Eukaryotic Microbes 3: Fungi Classification

Question 1

Give a basic description of Chytridiomycota.

Answer 1

• most primitive fungi we can find
• approx 1000 species
• many chytrids are aquatic
  L> exception = motile zoospores and gametes - only ones capable of movement
• Chytridiomycosis: disease in amphibians caused by Batrachochytrium dendrobatidis (Bd)

Question 2

Give a basic description of Glomeromycota.

Answer 2

• approx 230 species
• terrestrial and widespread
• members form arbuscular mycorrhizas ( >80% plants) -> form symbiosis with plant root system to gain more nutrients.
• fungus helps plant to capture nutrients such as phosphor, sulfur and nitrogen. Plats provide carbohydrates to the fungi.

Question 3

Give a basic description of Mucormycota.

Answer 3

• approx 1000 species
• zygosporangium with zygospores (very complex and resistant…this is for survival via bad conditions)
• • SEXUAL REPRODUCTION IN FUNGI IS NOT FUCKING COMMON, GET IT BRO.

Question 4

Mucormycota:

-what the heck is a sporangiospore?

Answer 4

• asexual spore formed in sac called sporangium at end of hyphae called sporangiophore.

Question 5

Mucormycota:

- describe it’s life cycle.

Answer 5

• two mating types: + and - (sexual reproduction) **remember it does not follow classical mating 100%
  1. + and - mating type meet up hyphae to hyphae
  2. gametangia with haploid nuclei (joining of the two mating types) -> Plasmogamy (exchange of cytoplasm)
  3. Young zygosporangium(heterokaryotic)
  4. Zygodporangia forms in between the two mating types hyphae. -> Karyogamy (fusion of nuclei)
  5. Diploid nuclei formed -> Meiosis occurs now.
  6. Sporangium has formed off of the diploid nuclei…it releases spores for dispersal and germination which can go on for sexual reproduction OR asexual reproduction.
  7. Asexual reproduction: dispersal and germination occur to form mycelium which give rise to sporangia (aerially)
  8. OR the spores go on to germination and dispersal forming + and negative mycelia.

Question 6

Mucormycota:

- Trisporic acid system?

Answer 6

• Beta carotene is degraded in each mating type individually, into an intermediate form. They need to find their mating type to degrade each other’s intermediate. They exchange them. The negative has the enzyme to degrade the positive’s intermediate and vice versa, yielding trisporic acid.
• this acid acts to yield zygospores which results in sporangia of + and - strains.

Question 7

Mucormycota:

- Rhizopus stolonifer, good guy or bad guy?

Answer 7

• bread mould
• Bad guy
• Mucormycosis via Rhizpous sp. and Mucor sp.
  90/100 pts die…very agressive.
  L> Mucormycosis is any fungal infection caused by fungi in the order Mucorales, this disease is often characterized by hyphae growing in and around blood vessels. Mucormycosis frequently infects the sinuses, brain, or lungs. While infection of the oral cavity or brain are the most common forms of mucormycosis, the fungus can also infect other areas of the body such as the gastrointestinal tract, skin, and other organ systems.[5] In rare cases, the maxilla may be affected by mucormycosis.[6] The rich blood vessel supply of maxillofacial areas usually prevents fungal infections, although more virulent fungi, such as those responsible for mucormycosis, can often overcome this difficulty.[6]

Question 8

Mucormycota:

- Phycomyces blakesleeanus, good guy or bad guy?

Answer 8

• good guy.

- research in sporangia phototropism aka growth towards light source.

Question 9

Give a basic description of Ascomycota.

Answer 9

• approx 65000 species - one of the biggest classes.

- Ascus with ascospores

Question 10

Ascomycota life cycle:
L> what is conidospore?
L> What is conidia?

Answer 10

• asexual spore formed at end of hyphae
• chains of conidospores on conidophore
• *they have both + and - mating types

Question 11

What are the steps in the Ascomycota life cycle?

Answer 11

1. • and + mating types meet up with their Antheridium and Ascogonium ->
2. plasmogamy occurs ->
3. Dikaryotic hyphae forms (has an ascocarp)
4. Ascus (dikaryotic) with dikaryotic hyphae
   ->
5. Karyogamy occurs
6. Diploid nucleus aka zygote
7. meiosis occurs yielding four haploid nuclei
8. Mitosis occurs yielding eight ascospores (n)
9. germination occurs forming mycelia of both + and - mating types.
   **These can now go on to repeat the above sexual life cycle or go on to do asexual reproduction.
   Asexual reproduction: spores from either mating type are released, germination occurs forming mycelium (n) which can release/form more spores to feed into either cycle.

Question 12

Explain the Ascomycota life cycle with respect to Saccharomyces cerevisiae in a genetic perspective.

