Intro Lecture

Question 1

What are the 3 fungal lifestyles?

Answer 1

Saprophytic
Parasitic
Mutualistic/Sybiotix

Question 2

What is saprophytic lifestyle?

Answer 2

Decomposition of organic matter.

Question 3

What is mutualistic/symbiotic lifestyle?

Answer 3

Non-pathogenic, obligatory associations with other microorganisms

Question 4

What fungal lifestyle is of veterinary importance?

Answer 4

Parasitic

Question 5

Are yeasts unicellular or multicellular?

Answer 5

Unicellular

Question 6

Are moulds unicellular or multicellular?

Answer 6

Multicellular

Question 7

What are three structural features of fungi?

Answer 7

Capsules, Cell Wall, Cytoplasmic Membrane

Question 8

What does a capsule provide?

Answer 8

Protection against phagocytosis. May possess antigens - stimulate an immune response in the host.

Question 9

What is a capsule made up of?

Answer 9

Slime = loose polysaccharide gelatinous sheath deposited around the cell wall.

Question 10

What is the cell wall made up of?

Answer 10

Net of polysaccharide microfibrils (chitin, glucan, mannan and cellulose). Cross linked by proteins/glycoproteins.

Question 11

What does the Fungi’s cell wall determine?

Answer 11

Morphology

Question 12

What is the cytoplasmic membrane?

Answer 12

Bilayered membrane containing sterols. Dissimilar to bacterial membranes, similar to other eukaryotes.

Question 13

What is mycelia?

Answer 13

A feeding system of colourless tubules.

Question 14

What are mycelium components of?

Answer 14

Thallus

Question 15

What is hypha?

Answer 15

A single branch of the mycelium. (Individual filament of the filamentous structure)

Question 16

What are vegetative mycelia?

Answer 16

Hyphae and mycelia embedded for support and nutrition in the surface of the substrate (soil, bread, skin) on which the fungus grows.

Question 17

What are aerial hyphae or conidiophores?

Answer 17

Fungal hyphae that grow above the the surface where the terminal portions often differentiate into reproductive spore-bearing structures.

Question 18

What are ascospores?

Answer 18

Spores produced as a result of sexual reproduction and are enclosed in microscopic sacs called asci.

Question 19

What are conidiospores or conidia?

Answer 19

Asexually produced spores that are produced at the tips of the hyphae often in chains or sticky masses.

Question 20

What shape are yeasts?

Answer 20

Oval/spherical

Question 21

What are the two modes of fungal replication?

Answer 21

Asexual and sexual.

Question 22

What occurs during sexual replication?

Answer 22

Fusion of 2 hyphal nuclei - followed by meiotic division. Resulting haploid spore (meiospores) = sexual spore.

Question 23

What is the sexual stage of replication referred to as?

Answer 23

Teleomorphic or perfect state.

Question 24

What occurs during asexual replication?

Answer 24

Mitosis of a single parent nucleus (spores or conidia). Sporulation or germinations, budding of yeast cells, fragmentation of hyphae. Conidia arise by budding off from a conidiophore or by differentiation of preformed hyphae. Asexual spores are commonly formed by cleavage of a sporangium.

Question 25

What are the 3 morphological types fungi are classified into?

Answer 25

Yeasts, moulds, dimorphic.

Question 26

What are the 3 main mechanisms of fungal disease in animals?

Answer 26

Tissue invasion, toxin production, induction of hypersensitivity.

Question 27

What are the general features of tissue invasion?

Answer 27

Superficial mycoses, subcutaneous mycoses and tumour like granulomas.

Question 28

What are the general features of toxin production?

Answer 28

Mycotoxicosis

Question 29

What are the general features of induction of hypersensitivity?

Answer 29

Immune complex induced tissue injury.

Question 30

What are the routes of entry of fungal diseases?

Answer 30

Endogenous commensals and exogenous fungal spores.

Question 31

What are endogenous commensals?

Answer 31

Already present on host in low numbers.

Question 32

How do exogenous fungal spores get into the host?

Answer 32

Deposited onto host, inhaled by host, ingested by host. Wounds, mucosa, macerated skin.

Question 33

What are the two laboratory test for diagnosis and identification of fungal infections?

Answer 33

SDA- Sabouraud's Dextrose Agar | DTM- Dermatophyte Test Medium

Question 34

What are the features of SDA?

Answer 34

pH 5.6 -slightly acidic pH helps to inhibit bacterial growth. Antimicrobials may be included.

Question 35

What are the features of DTM?

Answer 35

SDA with a pH indicator. Red colour change with dermatophytes.

Question 36

How do you grow fungi in the lab?

Answer 36

Culture two plates. One at 25C and one at 37C. Slow growers- will take a few days (yeast) and up to 3-6 weeks (dermatophytes). Examine two times a week.

Question 37

Are fungi eukaryotes?

Answer 37

Yes- they have a true nucleus

Question 38

How do fungi obtain energy?

Answer 38

No chlorophyll - obtain energy by breakdown of dead or living organic matter. *Heterotrophic*

Question 39

Where will fungal disease often be present?

Answer 39

In immune compromised animals.

Question 40

What is a dispersal spore?

Answer 40

Produced in large numbers and separate completely from parent mycelium. Launched by specialist hyphae. Germinate readily in available nutrients.

Question 41

What are survival spores?

Answer 41

May not completely separate from mycelium. Tend to be large. Retain substantial nutrient reserves. Germination only occurs after slow waning of dormancy or in response to a specific stimulus.

Question 42

How do yeasts reproduce?

Answer 42

Budding (blastospores)

Question 43

Are moulds strict aerobes?

Answer 43

Yes

Question 44

How do moulds grow?

Answer 44

Apical growth occurring at the tip of the hyphae. "Extension Zone" allows fungus to utilise distant food sources.

Question 45

What are the three zones of a mature mould colony?

Answer 45

Peripheral extension zone, fruiting/sporing zone and central aged zone.

Question 46

How can dimorphic fungi exist?

Answer 46

In hyphal/filamentous form or yeast form.

Question 47

What is the temperature dependent morphology of yeasts and moulds?

Answer 47

``` Yeast = 37C (body temperature) Moulds = 25C (room temperature) ```