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Ulf Karsten - One of the best experts on this subject based on the ideXlab platform.
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Klebsormidin A and B, Two New UV-Sunscreen Compounds in Green Microalgal Interfilum and Klebsormidium Species (Streptophyta) From Terrestrial Habitats.
Frontiers in microbiology, 2020Co-Authors: Anja Hartmann, Karin Glaser, Andreas Holzinger, Markus Ganzera, Ulf KarstenAbstract:The terrestrial green algal members of the genera Interfilum and Klebsormidium (Klebsormidiophyceae, Streptophyta) are found in biological soil crusts of extreme habitats around the world where they are regularly exposed, among other abiotic stress factors, to high levels of ultraviolet radiation (UVR). As a consequence those species synthesize and accumulate either one or two mycosporine-like amino acids (MAAs), but with a missing structural elucidation up to now. Therefore, in the present study both MAAs were chemically isolated and structurally elucidated. The two new compounds exhibit absorption maxima of 324 nm. MAA 1 has a molecular weight of 467 and MAA 2 of 305, and the latter (MAA 2) was identified as N-(4,5-dihydroxy-5-(hydroxymethyl)-2-methoxy-3-oxocyclohex-1-en-1-yl)-N-methylserine using one- and two-dimensional 1H and 13C-NMR spectroscopy. MAA 1 contains an additional sugar moiety. As trivial names for these two novel MAAs we suggest klebsormidin A and klebsormidin B. Different species from all previously described phylogenetic clades of Klebsormidiophyceae were chemically screened for their MAA composition in aqueous extracts using RP-HPLC and LC-MS. The novel klebsormidin A was present throughout all clades and hence could be suitable as a chemotaxonomic marker. Additionally, controlled UVR-exposure experiments with all investigated species showed that MAA biosynthesis and intracellular enrichment is strongly induced by short wavelengths, supporting the function of these compounds as natural UV-sunscreen as well as explaining the cosmopolitan distribution and ecological success of Interfilum and Klebsormidium in terrestrial habitats.
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ecophysiological changes and spore formation two strategies in response to low temperature and high light stress in Klebsormidium cf flaccidum klebsormidiophyceae streptophyta 1
Journal of Phycology, 2020Co-Authors: Fatima Miguez, Ulf Karsten, Andreas Holzinger, Beatriz Fernandezmarin, Jose Ignacio Garciaplazaola, Lydia GustavsAbstract:Members of the cosmopolitan streptophycean genus Klebsormidium live in various habitats, including sand dunes and polar/alpine environments. To survive in these harsh conditions they must possess an array of adaptive physiological and structural mechanisms, for example, to deal with chilling and photochilling stresses. Since these mechanisms have not been studied in detail, the objectives of this study were (i) to determine the physiological and biochemical responses of Klebsormidium cf. flaccidum (K. cf. flaccidum) to chilling (low temperature [LT]) and photochilling (LT in combination with high light [HL]) stresses; and (ii) to understand the cross-link between biochemical parameters and cellular ultrastructural changes. The results indicated that 5°C is a temperature threshold (i.e., at 5°C) but not at higher temperatures, physiological changes were observed (Fv /Fm and ETR decreased and energy-partitioning distribution changed, with an increase in Y[NPQ] under LT and an increase in Y[NO] under HL-LT). Also, pigment contents changed significantly, with increased concentrations of photoprotective pigments such as antheraxanthin, zeaxanthin, and total carotenes. All of these responses occurred under LT and, to a greater extent, under LT-HL, indicating that the two stresses (temperature and light) are additive. The cold treatment applied here induced the formation of spores under both LL and HL. The degree of photoinhibition was higher in spores than in vegetative cells, indicating that spores are less susceptible to photodamage. This study demonstrated a broad acclimation potential in different developmental stages of K. cf. flaccidum, which helps to explain the ecological success of this genus.
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cold acclimation improves the desiccation stress resilience of polar strains of Klebsormidium streptophyta
Frontiers in Microbiology, 2019Co-Authors: Martin Rippin, Ulf Karsten, Nadine Borchhardt, Burkhard BeckerAbstract:Biological soil crusts (BSCs) are complex communities of autotrophic, heterotrophic, and saprotrophic (micro)organisms. In the polar regions, these biocrust communities have essential ecological functions such as primary production, nitrogen fixation, and ecosystem engineering while coping with extreme environmental conditions (temperature, desiccation, and irradiation). The microalga Klebsormidium is commonly found in BSCs all across the globe. The ecophysiological resilience of various Klebsormidium species to desiccation and other stresses has been studied intensively. Here we present the results of transcriptomic analyses of two different Klebsormidium species, K. dissectum and K. flaccidum, isolated from Antarctic and Arctic BSCs. We performed desiccation stress experiments at two different temperatures mimicking fluctuations associated with global change. Cultures grown on agar plates were desiccated on membrane filters at 10% relative air humidity until the photosynthetic activity as reflected in the effective quantum yield of photosystem II [Y(II)] ceased. For both species, the response to dehydration was much faster at the higher temperature. At the transcriptome level both species responded more strongly to the desiccation stress at the higher temperature suggesting that adaptation to cold conditions enhanced the resilience of both algae to desiccation stress. Interestingly, the two different species responded differently to the applied desiccation stress with respect to the number as well as function of genes showing differential gene expression. The portion of differentially expressed genes shared between both taxa was surprisingly low indicating that both Klebsormidium species adapted independently to the harsh conditions of Antarctica and the Arctic, respectively. Overall, our results indicate that environmental acclimation has a great impact on gene expression and the response to desiccation stress in Klebsormidium.
