Eukaryotic Microorganisms: Fungi, Algae, and Protozoa

Eukaryotic Microorganisms

Overview of Fungi, Algae, and Protozoa

Eukaryotic microorganisms include fungi, algae, and protozoa. These groups share the characteristic of having eukaryotic cell structure, but differ in their cellular organization, cell wall composition, and metabolic properties.

• Fungi: Eukaryotic, may be unicellular or multicellular, have cell walls made of chitin, and are not photosynthetic.

• Algae: Eukaryotic, may be unicellular, colonial, or multicellular, have cell walls made of cellulose, and are photosynthetic.

• Protozoa: Eukaryotic, unicellular, lack cell walls, and may or may not be photosynthetic.

	Fungi	Algae	Protozoa
Cell Type	Eukaryotes	Eukaryotes	Eukaryotes
Cellularity	Unicellular or multicellular	Unicellular, colonial, or multicellular	Unicellular
Cell Wall	Yes (chitin)	Yes (cellulose)	No
Photosynthetic	No	Yes	Yes and no

Fungi

General Characteristics

Mycology is the study of fungi. Fungi are chemoheterotrophs, meaning they obtain energy by consuming organic matter. They play a crucial role in decomposing organic material and can be aerobic or facultative anaerobic.

• Nutrition: Absorptive; secrete enzymes to break down complex substances.

• Cellularity: All fungi except yeasts are multicellular; yeasts are unicellular.

• Reproduction: Sexual and asexual spores; no embryo formation.

Kingdom	Fungi
Nutritional Type	Chemoheterotroph
Cellularity	All, except yeasts
Cellular Arrangement	Unicellular, filamentous, fleshy
Food Acquisition Method	Absorptive
Characteristic Features	Sexual and asexual spores
Embryo Formation	None

Yeasts

Yeasts are the simplest fungi, typically unicellular. They reproduce asexually by budding (asymmetrical division) or fission (symmetrical division). Yeasts are facultative anaerobes and can ferment carbohydrates, which is important in baking and alcohol production.

• Budding: A small new cell forms and detaches from the parent cell.

• Fission: The cell divides into two equal daughter cells.

• Applications: Saccharomyces cerevisiae is used in bread and wine making.

Molds and Fleshy Fungi

Molds and fleshy fungi form visible colonies. The thallus (body) of these fungi consists of long filaments of cells called hyphae. Hyphae may be septate (with cross-walls) or coenocytic (without cross-walls). A mass of hyphae is called a mycelium.

• Vegetative hyphae: Involved in nutrient absorption.

• Aerial hyphae: Involved in reproduction and spore dispersal.

• Growth: Hyphae grow from spores, forming extensive networks.

Example: Rhizopus (bread mold) forms a mycelium composed of coenocytic hyphae.