Date of Award
Doctor of Philosophy
A descriptive study of the cell envelope of Deinococcus radiodurans strain Sark and an exploration of the major components of the cell envelope was undertaken. The cell envelope consisted of six layers as seen in thin sections: a plasma membrane, 8.0nm thick; a peptidoglycan layer, 30nm thick; a compartmentalized layer, 20 - 75nm thick; an outer membrane, 6.5nm thick; an electron transparent zone, 10nm thick, and a hexagonal surface array, 2 - 3nm thick.;The outer cell envelope layers formed blebs throughout the growth cycle, which were shed as large vesicles (0.5(mu) to 3.5(mu) in diameter) from 5% of the cell population. Instability of the compartmentalized layer immediately beneath the outer membrane was the cause of the vesicle production. This instability was accentuated by treatment with 10% NaCl, which released the outer cell envelope layers as vesicles from all of the cell population without disrupting the peptidoglycan layer. Any remaining portions of the compartmentalized layer could be removed from these vesicles by 3M urea, which yielded purified outer membrane vesicles. The outer membrane vesicles were 0.5(mu) to 3.5(mu) in diameter, had a density of 1.27g/cm('3), and were 16% (w/w) lipid, 80% (w/w) protein, and 3.9% (w/w) non chloroform-methanol extractable (non-lipid) carbohydrate. There were 43 protein bands present on polyacrylamide gels of the outer membrane; two were identified as the hexagonal surface array proteins. No lipopolysaccharide-like compound was found in the outer membrane.;The hexagonal surface array was isolated by digesting isolated outer membrane with 2% sodium dodecyl sulphate (SDS), which dissolved all non-array components. The isolated array consisted of a major 115,000 Dalton (D) protein and a minor 108,000D protein. The array could not be separated from the outer membrane by reagents that disrupt ionic bonds (pH, NaCl, LiCl, KCl), disulphid bonds (mercaptoethanol, dithiothreitol), hydrogen bonds (urea, guandine HCl), or by chelating agents (EDTA). Only disruption of the outer membrane with SDS, separated the outer membrane and the hexagonal surface array. This suggested that the hexagonal surface array was held onto the bacterial surface largely by non-specific (hydrophobic) interactions. The external surface of the hexagonal surface array was also found to be more hydrophilic than the surface of the outer membrane. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI
Thompson, Bradley George, "An Ultrastructural And Biochemical Study Of The Cell Envelope Of Deinococcus Radiodurans Strain Sark" (1982). Digitized Theses. 1223.