Zellwand-Eigenschaften und Bioadhäsion in verschiedenen Genotypen der aeroterrestrischen Grünalgengattung Klebsormidium aus alpinen Böden der österreichischen Alpen
Zusammenfassung der Projektergebnisse
Terrestrial green microalgae are typical components of biological soil crusts (BSC) in alpine regions of the Alps. Here they form in the uppermost millimetres an intimate association with soil particles, thereby exerting important ecological roles in primary production, nutrient cycling, water retention and stabilization of soils. The cell wall and mucilage properties of representative BSC green algae as a mechanical protection against terrestrial stress scenarios was studied. Confocal laser microscopy in combination with a set of fluorescence dyes to visualise cell biologically important structures under desiccation stress was successfully carried out with "Klebsormidium crenulatu" collected from a soil crust in Obergurgl (Tyrol) at 2,400m. In liquid culture K. crenulatum formed strong filaments up to several hundred μm in length. The outer surface of the cells appeared rough, while separated cross walls had a smooth appearance, they were convexly bent out due to the turgor pressure. When K. crenulatum filaments were desiccated marked changes characterized by a collapsed outer surface of the filament could be observed. The collapse of the filaments appeared over a long distance, the cross wall positions did not become visible on the surface of a desiccated K. crenulatum filament. Most striking was the appearance of cross walls in desiccated samples, which were strongly undulated, suggesting a high degree of mechanical flexibility. The diameters of the cells were in this case reduced to about 60 % of the dimension seen in cells obtained from liquid culture. In contrast, the outer cell walls were occasionally indented, but never with such an undulated appearance. This was the case in all desiccated samples regardless of the relative air humidity they have been exposed to. The chloroplasts of desiccated samples contained an elevated number of plastoglobules, and all key organelles were maintained. The composition and nanoscale mechanical characteristics of the adhesive from the BSC green alga “Coccomyxa” sp. was studied using Raman spectroscopy, chemical staining, and atomic force microscopy (AFM) in collaboration with Dr. Anika Mostaert, University College Dublin, Ireland. Raman spectroscopy confirmed the adhesive proteins to be predominantly in ß-sheet conformations and composed of a number of hydrophobic amino acid residues. Chemical staining with Congo red and thioflavin-T dyes further confirmed the presence of amyloid-like structures. Probing the adhesives with AFM revealed highly ordered and repetitive mechanical responses indicative of highly ordered structures within the adhesive. The mechanical data show how amyloid provides cohesive strength to the adhesives, and this intrinsic mechanical property of an amyloid-based adhesive explains the ecological success of attachment of this terrestrial microalga to BSCs.
Projektbezogene Publikationen (Auswahl)
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(2010) Ecophysiological performance of the aeroterrestrial green alga Klebsormidium crenulatum (Klebsormidiophyceae, Streptophyta) isolated from an alpine soil crust with an emphasis on desiccation stress. Journal of Phycology 46, 1187–1197
Karsten, U., Lütz, C. & Holzinger, A.
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(2011) Desiccation stress causes structural and ultra-structural alterations in the aeroterrestrial green alga Klebsormidium crenulatum (Klebsormidiophyceae, Streptophyta) isolated from an alpine soil crust. Journal of Phycology 47, 591–602
Holzinger, A., Lütz, C. & Karsten, U.
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(2012) Light, temperature and desiccation effects on photosynthetic activity, and drought-induced ultrastructural changes in the green alga Klebsormidium sp. (Streptophyta) from a high alpine soil crust. Microbial Ecology 63, 51-63
Karsten, U. & Holzinger, A.
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(2013) Desiccation stress and tolerance in green algae: Consequences for ultrastructure, physiological and molecular mechanisms. Frontiers in Plant Science 4, article 327
Holzinger, A. & Karsten, U.
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(2013) Photosynthetic performance of different genotypes of the green alga Klebsormidium sp. (Streptophyta) isolated from biological soil crusts of the Alps. Algological Studies 142, 45-62
Karsten, U., Pröschold, T., Mikhailjuk, T. & Holzinger, A.
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(2013) Unusual phenolic compounds contribute to the ecophysiological performance in the purple coloured green alga Zygogonium ericetorum (Zygnematophyceae, Streptophyta) from a high alpine habitat. Journal of Phycology 49, 648-660
Aigner, S., Remias, D., Lewis, La, Karsten, U. & Holzinger, A.
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(2014) Desiccation, temperature and light tolerance in members of the aeroterrestrial green algal genus Interfilum (Streptophyta) from biogeographically different temperate soils. Journal of Phycology 50, 804–816
Karsten, U., Herburger, K. & Holzinger, A.
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(2014) Green algae in alpine biological soil crust communities - acclimation strategies against ultraviolet radiation and dehydration. Biodiversity and Conservation 23, 1845-1858
Karsten, U. & Holzinger, A.
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(2014) Morphological and ultrastructural aspects of phylogenetically closely related genera Interfilum and Klebsormidium (Klebsormidiales, Streptophyta). European Journal of Phycology 49, 395–412
Mikhailyuk, T., Holzinger, H., Massalski, A. & Karsten, U.
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(2014) UV-induced effects on growth, photosynthetic performance and sunscreen contents in different populations of the green alga Klebsormidium fluitans (Streptophyta) from alpine soil crusts. Microbial Ecology 67, 327–340
Kitzing, C., Pröschold, T. & Karsten, U.
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(2015) Biodiversity of Klebsormidium (Streptophyta) from alpine biological soil crusts (Alps, Tyrol, Austria and Italy). Journal of Phycology 51, 750-767
Mikhailyuk, T., Glaser, K., Holzinger, A. & Karsten, U.
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(2015) Entransia and Hormidiella, sister lineages of Klebsormidium (Streptophyta), respond distinctly to light, temperature and desiccation stress. Protoplasma
Herburger, K., Karsten, U. & Holzinger, A.
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(2015) 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
Karsten, U., Herburger, K. & Holzinger, A.
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(2015) UV-induced effects on optimum quantum yield and sunscreen contents in members of the genera Interfilum, Klebsormidium, Hormidiella and Entransia (Klebsormidiophyceae, Streptophyta). European Journal of Phycology 50, 279-287
Kitzing, C. & Karsten, U.
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(2016) Prasiolin, a new UV-sunscreen compound in the terrestrial green macroalga Prasiola calophylla (Carmichael ex Greville) Kützing (Trebouxiophyceae, Chlorophyta). Planta 243,161–169
Hartmann, A., Holzinger, A., Ganzera, M. & Karsten, U.
