The possible metabolic role of C37 alkenones in Emiliania huxleyi
By B. Epstein, S. D’Hondt, P. Hargraves. 2001
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Abstract Ratios of C37 alkenones (U37K′ratios) produced by the haptophyte microalgae Emiliania huxleyi and Gephyrocapsa oceanica are often used as proxies for past sea surface temperatures. Previous studies suggested that these lipids might be either membrane molecules or metabolic storage molecules. In order to assess their cellular role, we cultured two strains of E. huxleyi at 12:12 and 0:24 light/dark cycles (North Pacific clone 55a and Sargasso Sea clone BT6). For both strains, alkenone concentrations (ng/ml) generally increased through both logarithmic and stationary phase in cultures with 12:12 light/dark cycles. This pattern of increasing concentration closely resembles the pattern of increasing triacylglycerol concentration observed in cultures of other marine phytoplankton. Triacylglycerols are used as metabolic storage molecules by many marine algae, but are under-represented or absent in E. huxleyi. When the E. huxleyi cultures were placed in continuous darkness, their alkenone concentrations fell. These findings, that alkenones increase in abundance from logarithmic to stationary phase and decrease in concentration when E. huxleyi is energy-deprived, suggest that Emiliania huxleyi uses alkenones for metabolic storage. Alkenone unsaturation (U37K′) ratios changed only slightly during net alkenone degradation in our dark experiments (by −0.035 and +0.046 U37K′ units in the dark incubations of BT6 and 55a, respectively), suggesting that metabolic utilization of C37 alkenones by E. huxleyi is unlikely to be a major source of uncertainty for paleotemperature estimation. If C37 alkenones are primarily used for metabolic storage, the temperature dependence of their unsaturation may result from differences in melting point, density, or enzymatic optima of biochemical pathways of the differently saturated alkenones.
Subfields: Global and Planetary Change, Oceanography, Renewable Energy, Sustainability and the Environment
View Paper: https://www.semanticscholar.org/paper/f72da1fdfe23ca78534cd4a73dd5f3e5e7c5dc79
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In Oceanography
Citations in the corpus
- Physiological impacts on alkenone paleothermometry (2003, unknown): “[ 16 ] The observations from our batch culture experiments are consistent with the suggested role of alkenones as cellular energy stores [ Epstein et al. , 2001; Pond and Harris , 1996].”
- PRODUCTION AND CELLULAR LOCALIZATION OF NEUTRAL LONG‐CHAIN LIPIDS IN THE HAPTOPHYTE ALGAE ISOCHRYSIS GALBANA AND EMILIANIA HUXLEYI 1 (2005, background): “…of unsaturation index depends on strain genetics (Conte et al. 1998) and environmental factors such as nutrient limitation or light availability (Epstein et al. 1998, 2001, Yamamoto et al. 2000, Versteegh et al. 2001, Prahl et al. 2003), and the utility of this tool remains limited by our lack…”