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Lipid studies in Neurospora crassa
Three strains of Neurospora crassa were used to correlate lipid metabolism with formation of conidia. Lindegren+, a wild type strain forms conidia when grown on C medium but forms no conidia or aerial hyphae when grown on M medium. During the period of maximum conidia formation of Lindegren+, there is a significant increase in the ratios of total lipid/dry weight and triglyceride/dry weight. When conidia are suppressed and growth is strictly vegetative, no such increase is observed during this period. In this case, the ratios of total lipid/dry weight and triglyceride/dry-weight show a slow but steady increase after three days. At four days of growth, these ratios are 26% and 39% less than those of cultures grown on C medium and remain less until the fifth and sixth days. Wild type strain 28A forms conidia when grown on C medium. Strain 7A, a mutant derived from 28A forms essentially no conidia. The ratios of lipid/dry weight and triglyceride/dry weight are 20% higher in strain 28A than 7A after four days of growth. The degree of unsaturation of the triglyceride fatty acids is correlated with the extension of aerial hyphae, a primary step in the formation of conidia. Fifty six per cent of the fatty acids derived from cultures of Lindegren+ grown on C medium are unsaturated whereas, 38% of the fatty acids derived from Lindegren+ grown on M medium are unsaturated. Strains 28A and 7A which both form aerial hyphae have a higher fraction of unsaturated fatty acids than cultures of Lindegren+ grown on M medium.