Chlorella ellipsoidea cultured using conventional methods under a 14: 10 light-dark regime in Bai j eririck ' s medium at 25?+ 1?with 700 ft-c illumination resulted in synchronous division with an n number of 4. Under identical conditions of light intensity, temperature, culture medium, and light-dark regime but in a closed system which was designs to study the effects of hydrostatic pressure on synchronous algae cultures, synchronous cell division did not occur and the n number was 2 or less at 1 atm. The most significant difference in the culture conditions arises because the concentrations of dissolved gases (mainly CCu and O^) remain relatively constant throughout the growth cycle in the open system while the gases vary in concentration continuously during the cycle in the closed system. In the closed system C>2 increases continuously c?CO-p decreases during the light period; the reverse is true in the dark. Analyses of the rati.os of dry weight, protein content, and cell size showed increases of approximately 2 in the closed system and 4 in the open system. The intent of this study was to determine effects of hydrostatic pressure on the physiology and morphology of algae. Therefore it was essential to develop techniques for successful culture in a closed system. Various modifications of culture conditions were made in attempts (only partially successful) to obtain equal growth in the two systems. 11 The effects of variations in some environmental parameters on the n number, dry weight, protein concentration, and cell size in the open and closed systems were investigated. With varied growing conditions of light intensity (15-700 ft--c), light- dark regimes (14: 10, 16: 8, 18: 6, 6: 18, 8: 16, 10: 14), media (Beijerinck, Burr, Sorokin, Tamiya and Morimura, and Beijerinck's modified with bicarbonate), CC^ concentration (0-100% saturation), and the addition of organic substances (glycolate, ascorbate, dithiothreitol) the n number and the ratios of increase in the other growth criteria were 4 in the open system but never more than 2 in the closed system. The n number and ratios of increase in dry weight, protein content and cell size were 4 in the open system at atmospheric Cu concentration but only 2 or less at high 02 (50 and 95%) concentration. These results indicate that high C>2 is probably responsible for the descrepancies in the n number and the rEitios of increase of the other criteria between the open and closed systems. Photosynthetically evolved 0^ in the closed system during the light period appears to be sufficient to induce this Warburg Effect. It was hypothesized that the Warburg Effect is responsible for the observed differences in increases in the growth criteria in the open and closed systems. Experiments were carried out to determine if photosynthetically evolved 02 was inhibiting cell growth. Using the Biological Oxygen Monitor algal samples were exposed to ? concentrations varying from 0 to 100% saturation at 25?with 700 ft-c Ill illumination. On the basis of these results which have indicated a decrease in the relative rates of O^ evolution at high 02 concentrations, it was concluded that Op evolved in the closed system could be responsible for the inhibition of photosynthesis. Synchronous growth under pressure has not yet been obtained. However, pressure effects on cell division were investigated. The n number was 4 in cells dividing while exposed to pressures of up to 200 atm, but pressures above 335 atm completely inhibited cell division. A possible mutagenic effect of pressure exposure on algal cells was considered.
Thesis (Ph.D.) - Dept. of Biological Sciences - Simon Fraser University
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Thesis advisor: Vidaver, William
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