Presentation on theme: "Fungal Diversity I. Introduction II. Fungal Phyla"— Presentation transcript:
1Fungal Diversity I. Introduction II. Fungal Phyla Reading: Chap. 31I. IntroductionA. What is a fungus?B. What does a fungus do?C. Basic fungal life cycleD. Who cares about fungi?II. Fungal PhylaA. OverviewB-E. Life cycles of the phylaIII. Fungal mutualismsA. LichensB. MycorrhizaeFungal DiversityII. Ecological importance:A. base of the food chain in aquatic ecosystems, both marine and freshwater; populations are controlled by seasonal climate shifts, predation, or nutrient limitation. Many very productive aquatic habitats - antarctic oceans, areas of upwelling off the Pacific coasts of N and S America are so because of abundant nutrients for phytoplankton. [Starr, fig. 37.3, OH 357]
2Characteristics of Fungi Non-motile eukaryotes lacking chlorophyllContain nucleus, mitochondria, 80S ribosomesPlasma membrane contains ergosterol instead of cholesterol.Cell wall is composed of chitin and various glucans, mannans, and complex polysaccharidesLarger than bacteriaRelatively simple nutritional requirements, wide range of growth ratesForm visible colonies in days to weeksUnicellular or multicellular depending on the species
3Molds 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 featuresAerial hyphae contain structures for production of spores (asexual propagules); usually only seen in culture
4FungiThe parts:Fig. 31.1Cell walls - made of chitin. Same material that is in the external skeletons of arthropods - insects, arachnids, and crustaceans.
5Molds - identification Identification based on colony morphology (pigment, texture) and morphology of reproductive structuresConidia - spores formed by budding (blastoconidia) or disarticulation of existing hypha (arthroconidia)Sporangiospores - produced by free-cell formation within sporangium in nonseptate molds11ConidiopsporesPhialidesVesicleConidiophoreSeptate hyphae3sporangiumsporangiophoreEndosporesNonseptatehyphae5. rhizoids2342545
6YEASTS Also yeasts - single-celled e.g., Saccharomyces cerevisiae Candida albicans31.15
7YeastsUnicellular, 3-5 µm, reproduce by budding (blastoconidia formation) or fissionIdentified 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).
9FUNGAL LIFE CYCLEAsexual - budding or cell divisionSexual - fusion of 2 mating types spore formation
10FUNGAL NUTRITION & ENVIRONMENT Organic compounds needed for growth saprophytes as feed on dead organic matterAdapted to: growth at pH growth on surfaces growth under high osmotic conditions growth at low water levels growth in low nitrogen environments growth on unusual nutrient sources
11B. What does a fungus do? Absorptive heterotroph Such as: Mutualist Parasite/pathogenMutualistDetritivore
12Also 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.
13C. Basic fungal life cycle 2. Fertilization doesn’t happen all at oncePlasmogamy - fusion of cytoplasmKaryogamy - fusion of nuclei (gametes)heterokaryoticdikaryoticfig. 31.2
14Classification of Fungi Taxonomy is based on structural features of the teleomorph (sexual phase).Zygomycota - includes all fungi with nonseptate hyphaeAscomycota - includes most human pathogensBasidiomycota - mainly saprobes or plant pathogensDeuteromycota (fungi imperfecti)Sexual phase unknown or doesn’t exist. Some can be assigned to above groups based on phylogenetic analysis.
15B. Zygomycota 1. No dikaryotic growth 2. Both sexual and asexual sporangia
17D. Basidiomycota - Life cycle 1. Dikaryotic growth2. Fruiting body: basidiocarp3. Fertile layer on gillswith basidia (“clubs”)4. Four spores perbasidium5. Asexual reproductionis rare
18E. Deuteromycota - “fungi imperfecti” 1. Not a true phylum (not a natural group): polyphyletic2. Fungi with no known sexual reproduction3. Asexual reproduction by conidia
19III. Fungal mutualisms Definitions: Symbiosis - 2 organisms living together in intimate physical contactMutualism - both organisms benefit from the relationshipParasitism - one benefits, one losesCommensalism - one benefits, other not affected
20A. 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
21A. Lichens 2. Anatomy a. most of lichen body is fungal hyphae b. photosynthetic partner in a distinct layerc. sexual reproduction of fungal partner onlyd. asexual reproduction: soredia, fragmentation2. Anatomymedulla
22Figure 29.9a Ectomycorrhizal fungi (EMF) Root cells EMF Figure: 29.9a Caption:(a) Ectomycorrhizal fungi (EMF) form a dense network around the roots of plants. The combination of root and fungus is called a mycorrhiza. The drawing shows how the interaction works in EMF. Note that their hyphae penetrate the intercellular spaces of the root, but do not enter the cells themselves. EMF