fungi stuff

Question 1

saprophytes

Answer 1

absorb nutrients from a dead organism

(most fungi)

Question 2

necrophytes

Answer 2

derive nutrients from a organism they have killed

(parasite)

Question 3

biotrophs

Answer 3

derive nutrients from living host

(parasite)

produce haustoria (growths in infected cells)

Question 4

Cell wall made of?

Answer 4

chitin and polysacharrides

Question 5

Where does mitosis take place in fungi?

Answer 5

In the nucleus

(other eukaryotes, mitosis occurs after nucleus broken down)

Question 6

pseudohyphae

Answer 6

fungi can aggregate to form a colony or chain of cells

3 to 5 microns in diameter

Question 7

What form do most fungi exist in?

Answer 7

filamentous form

Question 8

Form of yeast

Answer 8

single cells with one nucleus, oval or spherical and reproduce asexually by budding off an identical daughter cell.

Question 9

How do filamentous fungi grow?

Answer 9

grow by polarised tip growth where the growth is at the tip and not the base of the cell.

tip is where new cell wall and cytosol is synthesised

Question 10

mycelium

Answer 10

collection of hyphae

Question 11

dimorphic yeast

Answer 11

can grow as both yeasts and filamentous form.

environmental cues trigger transition(temp).

Question 12

3 main type of spores and what they are.

Answer 12

condidospores - formed from specialised structure in a line of spores

sporangiospores - formed in specialised sac-like structures

arthrospores - formed from terminal cells of growing hyphae cells budding off.

Question 13

when do fungi produce spore?

Answer 13

when they feel/sense stress

Question 14

what are the two forms of sexual sporulation?

Answer 14

heterothallism - when two distinct parent cells which are sexually compatible join to form a unique offspring.

homothalism - when one fungus can self fertilise. no exchange of genetic material.

Question 15

How are sexual spores generated?

Answer 15

Two haploid hyphae fuse and form a specialised cell in the dikaryon state ( the cell has two nuclei)

Then development of specialised cell which becomes diploid.

Then either:

generates diploid sexual spores and after germination it restores back to haploid state via meiosis.

or there is meiosis prior to sore formation and produces haploid sexual spores

Question 16

dikaryon state

Answer 16

cell has two nuclei

Question 17

fungal groups

Answer 17

zygomycetes

ascomycetes

basidiomycetes

chytridiomycetes (small group)

deutromycetes (an artificial grouping in that those fungi lack a sexual cycle)

Question 18

Zygomycetes

Answer 18

produce sporangiospres in a sac structure, burst to release

aseptate hyphae

Question 19

aseptate hyphae

Answer 19

no cross-cell wall and the long filamentous cell is a continuous large cell.

Question 20

sexual reproduction in zygomycetes

Answer 20

plus and minus types are sexually compatible to fuse and form a zygosporangium and from this a diploid zygospore which undergoes meiosis to produce haploid spores which germinates to produce hyphae.

Question 21

septate hyphae

Answer 21

filamentous cells are divided into smaller cells.

Question 22

What kind of asexual spores do zygomycetes produce

Answer 22

haploid

Question 23

example of glomeromycetes

Answer 23

mycohizzal fungi, symbiosis

Question 24

What feeding mechanism are they?

Answer 24

saprophytes

Question 25

Asexual reproduction in ascomycetes

Answer 25

ascomycetes form asexual condiospores from specialised aerial structures

Question 26

sexual cycle of ascomycetes

Answer 26

cell fusion event and the formation of specialised dikaryon structures. From these structures, the cell fuses the nuclei to form the dikaryon state. The cell undergoes meiosis to produce four haploid sexual spores and each spore undergoes mitosis to form a total of eight spores. (ascospores)

Question 27

ascomycetes

Answer 27

haploid septate hyphae

saprophytes

Question 28

sexual reproduction in basidiomycetes

Answer 28

asexual reproduction rare

Spores are released from the fruiting body (e.g. toadstool) and two spores will germinate followed by fusion of the hyphal cell to make a single organism with two nuclei (dikaryon state). They propagate and grow as a dikaryon for most of the time as septate hyphae. It spends most of the time in the soil and when the conditions are favourable, they form a fruiting body (e.g. the mushroom) and from the gills spores are released

