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BOT 306 > Oomycetes > Flashcards

Oomycetes Flashcards

1
Q

What are the main characteristics of slime molds?

A

Eukaryotic
Found all over the world (cosmopolitan)
Protozoans = not true fungi
The vegetative body is an amoeba in the form of a plasmodium
Spores with a cell wall, formed in sporophores, sorocarps, in sporocarps or alone
Feed by phagocytosis

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2
Q

How do slime molds feed by phagocytosis?

A

Entrapment of a food particle
Formation of a food vacuole within the cell
Fusion of lysosomes with the food vacuole
Digestion of the food particle

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3
Q

What are the 3 main classes in Amoebozoa?

A

Myxogastria
Protostelea
Dictyostelia

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4
Q

What are the main characteristics of myxomycetes?

A

The largest of the 3 groups
Has 3 vegetative forms
-myxamoeba (haploid)
-swarmer cells (haploid)
-plasmodia (diploid) = wall-less protoplasms with 3 types

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5
Q

What can all vegetative forms produce?

A

Pseudopodia

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6
Q

What are the two types of pseudopodia?

A

Lobose or filose

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7
Q

What type of pseudopodia are found in Myxogastria?

A

Filose

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8
Q

What are the main characteristics of swarmer cells?

A

Flagellated
Have haploid gametes
Isogamous sex cells of any mating type, both gametes look alike

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9
Q

What is the main characteristic of plasmodia?

A

Wall-less (coenocytic) protoplasms that contain thousands of nuclei

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10
Q

What is the phaneroplasmodia plasmodial type?

A

Large, veined feeding structures with rhythmic streaming

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11
Q

When will a resting state or sclerotia form?

A

When the spore has to be resistant to extreme environmental conditions

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12
Q

What condition needs to be met for myxomycetes to form?

A

It has to be wet enough

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13
Q

What are the 3 common types of myxogastrial sporophores?

A

Sporangium
Aethalium
Plasmodiocarp

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14
Q

What does sporangium in myxomycetes contain?

A

Columella, capillitium, and spores

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15
Q

When does Aethalia occur?

A

When the entire plasmodium is converted into a cushion-like structure surrounded by one common peridium

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16
Q

How do plasmodiocarps occur?

A

Spores form in main veins of the plasmodium and are enclosed by peridium

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17
Q

What are the main characteristics of Dictylostelids?

A

The vegetative forms are amoeba, pseudoplasmodium, and slug
Fruiting bodies are usually sorocarps
Sorocarps contain haploid spores
“social amoebae”

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18
Q

What is the pseudoplasmodium of Dictylostelids made up of?

A

Many individual amoebae

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19
Q

How does sorocarp development occur?

A

Through chemotaxis
As the food supply drops, cAMP is secreted

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20
Q

What are the anterior (forward) cells in Dictylostelids converted into?

A

Stalk cells

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21
Q

Which cells in Dictylostelids get to reproduce?

A

Amoebae in the front of the slug become stalk cells
Cells positioned in the back are converted into spores

22
Q

What are cheater line cells?

A

Cells that are known to avoid duty in the anterior part of the slug

23
Q

What are the two types of cheater cell lines?

A

Those that perform tip duty if no others are available

Those that are unable to form a fruiting body in the absence of non-cheaters on whose backs they ride

24
Q

What are the main characteristics of Protostelids?

A

Common on decaying matter, humus, dung, and in fresh water
Found everywhere, from the tundra to the tropics
Non-cellular
Filose pseudopodia

25
Q

How are sorocarps formed?

A

The amoeba stops feeding

“Hat” stage

Steliogen begins to form

Extension and differentiation of apophysis and spore

Spore detaches

26
Q

What are the main characteristics of Acrasids?

A

Common in decaying plant matter, soil, dung, and rotting mushrooms
Too small to be readily detected without a dissecting scope
Grown on nutrient-poor media and fed with yeasts
Chemical signal for aggregation is unknown, but it is not cAMP
Lonose pseudopodia

27
Q

What is the similarity between Acrasids and Dictyostelids?

A

They are both cellular slime molds, but they are only distantly related

28
Q

Where do Acrasids carry spores?

A

They carry spores in sorocarps that germinate and produce aggregating amoebae

29
Q

Which major slime molds are plasmodial?

A

Mycetozoa
Protostelids

30
Q

Which major slime molds are cellular?

A

Dictyostelids
Acrasids

31
Q

Which major slime mold has a peridium?

A

Mycetozoa

32
Q

Which major slime molds do not have a peridium?

A

Dictyostelids
Protostelids
Acrasids

33
Q

Which major slime mold uses sporophores/sporangia?

A

Mycetozoa

34
Q

Which major slime molds use sorocarps?

A

Dictyostelids
Acrasids

35
Q

What major slime mold uses sporocarps?

A

Protostelids

36
Q

Which major slime molds have filose morphology?

A

Mycetozoa
Dictyostelids
Protostelids

37
Q

What major slime mold has lobose morphology?

A

Acrasids

38
Q

Which major slime molds make use of plasmodium?

A

Mycetozoa
Protostelids

39
Q

Which major slime molds make use of pseudoplasmodium?

A

Dictyostelids
Acrasids

40
Q

What are oomycetes also known as?

A

Water moulds, downy mildews, seedlings blights, damping off, foliar blights

41
Q

What is unique about oomycete flagella?

A

They are dissimilar and are indicative of spore type

42
Q

What are the main characteristics of oomycetes?

A

“Egg fungus”
Saprotrophs or parasites in many terrestrial habitats
They form hyphae, and are assimilative heterotrophs like fungi
Hyphae are coenocytic
Vegetative cells are diploid
Zoospores are heterokontic

43
Q

What is the major difference between heterokont and fungal mitochondria?

A

Heterokonts = mitochondria have an inner tubular network
Fungi = mitochondria have internal lamellae

44
Q

What is the major difference between heterokont and fungal cell walls?

A

Heterokonts = cellulose
Fungi = chitin

45
Q

What are some unique features of the life cycle in phytophthora (oomycete)

A

Delayed karyogamy
Penetration by fertilization tube
One meiotic event in each parent

46
Q

What are the 3 layers in oomycete oospores?

A

Ooplast
Cytoplasm with lipid droplets
Endospore

47
Q

Where do the zoospores in oomycetes discharge?

A

From the zoosporangium

48
Q

How did oomycetes acquire pathogenicity?

A

From horizontal gene transfer with fungi

49
Q

What are the main characteristics of plasmodiophorids?

A

Obligate parasites, mostly of plants
Propagate in part through zoospores
Zoospores possess two identical whiplash flagella
The vegetative state in an amoeba which can enlarge to become a plasmodium that feeds through phagocytosis
Lacks cellular differentiation

50
Q

What do plasmodiophorids do?

A

They attack root hairs and inject their cytoplasm

51
Q

How can we combat plasmodiophorid pests?

A

Liming
Mercury-based compounds used to be used, but are now banned

BOT 306 (16 decks)

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