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usual alga from unusual habitats biodiversity of Klebsormidium klebsormidiophyceae streptophyta from the phylogenetic superclade g isolated from biological soil crusts
Molecular Phylogenetics and Evolution, 2019Co-Authors: Elena Samolov, Tatiana Mikhailyuk, Alena Lukesova, Karin Glaser, Burkhard Budel, Ulf KarstenAbstract:Seven new species and two varieties of Klebsormidium were described using an integrative approach on the base of 28 strains from the poorly studied phylogenetic superclade G. These strains originated from the unusual and exotic habitats (semi-deserts, semi-arid shrublands, Mediterranean shrub and deciduous vegetation, temperate Araucaria forests, peat bogs, dumps after coal mining, maritime sand dunes etc.) of four continents (Africa, South and North America, and Europe). Molecular phylogenies based on ITS-1,2, rbcL gene and concatenated dataset of ITS-1,2-rbcL, secondary structure of ITS-2, morphology, ecology and biogeography, micrographs and drawings of the investigated strains were assessed. Additionally, phylogeny and morphology of 18 Klebsormidium strains from other lineages isolated from the same localities (different vegetation types of Chile and maritime sand dunes of Germany) were investigated for the comparison with representatives of clade G. Clade G Klebsormidium is characterized by distant phylogenetic position from the other Klebsormidium lineages and prominent morphology: four-lobed chloroplasts and mostly short swollen cells in young culture, compact small pyrenoids, curved or disintegrated filaments, unusual elongation of cells in old culture, formation of specific cluster- and knot-like colonies on agar surface, especially prominent in strains isolated from desert regions, from which the group probably originated. Comparison of Klebsormidium diversity from different biogeographic regions showed that the representatives of clade G are common algae in regions of the southern hemisphere (South Africa and Chile) and rare representatives in terrestrial ecosystems of the northern hemisphere. Further investigation of mostly unstudied territories of the southern hemisphere could bring many surprises and discoveries, leading to a change of the present concept that Klebsormidium is cosmopolitan in distribution.
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light and dehydration but not temperature drive photosynthetic adaptations of basal streptophytes hormidiella streptosarcina and streptofilum living in terrestrial habitats
Microbial Ecology, 2019Co-Authors: Ulf Karsten, Tatiana Mikhailyuk, Mattia Pierangelini, Karin Glaser, Andreas HolzingerAbstract:Streptophyte algae are the ancestors of land plants, and several classes contain taxa that are adapted to an aero-terrestrial lifestyle. In this study, four basal terrestrial streptophytes from the class Klebsormidiophyceae, including Hormidiella parvula; two species of the newly described genus Streptosarcina (S. costaricana and S. arenaria); and the newly described Streptofilum capillatum were investigated for their responses to radiation, desiccation and temperature stress conditions. All the strains showed low-light adaptation (Ik < 70 μmol photons m−2 s−1) but differed in photoprotective capacities (such as non-photochemical quenching). Acclimation to enhanced photon fluence rates (160 μmol photons m−2 s−1) increased photosynthetic performance in H. parvula and S. costaricana but not in S. arenaria, showing that low-light adaptation is a constitutive trait for S. arenaria. This lower-light adaptation of S. arenaria was coupled with a higher desiccation tolerance, providing further evidence that dehydration is a selective force shaping species occurrence in low light. For protection against ultraviolet radiation, all species synthesised and accumulated different amounts of mycosporine-like amino acids (MAAs). Biochemically, MAAs synthesised by Hormidiella and Streptosarcina were similar to MAAs from closely related Klebsormidium spp. but differed in retention time and spectral characteristics in S. capillatum. Unlike the different radiation and dehydration tolerances, Hormidiella, Streptosarcina and Streptofilum displayed preferences for similar thermal conditions. These species showed a temperature dependence of photosynthesis similar to respiration, contrasting with Klebsormidium spp. and highlighting an interspecific diversity in thermal requirements, which could regulate species distributions under temperature changes.
Andreas Holzinger - One of the best experts on this subject based on the ideXlab platform.
