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BOT 306 > Ascomycetes > Flashcards

Ascomycetes Flashcards

1
Q

What is the difference between ascus and basidium meiospores?

A

Basidium = spores are borne exogenously
Ascus = spores are borne endogenously

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2
Q

What is a sporangium?

A

A specialized cell within which spores develop

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3
Q

What types of spores do mitosporangia produce?

A

Spores developed through mitosis

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4
Q

What type of spores do meiosporangia produce?

A

Spores developed through meiosis

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5
Q

How are clamps formed in basidiomycetes?

A

Two nuclei that both need mitotic division
The division leaves a clamp behind

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6
Q

How are croziers formed in Ascomycota?

A

They are formed immediately before sexual reproduction - don’t last long

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7
Q

How do spores develop in the ascus?

A

Meiosis yields 4 haploid nuclei in the developing ascus
Post-meiotic mitosis happens directly in the ascus
Goes from 4 to 8 spores

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8
Q

How have asci evolved to eject their spores?

A

Their walls
Their openings
Terminal Thickenings

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9
Q

What is a prototunicate ascus wall?

A

Single wall, dissolves when mature

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10
Q

What is a unitunicate ascus wall?

A

Single wall that can have openings in various locations

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11
Q

What is a bitunicate ascus wall?

A

2 walls - jack-in-the-box mechanism that facilitates the ejection of the entire spore pack

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12
Q

What is a lid on the ascus referred to as?

A

An operculum

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13
Q

How are spores actively discharged from asci?

A

A young ascus is filled with glycogen
As ascospores mature, glycogen is converted in low molecular weight osmolyte
The osmolyte takes up water as the ascospores mature, causing the asci to swell and develop turgor pressure
When a critical point is reached, the ascus bursts

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14
Q

What is a key step in many ascomycete species?

A

The production of conidia

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15
Q

What are conidia?

A

Non-motile fungal mitospores that are not formed inside a sporangium

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16
Q

How are conidia produced?

A

They are borne on conidiophores in/on special receptacles called conidiomata

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17
Q

What is enclosed conidioma referred to as?

A

Pycnidia

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18
Q

What is cushioned conidioma referred to as?

A

Sporodochia

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19
Q

What are conidiophores in a broom referred to as?

A

Synnemata

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20
Q

What are conidia used for?

A

Asexual reproduction
The self-propagating asexual phase is known as the anamorph

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21
Q

What are the names of fungi that have enclosed and non-enclosed conidiomata?

A

Enclosed = coelomycetes

Non-enclosed = hyphomycetes

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22
Q

What is the teleomorph form also referred to as?

A

The meiotic form

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23
Q

What is the anamorphic form also referred to as?

A

The mitotic form

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24
Q

What did Schwendener do?

A

He demonstrated that there was no difference between green blobs and free-living algae
Proposed that lichens are made up of two organisms = symbiosis

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25
Q

What does algae do for fungi?

A

Produce sugars for the fungi to consume

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26
Q

What does fungi do for algae?

A

Protection from herbivory, fungi produce secondary metabolites that are deterrents to herbivores

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27
Q

What are some common chemical tests to visualize lichen secondary metabolites?

A

Household bleach (C)
Potassium hydroxide (K)

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28
Q

In general, how are lichen named?

A

They are given the fungal name

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29
Q

What group are both major symbionts of lichen in?

A

Polyphyletic groups

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30
Q

What are crustose lichens?

A

Lichens that are so closely attached to the substrate that they cannot be removed without also damaging the substrate

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31
Q

What are foliose lichens?

A

Lichens that are flat with an upper surface that is colored differently than the lower surface. Sometimes it has a lower surface with outgrowths called rhizines

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32
Q

What are the forms of fruticose lichens?

A

Hair-like
Shrub-like
Club-like

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33
Q

If we section through the thallus of a lichen, what do we see?

A

The upper cortex
The photobiont
The medulla
The lower cortex

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34
Q

How do lichens form?

A

The fungus forms a thallus with algal cells and loose internal hyphae (medulla)

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35
Q

What type of algae can lichen fungi associate with?

A

Green algae
Cyanobacteria
Sometimes lichen associated with both and is called tripartite

36
Q

What describes the horizontal transmission of symbionts?

A

If the fungus produces spores, then these need to find a suitable photobiont
The fungus and the algae need to meet somehow

37
Q

What describes the vertical transmission of symbionts?

A

They can disperse asexually in combined fungal-algal packets

38
Q

What are some surface modifications that serve for the propagation of lichens?

A

Isidia
Soredia

39
Q

What are isidia and where are they found?

A

It is a vegetation means of propagation
Normally found on the outer cortex of the lichen
Fungal and algal cells are combined in a column-like structure that can break off and establish elsewhere

40
Q

What are soredia and where are they found?

A

powdery propagules composed of fungal hyphae wrapped around cyanobacteria or green algae
Can be scattered diffusely across the surface of the lichen’s thallus, or produced in localized structures called soralia

41
Q

What are the uniting features of non-lichen ascomycetes?

A

Typically less expansive mycelia than Basidiomycetes
Many are ephemeral (appear and disappear again) and seasonal (unlike most lichens)
Many are pathogens

42
Q

What phylogenetic group are all ascocarps in?

