4. Fungi

Question 1

What are some uses of fungi for humans?

Answer 1

• Sources of food or used for food fermentation
• Sources of pharmaceuticals
• Sources of enzymes
• Cause plant and animal diseases

Question 2

What are the two ways in which fungi may grow?

Answer 2

Grow as filaments or as yeast

Question 3

What is a mycelium?

Answer 3

The vegetative (feeding) structure is a mycelium
- Mycelium is a network of hyphae

Question 4

What are hyphae?

Answer 4

Monofilaments (cytoplasm in a tube) with large surface area: volume ratio

Question 5

What are the cell walls of fungi like?

Answer 5

Cell walls feature chitin microfibrils embedded in a matrix of polysaccharides, protein and lipids

Question 6

What is the mitosis yeast life cycle?

Answer 6

1. Spindle pole replication
2. Bud emergence
3. DNA cell replication
4. Nucleus migrates into the daughter cell
5. Spindle formation
6. Chromosome segregation; nuclear division
7. Cytokinesis separated into mother cell and daughter cell

Question 7

How are fungal hyphae divided?

Answer 7

Hyphae may be divided by cross walls called septa

Question 8

What is the purpose of septa?

Answer 8

They are incomplete, allowing cytoplasmic continuity.

- Usually have pores that enable communication between cellular compartments

Question 9

What happens when hyphae fuse?

Answer 9

Hyphae can fuse (anastomose), forming cells with mixed nuclei

Question 10

What are cells with mixed nuclei known as?

Answer 10

Heterokaryons

Question 11

What are all the different variations of fungal reproduction?

Answer 11

• Reproduce by producing hyphae
• Budding/fission (yeasts)
• Formation of sexual/asexual spores

Question 12

What are dikaryons?

Answer 12

One haploid nucleus plus another haploid nucleus

Question 13

How are dikaryons formed?

Answer 13

Plasmogamy (when plasma membranes fuse) of compatible mating types, then the fungus has nucleus from both parents

Question 14

How do fungi receive their nutrition?

Answer 14

• They are heterotrophs
• Secrete enzymes and digest food externally
  (Food absorbers)

Question 15

What are food reserves in fungi stored as?

Answer 15

Reserves stored as glycogen, fats and oils

Question 16

What do saprophytic fungi consume?

Answer 16

They decompose cellulose and lignin

Question 17

Which environments do saprophytic fungi go in?

Answer 17

Environmental tolerance means they grow almost everywhere other organisms are found

Question 18

What are mycorrhizae?

Answer 18

Fungal associates with plant roots in which fungus grows between and even into plant root cells

Question 19

What do the fungi do in mycorrhizae?

Answer 19

Fungi extract sugars and fats from the plant in exchange for mineral nutrients and water it extracts from the soil

Question 20

Why are fungi efficient soil nutrients extractors?

Answer 20

Due to large surface area to volume ratio of mycelia

Question 21

What are endophytes?

Answer 21

Microbes that grow between leaf or root material, do not cause harm to the plant

Question 22

What are lichens?

Answer 22

Fungi and algae beneficial associations

Question 23

What have fungi evolved from?

Answer 23

Evolved from a protist similar to extant choanoflagellates - one line led to the sponges and animals, the other to the chytrids and other fungi

Question 24

Ascomycota and … evolved from a shared ancestor?

Answer 24

Ascomycota and basidiomycota evolved from a shared ancestor “dikarya”

Question 25

What environment are chytrids suited to?

Answer 25

Aquatic or soil borne

Question 26

What is the motility of chytrids?

Answer 26

They are motile zoospores with a posterior flagellum

- The only fungi with flagella

Question 27

What is the structure of the mycelium in chytrids?

Answer 27

Limited coenocytic mycelium ( no regular septa)

Question 28

What are the relationships of chytrids with other organisms?

Answer 28

Parasites, saprophytes and mutualises

Question 29

What is the structure of the mycelium of zygomycetes?

Answer 29

Hyphae are coenocytic (no regular septa)

Question 30

What are zygospores?

Answer 30

Sexual spores of zygomycetes

Question 31

What are sporangiospores?

Answer 31

Asexual spores of zygomycetes

Question 32

What are some examples of zygomycetes?

Answer 32

Fruit moulds, insect pathogens

- Uncommon human pathogens

Question 33

What are ascomycotes? Examples

Answer 33

Yeast, truffles, cup fungi, moulds

Question 34

What is the structure of the mycelium of ascomycetes?

Answer 34

Hyphae have regular septa

Question 35

Where is dikaryon seen in ascomycetes?

Answer 35

Dikaryon limiters to reproductive tissue

Question 36

What is the role of meiosis in the ascomycete reproductive cycle?

Answer 36

Meiosis follows zygote formation within the ascus, forming ascospores
- Asci may be surrounded by a fruiting body (ascocarp)

Question 37

What are the asexual spores of ascomycetes known as?

Answer 37

Condia

Question 38

What are some examples of basidiomycota?

Answer 38

Mushrooms, toadstools, rusts, puffballs

Question 39

What is the mycelium structure of basidiomycota?

Answer 39

Vegetative hyphae are septate

Question 40

Are conidia present in basidiomycota?

Answer 40

Asexual conidia are uncommon

Question 41

What is the reproductive cycle of basidiomycota?

Answer 41

1. The basidium is the characteristic sexual reproductive structure of the basidiomycetes. Basidiospores form outside the basidium
2. Basidiospores give rise to haploid hyphae
3. Haploid hyphae of different mating types fuse, forming dikaryotic hyphae
4. The dikaryotic mycelium grows and eventually produces a fruiting structure, the basidiocarp
5. The basidiocarp is topped by a cap, or pileus, which has gills on its underside
6. Basidia develop on the surface of the gills
7. Nuclear fusion and meiosis take place in the developing basidium

Question 42

What does the MAT locus control?

Answer 42

A mating type locus has been found in all fungi to date to control their ability to undergo sexual reproduction.

Question 43

What genes are encoded on the MAT locus?

Answer 43

Genes encode global regulators such as high mobility group (HMG) transcription factors (which are similar to human SRY gene on Y chromosome which controls male development)