Effect of respiratory deficiency and temperature on the mitochondrial lipid metabolism of Aspergillus niger.

A comparative study of the mitochondrial lipid composition of a wild strain (V 35) and a respiratory-deficient mutant (rd3) of Aspergillus niger grown at different temperatures (25, 30, 35, and 40 degrees C) has been performed. The lipid spectrum, though qualitatively similar, differs quantitatively in both cases. At the optimum growth temperature (30 degrees C) depletion in ergosterol (40%) and cardiolipin (52%) was observed. This probably indicates the formation of defective mitochondria in the mutant with a resultant impaired respiratory system. Complete depletion of cardiolipin species containing fatty acid (20:5omega3) in the respiratory-deficient mutant suggests a possible role of this lipid in mitochondriogenesis at least in A. niger. The effect of temperature is predominantly on the degree of unsaturation and sterol ester formation. The linoleic acid (18:2omega6) content decreases with a concomitant increase in oleic acid (18:1omega9) content as the growth temperature increases for both cell types. Some morphological changes and effects on the vegetative life cycle have been observed with variation in growth temperature in the wild type and also in the mutant form.