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cell wall reinforcements accompany chilling and freezing stress in the streptophyte green alga Klebsormidium crenulatum
Frontiers in Plant Science, 2020Co-Authors: Philip Steiner, Sabrina Obwegeser, Gerhard Wanner, Othmar Buchner, Ursula Lutzmeindl, Andreas HolzingerAbstract:Adaptation strategies in freezing resistance were investigated in Klebsormidium crenulatum, an early branching streptophyte green alga related to higher plants. Klebsormidium grows naturally in unfavorable environments like alpine biological soil crusts, exposed to desiccation, high irradiation and cold stress. Here, chilling and freezing induced alterations of the ultrastructure were investigated. Control samples (kept at 20°C) were compared to chilled (4°C) as well as extracellularly frozen algae (-2 and -4°C). A software-controlled laboratory freezer (AFU, automatic freezing unit) was used for algal exposure to various temperatures and freezing was manually induced. Samples were then high pressure frozen and cryo-substituted for electron microscopy. Control cells had a similar appearance in size and ultrastructure as previously reported. While chilling stressed algae only showed minor ultrastructural alterations, such as small inward facing cell wall plugs and minor alterations of organelles, drastic changes of the cell wall and in organelle distribution were found in extracellularly frozen samples (-2°C and -4°C). In frozen samples, the cytoplasm was not retracted from the cell wall, but extensive three-dimensional cell wall layers were formed, most prominently in the corners of the cells, as determined by FIB-SEM and TEM tomography. Similar alterations/adaptations of the cell wall were not reported or visualized in Klebsormidium before, neither in controls, nor during other stress scenarios. This indicates that the cell wall is reinforced by these additional wall layers during freezing stress. Cells allowed to recover from freezing stress (-2°C) for 5 h at 20°C lost these additional cell wall layers, suggesting their dynamic formation. The composition of these cell wall reinforcement areas was investigated by immuno-TEM. In addition, alterations of structure and distribution of mitochondria, dictyosomes and a drastically increased endoplasmic reticulum were observed in frozen cells by TEM and TEM tomography. Measurements of the photosynthetic oxygen production showed an acclimation of Klebsormidium to chilling stress, which correlates with our findings on ultrastructural alterations of morphology and distribution of organelles. The cell wall reinforcement areas, together with the observed changes in organelle structure and distribution, are likely to contribute to maintenance of an undisturbed cell physiology and to adaptation to chilling and freezing stress.
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Klebsormidin A and B, Two New UV-Sunscreen Compounds in Green Microalgal Interfilum and Klebsormidium Species (Streptophyta) From Terrestrial Habitats.
Frontiers in microbiology, 2020Co-Authors: Anja Hartmann, Karin Glaser, Andreas Holzinger, Markus Ganzera, Ulf KarstenAbstract:The terrestrial green algal members of the genera Interfilum and Klebsormidium (Klebsormidiophyceae, Streptophyta) are found in biological soil crusts of extreme habitats around the world where they are regularly exposed, among other abiotic stress factors, to high levels of ultraviolet radiation (UVR). As a consequence those species synthesize and accumulate either one or two mycosporine-like amino acids (MAAs), but with a missing structural elucidation up to now. Therefore, in the present study both MAAs were chemically isolated and structurally elucidated. The two new compounds exhibit absorption maxima of 324 nm. MAA 1 has a molecular weight of 467 and MAA 2 of 305, and the latter (MAA 2) was identified as N-(4,5-dihydroxy-5-(hydroxymethyl)-2-methoxy-3-oxocyclohex-1-en-1-yl)-N-methylserine using one- and two-dimensional 1H and 13C-NMR spectroscopy. MAA 1 contains an additional sugar moiety. As trivial names for these two novel MAAs we suggest klebsormidin A and klebsormidin B. Different species from all previously described phylogenetic clades of Klebsormidiophyceae were chemically screened for their MAA composition in aqueous extracts using RP-HPLC and LC-MS. The novel klebsormidin A was present throughout all clades and hence could be suitable as a chemotaxonomic marker. Additionally, controlled UVR-exposure experiments with all investigated species showed that MAA biosynthesis and intracellular enrichment is strongly induced by short wavelengths, supporting the function of these compounds as natural UV-sunscreen as well as explaining the cosmopolitan distribution and ecological success of Interfilum and Klebsormidium in terrestrial habitats.
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ecophysiological changes and spore formation two strategies in response to low temperature and high light stress in Klebsormidium cf flaccidum klebsormidiophyceae streptophyta 1
Journal of Phycology, 2020Co-Authors: Fatima Miguez, Ulf Karsten, Andreas Holzinger, Beatriz Fernandezmarin, Jose Ignacio Garciaplazaola, Lydia GustavsAbstract:Members of the cosmopolitan streptophycean genus Klebsormidium live in various habitats, including sand dunes and polar/alpine environments. To survive in these harsh conditions they must possess an array of adaptive physiological and structural mechanisms, for example, to deal with chilling and photochilling stresses. Since these mechanisms have not been studied in detail, the objectives of this study were (i) to determine the physiological and biochemical responses of Klebsormidium cf. flaccidum (K. cf. flaccidum) to chilling (low temperature [LT]) and photochilling (LT in combination with high light [HL]) stresses; and (ii) to understand the cross-link between biochemical parameters and cellular ultrastructural changes. The results indicated that 5°C is a temperature threshold (i.e., at 5°C) but not at higher temperatures, physiological changes were observed (Fv /Fm and ETR decreased and energy-partitioning distribution changed, with an increase in Y[NPQ] under LT and an increase in Y[NO] under HL-LT). Also, pigment contents changed significantly, with increased concentrations of photoprotective pigments such as antheraxanthin, zeaxanthin, and total carotenes. All of these responses occurred under LT and, to a greater extent, under LT-HL, indicating that the two stresses (temperature and light) are additive. The cold treatment applied here induced the formation of spores under both LL and HL. The degree of photoinhibition was higher in spores than in vegetative cells, indicating that spores are less susceptible to photodamage. This study demonstrated a broad acclimation potential in different developmental stages of K. cf. flaccidum, which helps to explain the ecological success of this genus.
