Fungi: General Characteristics

Introduction to Mycology

Mycology is the branch of microbiology that studies fungi, a diverse group of eukaryotic organisms. Fungi play essential roles in ecosystems as decomposers, pathogens, and sources of industrial products.

• Mycology: The scientific study of fungi.

• Chemoheterotrophs: Fungi obtain energy and carbon by decomposing organic matter.

• Most fungi are aerobic or facultative anaerobes.

Comparison of Fungi and Bacteria

Fungi and bacteria differ in cellular structure, metabolism, and reproduction. The following table summarizes key differences:

Major Features of Fungi

Fungi are a large and diverse group of organisms with unique biological properties.

• There are over 600,000 different species of fungi.

• Most fungi are multicellular; yeasts are unicellular.

• Fungi do not carry out photosynthesis.

• They absorb nutrients from their environment.

• Fungi include pathogens and saprobes (decomposers).

Nutritional Adaptations of Fungi

Environmental Tolerance

Fungi are adapted to survive and thrive in a variety of environmental conditions that may inhibit other organisms.

• Fungi grow best at pH 5, which is more acidic than most bacteria prefer.

• They can grow in high sugar and salt concentrations, making them resistant to osmotic pressure.

• Fungi can grow in low moisture content environments.

• They are capable of metabolizing complex carbohydrates.

Vegetative Structures of Fungi

Molds and Fleshy Fungi

The main body of a fungus is called the thallus, which consists of long filaments known as hyphae. A mass of hyphae forms a mycelium.

• Vegetative hyphae are responsible for nutrient absorption.

• Aerial hyphae are involved in reproduction.

Yeasts

Yeasts are unicellular fungi that reproduce by budding or fission.

• Budding yeasts divide unevenly, forming a smaller daughter cell.

• Fission yeasts divide evenly to produce two new cells.

Dimorphic Fungi

Dimorphic fungi can exist in two forms depending on environmental conditions, often related to temperature.

• Yeastlike at 37°C (body temperature), moldlike at 25°C (room temperature).

• Dimorphism is common among pathogenic fungi.

• Dimorphic fungi cycle between having hyphae and living as a yeast-like form.

Example:

Candida albicans is a dimorphic fungus that can cause opportunistic infections in humans.

Additional info: Dimorphism allows fungi to adapt to different host environments and is a key factor in their pathogenicity.