Zygomycota Flashcards
What percent of true fungi do zygomycota contain?
1%
Most famous zygomycota fungi are those that …..
Grow fast on fruit or other high sugar content food
Zygomycota lack ________
Instead they have….
Motile stage of life cycle
-asexual reproduction by spores:
1. Aplanospores (non-motile)
2. Sporangiophores (within sporangia)
Zygomycota spore dispersal
- passive by wind, insects or rain splash
Or
-violent liberation of entire sporangia
Mycelial organization of zygomycota
Coenocytic
Anaerobic vs aerobic growth form of zygomycota
Anaerobic: yeast form
Aerobic: filamentous form
Sexual reproduction of zygomycota involves what structure?
How is it formed?
Zygospores
-formed via plasmogamy between isogameous gametangia
-nuclear fusion may be right away or delayed until shortly before meiosis and zygospore germination
-gametangia that will fuse to form zygospores may be uninucleate or multinucleate therefore they may have 1 or more nuclei
Zygospores
Large, Thick walled, warty structures with abundant lipid reserves and are unsuitable for long-distance dispersal
Usually remain the the position in which they were formed and awaiting suitable conditions for further development
Zygomycota cell wall structure
Made of chitin
Chitin fibers however are modified after their synthesis by partial or complete de-acetylation to produce chitosan
Zygomycota evolutionary history
May have diverged from chytrids
Zygomycota most likely gave rise to ascomycota and basidiomycota
There most prominent orders of zygomycota and their lifestyles
Mucorales: mostly saprotrophs, in soils and dung
Entomorphthorales: insect parasites, but some are saprotrophs
Glomales: mutualistic symbionts with terrestrial plants as arbuscular mycorrhizae
Mucroales
Where are asexual spores?
Contained in globose sporangia born on the tips of aerial sporangiophores that are often phototropic
Sporangiophores of mucorales structure and special features
Single-celled, erect, cylindrical aerial hyphae
Sensitive to 4 stimuli: light, stretch, gravity and unknown stimulus to avoid solid objects
Sexual reproduction of Rhizopus stolonifer
Heterothallic-consorting of two mating types (+ and -)
-two compatible strains that rarely differ in appearance
-mating hormones switch the vegetative mycelium from asexual to sexual development
-trisporic acid derived from B-carotene is synthesized by collaborative metabolism of two mating strains: each strain has an incomplete enzyme pathway for the synthesis of trisporic acid.
-mycelia show directional growth towards each other in response to volatile mating type-specific hormones: methyl-4-dihydrosporate (+) and tri sporal of (-) strain
-hyphae of two strains approach each increase in size at their tips and rise above the substrate =pro gametangia
-transverse septa are laid down; delineate multinucleate tips of each branch. the delimitated portions called gametangia are considered to be multinucleate gametangia
-walls between the tips of contiguous gametangia dissolve; cytoplasm and nuclei within a single lumen=dikaryotic
-a thick wall is secreted by the zygote (only diploid stage) creating a zygospore and then meiotic division during germination
Rhizopus Rot
-10 species of Rhizopus grow in soil, on fruits, other foods, decaying material
-appears as large masses of black- grey fungus extending outward from the fruit in a whisker-like effect
-symptoms rarely develop in the orchard unless fruit are left to ripen on tree -> fungus is a wound parasite, breaks in the skin favour disease development
Commercial food production of zygomycota
-used in fermentation of soybeans to produce Sufu, tempeh, Millet and Ragi
Their fermentation action on carbohydrates causes soybeans to curdle to create soybean cakes
Economic importance of zygomycota enzymes
Rennin: cheese making
Cortisol: treat skin problems
Pilobolus sp. of mucorales
-habitat
-appearance
-dung of grass-eating animals
-one of the first fungi to grow on dung
-have explosive spore dispersal
-beneath the black apical mitosporangium is a lens-like subsporangial vesicle
-light-sensitive “retina” controls the growth of the sporangiophore, aiming towards light
Entomophthorales are known as
The fly killer fungus
-most species are very host specific, infecting only a certain species of insect or a group of closely related insects
Entomophthora sp.
How it works
-Fungus is transmitted by airborne spores->hyphae penetrate through the flys exoskeleton and through the body
-hyphae force small cracks in the intersegmental areas of the abdomen and produce sporangia-> spores are released explosively
-fungus may also be transmitted by male house flies attracted to infected dead female flies
-fungus may interfere with the flies oxygen intake t he ouch the breathing spiracles-> fly seems an elevated position to maximize airflow
-irritation causes the fly to raise its winds away from contact with fungus. Elevated location and posture improve chances that fungal spores will leave cadaver and infect new hosts
Behavioural alteration on insects by entomophthorales is accompanists by…..
Formation of glue-like materials secreted by hyphae for attachment. Fly becomes attached by its extended proboscis to the surface, where it may remain for days or even weeks
Life cycle of Entomopthora muscae infecting a fly
- Beginning of infection, germination of primary infectious conidia on multiple locations in the host surface, producing hyphae and conidia
- Infected fly in intermediate stage of incubation with interior hyphae bodies in insect blood and tissues within the body cavity
- Actively sporulation cadaver; fungal conidiophores with young conidia emerging from membranous areas of host abdominal cuticle
- Mummified fly cadavers possible reservoir for overwintering resting spores
What body position do infected flies take?
Sticky Conidia stick head and appendages onto top of leaf.
Irritation causes fly to lift wings
Attracts males for mating=spread
