Fungi and fungus-like organisms Flashcards
1
Q
myxomycetes
A
- plasmodial slime moulds
- kingdom amoebozoa
- acellular, giant coenocytic cells
- live in soil/wood
- predate on bacteria and fungi
- movement by cytoplasmic shuttle streaming
- produce spores
2
Q
slime mould live cycle
A
- amoeboid state
- swarming and nuclear division without cell division
- plasmodium
- starvation/unfavourable conditions
- fruiting body
- spore dispersal and germination
- amoeboid state
3
Q
oomycetes
A
- stramenopile kingdom
- mycelial
- cellulose cell wall
- anisogamic
- includes saprolegniales (water moulds) and peronosporales (important plant pathogens)
4
Q
oomycetes, reproductive strategy
A
- asexual reproduction with biflagellate zoospores (tinsel and whiplash flagella) formed in sporangia
- sexual reproduction, male antheridia fertilise female oogonia, oospores develop inside fertilised oogonium
- sexual reproduction can occur between individuals or within a hermaphrodite individual
- zoospores are short lived and important for dispersal in space
- oospores have a thick cell wall and can overwinter, so important for dispersal in time
5
Q
saprolegniales
A
- oomycetes
- water moulds
- mostly aquatic
- some cause fish diseases e.g. S. ferax in salmon
6
Q
Peronosporales
A
- oomycetes
- important plant pathogens
- peronospora, downy mildews
- pythium, damping off disease
- phytophthora e.g. potato blight
7
Q
Phytophthora infestans
A
- potato blight
- spreads in cool wet weather
- zoospores released in droplet of water on potato leaf
- spores invade leaf, causing necrosis and defoliation
- arrival of blight in Ireland from US in 1845 caused mass famine and emigration
8
Q
anisogamic
A
- sexes are morphologically different
- e.g. humans, oomycetes
9
Q
isogamic
A
- sexes are not morphologically different
- e.g. fungi
10
Q
zygomycetes
A
pin moulds
11
Q
basidiomycetes
A
mushroom forming fungi
12
Q
ascomycetes
A
cup fungi, bread mould, yeast
13
Q
inter-kingdom HGT from fungi to oomycetes?
A
- genomics found genes in oomycetes from osmotrophy that looked different to rest of genome, evidence of acquisition from fungi
- also evidence that they lost chloroplast, many stramenopile relatives possess chloroplasts
14
Q
osmotrophy
A
- fungi and oomycetes secrete extracellular enzymes and then absorb soluble nutrients produced
- animals and many protists including slime moulds are phagotrophic
15
Q
convergent evolution, oomycetes and fungi
A
- both oomycetes and chytridiomycetes (basal group of fungi) are zoosporic, osmotrophic, not fully terrestrial and are made up of long thin tubes
- however different kingdoms
- oomycetes have mycelium, cellulose cell walls and aseptate hyphae
- chytrids have a thallus, chitin cell walls and rhizoids
16
Q
fungi kingdom
A
- chitin cell walls
- non-motile spores (except chytrids) as zoospores are only useful in water
- mycelial growth (except chytrids and yeast, secondary simplification)
- haploid nuclei except in sex organs (cells need to be diploid in order to produce haploid spores through meiosis)
- septa between cells, act as valves to control flow of liquid over large areas of mycelium
- loss of flagellum in fungal evolution after chytrids
17
Q
fungal fossil records
A
- poor fossil records, ~10 found
- divergence from 600-1200mya, linked to second great oxygenation event 500-1000mya
- proliferation of higher fungi after plant colonisation of land
18
Q
using fungi in biotechnology
A
- produce a wide range of complex extracellular enzymes as they are osmotrophs than can be exploited e.g. in fermenters
- have a complex secondary metabolism, secondary metabolites such as penicillin have useful medical properties
19
Q
chytrids, phylum Chytridiomycota
A
- basal fungal group
- simple structure
- usually unicellular
- not yet mycelial, thallus with rhizoids that extend into substrate
- uniflagellate spores
- aquatic, soil, rumen habitats
- e.g. BD, amphibian disease, parasites of phytoplankton
20
Q
Batrachochytrium dendrobatidis, BD
A
- fungus that causes disease in amphibians
- kills frogs within 120 days
- spread from Africa, global trade in X. laevis, asymptomatic carriers
- 90 amphibian species extinct since 1970s
21
Q
BD life cycle
A
- mature fungus on frog develops into sporangium
- spores released after 4-5 days
- spores swim towards amphibian
- spores burrow into skin and develop into thallus
22
Q
rumen fungi
A
- chytrids
- only fungus that is an obligate anaerobe
- found in digestive tracts of ruminants (cattle, sheep) and hind-gut fermenting animals (horses)
- produce cellulase, important in grass digestion, all herbivores rely on them
- found in tortoises, have been mutualists in herbivores before mammals evolved
- produce aerobic survival spores that can survive being pooed out of organism until it is consumed by another herbivore
e.g. N. frontalis
23
Q
rumen fungi, fermentation process
A
- zoospores colonise ingested grass
- germinate into fungus, rhizoids penetrate into grass and decompose it with enzymes and by pushing cells apart with rhizoids, makes space for bacteria to colonise it
- breaks insoluble cellulose into soluble volatile fatty acids that can diffuse across rumen wall into the bloodstream
