Growth kinetics and morphology of colonies of the filamentous form of Candida albicans

The growth and development of mycelia of the dimorphic fungus Candida albicans in serum-containing medium is described. Initially, colonies are undifferentiated (all hyphae in the mycelium having approximately the same diameter, extension rate, apical and intercalary compartment lengths) whereas older mycelia differentiate at the colony margin to produce leading hyphae that are wider, faster growing and have longer apical and intercalary compartment lengths than the branches they subtend. Early colony development exhibits unusual features: germ tube extension is linear (not exponential as in other fungi) and there is a prolonged delay between septation and the onset of branch formation. The subsequent patterns of growth and branching are similar in all other respects to those of other mycelial moulds. Mycelia have septa that delimit single nuclei within compartments. The septa do not prevent cytoplasmic flow and consequently allow the peripheral growth zone to span several compartments. From these results we conclude that filamentous growth of C. albicans in this medium is best described as truly mycelial.