Sterol Metabolism during Germination of Conidia of Aspergillus fumigatus

Abstract

I97The sterol content of germinating conidia of the opportunistic pathogenic fungus AspergilZus fumigatus has been correlated with germination phase and sensitivity to polyene antibiotics. The sterol and sterol ester contents of walls did not change during germination. The sterol ester content of membranes and cell sap remained constant during germination, whereas the sterol content increased during the outgrowth of germ tubes. On the basis of differential extraction studies it was concluded that the loss of. resistance to polyenes that occurred in the early stages of swelling of conidia during germination was not due to a movement of sterol or sterol ester out of the wall.Radioactive-labelling experiments demonstrated that, although the amounts of conidial wall sterol and sterol ester did not change during germination, they were metabolically active. Changes in the turnover rate of wall and membrane sterol and sterol ester during germination were investigated and their relationship to a possible mechanism for the change from resistance to sensitivity to polyene antibiotics is discussed.

Kinetics of Inactivation of Aspergillus flavus and Aspergillus terreus Conidiospores by Amphotericin B in the Presence of Serum

“…These observations are consistent with those of Russell et al (1975) on the sensitivity of A . fumigatus conidiospores to amphotericin B methyl ester at different stages in germination.…”

“…Moreover, the conidiospores of A . fumigatus become sensitive to amphotericin B methyl ester at a point in the pregermination process when membrane sterol turnover is maximal (Russell et al 1977). If the situation is similar in A .…”

The polyene antimycotics nystatin and filipin disrupt the plasma membrane, whereas natamycin inhibits endocytosis in germinating conidia ofPenicillium discolor

“…A pretreatment with nata-mycin can effectively decreases the fluorescence of filipin binding to germinating conidia of P. discolor. This indicates that both compounds bind to ergosterol in these Russell et al (1975Russell et al ( , 1977 have shown that freshly harvested conidia of Aspergillus fumigatus were insensitive to amphotericin B, but became sensitive during the early swelling stage of germination and later (Russell et al 1975). Sensitivity towards polyenes is manifested by the inhibition of conidial swelling, phase darkening and germ tube formation.…”

“…2008). Russell et al. (1975, 1977) have shown that freshly harvested conidia of Aspergillus fumigatus were insensitive to amphotericin B, but became sensitive during the early swelling stage of germination and later (Russell et al.…”

Physiological and Biochemical Alterations during the Germination of Aspergillus Niger Conidia

“…Sterols exert a pivotal role in both the structural integrity [53] and permeability modulation of membranes [54][55][56]. Variations in the proportions of sterols to lipids prompt distinct molecular arrangements within the lipophilic constituents of the phospholipid layer, consequently altering membrane permeability [57].…”