Ascomycota Flashcards
What is the largest group of fungi
Ascomycota
Estimated 32,000 species
Destructive and beneficial properties of ascomycota
Devastating plant disease: Dutch elm disease, chestnut blite, peach leaf curl
Yeasts in commercial beer and bread making, Penicillin, ergot
Hyphal structure in ascomycota
-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
Do ascomycota have flagella in their life cycle?
No
Woronin body Structure and purpose
-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
Mycelia of most ascomycota are ________
Reproduction?
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)
Sectoring of mycelial body in ascomycota
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
Ascospores give rise to a _______ mycelia
Monokaryotic
Do all Ascomycetes reproduce sexually
No, some only asexual
Asexual (Conidial) stage in the life cycle of a fungus is called an _______
Anamorph: produces spores without meiotic Division
Development of Conidia arise from what two mechanisms
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
Sexual reproduction in ascomycota involves what?
-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
How do yeasts reproduce
Binary fission, budding
Yeast sexual reproduction with reduced food supply
Fusion of compatible cells forms zygote-Holocarpic
What does brewers or bakers yeast do that is economically important?
Convert sugars and other carbon sources into ethanol (anaerobic)
Converts sugars into carbon dioxide and water (aerobic)
Pathogenic Yeast
-can cause mouth thrush or cryptococcosis or meningitis
What is the blue colour on blue cheese?
Condia of fungus
What was the first antibiotic and how does it work
Penicillin (ascomycota)
Inhibits transpeptidase that catalyses cell wall biosynthesis
Fleming, chain and florey
What order of ascomycota causes chest nut blight?
What does the disease do?
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.
The fungus causing chestnut blight can also use alternative hosts such as
Oak, maple, hickory, sumac
What is being done to help chestnut blight infected trees
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
Dutch elm disease is caused by which order or ascomycota and what is another name for the disease
Order ophiostomatales
Vascular wilt disease
How is Dutch elm disease spread
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
How does Dutch elm disease work inside the tree
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