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light and dehydration but not temperature drive photosynthetic adaptations of basal streptophytes hormidiella streptosarcina and streptofilum living in terrestrial habitats
Microbial Ecology, 2019Co-Authors: Ulf Karsten, Tatiana Mikhailyuk, Mattia Pierangelini, Karin Glaser, Andreas HolzingerAbstract:Streptophyte algae are the ancestors of land plants, and several classes contain taxa that are adapted to an aero-terrestrial lifestyle. In this study, four basal terrestrial streptophytes from the class Klebsormidiophyceae, including Hormidiella parvula; two species of the newly described genus Streptosarcina (S. costaricana and S. arenaria); and the newly described Streptofilum capillatum were investigated for their responses to radiation, desiccation and temperature stress conditions. All the strains showed low-light adaptation (Ik < 70 μmol photons m−2 s−1) but differed in photoprotective capacities (such as non-photochemical quenching). Acclimation to enhanced photon fluence rates (160 μmol photons m−2 s−1) increased photosynthetic performance in H. parvula and S. costaricana but not in S. arenaria, showing that low-light adaptation is a constitutive trait for S. arenaria. This lower-light adaptation of S. arenaria was coupled with a higher desiccation tolerance, providing further evidence that dehydration is a selective force shaping species occurrence in low light. For protection against ultraviolet radiation, all species synthesised and accumulated different amounts of mycosporine-like amino acids (MAAs). Biochemically, MAAs synthesised by Hormidiella and Streptosarcina were similar to MAAs from closely related Klebsormidium spp. but differed in retention time and spectral characteristics in S. capillatum. Unlike the different radiation and dehydration tolerances, Hormidiella, Streptosarcina and Streptofilum displayed preferences for similar thermal conditions. These species showed a temperature dependence of photosynthesis similar to respiration, contrasting with Klebsormidium spp. and highlighting an interspecific diversity in thermal requirements, which could regulate species distributions under temperature changes.
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localisation and substrate specificities of transglycanases in charophyte algae relate to development and morphology
Journal of Cell Science, 2018Co-Authors: Klaus Herburger, Zoë A. Popper, Louise Ryan, Andreas HolzingerAbstract:Cell wall-modifying enzymes were previously investigated in charophyte green algae (CGA) from cultures of uniform age, giving limited insight into their roles. Therefore, we investigated the in situ localisation and specificity of enzymes acting on hemicelluloses in CGA genera of different morphologies and developmental stages. In vivo transglycosylation between xyloglucan and an endogenous donor in filamentous Klebsormidium and Zygnema showed action in longitudinal cell walls of young (1 month) but not old cells (1 year), suggesting involvement in cell growth. Contrastingly, in parenchymatous Chara , transglycanase action occurred in all cell planes. In Klebsormidium and Zygnema , enzyme action predominately co-localised with xyloglucans and mannans, to a lesser extent mixed-linkage β-glucan (MLG), indicating predominantly xyloglucan:xyloglucan endotransglucosylase (XET). Novel transglycosylation activities between xyloglucan and xylan, and xyloglucan and galactomannan were identified in vitro , in both genera. Our results show that several cell wall-modifying enzymes are present in CGA and that differences in morphology and cell age are related to enzyme localisation and specificity. This indicates an evolutionary significance of cell wall modifications, as similar changes are known from their immediate descendants, the land plants.
Karin Glaser - One of the best experts on this subject based on the ideXlab platform.
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Klebsormidin A and B, Two New UV-Sunscreen Compounds in Green Microalgal Interfilum and Klebsormidium Species (Streptophyta) From Terrestrial Habitats.
Frontiers in microbiology, 2020Co-Authors: Anja Hartmann, Karin Glaser, Andreas Holzinger, Markus Ganzera, Ulf KarstenAbstract:The terrestrial green algal members of the genera Interfilum and Klebsormidium (Klebsormidiophyceae, Streptophyta) are found in biological soil crusts of extreme habitats around the world where they are regularly exposed, among other abiotic stress factors, to high levels of ultraviolet radiation (UVR). As a consequence those species synthesize and accumulate either one or two mycosporine-like amino acids (MAAs), but with a missing structural elucidation up to now. Therefore, in the present study both MAAs were chemically isolated and structurally elucidated. The two new compounds exhibit absorption maxima of 324 nm. MAA 1 has a molecular weight of 467 and MAA 2 of 305, and the latter (MAA 2) was identified as N-(4,5-dihydroxy-5-(hydroxymethyl)-2-methoxy-3-oxocyclohex-1-en-1-yl)-N-methylserine using one- and two-dimensional 1H and 13C-NMR spectroscopy. MAA 1 contains an additional sugar moiety. As trivial names for these two novel MAAs we suggest klebsormidin A and klebsormidin B. Different species from all previously described phylogenetic clades of Klebsormidiophyceae were chemically screened for their MAA composition in aqueous extracts using RP-HPLC and LC-MS. The novel klebsormidin A was present throughout all clades and hence could be suitable as a chemotaxonomic marker. Additionally, controlled UVR-exposure experiments with all investigated species showed that MAA biosynthesis and intracellular enrichment is strongly induced by short wavelengths, supporting the function of these compounds as natural UV-sunscreen as well as explaining the cosmopolitan distribution and ecological success of Interfilum and Klebsormidium in terrestrial habitats.
