Explain the Structure of Fungi?

The vegetative structure of a fungus is called thallus. It varies in complexity and size, ranging from unicellular yeasts to multicellular moulds. A yeast is a unicellular fungus, producing moist to waxy colony in culture. It is about 5-10 times larger than bacteria and reproduces asexually by budding or transverse division and sexually through spore formation. Morphologically, these are usually spherical or ellipsoidal in shape. A mould produces leathery, cottony or profuse powdery growth on medium. It consists of a mass of intercoiling branched, threadlike structures called hyphae. The mass is known as mycelium. Depending on the fungal type, the hyphae may be septate, i.e., have cross wall or septum to produce multicells or aseptate, i.e., septum is absent and the cytoplasm is coenocetic. The hyphae grows on or within the surface of nutrient media to get nutrients. This represents vegetative mycelium. Some of the specialized hyphae arise upward away from the medium surface. It is called the aerial mycelium on which the reproductive structure or spores are formed.

Some fungi are dimorphic, that is, at 37°C these grow as yeast (Y) but at 25°C change to mould (M) structure. This shift is known as YM shift.