A

Polyphyletic

43
Q

What is apotheciate (cup) fungi?

A

A cup-shaped ascocarp that is polyphyletic

44
Q

What is an example of an inside-out Asco?

A

Devil’s cigar
The ascus and ascospore are pointed inside

45
Q

Many cup fungi can also have what?

A

Anamorphs

46
Q

Which type of fungi have evolved to capture and consume nematodes?

A

Cup fungi

47
Q

What do fertile pyrenomycetes possess?

A

A perithecium

48
Q

What are the two types of ontogeny that perithecia encompass?

A

Perithecium
Pseudothecium

49
Q

What describes perithecium?

A

The fruiting body forms together with sexual hyphae

50
Q

What describes pseudothecium?

A

Fruiting body forms first, followed by the formation of ascus-bearing hyphae

51
Q

What do some species produce perithecia in?

A

A stroma where you will see clusters of perithecia

52
Q

What is found in the ergot life cycle?

A

The sclerotium and the actual fruiting body is also a peritheciate stroma

53
Q

What is the sclerotium?

A

A mass of hyphae with protective rind and containing food reserves

54
Q

What does the consumption of ergot cause?

A

Ergotism which causes hallucinations, itching and burning skin, gangrene, and sometimes death

55
Q

What is ergot the building block of?

A

LSD

56
Q

What is a cleistothecium?

A

An ascocarp that is round and closed and often differentiated into cleistothecia and chasmothecia (in which asci are formed at one level and the globular structure breaks open through a predetermined line of weakness

57
Q

If the globular case is formed from a net of hyphae, what is it called?

A

A gymnothecium

58
Q

How are asci scattered in cleistothecia?

A

Asci are scattered through the closed case, not embedded in a gel

59
Q

Which significant fungi do cleistothecium-forming Eurotiomycetes form?

A

Aspergillus = used in the production of soy sauce
Penicillium = used in the production of cheese and penicillin

60
Q

How fast does Aspergillus develop?

A

Mycelia develop conidiophores within 16 hours of germinating, first conidia are dispenses 8 hours later = 24 hour life cycle

61
Q

What is A. oryzae involved in?

A

Starch degradation for making sake
Proteolytic and amylolytic activity for two-stage fermentation of soy sauces

62
Q

What is A. niger involved in?

A

The production of most of the worlds citric acid
95% efficiency for conversion of sugar to citric acid

63
Q

When is an ascocarp referred to as a gymnothecia?

A

When the ascocarp forms an unsealed hyphal wad, the hyphae give rise to asci

64
Q

What ascomycete is mycorrhizal?

A

Truffles

65
Q

What is the exception to the anamorphic/asexual life cycle in yeasts?

A

Bakers yeast
It does have a sexual stage without a hyphal teleomorph

66
Q

Which classes are sexual yeasts found in?

A

Saccharomycetes and Schizosaccharomycetes

67
Q

What does S. cerevisiae do?

A

Fermentation of glucose and other sugars via pyruvic acid into ethanol and CO2

68
Q

What do candida yeasts produce?

A

Pseudohyphae - yeasts in a chain

69
Q

What are the characteristics of candida yeasts?

A

Can grow as true yeasts, true septate hyphae or as pseudohyphae
Pseudohyphae are intermediate between hyphae and yeasts
Candida is one of the few true fungi in which the vegetative state is diploid

70
Q

What does candida cause?

A

Candidiasis infections

71
Q

Where are Metschnikowia yeasts found?

A

In floral nectar

72
Q

What happens to Metschnikowia yeasts at high cell densities?

A

The yeasts will eventually degrade nectar up to the extreme of depleting virtually all of its sugar
They also warm up the flower interior of some winter-flowering plants

73
Q

What are the characteristics of fission yeasts?

A

Chitin is present only in traces in the cell wall
It can uniquely split into two equal-sized cells by septation
Distantly related to other years and evolutionarily isolated
It is the fermenting agent of African millet beer and arak

74
Q

What triggers the hyphal-yeast switch?

A

Temperature: many pathogens are hyphal at 25 degrees but switch to yeast growth around 37 degrees - causes disease
Changes in the chemical environment, especially nutrient starvation

75
Q

What triggers the hyphal-yeast switch in Candida?

A

Switching the environment to neutral or alkaline pH
Carbon starvation
Nitrogen starvation
Cell density via quorum sensing molecules
Low oxygen and elevated CO2
presence of N-acetylglucosamine

76
Q

What are saprotrophs?

A

Utilize already dead matter

77
Q

What do biotrophs consume?

A

Living organisms

78
Q

What do hemibiotrophs consume?

A

Tap into living organisms, continue in dead organisms

79
Q

What are necrotrophs?

A

Pathogens which feed by killing hosts

80
Q

How do anamorphs persist in Ascomycota?

A

By forming conidia

81
Q

How do teleomorphs persist in Ascomycota?

A

By forming asci

82
Q

What is a holomorph?

A

A fungus that is characterized by both sexual and asexual reproductive states

83
Q

How do anamorphs persist in Basidiomycota?

A

By budding

84
Q

How do teleomorphs persist in Basidiomycota?

A

By forming basidia

85
Q

Is dimorphism related to sex?

A

NO!
Any anamorph or teleomorph can be either sex type, changing the state does not change the sex

BOT 306 (16 decks)

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