Presentation on theme: "Fungal Diversity Reading: Chap. 31 I. Introduction A. What is a fungus? B. What does a fungus do? C. Basic fungal life cycle D. Who cares about fungi?"— Presentation transcript:
Fungal Diversity Reading: Chap. 31 I. Introduction A. What is a fungus? B. What does a fungus do? C. Basic fungal life cycle D. Who cares about fungi? II. Fungal Phyla A. Overview B-E. Life cycles of the phyla III. Fungal mutualisms A. Lichens B. Mycorrhizae
Characteristics of Fungi Non-motile eukaryotes lacking chlorophyll Contain nucleus, mitochondria, 80S ribosomes Plasma membrane contains ergosterol instead of cholesterol. Cell wall is composed of chitin and various glucans, mannans, and complex polysaccharides Larger than bacteria Relatively simple nutritional requirements, wide range of growth rates Form visible colonies in days to weeks Unicellular or multicellular depending on the species
Molds Multicellular, tubular structures (hyphae) Hyphae can be septate (regular crosswalls) or nonseptate (coenocytic) depending on the species (grow by apical extension) Vegetative hyphae grow on or in media (absorb nutrients); form seen in tissue, few distinguishing features Aerial hyphae contain structures for production of spores (asexual propagules); usually only seen in culture
Fungi The parts: Fig Cell walls - made of chitin. Same material that is in the external skeletons of arthropods - insects, arachnids, and crustaceans.
Molds - identification Identification based on colony morphology (pigment, texture) and morphology of reproductive structures Conidia - spores formed by budding (blastoconidia) or disarticulation of existing hypha (arthroconidia) Sporangiospores - produced by free-cell formation within sporangium in nonseptate molds 1.sporangium 2.sporangiophore 3.Endospores 4.Nonseptate hyphae 5.rhizoids Conidiopspores 2.Phialides 3.Vesicle 4.Conidiophore 5.Septate hyphae
Yeasts Unicellular, 3-5 µm, reproduce by budding (blastoconidia formation) or fission Identified by microscopic morphology (grow on cornmeal agar) and biochemical tests (sugar assimilation, enzymatic activity). Molds and yeast are not exclusive forms, some species may exist in both yeast and mold forms (dimorphism).
Colonial Morphology of Fungi Cryptococcus neoformans Candida albicans Wangiella dermatitidis Aspergillus fumigatus T. menta- grophytes Trichophyton tonsurans
FUNGAL LIFE CYCLE Asexual - budding or cell division Sexual - fusion of 2 mating types spore formation
FUNGAL NUTRITION & ENVIRONMENT Organic compounds needed for growth saprophytes as feed on dead organic matter Adapted to: growth at pH 5 growth on surfaces growth under high osmotic conditions growth at low water levels growth in low nitrogen environments growth on unusual nutrient sources
B. What does a fungus do? Absorptive heterotroph Such as: Parasite/pathogen Mutualist Detritivore
Also eat: - wood in houses, boats, fences; - food; - other materials - cloth, paint, leather, waxes, jet fuel, petroleum, paper, wire insulation, photographic film, - to name a few. What do all of these materials have in common? They are all C-based.
C. Basic fungal life cycle fig Fertilization doesn’t happen all at once Plasmogamy - fusion of cytoplasm Karyogamy - fusion of nuclei (gametes) heterokaryotic dikaryotic
Classification of Fungi Taxonomy is based on structural features of the teleomorph (sexual phase). Zygomycota - includes all fungi with nonseptate hyphae Ascomycota - includes most human pathogens Basidiomycota - mainly saprobes or plant pathogens Deuteromycota (fungi imperfecti) Sexual phase unknown or doesn’t exist. Some can be assigned to above groups based on phylogenetic analysis.
B. Zygomycota 1. No dikaryotic growth 2. Both sexual and asexual sporangia
C. Ascomycota - Life cycle 1. Dikaryotic growth 2. Fruiting body: ascocarp 3. Fertile layer with asci 4. Eight ascospores per ascus (sac) 5. Asexual reproduction via conidia
D. Basidiomycota - Life cycle 1. Dikaryotic growth 2. Fruiting body: basidiocarp 3. Fertile layer on gills with basidia (“clubs”) 4. Four spores per basidium 5. Asexual reproduction is rare
E. Deuteromycota - “fungi imperfecti” 1. Not a true phylum (not a natural group): polyphyletic 2. Fungi with no known sexual reproduction 3. Asexual reproduction by conidia
III. Fungal mutualisms Definitions: Symbiosis - 2 organisms living together in intimate physical contact Mutualism - both organisms benefit from the relationship Parasitism - one benefits, one loses Commensalism - one benefits, other not affected
A. Lichens 1. Partners a. Fungal partner - gives protection - mostly Ascomycetes (~25,000 spp.) - only found in lichens (not free-living) b. Photosynthetic partner - gives fixed carbon (sugars) - green alga or cyanobacterium - can be free-living
A. Lichens 2. Anatomy medulla a. most of lichen body is fungal hyphae b. photosynthetic partner in a distinct layer c. sexual reproduction of fungal partner only d. asexual reproduction: soredia, fragmentation
A. Lichens 3. Morphology fruticose foliose crustose
A. Lichens 4. Importance a. rock weathering, soil formation in primary succession - acid secretion - trapping particulates -nitrogen fixation (cyanobacteria) b. Indicators: susceptible to pollutants