Fungi, Viruses, and Prions

Molds

The fungal thallus (growth) consists of hyphae (long strands of cells)

• a mass of hyphae is a mycelium

Yeasts

• Unicellular fungi

• Fission yeasts divide symmetrically

• Budding yeasts divide asymmetrically

Systematic mycosis

Deep within body

Subcutaneous mycoses

Beneath the skin

Cutaneous mycoses

Affect hair, skin, nails

Superficial mycoses

Localized, e.g., hair shafts

Opportunistic mycoses

Caused by normal microbiota or fungi that are usually not pathogenic

What are viruses composed of

Nucleic Acid & Protein

Do viruses have metabolic activity?

No

Each virus has

a host range

Do viruses have both DNA and RNA?

No, one or the other

Capsid

Protein shell enclosing the viral genome (built from proteins called capsomeres)

Viral envelope

Some have lipid membranes:

• the viral envelope contains the capsid and aids in entry to the cell

Prion

Infectious proteins that cause brain diseases in mammals by building up in the nervous system

How do prions propegate

By converting normal proteins into the prion

version

Examples of prion infections

Creutzfeldt-Jakob disease

Scrapie

Mad Cow disease (variant Creutzfeldt-Jakob disease)