Oomycetes

Question 1

What are the main characteristics of slime molds?

Answer 1

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

Question 2

How do slime molds feed by phagocytosis?

Answer 2

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

Question 3

What are the 3 main classes in Amoebozoa?

Answer 3

Myxogastria
Protostelea
Dictyostelia

Question 4

What are the main characteristics of myxomycetes?

Answer 4

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

Question 5

What can all vegetative forms produce?

Answer 5

Pseudopodia

Question 6

What are the two types of pseudopodia?

Answer 6

Lobose or filose

Question 7

What type of pseudopodia are found in Myxogastria?

Answer 7

Filose

Question 8

What are the main characteristics of swarmer cells?

Answer 8

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

Question 9

What is the main characteristic of plasmodia?

Answer 9

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

Question 10

What is the phaneroplasmodia plasmodial type?

Answer 10

Large, veined feeding structures with rhythmic streaming

Question 11

When will a resting state or sclerotia form?

Answer 11

When the spore has to be resistant to extreme environmental conditions

Question 12

What condition needs to be met for myxomycetes to form?

Answer 12

It has to be wet enough

Question 13

What are the 3 common types of myxogastrial sporophores?

Answer 13

Sporangium
Aethalium
Plasmodiocarp

Question 14

What does sporangium in myxomycetes contain?

Answer 14

Columella, capillitium, and spores

Question 15

When does Aethalia occur?

Answer 15

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

Question 16

How do plasmodiocarps occur?

Answer 16

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

Question 17

What are the main characteristics of Dictylostelids?

Answer 17

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

Question 18

What is the pseudoplasmodium of Dictylostelids made up of?

Answer 18

Many individual amoebae

Question 19

How does sorocarp development occur?

Answer 19

Through chemotaxis
As the food supply drops, cAMP is secreted

Question 20

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

Answer 20

Stalk cells

Question 21

Which cells in Dictylostelids get to reproduce?

Answer 21

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

Question 22

What are cheater line cells?

Answer 22

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

Question 23

What are the two types of cheater cell lines?

Answer 23

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

Question 24

What are the main characteristics of Protostelids?

Answer 24

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

Question 25

How are sorocarps formed?

Answer 25

The amoeba stops feeding "Hat" stage Steliogen begins to form Extension and differentiation of apophysis and spore Spore detaches

Question 26

What are the main characteristics of Acrasids?

Answer 26

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

Question 27

What is the similarity between Acrasids and Dictyostelids?

Answer 27

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

Question 28

Where do Acrasids carry spores?

Answer 28

They carry spores in sorocarps that germinate and produce aggregating amoebae

Question 29

Which major slime molds are plasmodial?

Answer 29

Mycetozoa Protostelids

Question 30

Which major slime molds are cellular?

Answer 30

Dictyostelids Acrasids

Question 31

Which major slime mold has a peridium?

Answer 31

Mycetozoa

Question 32

Which major slime molds do not have a peridium?

Answer 32

Dictyostelids Protostelids Acrasids

Question 33

Which major slime mold uses sporophores/sporangia?

Answer 33

Mycetozoa

Question 34

Which major slime molds use sorocarps?

Answer 34

Dictyostelids Acrasids

Question 35

What major slime mold uses sporocarps?

Answer 35

Protostelids

Question 36

Which major slime molds have filose morphology?

Answer 36

Mycetozoa Dictyostelids Protostelids

Question 37

What major slime mold has lobose morphology?

Answer 37

Acrasids

Question 38

Which major slime molds make use of plasmodium?

Answer 38

Mycetozoa Protostelids

Question 39

Which major slime molds make use of pseudoplasmodium?

Answer 39

Dictyostelids Acrasids

Question 40

What are oomycetes also known as?

Answer 40

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

Question 41

What is unique about oomycete flagella?

Answer 41

They are dissimilar and are indicative of spore type

Question 42

What are the main characteristics of oomycetes?

Answer 42

"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

Question 43

What is the major difference between heterokont and fungal mitochondria?

Answer 43

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

Question 44

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

Answer 44

Heterokonts = cellulose Fungi = chitin

Question 45

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

Answer 45

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

Question 46

What are the 3 layers in oomycete oospores?

Answer 46

Ooplast Cytoplasm with lipid droplets Endospore

Question 47

Where do the zoospores in oomycetes discharge?

Answer 47

From the zoosporangium

Question 48

How did oomycetes acquire pathogenicity?

Answer 48

From horizontal gene transfer with fungi

Question 49

What are the main characteristics of plasmodiophorids?

Answer 49

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

Question 50

What do plasmodiophorids do?

Answer 50

They attack root hairs and inject their cytoplasm

Question 51

How can we combat plasmodiophorid pests?

Answer 51

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