THE RELATIONSHIP OF CELL WALL STRUCTURE AND COMPOSITION TO COPPER SUSCEPTIBILITY IN PITHOPHORA OEDOGONIA
Abstract
The cell wall of Pithophora oedogonia (Montagne) Wittrock was examined to determine whether the wall components were involved in the resistance of this alga to copper poisoning. Physical, biochemical and cytochemical techniques, as well as light and electron microscopy, were used to identify the cell wall components. Sorbed copper was detected by atomic absorption spectrophotometry and cytochemistry. The major polysaccharides of P. oedogonia walls were chitin and cellulose. N-acetylgalactosamine, galactose, arabinose, fucose, mannose, xylose, and galacturonic acid were the other sugars, amino sugars, and sugar derivatives detected. The wall was estimated to be 65 percent non-nitrogenous hexose and 6 percent chitin. Chitin was present in the crosswall disks and outer wall, whereas cellulose was confined to the inner wall. Protein and N-acetylgalactosamine were concentrated in the chitin-rich wall fraction. Polyphosphate was present in the outer wall and on the cell surface, and alkaline phosphatase activity was detected on the surface of the cell. The location of chitin in the P. oedogonia wall is suggested to be a basis for morphological differences between Cladophora and Pithophora. A procedure was developed to selectively stain chitin. Chitin was visualized in walls after KOH hydrolysis and postfixation in OsO(,4). To confirm the detection of chitin by this method, the cell walls of two fungi, Ceratocystis ulmi Buism. (C. Moreau) and Blastocladiella emersonii Cantino and Hyatt, were examined. Copper uptake in P. oedogonia was determined to be a 2-step process. The first step, resulting in the algistatic (inhibitory) effect on subsequent growth, was probably due to a sublethal dose of copper in the cytoplasm. Most of the copper to which the cell was exposed, was sorbed on wall-binding sites and the cell surface. The second step results in the algicidal action of copper. After wallbinding sites are saturated, excessive copper enters the cytoplasm and causes irreversible poisoning. Ultrastructural observations of copper-inhibited akinetes verified that little copper penetrated the cytoplasm; most was on the cell surface and in the outer wall. Copper permeated the cytoplasm of non-viable akinetes. In copper-free medium, viable spores lost wall-bound copper initially from the cell surface then from the outer wall. Akinetes were more copper-resistant than filamentous cells. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI
Degree
Ph.D.
Subject Area
Botany
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