Morphological studies of N-acetylglucosamine induced germ tube formation by Candida albicans

Abstract

In N-acetylglucosamine induced germ tube formation by Candida albicans, multiple (up to five) protuberances appeared within 90 min at 37 degrees C on each yeast cell. The protuberances were extensions of the cytosol and contained vesiclelike structures. Usually only one protuberance subsequently developed into a germ tube. The germ tubes emanated from all aspects of the cell surface but seldom from the budding (long axis) poles. Pseudohyphae, which originated from the budding pole, exhibited a marked constriction at the site of emergence and were 0.6-2.5 microns in diameter compared with a diameter of 0.6-0.8 micron for germ tubes. The presence of septa confirmed that germ tubes are precursors of septate mycelia. Ultrathin-section transmission electron microscopy of aldehyde plus osmium fixed cells revealed electron-lucent walls with a thin electron-dense outer layer. A fibrillar border was also routinely associated with germ tubes. Poststaining with potassium permanganate revealed, in addition, a previously invisible fuzzy layer on the outer region of the cell wall which extended over bud scars and germ tubes and which coalesced at sites of contact between cells.

ABC transporters Cdr1p, Cdr2p and Cdr3p of a human pathogen Candida albicans are general phospholipid translocators

“…interconversion, little is known about sensors or events occurring at or within the cellular membrane during the induction of the morphogenetic program of dimorphism (Hubbard et al, 1985;Stoldt et al, 1997;White and Larsen, 1997). Our earlier finding, that the availability of PE in the outer monolayer of membrane was considerably enhanced in the mycelial form of C. albicans, may suggest that changes in lipid asymmetry could influence phenotypic divergence of this yeast .…”

Melaleuca alternifolia (tea tree) oil inhibits germ tube formation by Candida albicans

“…The presence of septa was noted. A protuberance was de ned as a cell bearing a rounded outgrowth less than or equal to the parent cell diameter, not constricted at the base [26]. A bud was de ned as being as large as the parent cell and:or fully delimited by a septum [25].…”

H+-ATPases from mitochondria, plasma membranes, and vacuoles of fungal cells

“…With two exceptions [5,133] the K,,, values for the fungal plasma membrane ATPase have fallen in the range of 0.8-4.8 mM MgATP [13,16,19,53,76,109]. This is quite high compared to K,,, values for the ATPases on other fungal membranes, as well as to values for plasma membrane ATPases of animal cells [39].…”

“…First, both yeast and N. crassa ATPases have a high affinity site (Kin = 5-20/~M), which activates ATPase activity and protects against inhibition by N-ethylmaleimide. Second, the ATPases have a low affinity site (Km 0.4-3.5 mM), which lowers ATPase activity and promotes inhibition by N-ethylmaleimide [3,5,36,37,76,83]. Mg 2+ binding also appears to facilitate the binding of vanadate [16].…”