Lipids of Spores from Phycomyces in Relation to Heat-induced Germination

Abstract

Fatty acids of the triglycerides and free lipids of Phycomyces blakesleeanus spores were extracted, isolated and separated by thin layer, liquid and gas chromatography, and the free levels of carotenes and free glycerol determined both before and after activation by heat-shock procedure (3 minutes at 50°C). Lipids account for about 3% of the dry weight, with triglycerides being the major constituents (25% of the total lipids). The fatty acids were almost exclusively unsaturated, and in both triglycerides and other lipids, the unbranched 16: 0 (5%), 18: 1 (12%), 18: 2 (31%), and 18: 3 (45%) were predominant. The only compound with an odd number of carbon atoms found in the spores was a 15: 0 acid which made up only 0.1% of the total fatty acids. β -carotene accounts for more than 95% of all colored carotenes (about 3.5 μ moles/100 mg spores) and it is probably located in the protoplast rather than in the cell wall. The levels of these substances are not influenced by heat-activation whereas the content of free glycerol shows a 300 fold increase 60 minutes after the spores were heat-activated. The results indicate that heat-activation does not stimulate lipid metabolism. The remarkable alterations in the free glycerol content (from 0.1 μ moles/100 mg dormant spores to 30 μ moles/100 mg heat-activated ones) is not a result of fat decomposition but rather a product of the stimulated carbohydrate breakdown which is known to occur when spores are submitted to heat-shock procedure.