Abstract
Abstract The total lipid content of differentiating Dictyostelium discoideum was 100 to 125 mg per g dry weight; of this, about 95 mg per g was polar lipid (mainly phospholipid) and 25 mg per g was neutral lipid in the early stages. During culmination and maturation of the sorocarp, polar lipid declined to 75 mg per g, while neutral lipid increased to 40 mg per g. Per 1010 cells, polar lipid declined from 135 to 75 mg and neutral lipid increased from 33 to 45 mg. The neutral lipid fraction was resolved into its major components and the level of each in milligrams per g dry weight was determined at 10 different stages of slime mold differentiation. Stigmast-22-en-3β-ol remained near 10 to 11 during the early stages, rose to 15 at the beginning of migration, and then declined back to about 12; stigmastenol C16-C18 esters began a prolonged rise from 1 to 2 during early aggregation, ultimately reaching 15 in 3-day sorocarps; ubiquinone declined from 0.5 to 0.2 to 0.3 during aggregation where it remained until culmination, when it rose rapidly to a maximum of 1 to 2 in mature sorocarps; free fatty acids increased to a maximum of 7 during early aggregation and then fell sharply to less than 2 during migration; and triglycerides and diglycerides declined from initial levels of 2 to 4 to about 1 during the early stages. Approximate balances among the different lipid components were calculated from the changes in quantities. During the period prior to early aggregation, a net synthesis of lipid (phospholipid, sterol, and sterol ester) occurred from unidentified precursors. During aggregation metabolism shifted toward a net degradation, characterized by a rapid conversion of free fatty acids to unidentified products. This net degradation continued during the migration-preculmination period, although phospholipid replaced the nearly exhausted triglyceride and free fatty acid reserves as the major source of lipid. During the later periods net sterol synthesis ceased, but sterol ester synthesis continued at the expense of preformed free sterol.
Highlights
The total lipid content of differentiating Dictyostelium discoideum was 100 to 125 mg per g dry weight; of this, about 95 mg per g was polar lipid and
C16-CJ8 esters began a prolonged rise from 1 to 2 during early aggregation, reaching 15 in 3-day sorocarps; ubiquinone declined from 0.5 to 0.2 to 0.3 during aggregation where it remained until culmination, when it rose rapidly to a maximum of 1 to 2 in mature sorocarps; free fatty acids increased to a maximum of 7 during early aggregation and fell sharply to less than 2 during migration; and triglycerides and diglycerides declined from initial levels of 2 to 4 to about 1 during the early stages
During aggregation metabolism shifted toward a net degradation, characterized by a rapid conversion of free fatty acids to unidentified products
Summary
Preparation of Spore Stocks-Maintenance cultures of D. discoideum, strain NC-4 (haploid) (ATCC No 11735), were grown to mature sorocarps on SM agar [12] with Aerobacter uerogenes and stored for no longer than 2 weeks at 4”. 0.5 g of lyophilized spores was mixed with 75 ml of a 24-hour liquid culture of A. uerogenes, and a 7-ml aliquot was spread with a bent-glass rod over 500 to 700 ml of solid SM agar contained in a 16 x 11 x 1 inch covered. When periods of incubation exceeding 10 hours were necessary, buffer pads soaked with 1 M KH2PO( were attached to the pan lids before inoculation to absorb the ammonia generated [15]
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