- hydrogen biproduct, converted into methane by Archaea
24
Q
Zygomycetes
A
- originally zygomycota phylum, now recognised to be multiple phyla
- zygospores from sexual reproduction
- sporangiospores from asexual reproduction
- all lack flagellate spores as they are higher fungi
- phylum zoopagomycota include animal parasites
- phylum mucomycota include pin moulds and mycorrhizas
25
Q
Ascomycota
A
- ‘cup fungi’
- most diverse phyla
- isogamic but a - and + sex
- form ascospores
- can produce asexual spores
26
Q
Ascomycota, sexual reproduction
A
- fusion of two haploid parent nuclei to form diploid nucleus
- meiosis and a further mitosis to form 8 haploid ascospores arranges in an ascus
- big, thick walled spores, optimised for dispersial in time
- germinate to form mycelium
27
Q
Ascomycota, asexual reproduction
A
- conidiospores released from conidiophore at foot cell of mycelium
- very small, short lived, carried by wind, optimised for dispersal through space
28
Q
ascocarp morphology
A
- naked ascus e.g. Saccharomyces, yest (secondary simplification)
- apothecium e.g. Peziza, cup fungus, spores on upper surface dispersed by wind
- Perithecium e.g. Sorderia, flask shaped, spores pushed out top
- Cleistothecium e.g. Aspergillus, closed cup, spores pushed out when burst
29
Q
mitosporic ascomycetes
A
-e.g. Aspergillus niger
- have the genes for sexual reproduction but have never been observed sexually reproducing
- either very rarely or never reproduce sexually
30
Q
fungal secondary metabolites, penicillin
A
- Produced by Aspergillus spp. and Penicillium spp. notable P. chrysogenum
- selective toxin
- antibacterial beta lactam compound targets the peptidoglycan component of bacteria cell walls
31
Q
Penicillin, variation of R group
A
- variation of R-group attached to beta lactam can create variations of penicillin more suited to different bacteria/environments
- e.g. ampicillin, amoxcillin
- can be used to make it more lipophilic, penicillin is more immediately effective on gram positive bacteria as their cell wall is more exposed to the environment, more lipophilic variations of penicillin can more easily penetrate the outer membrane of gram negative bacteria to reach the cell wall
32
Q
yield increase of penicillin
A
- 100 micrograms/l when first discovered in 1928
- industrial processing by Florey and Chain raised yield to 2mg/l (1940s)
- further development in US 1950s, 60mg/l
- recent mutagenesis and strain selection, 30g/l
33
Q
other useful fungal secondary metabolites
A
- statins, lovostatins (first statin) from oyster mushrooms
- cyclosporin, immunosuppressive drug used in organ transplants from T.inflatum
- psilocybin from Psilocybe spp. has a potential for treating depression and anxiety
34
Q
Claviceps purpurea, ergot
A
- alkaloid related to LSD
- grows on grains
- related to St Anthony’s fires in medieval times and Salem witch trials
- ergometrine now used to induce childbirth
35
Q
bioprospecting for novel fungi
A
95% fungal species undiscovered, huge potential reservoir for novel drugs
36
Q
Amanita muscaria, Fly Agaric
A
- hallucinogen (muscarine)
- liver toxin (amanitin)
37
Q
Basidiomycetes
A
- phylum basidiomycota
- subphylum Agariomycotina (mushroom forming)
- subphylum Pucciniomycotina (rusts)
- subphylum Ustilagomycotina (smuts, dandruff)
- basidium (sexual reproduction, spore producing structure)
- hyphae with clamp connections
- mycelium with dolipore septa
- dikaryotic, 2 haploid nuclei per cell (one from each parent, heterozygous advantage)
- multiple sexes
38
Q
basidium, sexual reproduction in basidiomycetes
A
- nuclear fusion of the two haploid parent nuclei
- meiosis and further mitosis in basidium to form 4 basidiospores that are released
- spores on the gills of agariomycotina are seen in sets of 4, 4 per basidium
39
Q
life cycle of basidiomycetes
A
- basidiospore germinates into primary mycelium (haploid, one nucleus per cell, no clamps)
- sexual preproduction, primary mycelium develops into secondary mycelium (dikaryotic, clamp connections)
- karygomy occurs in basidium (fusion of nuclei followed by meiosis)
- basidiospores formed and released
40
Q
hyphae with clamp connections in basidiomycetes
A
- ensures 2 haploid nuclei can migrate through mycelium together, allows fungi to grow long mycelial networks
- one of the nuclei moves into the clamp cell
- cell division of both the nuclei
- clamp fuses with cell and septa form, creating 2 dikaryotic cells with a nuclei from each parent
41
Q
diverse basidiocarp morphologies
A
- agaric (classic mushroom shape with gills)
- bracket
- poroid (spores inside pores)
- hydnoid (spores on spines)
all evolved to be very effective for spore dispersal, wind blows over surface and ‘sucks’ spores out
42
Q
basidiomycetes, subphylum Pucciniomycotina
A
- rusts
- important agriculturally
- wheat and barley rusts reduce crop yield
43
Q
basidiomycetes, subphylum Ustilagomycotina
A
- smuts and danrduff
- many smuts affect anthus of plants, pollinators pick up spores and disperse them instead of pollen
- corn-smut infects maize cobs, U. maydis (Mexican delicacy)
- complicated life cycles, 5 spore types, 2 plant hosts