Answer 12

• a and alpha mating type
• mating is controlled by the MAT gene locus which is flanked by two other loci - MATa and MATalpha.
• a copy of one of the flanking loci is inserted into the MAT locus and determines mating type.
• MAT switching can occur after each budding. Within a population they can ensure there is enough genetic swapping.

Question 13

Explain the steps in Ascomycota life cycle with respect to Saccharomyces cerevisiae.

Answer 13

1. Conjugation between a and alpha haploids. Budding can occur or spore formation.
2. Spores can go on to either form a haploid cells or alpha haploid cells. These cells can undergo budding to make up more a or alpha cells.
3. After budding from the a/alpha diploid mating type can be determined then without the spore step as well.

Question 14

Ascomycota: 
Good or bad guys? 
1. Saccharomyces cerevisiae 
2. Schizosaccharomyces pombe 
3. Neurospora crassa 
4. Morchella sp. and Tuber sp. 
5. Penicillium chrysogenum 
6.Sacchoromyces carlsbergensis 
7. Saccharomyces cerevisiae 
8.Penicillium roqueforti 
9.Aspergillus oryzae

Answer 14

• good guys
• 1, 2 and 3 are main biological model systems
• 4 and 5 are used in antibiotic production
• 6, 7, 8 and 9 are used in food production

Question 15

Ascomycota:

• Good or bad guys?
  1. Trichophyton rubrum
  2. Malassezia globosa
  3. Candida albicans
  4. Aspergillus fumigatus
  5. Histoplasma capsulatum
  6. Coccidioides immitis
  7. Magnaporthe oryzae
  8. Septoria tritici
  9. Claviceps purpurea

Answer 15

• bady guys
• 1 and 2 are superficial diseases
• 3 is part of our normal flora in themouth but in high concentrations can be bad.
• 3 and 4 = opportunistic species aka need to have the immune system weak before infection to occur.
• 5 and 6 form primary infections …6 = infection of lungs which can involve CNS.
• 7, 8 and 9 are crop/plant disease involved

Question 16

Give a basic description of Basidiomycota.

Answer 16

• approx 30,000 species
• basidium with basidospores
• can form basidiocarp (fruiting body)
• many are commonly recognized mushrooms and toadstools (edible and poisonous)

Question 17

What are the five traditional major fungal groups?

Answer 17

1. Chytridiomycota
2. Mucotmycota (re-named)
3. Glomeromycota
4. Ascomycota
5. Basidiomycota

Question 18

Describe the life cycle of Basidiomycota!

Answer 18

• they have two mating types : - and +
• their haploid mycelia fuse together –> Plasmogamy
• this forms a dikaryotic (two nuclei per cell) mycelium
• next when environmental conditions are favourable (wet and cool weather) the dikaryotic mycelium will develop into a fruiting body called a basidiocarp. It’s gills (underside of fruiting body) are lined with besidia
• these besidia (diploid) will undergo karyogamy forming diploid nuclei.
• meiosis next..basidium containing four haploid nuclei (each becomes a spore) –> basidium with four appendages which release basidiospores ….dispersal and germination now occurs to produce haploid mycelium

Question 19

Name examples of Basidiomycota that are beneficial to humans. (7)

Answer 19

1. Agaricus bisporus - portobello mushroom (edible)
2. Boletus edulis -
3. Cantharellus cibarius
4. Grifola frondosa
5. Gyromitra esculenta
6. Hericium erinaceus
7. Tricholoma matsutake - Mycorrhizal mushroom that is edible
   * * all are edible

Question 20

Name some basidiomycota that are harmful towards humans. (5)

Answer 20

1. Amanita muscaria - “Fly agaric” - consumed after parboiling for psychoactive properties however if consumed raw it can be lethal
2. Amanita phalloides - “Death cap” - deadly poisonous
3. Coprinopsis atramentaria - “Ink cap” - edible unless taken with alcohol!! It can be lethal then…. remember the story about the parents and children eating it at supper…who died? Why?
4. Cryptococcus neoformans - an encapsulated yeast that is commonly found in bird excrement. Infection of the lung… via Cryptococcus
5. C. gattii - basal meningitis , cerebral cryptococcomas and pulmonary cryptococcosis

Question 21

What are the Oomycetes ?

Answer 21

• a protist (diverse group of eukaryotic microorganisms)
• distinct lineage
• have fungal characteristics : heterotroph, morphology (water mold)
• plant characteristics: cellulose cell wall (very diff vs chitin cell wall) and some have chloroplasts

Question 22

What are Microsporidia?

Answer 22

• originally thought to be primitive protists
• actually close sister group to fungi
• they are a derived group aka they have LOST many features via evolution
• they are all obligate parasites of animals aka relies on being inside a host to replicate and this is why it has lost the features that would help us classify it as fungi