Poster: Temperature Responses
Abs #
172: Red snow: Structural analysis of cryophilic green algae Chlamydomonas nivalis using ESEM and high pressure freeze fixation/freeze substitution techniques for TEM
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Presenter: |
Holzinger, Andreas , Andreas.Holzinger@uibk.ac.at |
Authors | Holzinger, Andreas (A) Remias, Daniel (A) Luetz, Cornelius (A) | | Affiliations: |
(A): Institute of Botany, Department of Physiology and Cell Physiology of Alpine Plants
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| Web Site: | http://botany.uibk.ac.at/ | |
Blooming of snow algae color snow fields worldwide red or orange, and represent a life form, special adapted to low temperature, poor nutrition, permanent freeze- thaw cycles and occasionally high irradiation. Our samples were collected in the Austrian Alps, at an altitude of 1800-3000 m, and in Ny Alesund, Svalbard (Norway) at 78.9° N, at sea level. In all habitats the dominating species is Chlamydomonas nivalis, however, also Chloromonas alpina, Chloromonas nivalis, Scotiella cryophila were detected. The red colored hypnoblasts, which are exposed to the aforementioned extreme conditions, are studied, besides investigations of photosynthesis and pigment analysis, to understand if survival strategies can be recognized by ultrastructural analysis like environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM) techniques. Especially hypnoblasts of Chlamydomonas nivalis, with nodules at the cell wall show the tendency of covering their surface with particles rich in silicate as investigated by element analysis. These inorganic particles may form a protection shield, mostly overseen as washed away in classical SEM preparation protocols.
Chemical fixations for TEM with these organisms did not result in satisfactory preservation of the ultrastructure in most cases. High pressure freeze fixation, followed by freeze substitution in acetone containing osmium tetroxide and uranyl acetate allowed especially well preservation of details of the chloroplast, and crystallized structures inside secondary metabolic depots were detected. These represent most likely crystallized carotenoide esters. Moreover, mucilage layers, covering the cell wall adhering the inorganic particles to the surface of the cell walls are observed.
