RS07 - Introduction to Fungi

What type of cells are fungi?

Fungi are eukaryotes (nucleus, mitochondria).

Fungi are distinct from what other organisms?

Distinct from plants and animals.

How do fungi often obtain nutrients?

Often feed on dead material (saprophytic).

How do fungi destroy organic matter to obtain nutrients?

Secrete hydrolytic enzymes that destroy organic matter.

What is mycology?

Mycology: the study of fungi.

What is a mycosis?

Mycosis (plural-mycoses): any disease caused by a fungus.

What types of diseases do many fungi cause besides infections?

Many cause allergic diseases.

What toxic substances can some fungi produce?

Mycotoxins.

What organisms are commonly affected by fungal disease?

Plants.

Who is most susceptible to fungal infections?

Immunocompromised people.

What are the morphological forms of fungi?

• Yeasts: single-celled fungi

• Molds: Filamentous fungi

• Mushrooms: reproductive structures of certain fungi

What does the fungal cell membrane contain?

Ergosterol – target for anti-fungals (not cholesterol).

What does the fungal cell wall contain?

Chitin.

What are β-glucans?

Branched polymers of glucose in the fungal cell wall.

What other components are found in the fungal cell wall?

Other sugars and glycosylated proteins.

What is the mechanism of action of azoles (antifungals)?

Impair ergosterol synthesis, damages cell membrane.

What are examples of azoles?

Clotrimazole, Ketoconazole, Fluconazole.

How is clotrimazole administered?

Given as lozenges or oral suspension, or topical cream.

What is the mechanism of action of polyenes (antifungals)?

Binds to ergosterol component and disrupts cell membrane.

What are examples of polyenes?

Nystatin, Amphotericin B.

What is notable about nystatin?

Given as lozenges or oral suspension, 1950s became the first effective treatment for oral candidiasis.

What is Amphotericin B used for?

IV treatment of life-threatening fungal infections.

What is the mechanism of action of echinocandins?

Mechanism: interfere with candidal cell wall synthesis (disrupts β-1,3-glucan synthesis).

What are yeasts?

Yeasts: Single-celled fungi.

What is the typical size of yeasts compared to bacteria?

Usually 3–5 μM (5–10x bigger than bacteria).

What shapes can yeasts be?

Spherical, oval or cylindrical.

How do yeasts divide?

Divide by budding.

What are molds?

Filamentous – multicellular fungi.

What is a hypha (hyphae plural)?

Threadlike filaments.

What is a mycelium?

Collection of hyphae.

How do hyphae develop?

Develop from fungal spores.

In what direction do hyphae grow?

Extend towards food sources, allows maximal absorption of nutrients.