Question 29

Specialised cell form of mushroom gills

Answer 29

basidium

Question 30

basidiomycetes

Answer 30

septate dikaryon hyphae

asexual cycle uncommon

sexual haploid basidiospore in fruiting bodies

Most are saprophytes

Question 31

fruiting bodies of basidiomycetes

Answer 31

basidiocarps - includes: toadstools, mushrooms and brackets and puffballs

Question 32

How are fungi categorised/ grouped

Answer 32

based off sexual and asexual characteristics

Question 33

deuteromycetes

Answer 33

absence of sexual reproduction cycle

The asexual spores can be produced in a variety of ways

Question 34

mycoses

Answer 34

diseases caused by fungi

Question 35

mycotoxins

Answer 35

produced by fungi can cause liver failure

Question 36

true pathogen

Answer 36

affects healthy host

adapted to low oxygen tension and high temperatures

geographically restricted.

display thermal dimorphism (going from the fungal form to the pathogenic yeast form)

usually asymptomatic in host

Question 37

obligate parasites

Answer 37

need to infect host to complete life cycle

Question 38

thermal dimorphism

Answer 38

going from fungal form to pathogenic yeast form

hyphal form reproducing via spore production and being saprophytic at temperature less than 30 Celsius. If the spores become ingested, then the increase in temperature induces the yeast growth by budding or producing endospores (similar to that seen in bacteria) and they live a parasitic life deriving nutrients from the host. If it becomes systemic then this causes complications. On leaving the host environment, it reverts to its filamentous form

Question 39

opportunistic fungal pathogens

Answer 39

host is usually compromised

hardy to host environment.

Question 40

Commensalism

Answer 40

long-term biological interaction in which members of one species gain benefits while those of the other species are neither benefited nor harmed.

Question 41

necrosis

Answer 41

death of body tissue

Question 42

Dermatophytes

Answer 42

skin plants (translation)

They cause superficial infections on healthy host. They are not diseases and only cause discomfort.

Question 43

key drugs to control fungal infections.

Answer 43

azoles (e.g. ketoconazole and fluconazole) and these prevent the demethylation of sterol to ergosterol (and essential component in fungal membrane lipid and is specific to fungi)

polyenes (e.g. amphotericin B); it is rather toxic to the host in that it causes liver and kidney failure but if you are being administered this drug then you are rather ill from a fungal infection!
It makes the membrane of the fungal cells leaky and the cytosol leaks out. It prefers fungi because it has a high binding affinity for ergosterol

5 fluorocytosine. It acts as a fungistatic (it slows and stops growth but does not kill the fungus and so when you come off the drug the fungus can regrow!). It works by replacing the cytosine in RNA synthesis and the RNA is non functional and it inhibits the fungus from making new proteins and thus stops or retards growth.
fungal cells more readily absorb the flourocytosine than animal cells making it partially fungal specific

Question 44

phytopathogenic

Answer 44

cause diseases in plants

Question 45

pathogens of mature tissue

Answer 45

either neurotrophic or biotrophic

show high degree of host specificity

Question 46

rhizomorphs

Answer 46

macrostructures composed of filaments or hyphae cells.

Question 47

haustauria

Answer 47

growth in infected cells

haustorium does not break and damage the plant cell plasma membrane (it only damages the cell wall), it grows inside the plant cell as a separate cell with its membrane up against the intact membrane of the plant cell. So the plant cell is functioning and the fungal cell takes nutrients from the cell from across the plant cell membrane. The haustorium becomes a nutrient sink.

Question 48

typical infection cycle of fungi infecting insects

Answer 48

attachment of the spore to the cuticle,

this is followed by germination of an infection peg which penetrates the cuticle at the intersegmental portion gaining entry to the inside of the insect (it does this by employing cuticle digesting enzymes such as lipases, chitinases and proteases).

Following entry to the insect, it proliferates and sporulates in a yeast phase (they usually show dimorphism) and this results in one of two things; either the insect is drained of resource which eventually kills the insect or a toxin is used to kill the insect and the fungus derives nutrients from the dead insect. Following infection, the fungus can sporulate and produce spores for another cycle of infectio

Question 49

intersegmental portion

Answer 49

weak point of cytoskeleton of insect.

Question 50

control of fungi that parasite other plants, 3 things to consider

Answer 50

Parasitism of the target pathogen, using fungi to produce antibiotics targeted at the pathogenic fungus

and then competition in which a second fungus is introduced to out compete the target pathogenic fungus for nutrients.

Question 51

mycoprotein

Answer 51

types of food that comes from a fungus

Question 52

statins

Answer 52

fungal metabolites that inhibit the biosynthesis of cholesterol and are used to reduce plasma cholesterol levels which translates. into lower the incidence of heart disease.

statins inhibit a specific enzyme in the synthesis of chloresterol