)
The symbiotic relationships often represent not only the permanent cohabitation of two organisms, but they can evolve and change over time. Many papers published so far focused on the the specificity of lichens, characterising both highly specific species and those that can establish a symbiosis with many algal genotypes. In this second case we can imagine the possibility of a photobiont exchange during the life of lichen - the dynamics of lichen symbiosis. In this thesis I compared the occurence and diversity of photobionts within the thalli of lichens growing on the disturbed localities and on the the localities without the disturbance. These two types of localities were similar to species richness of photobionts, but the disturbed localities dominated by the number of photobiont genera. These localities also reached a higher value of phylogenetic diversity. Conversely, non-phylogenetic analysis revealed the higher level of photobiont diversity on non-disturbed localities, where the core of diversity was formed by different lineages of Trebouxia. I have also found the lichens, which cooperate with different algae on disturbed and non-disturbed localities. The photobiont distribution presented in this paper shows the possibility of photobiont exchange during the community succesion. The...
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Photobiont diversity in lichen thallus Psora decipiens
Jadrná, Iva ; Škaloud, Pavel (advisor) ; Peksa, Ondřej (referee)
Psora decipiens is a characteristic species of the terricolous lichen community Toninio-Psoretum decipientis distributed mostly on calcareous or basic substrates. The community consists in various modifications of lichens Placidium squamulosum, Toninia sedifolia, T. opuntioides, Fulgensia fulgens, F. bracteata and others. Photobionts of the lichen Psora decipiens were determined. Psora decipiens shared with Placidium sp. the single photobiont species, a common terrestrial alga Myrmecia israeliensis. Cloning of ITS rDNA revealed high intrathalline variability in M. israeliensis within a single lichen thallus. Several genotypes were often found in a thallus, uncovering either a high mutation rate of the algae or constant relichenization processes. Saxicolous Psora species (P. testacea, P. himalayana, P. valesiaca and P. rubiformis) had M. biatorellae as a photobiont, indicating a possible photobiont influence on substrate specifity of Psora lichens. Finally, the proper methodology used for identification of lichen photobionts is discussed. For a correct photobiont identification, morphological investigations of intrathaline diversity combined with coherent molecular techniques are needed. Such procedure was not applied in the former studies of Psora decipiens, resulting in a poor characterization of...
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