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usual alga from unusual habitats biodiversity of Klebsormidium klebsormidiophyceae streptophyta from the phylogenetic superclade g isolated from biological soil crusts
Molecular Phylogenetics and Evolution, 2019Co-Authors: Elena Samolov, Tatiana Mikhailyuk, Alena Lukesova, Karin Glaser, Burkhard Budel, Ulf KarstenAbstract:Seven new species and two varieties of Klebsormidium were described using an integrative approach on the base of 28 strains from the poorly studied phylogenetic superclade G. These strains originated from the unusual and exotic habitats (semi-deserts, semi-arid shrublands, Mediterranean shrub and deciduous vegetation, temperate Araucaria forests, peat bogs, dumps after coal mining, maritime sand dunes etc.) of four continents (Africa, South and North America, and Europe). Molecular phylogenies based on ITS-1,2, rbcL gene and concatenated dataset of ITS-1,2-rbcL, secondary structure of ITS-2, morphology, ecology and biogeography, micrographs and drawings of the investigated strains were assessed. Additionally, phylogeny and morphology of 18 Klebsormidium strains from other lineages isolated from the same localities (different vegetation types of Chile and maritime sand dunes of Germany) were investigated for the comparison with representatives of clade G. Clade G Klebsormidium is characterized by distant phylogenetic position from the other Klebsormidium lineages and prominent morphology: four-lobed chloroplasts and mostly short swollen cells in young culture, compact small pyrenoids, curved or disintegrated filaments, unusual elongation of cells in old culture, formation of specific cluster- and knot-like colonies on agar surface, especially prominent in strains isolated from desert regions, from which the group probably originated. Comparison of Klebsormidium diversity from different biogeographic regions showed that the representatives of clade G are common algae in regions of the southern hemisphere (South Africa and Chile) and rare representatives in terrestrial ecosystems of the northern hemisphere. Further investigation of mostly unstudied territories of the southern hemisphere could bring many surprises and discoveries, leading to a change of the present concept that Klebsormidium is cosmopolitan in distribution.
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light and dehydration but not temperature drive photosynthetic adaptations of basal streptophytes hormidiella streptosarcina and streptofilum living in terrestrial habitats
Microbial Ecology, 2019Co-Authors: Ulf Karsten, Tatiana Mikhailyuk, Mattia Pierangelini, Karin Glaser, Andreas HolzingerAbstract:Streptophyte algae are the ancestors of land plants, and several classes contain taxa that are adapted to an aero-terrestrial lifestyle. In this study, four basal terrestrial streptophytes from the class Klebsormidiophyceae, including Hormidiella parvula; two species of the newly described genus Streptosarcina (S. costaricana and S. arenaria); and the newly described Streptofilum capillatum were investigated for their responses to radiation, desiccation and temperature stress conditions. All the strains showed low-light adaptation (Ik < 70 μmol photons m−2 s−1) but differed in photoprotective capacities (such as non-photochemical quenching). Acclimation to enhanced photon fluence rates (160 μmol photons m−2 s−1) increased photosynthetic performance in H. parvula and S. costaricana but not in S. arenaria, showing that low-light adaptation is a constitutive trait for S. arenaria. This lower-light adaptation of S. arenaria was coupled with a higher desiccation tolerance, providing further evidence that dehydration is a selective force shaping species occurrence in low light. For protection against ultraviolet radiation, all species synthesised and accumulated different amounts of mycosporine-like amino acids (MAAs). Biochemically, MAAs synthesised by Hormidiella and Streptosarcina were similar to MAAs from closely related Klebsormidium spp. but differed in retention time and spectral characteristics in S. capillatum. Unlike the different radiation and dehydration tolerances, Hormidiella, Streptosarcina and Streptofilum displayed preferences for similar thermal conditions. These species showed a temperature dependence of photosynthesis similar to respiration, contrasting with Klebsormidium spp. and highlighting an interspecific diversity in thermal requirements, which could regulate species distributions under temperature changes.
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habitat specific composition of morphotypes with low genetic diversity in the green algal genus Klebsormidium streptophyta isolated from biological soil crusts in central european grasslands and forests
European Journal of Phycology, 2017Co-Authors: Karin Glaser, A. Donner, Tatiana Mikhailyuk, M. Albrecht, Ulf KarstenAbstract:Terrestrial filamentous green algae of the widely distributed, cosmopolitan genus Klebsormidium (Klebsormidiophyceae, Streptophyta) are typical components of biological soil crusts (BSCs). These co...
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Ecophysiological Response on Dehydration and Temperature in Terrestrial Klebsormidium (Streptophyta) Isolated from Biological Soil Crusts in Central European Grasslands and Forests.
Microbial ecology, 2016Co-Authors: A. Donner, Nadine Borchhardt, Karin Glaser, Ulf KarstenAbstract:The green algal genus Klebsormidium (Klebsormidiophyceae, Streptophyta) is a typical member of biological soil crusts (BSCs) worldwide. Ecophysiological studies focused so far on individual strains and thus gave only limited insight on the plasticity of this genus. In the present study, 21 Klebsormidium strains (K. dissectum, K. flaccidum, K. nitens, K. subtile) from temperate BSCs in Central European grassland and forest sites were investigated. Photosynthetic performance under desiccation and temperature stress was measured under identical controlled conditions. Photosynthesis decreased during desiccation within 335–505 min. After controlled rehydration, most isolates recovered, but with large variances between single strains and species. However, all K. dissectum strains had high recovery rates (>69%). All 21 Klebsormidium isolates exhibited the capability to grow under a wide temperature range. Except one strain, all others grew at 8.5 °C and four strains were even able to grow at 6.2 °C. Twenty out of 21 Klebsormidium isolates revealed an optimum growth temperature >17 °C, indicating psychrotrophic features. Growth rates at optimal temperatures varied between strains from 0.26 to 0.77 μ day−1. Integrating phylogeny and ecophysiological traits, we found no phylogenetic signal in the traits investigated. However, multivariate statistical analysis indicated an influence of the recovery rate and growth rate. The results demonstrate a high infraspecific and interspecific physiological plasticity, and thus wide ecophysiological ability to cope with strong environmental gradients. This might be the reason why members of the genus Klebsormidium successfully colonize terrestrial habitats worldwide.
