The effects of manipulations of the concentrations of O₂, CO₂, total inorganic carbon, and glycidate on the Warburg effect in two species of marine unicellular algae
| dc.contributor.author | Morris, William James | en_US |
| dc.date.accessioned | 2024-08-14T22:53:32Z | |
| dc.date.available | 2024-08-14T22:53:32Z | |
| dc.date.copyright | 1979 | en_US |
| dc.date.issued | 1979 | |
| dc.degree.department | Department of Biology | |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | The photosynthetic CO₂ assimilation rate of Isochrysis galbana was depressed by dissolved [O₂] greater than zero. The depression was linear between 80 and 945 µM o2 and independent of [HC03-J or [CO2] at high [02]. The depression caused by 330 µM O₂ compared to 115 µM 0₂ was relieved by 5.05 mM carbon. At least 10 µM CO₂ was required for half-maximal photosynthesis, and 300 µM O₂ was sufficient to cause half-maximal O₂ inhibition. The pH optimum of photosynthesis was narrow (7.25 to 7.50) and correlated with the [CO₂]. Glycidate inhibited photosynthesis and the depression was independent of [O₂]. Optimal photosynthesis in Thalassiosira fluviatilis occurred at [O₂] between 220 and 500 µMat 2.0 mM carbon and between 125 and 225 µM at 0.2 mM carbon. A slight depression in photosynthesis was sometimes observed at [O₂] > 800 µM compared to [O₂] < 100 µM. This depression was sensitive to [carbon] and relieved by 2.0 mM carbon. Only 2.5 µM CO₂ was required for half-maximal photosynthesis and at least 700 µM O₂ was required for half-maximal O₂ inhibition. The pH optimum of photosynthesis was broad (< 7.00 to 8.25) and not closely correlated with [CO₂]. Glycidate stimulated photosynthesis and the stimulation was inversely related to [O₂]. These data are consistent with exclusive C-3 metabolism in I. galbana and the presence of photorespiration, although the absence of stimulation of photosynthesis by glycidate is not consistent with previous studies on C-3 terrestrial plants. In I. galbana the Warburg effect at high [O₂] was not relieved by elevated [CO₂] which indicated that O₂ inhibition can be caused by mechanisms other than photorespiration. The absence of a Warburg effect and the high affinity for CO₂ in T. fluviatilis are consistent with efficient recycling of photorespiratory CO₂ by C-4 metabolism. However, other mechanisms can explain these results; these include the dehydration of HC0₃⁻ in the chloroplast through the activity of carbonic anhydrase or absence of photorespiration per se resulting from a low intrinsic activity of RuDP oxygenase. Regardless of the causes of these differences, the high affinity for CO₂ broad pH tolerance, and absence of a Warburg effect in T. fluviatilis suggest that this species would have a considerable competitive advantage over a species like I. galbana in near-shore areas where high cell densities and high photosynthetic rates could result in alkaline pH values and O₂ supersaturation. | en_US |
| dc.format.extent | 106 pages | |
| dc.identifier.uri | https://hdl.handle.net/1828/19045 | |
| dc.rights | Available to the World Wide Web | en_US |
| dc.title | The effects of manipulations of the concentrations of O₂, CO₂, total inorganic carbon, and glycidate on the Warburg effect in two species of marine unicellular algae | en_US |
| dc.type | Thesis | en_US |
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