announcements next week – no lab wednesday evening –lab closes 5pm for biol 203 exam –lab will...
TRANSCRIPT
Announcements
• Next week – no lab Wednesday evening– Lab closes 5pm for Biol 203 exam– Lab will be open Tuesday 5-10 pm
• Biol 204 notes– www.usask.ca– Biology– Class notes -- Biol 204 – kaminskyj– 2004 lectures
Cytoplasmic migration in tip growth
Fungal cell walls
• Thin• Fiber reinforced
– Taxonomically relevant
• Plastic/extensible at tip
• Elastic/inextensible at maturity
Wall vesicle exocytosis at Saprolegnia hyphal tip
Hydrophobins
• Without hydrophobins, hyphae cannot break through the surface tension of water
• Hydrophobins are essential for mold sporulation and mushroom formation
Hydrophobin rodlets
Diverse features of Protista (P), Chromista (C), Eumycota (F)
• Walls in vegetative phase– Lacking (P)– Having (C, F)
Diverse features of Protista (P), Chromista (C), Eumycota (F)
• Walls in vegetative phase
• Mode of nutrition (always heterotrophic)– Ingestive (P)– Absorptive (C, F)
Protistan fungi – three taxa
• Myxomycota – “acellular” slime molds
Dictyosteliomycota – cellular slime molds
Plasmodiophoromycota – endoparasitic slime molds
Common features of Protistan fungi
• Nutrition by ingestion– Possible because vegetative stages do not
have walls
Common features of Protistan fungi
• Nutrition by ingestion
• Lifestyle – Individual cells or colonies– Dictyosteliomycota -> Alternating individual
and colonial stges
Common features of Protistan fungi
• Nutrition by ingestion• Lifestyle
– Individual cells or colonies
– Alternating individual and colonial stges (Dictyosteliomycota)
• Sexual reproduction by spore formation– Only walled stage– Fibrils of peptidoglycan, cellulose, chitin
Myxomycete plasmodia
Physarum – nuclear behaviour
Myxomycete plasmodia can distinguish nonself and self
Physarum on heterogeneous substrate – food preference
Myxomycete spores in sporangia
Physarum Stemonitis
Myxomycete spore walls contain peptidoglycan
Dictyosteliomycota – “cellular” slime molds
Dictyostelium
Aggregation of amoebae uses chemical signals
Dictyostelium cell differentiation model system
www2.mrc-lmb.cam.ac.uk
Dictyostelium spore walls contain cellulose
niko.unl.edu
Plasmodiophoromycota – endoparasitic slime molds
Plasmodiophora in cabbage root hair
Plasmodiophora resting spores
Chromistan fungi – Oomycetes
• Saprobes, parasites/pathogens
Chromistan fungi – Oomycetes
• Saprobes, parasites/pathogens
• Obligate parasites – must have a living host to complete life cycle – aggressive
• Facultative parasites – parasitism is optional – less aggressive
Saprophytes and facultative parasites
Asexual zoospores ofAchlya biusexualis
Attachment, infection, colonization
• In nature, infective stage is motile flagellated zoospores – primary and secondary
• Heterokont flagella• Zoospores find a food
source by chemotaxis
Attachment, infection, colonization
• In nature, infective stage is motile flagellated zoospores – primary and secondary
• Heterokont flagella
• Zoospores locate a food source by chemotaxis
Attachment, infection, colonization
• In nature, infective stage is motile flagellated zoospores – primary and secondary
• Zoospores find food a source by chemotaxis
• Attachment is followed by shedding flagella
• Infection requires growth of a penetrating hypha
Saprophyte attachment and germination
1° zoospore
1° cyst
2° zoospore
2° cyst
germinationandinfection
Morphology and parasitic aggressiveness
Parasitism
The joy of slime
Oomycetes as plant pathogens Phytophthora infestans
www.scisoc.org/feature/lateblit/chapter1/epidemic.htm
Understanding late blight
• disease attributed to – excess water in the plants, – effects of the newly
introduced steam locomotives
• Reverend M.J. Berkeley– Early 1850’s– Fungal pathogen
Phytophthora sporangia and zoospores
www.scisoc.org/feature/lateblit/chapter1/epidemic.htm
Drier soils -> direct germination
Wet soils -> zoospores
Social consequences of Phytophthora infestans riots, eviction, emigration
Sexual spores of oomycetes
Major significance in genetic recombination -> development of new pathotypes
Next time:it’s not easy being green