Klaus Herburger - One of the best experts on this subject based on the ideXlab platform.
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localisation and substrate specificities of transglycanases in charophyte algae relate to development and morphology
Journal of Cell Science, 2018Co-Authors: Klaus Herburger, Zoë A. Popper, Louise Ryan, Andreas HolzingerAbstract:Cell wall-modifying enzymes were previously investigated in charophyte green algae (CGA) from cultures of uniform age, giving limited insight into their roles. Therefore, we investigated the in situ localisation and specificity of enzymes acting on hemicelluloses in CGA genera of different morphologies and developmental stages. In vivo transglycosylation between xyloglucan and an endogenous donor in filamentous Klebsormidium and Zygnema showed action in longitudinal cell walls of young (1 month) but not old cells (1 year), suggesting involvement in cell growth. Contrastingly, in parenchymatous Chara , transglycanase action occurred in all cell planes. In Klebsormidium and Zygnema , enzyme action predominately co-localised with xyloglucans and mannans, to a lesser extent mixed-linkage β-glucan (MLG), indicating predominantly xyloglucan:xyloglucan endotransglucosylase (XET). Novel transglycosylation activities between xyloglucan and xylan, and xyloglucan and galactomannan were identified in vitro , in both genera. Our results show that several cell wall-modifying enzymes are present in CGA and that differences in morphology and cell age are related to enzyme localisation and specificity. This indicates an evolutionary significance of cell wall modifications, as similar changes are known from their immediate descendants, the land plants.
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Photosynthetic plasticity in the green algal species Klebsormidium flaccidum (Streptophyta) from a terrestrial and a freshwater habitat.
Phycologia, 2017Co-Authors: Ulf Karsten, Klaus Herburger, Andreas HolzingerAbstract:Abstract: The genus Klebsormidium (Klebsormidiales, Streptophyta) has a worldwide distribution in terrestrial habitats. In the present study, we focused on two strains of Klebsormidium flaccidum, the type species of the genus. The isolates used in this study were isolated from soil and freshwater habitats. Photosynthetic activity was evaluated under different controlled gradients of light, temperature and desiccation. The data clearly indicate that both isolates of K. flaccidum exhibit conspicuously different photosynthetic response patterns to photon fluence rate, temperature and desiccation, and thus can be related to their different habitats. Although both strains represent the same species, their physiological response patterns to abiotic gradients as well as their morphology differed to some extent. This indicates high phenotypic plasticity of K. flaccidum, which was maintained even after long-term culture and thus can be explained by the formation of physiologically distinct ecotypes.
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Entransia and Hormidiella, sister lineages of Klebsormidium (Streptophyta), respond differently to light, temperature, and desiccation stress
Protoplasma, 2016Co-Authors: Klaus Herburger, Ulf Karsten, Andreas HolzingerAbstract:The green-algal class Klebsormidiophyceae (Streptophyta), which occurs worldwide, comprises the genera Klebsormidium , Interfilum , Entransia , and Hormidiella . Ecophysiological research has so far focused on the first two genera because they are abundant in biological soil crust communities. The present study investigated the photosynthetic performances of Hormidiella attenuata and two strains of Entransia fimbriata under light, temperature, and desiccation stress. Their ultrastructure was compared using transmission electron microscopy. The two Entransia strains showed similar physiological responses. They used light more efficiently than Hormidiella , as indicated by higher oxygen production and relative electron transport rate under low light conditions, lower light saturation and compensation points, and higher maximum oxygen production during light saturation. Their requirement for low light levels explains the restriction of Entransia to dim limnetic habitats. In contrast, Hormidiella , which prefers drier soil habitats, responded to light gradients similarly to other aero-terrestrial green algae. Compared to Entransia , Hormidiella was less affected by short-term desiccation, and rehydration allowed full recovery of the photosynthetic performance. Nevertheless, both strains of Entransia coped with low water availability better than other freshwater algae. Photosynthetic oxygen production in relation to respiratory consumption was higher in low temperatures ( Entransia : 5 °C, Hormidiella : 10 °C) and the ratio decreased with increasing temperatures. Hormidiella exhibited conspicuous triangular spaces in the cell wall corners, which were filled either with undulating cell wall material or with various inclusions. These structures are commonly seen in various members of Klebsormidiophyceae. The data revealed significant differences between Hormidiella and Entransia , but appropriate adaptations to their respective habitats.
