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Fatty acid composition of the cellular slime mold Polysphondylium pallidum
1Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
Abstract:
The cellular slime mold Polysphondylium pallidum was grown upon Escherichia coli B/r, and the fatty acid compositions of total lipids obtained from vegetative amebae and aggregation-competent cells were compared. Fatty acids isolated from vegetative cells included C-17 and C-19 cyclopropane fatty acids and also straight-chain, saturated fatty acids. The cyclopropane fatty acids were derived from the ingested bacteria. Development of amebae to aggregation-competent cells was accompanied by a substantial decrease in saturated cyclopropane fatty acids and a concomitant increase in unsaturated fatty acids and unsaturated cyclopropane fatty acids, mostly as 18:3 (5,9,12). We report here the fatty acid composition and identify the occurrence of delta 5 desaturation of cyclopropane fatty acids, namely, 9,10-methylene 5-hexadecenoic acid and 11,12-methylene 5-octadecenoic acid. These fatty acids have not been reported previously in the related species Dictyostelium discoideum, which also feeds on E. coli B/r and has delta 5-desaturation activity.
Insights
Cellular slime molds change their fatty acid composition during development. Polysphondylium pallidum shifts from saturated cyclopropane fatty acids to unsaturated ones, including novel desaturated cyclopropane fatty acids.
Area of Science:
- Cell Biology
- Biochemistry
- Microbiology
Background:
- Cellular slime molds like Polysphondylium pallidum are model organisms for studying cellular differentiation.
- Fatty acid composition is crucial for cell membrane structure and function.
- Dietary fatty acids from ingested bacteria can influence the host's lipid profile.
Purpose of the Study:
- To compare the fatty acid composition of Polysphondylium pallidum during vegetative growth and developmental stages.
- To identify specific fatty acids and metabolic pathways involved in cellular differentiation.
- To investigate the occurrence of novel desaturated cyclopropane fatty acids.
Main Methods:
- Culturing Polysphondylium pallidum on Escherichia coli B/r.
- Extraction and analysis of total lipids from vegetative and aggregation-competent cells.
- Gas chromatography-mass spectrometry (GC-MS) for fatty acid profiling.
- Identification of cyclopropane fatty acids and their desaturation products.
Main Results:
- Vegetative cells contained saturated straight-chain and cyclopropane fatty acids derived from E. coli.
- Development led to a decrease in saturated cyclopropane fatty acids and an increase in unsaturated fatty acids.
- Novel unsaturated cyclopropane fatty acids, including 9,10-methylene 5-hexadecenoic acid and 11,12-methylene 5-octadecenoic acid, were identified.
- Evidence for delta 5 desaturation of cyclopropane fatty acids was observed.
Conclusions:
- Polysphondylium pallidum undergoes significant changes in fatty acid metabolism during differentiation.
- The delta 5 desaturation of cyclopropane fatty acids represents a novel metabolic pathway in this organism.
- These findings provide insights into lipid remodeling during cellular development in slime molds.