Presentation on theme: "Fungal Diversity I. Introduction II. Fungal Phyla"— Presentation transcript:
1 Fungal 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]
2 Characteristics 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
3 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 featuresAerial hyphae contain structures for production of spores (asexual propagules); usually only seen in culture
4 FungiThe parts:Fig. 31.1Cell walls - made of chitin. Same material that is in the external skeletons of arthropods - insects, arachnids, and crustaceans.
5 Molds - 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
7 YeastsUnicellular, 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).
9 FUNGAL LIFE CYCLEAsexual - budding or cell divisionSexual - fusion of 2 mating types spore formation
10 FUNGAL 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
11 B. What does a fungus do? Absorptive heterotroph Such as: Mutualist Parasite/pathogenMutualistDetritivore
12 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.
13 C. Basic fungal life cycle 2. Fertilization doesn’t happen all at oncePlasmogamy - fusion of cytoplasmKaryogamy - fusion of nuclei (gametes)heterokaryoticdikaryoticfig. 31.2
14 Classification 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.
15 B. Zygomycota 1. No dikaryotic growth 2. Both sexual and asexual sporangia
16 C. Ascomycota - Life cycle 1. Dikaryotic growth2. Fruiting body: ascocarp3. Fertile layer with asci4. Eight ascospores perascus (sac)5. Asexual reproductionvia conidia
17 D. Basidiomycota - Life cycle 1. Dikaryotic growth2. Fruiting body: basidiocarp3. Fertile layer on gillswith basidia (“clubs”)4. Four spores perbasidium5. Asexual reproductionis rare
18 E. Deuteromycota - “fungi imperfecti” 1. Not a true phylum (not a natural group): polyphyletic2. Fungi with no known sexual reproduction3. Asexual reproduction by conidia
19 III. 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
20 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
21 A. 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
22 Figure 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
23 A. Lichens3. Morphologyfruticosecrustosefoliose
24 A. Lichens4. Importancea. rock weathering, soil formation in primary succession- acid secretion- trapping particulatesnitrogen fixation (cyanobacteria)b. Indicators: susceptible to pollutants