Eukaryotic Microorganisms

Question 1

What are the four main types of eukrayotes (true nucleus)?

Answer 1

1) Fungi
2) Protozoa - single celled animals (e.g. malaria)
3) Helminths - parasitic worms (e.g. tapeworms)
4) Prions (infectious agents)

Question 2

What is the structure of Fungi and the types of infection?

Answer 2

Structure of fungi: 2 forms

Filamentous (multicellular)

• made up of microscopic filaments called hyphae which form a branched structure- mycelium

Yeasts (single celled - unicellular)

• larger than bacteria, oval shaped

Dimorphic: SOME SPEICIES ARE CAPABLE OF BOTH FILAMENTOUS AND UNICELLULAR GROWTH

- 25’C (room temp): filamentous structure, growth in mould can form on culture media

-37’C(body temp): Unicellular, grow in colony form on culture media

Some types of infection include:

• Superficial (hair shaft, dead layer of skin)
• Cutaneous (epidermis, hair nails)
• Subcutaneous (dermis, subcutis)
• Systemic (internal organs)
• Oppurtunistic (internal organs)

Question 3

How does fungal growth occur?

Answer 3

Filamentous form: Grow by extension of the ends of hyphae

Yeast: Can grow by budding or binary fission

Fungi reproduce through spores formation: either asexual and/or sexual

Question 4

What are the components that make up the fungal cell wall structure?

Answer 4

Possess different molecules to bacteria and mammalian cells - drug targets

Ergosterol- cell membrane, high content

• Not found in mammalian cell membrane
• Equivalent to cholestorol in mammals
• Target for antifungals

Chitin (polysaccharide)

​B-glucan (cellulose)

• Cross-linked and provide rigidity to the wall

Question 5

What is the structure of protozoa and what is their two-stage life cycle?

Answer 5

Unicellular

• Do not have a cell wall (like bacteria and fungi )
• Capable of movement
• Both intracellular and extracelullar (malaria) types exist
• Found in soil and water

Life cycle: 2 stages

Trophozite

> Motile, feeding and dividing stage

Cyst

> Non-motile, dormant, survival stage, usually the infective stage

Question 6

What are the routes of transmission for helminths?

Answer 6

• GIT is a major site of helminth interactions
• Faecal-Oral route
• Flukes + Nematodes atively feed on host tissues and intestinal contents
• Tapeworms feed by absorption of intestinal contents

Size of helminths make them very difficult for the immune system to deal with

Question 7

What are prions and how do they damage cells?

Answer 7

Non-cellular infectious agents, composed of protein

• Abnormal prion proteins can bind to normal prior protiens and cause structural changes
• Abnormal proteins accumulate and form aggregates –> causes cellular damage
• No treatment
• Disease is very slow in progression (decades)