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Localization and Quantification of Callose in the Streptophyte Green Algae Zygnema and Klebsormidium: Correlation with Desiccation Tolerance
2016Co-Authors: Klaus Herburger, Andreas HolzingerAbstract:Freshwater green algae started to colonise terrestrial habitats about 460 million years ago, giving rise to the evolution of land plants. Today, several streptophyte green algae occur in aero-terrestrial habitats with unpredictable fluctuations in water availability, severing as ideal models for investigating desiccation tolerance. We tested the hypothesis that callose, a β-D-1,3-glucan, is incorporated specifically in strained areas of the cell wall due to cellular water loss, implicating a contribution to desiccation tolerance. In the early diverging genus Klebsormidium, callose was drastically increased already upon 30 min of desiccation stress. Localization studies demonstrated an increase of callose in the undulating cross cell walls during cellular water loss, allowing a regulated shrinkage and expansion after rehydration. This correlates with a high desiccation tolerance demonstrated by a full recovery of the photosynthetic yield visualized at the subcellular level by Imaging-PAM. Furthermore, abundant callose in terminal cell walls might facilitate cell detachment to release dispersal units. In contrast, in the late diverging Zygnema callose content did not change upon desiccation for up to 3.5 h and was primarily localized in the corners between individual and at terminal cells. While these callose deposits still imply reduction of mechanical damage, the photosynthetic yield did not recover fully in the investigated young cultures of Zygnema upon rehydration. The abundance and specific localization of callose correlates with the higher desiccation tolerance in Klebsormidium when compared to Zygnema. Keywords aero-terrestrial green algae; cell wall; evolutionary biology; Imaging-PAM; phylogeny; terrestrialization This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial Licens
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living in biological soil crust communities of african deserts physiological traits of green algal Klebsormidium species streptophyta to cope with desiccation light and temperature gradients
Journal of Plant Physiology, 2016Co-Authors: Ulf Karsten, Klaus Herburger, Andreas HolzingerAbstract:Green algae of the genus Klebsormidium (Klebsormidiales, Streptophyta) are typical members of biological soil crusts (BSCs) worldwide. The phylogeny and ecophysiology of Klebsormidium has been intensively studied in recent years, and a new lineage called superclade G, which was isolated from BSCs in arid southern Africa and comprising undescribed species, was reported. Three different African strains, that have previously been isolated from hot-desert BSCs and molecular-taxonomically characterized, were comparatively investigated. In addition, Klebsormidium subtilissimum from a cold-desert habitat (Alaska, USA, superclade E) was included in the study as well. Photosynthetic performance was measured under different controlled abiotic conditions, including dehydration and rehydration, as well as under a light and temperature gradient. All Klebsormidium strains exhibited optimum photosynthetic oxygen production at low photon fluence rates, but with no indication of photoinhibition under high light conditions pointing to flexible acclimation mechanisms of the photosynthetic apparatus. Respiration under lower temperatures was generally much less effective than photosynthesis, while the opposite was true for higher temperatures. The Klebsormidium strains tested showed a decrease and inhibition of the effective quantum yield during desiccation, however with different kinetics. While the single celled and small filamentous strains exhibited relatively fast inhibition, the uniserate filament forming isolates desiccated slower. Except one, all other strains fully recovered effective quantum yield after rehydration. The presented data provide an explanation for the regular occurrence of Klebsormidium strains or species in hot and cold deserts, which are characterized by low water availability and other stressful conditions.
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usual alga from unusual habitats biodiversity of Klebsormidium klebsormidiophyceae streptophyta from the phylogenetic superclade g isolated from biological soil crusts
Molecular Phylogenetics and Evolution, 2019Co-Authors: Elena Samolov, Tatiana Mikhailyuk, Alena Lukesova, Karin Glaser, Burkhard Budel, Ulf KarstenAbstract:Seven new species and two varieties of Klebsormidium were described using an integrative approach on the base of 28 strains from the poorly studied phylogenetic superclade G. These strains originated from the unusual and exotic habitats (semi-deserts, semi-arid shrublands, Mediterranean shrub and deciduous vegetation, temperate Araucaria forests, peat bogs, dumps after coal mining, maritime sand dunes etc.) of four continents (Africa, South and North America, and Europe). Molecular phylogenies based on ITS-1,2, rbcL gene and concatenated dataset of ITS-1,2-rbcL, secondary structure of ITS-2, morphology, ecology and biogeography, micrographs and drawings of the investigated strains were assessed. Additionally, phylogeny and morphology of 18 Klebsormidium strains from other lineages isolated from the same localities (different vegetation types of Chile and maritime sand dunes of Germany) were investigated for the comparison with representatives of clade G. Clade G Klebsormidium is characterized by distant phylogenetic position from the other Klebsormidium lineages and prominent morphology: four-lobed chloroplasts and mostly short swollen cells in young culture, compact small pyrenoids, curved or disintegrated filaments, unusual elongation of cells in old culture, formation of specific cluster- and knot-like colonies on agar surface, especially prominent in strains isolated from desert regions, from which the group probably originated. Comparison of Klebsormidium diversity from different biogeographic regions showed that the representatives of clade G are common algae in regions of the southern hemisphere (South Africa and Chile) and rare representatives in terrestrial ecosystems of the northern hemisphere. Further investigation of mostly unstudied territories of the southern hemisphere could bring many surprises and discoveries, leading to a change of the present concept that Klebsormidium is cosmopolitan in distribution.
