Ascomycota

Question 1

What is the largest group of fungi

Answer 1

Ascomycota

Estimated 32,000 species

Question 2

Destructive and beneficial properties of ascomycota

Answer 2

Devastating plant disease: Dutch elm disease, chestnut blite, peach leaf curl

Yeasts in commercial beer and bread making, Penicillin, ergot

Question 3

Hyphal structure in ascomycota

Answer 3

-hyphae separated by septa and made of chitin
-septa walls taper to central pore
-woronin bodies remain near central pore even when cytoplasmic streaming occurs

Question 4

Do ascomycota have flagella in their life cycle?

Answer 4

No

Question 5

Woronin body Structure and purpose

Answer 5

-surrounded by membrane and has crystalline contents consisting largely of protein
-in healthy hyphae, they stay in usual position in cytoplasm adjacent to pore
-in unhealthy conditions (old age or damage) they move to block the central pore and become a plug

Question 6

Mycelia of most ascomycota are ________

Reproduction?

Answer 6

Homokaryotic (monokaryotic)

Fusion of compatible hyphae creates matrix of mono and heterokryotic (dikaryotic) cells-> genetic flexibility

Different types of nuclei divide at different rates -> ratio of monokaryotic: heterokaryotic cells may change with environment (nutrients)

Question 7

Sectoring of mycelial body in ascomycota

Answer 7

Slow-growing wild type mycelium appears dark due to the formation of mealanized cleistothecia.

Two-non fruiting (not reproductive) sectors have formed which show faster vegetative growth but no sporulation

Question 8

Ascospores give rise to a _______ mycelia

Answer 8

Monokaryotic

Question 9

Do all Ascomycetes reproduce sexually

Answer 9

No, some only asexual

Question 10

Asexual (Conidial) stage in the life cycle of a fungus is called an _______

Answer 10

Anamorph: produces spores without meiotic Division

Question 11

Development of Conidia arise from what two mechanisms

Answer 11

Blastic conidial development: conidium develops by blowing out of cell wall at tip of hypha

Thallic Conidial development= conversion of a hyphal tip to a conidium by a septal wall

Question 12

Sexual reproduction in ascomycota involves what?

Answer 12

-occurs only in Ascomycetes that produce asci
-plasmogamy is initiated when male gametangium (antheridium) reaches the female ascogonium via Trichogyne
-Karyogamy is delayed-> dikaryotic condition is prolonged by forming a succession of dikaryotic cells, or by forming a special hyphal system, the ascogenous hyphae
-each ascogenous hypahe produces a branch from one or more of its dikaryotic cells, the tip of which bends to form a hook (crozier), containing two compatible nuclei, which now divide by mitosis
-two septa develop in such a way that the crozier becomes divided into 3 compartments
-middle compartment is binucleate (Ascus mother cell->destined to become an Ascus) with 8 Ascospores

Question 13

How do yeasts reproduce

Answer 13

Binary fission, budding

Question 14

Yeast sexual reproduction with reduced food supply

Answer 14

Fusion of compatible cells forms zygote-Holocarpic

Question 15

What does brewers or bakers yeast do that is economically important?

Answer 15

Convert sugars and other carbon sources into ethanol (anaerobic)

Converts sugars into carbon dioxide and water (aerobic)

Question 16

Pathogenic Yeast

Answer 16

-can cause mouth thrush or cryptococcosis or meningitis

Question 17

What is the blue colour on blue cheese?

Answer 17

Condia of fungus

Question 18

What was the first antibiotic and how does it work

Answer 18

Penicillin (ascomycota)

Inhibits transpeptidase that catalyses cell wall biosynthesis

Fleming, chain and florey

Question 19

What order of ascomycota causes chest nut blight?

What does the disease do?

Answer 19

Order Diaporthales

Parasitic fungus causes cankers that girdle the tree trunk and cause the crown (vascular tissue) to wither and die

<1% of original population remains. Surviving trees are immature or stumps that only produce shoots but no seeds.

Question 20

The fungus causing chestnut blight can also use alternative hosts such as

Answer 20

Oak, maple, hickory, sumac

Question 21

What is being done to help chestnut blight infected trees

Answer 21

Attempts to inoculate hypo virulent strains to try and contain the spread of the disease

Hypovieulent strains do not kill trees

Fusion of hyphae of virulent and hypovirulent hyphae

Question 22

Dutch elm disease is caused by which order or ascomycota and what is another name for the disease

Answer 22

Order ophiostomatales
Vascular wilt disease

Question 23

How is Dutch elm disease spread

Answer 23

Bark boring beetles like elm bark beetles are attracted to healthy elms by volatile chemicals produced by the trees. Females tunnel galleries under the bark of an elm to lay eggs which disperse Ascospores and Conidia

Fungus may be passed between tree root contact

Question 24

How does Dutch elm disease work inside the tree

Answer 24

Fungus moves upward and downward inside tree. Conidia within xylem fluid and growth of hyphae between xylem vessels.

Production of gums cause loss of water conduction and increase the pressure, thereby expanding protoplast of a parenchyma cell

This leads to flagging or wilting and yellowing of leaves

Fungus persists as saprotrophs in bark of dead trees

Question 25

Sclerotia of order Claviceps (ergots) leads to what type of poisoning?

Answer 25

Ergotism poisoning

St Anthony’s fire: ergotamine and ertotaline=smooth muscle construction leading to restriction of peripheral blood supplies ——> gangrene, death (hallucinations and burning sensation)

Question 26

Alkaloids of Claviciptales cause what

Answer 26

Ergine (LSD)

Question 27

What order do morchella mushrooms come from

Answer 27

Order pezizales

Question 28

The Ascomata of Pezizales are hypogeous: this means what

Answer 28

Odours attract animals and disperse spores by digging

Question 29

What order of ascomycota causes white nose syndrome and what does it do

Answer 29

Order Helotiales

Infected bats wake during hibernation and dehydrate due to damage the fungus causes to wings