Temporal and spatial differences in septation during synchronous mycelium and bud formation by Candida albicans

Abstract

We have examined the time and location of the first septa formed by cells of Candida albicans when such cells were induced to grow synchronously as either mycelial or budding cultures. Synchronous growth was initiated by inoculating stationary-phase cells into an amino acid medium with a pH of either 6.5 or 4.5. Septa were visualized with the fluorescent stain Calcofluor. Evidence is presented that: (1) During both synchronous mycelium and bud formation, lightly staining septa first appear and 30 to 40 minutes later abruptly convert to darkly staining septa. (2) Although the times of evagination for mycelium and bud formation are the same, the times of septum formation differ. During bud formation the average septum forms very close to the time of initial evagination; during mycelium formation the average septum forms 30 minutes after evagination. (3) The location of septum formation differs. During bud formation, the septa invariably form at the junction of the mother cell and bud; during mycelium formation, the average septum forms in the tube approximately 2 μ m from the junction of mother cell and tube. (4) During mycelium formation, the average septum forms when the mycelium is approximately 7 μ m in length, and no tube elongation occurs between septum and mother cell once the initial septum is formed. A mutant strain, M11, is also described which begins to form a mycelium under conditions conducive to mycelium formation, but upon septation generates a bud distal to the septum.