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light and dehydration but not temperature drive photosynthetic adaptations of basal streptophytes hormidiella streptosarcina and streptofilum living in terrestrial habitats
Microbial Ecology, 2019Co-Authors: Ulf Karsten, Tatiana Mikhailyuk, Mattia Pierangelini, Karin Glaser, Andreas HolzingerAbstract:Streptophyte algae are the ancestors of land plants, and several classes contain taxa that are adapted to an aero-terrestrial lifestyle. In this study, four basal terrestrial streptophytes from the class Klebsormidiophyceae, including Hormidiella parvula; two species of the newly described genus Streptosarcina (S. costaricana and S. arenaria); and the newly described Streptofilum capillatum were investigated for their responses to radiation, desiccation and temperature stress conditions. All the strains showed low-light adaptation (Ik < 70 μmol photons m−2 s−1) but differed in photoprotective capacities (such as non-photochemical quenching). Acclimation to enhanced photon fluence rates (160 μmol photons m−2 s−1) increased photosynthetic performance in H. parvula and S. costaricana but not in S. arenaria, showing that low-light adaptation is a constitutive trait for S. arenaria. This lower-light adaptation of S. arenaria was coupled with a higher desiccation tolerance, providing further evidence that dehydration is a selective force shaping species occurrence in low light. For protection against ultraviolet radiation, all species synthesised and accumulated different amounts of mycosporine-like amino acids (MAAs). Biochemically, MAAs synthesised by Hormidiella and Streptosarcina were similar to MAAs from closely related Klebsormidium spp. but differed in retention time and spectral characteristics in S. capillatum. Unlike the different radiation and dehydration tolerances, Hormidiella, Streptosarcina and Streptofilum displayed preferences for similar thermal conditions. These species showed a temperature dependence of photosynthesis similar to respiration, contrasting with Klebsormidium spp. and highlighting an interspecific diversity in thermal requirements, which could regulate species distributions under temperature changes.
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Biological Soil Crusts of Arctic Svalbard—Water Availability as Potential Controlling Factor for Microalgal Biodiversity
Frontiers in microbiology, 2017Co-Authors: Nadine Borchhardt, Tatiana Mikhailyuk, Christel Baum, Ulf KarstenAbstract:In the present study the biodiversity of biological soil crusts (BSCs) formed by phototrophic organisms were investigated on Arctic Svalbard (Norway). These communities exert several important ecological functions and constitute a significant part of vegetation at high latitudes. Non-diatom eukaryotic microalgal species of BSCs from 20 sampling stations around Ny-Alesund and Longyearbyen were identified by morphology using light microscopy, and the results revealed a high species richness with 102 species in total. 67 taxa belonged to Chlorophyta (31 Chlorophyceae and 36 Trebouxiophyceae), 13 species were Streptophyta (11 Klebsormidiophyceae and two Zygnematophyceae) and 22 species were Ochrophyta (two Eustigmatophyceae and 20 Xanthophyceae). Surprisingly, Klebsormidium strains belonging to clade G (Streptophyta), which were so far described from Southern Africa, could be determined at 5 sampling stations. Furthermore, comparative analyses of Arctic and Antarctic BSCs were undertaken to outline differences in species composition. In addition, a pedological analysis of BSC samples included C, N, S, TP (total phosphorus) and pH measurements to investigate the influence of soil properties on species composition. No significant correlation with these chemical soil parameters was confirmed but the results indicated that pH might affect the BSCs. In addition, a statistically significant influence of precipitation on species composition was determined. Consequently, water availability was identified as one key driver for BSC biodiversity in Arctic regions.
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habitat specific composition of morphotypes with low genetic diversity in the green algal genus Klebsormidium streptophyta isolated from biological soil crusts in central european grasslands and forests
European Journal of Phycology, 2017Co-Authors: Karin Glaser, A. Donner, Tatiana Mikhailyuk, M. Albrecht, Ulf KarstenAbstract:Terrestrial filamentous green algae of the widely distributed, cosmopolitan genus Klebsormidium (Klebsormidiophyceae, Streptophyta) are typical components of biological soil crusts (BSCs). These co...
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Habitat-specific composition of morphotypes with low genetic diversity in the green algal genus Klebsormidium (Streptophyta) isolated from biological soil crusts in Central European grasslands and forests
2017Co-Authors: K. Glaser, Tatiana Mikhailyuk, A. Donner, M. Albrecht, U. KarstenAbstract:Terrestrial filamentous green algae of the widely distributed, cosmopolitan genus Klebsormidium (Klebsormidiophyceae, Streptophyta) are typical components of biological soil crusts (BSCs). These communities occur in all climatic zones and on all continents, where soil moisture is limited or where there has been disturbance. BSCs form water-stable aggregates that have important ecological roles in primary production, nitrogen fixation, nutrient cycling, water retention and stabilization of soils. Although available data on Klebsormidium are limited, its functional importance in BSCs is regarded as high. Therefore, in the present study Klebsormidium strains were isolated from BSCs sampled from various grassland and forest plots of different land use intensities in Central Europe, as provided by the Biodiversity Exploratories, and its intraspecific genetic diversity was evaluated. Previous phylogenetic analyses revealed a relationship between sequence similarity and habitat preference with a higher genetic diversity than expected from a morphological classification. We isolated and sequenced 75 Klebsormidium strains. The molecular phylogeny based on the ITS regions showed that all strains belong to either the previously described clade B/C or clade E. This classification was supported by morphological characteristics: strains assigned to clade B/C were identified as Klebsormidium cf. flaccidum or Klebsormidium cf. dissectum, and strains from clade E as K. nitens or Klebsormidium cf. subtile. Within one clade the strains showed low sequence divergences. These minor differences were independent of the sampling region and land use intensity. Interestingly, most of the strains assigned to clade E were isolated from forest sites, whereas strains from clade B/C occurred equally in grassland and forest sites. Therefore, it is reasonable to assume that habitat with its microenvironmental conditions, and not biogeography, controls genetic diversity in Klebsormidium.