Membrane lipid and cytosol carbohydrate composition in Aspergillus niger under heat shock

A submerged Aspergillus niger culture exposed to heat shock (40-41A degrees C) for 1, 3, and 6 h acquires resistance to a more severe, lethal heat shock (55A degrees C, 20 min). A general trend characteristic of a heat shock occurring during the trophophase or idiophase (regardless of its duration) is an increase in the trehalose level in the cytosol carbohydrate fraction and in the content of sphingolipids and phosphatidic acid in the membrane lipid fraction. Contrary to generally accepted views, no increase in the content of unsaturated fatty acid in the main phospholipid fraction, sterol level, and share of bilayer phospholipids was detected. The results obtained are discussed in terms of the current hypotheses concerning membrane protection under heat shock and our own suggestion on this subject.