Oh goodness

1. Oh goodness There is a fungus among us!!!!!!

2. What is a fungus? • A eukaryotic, heterotrophic organism devoid of chlorophyll that obtains its nutrients by absorption, and reproduces by spores.

3. Characteristics • 1. All are eukaryotic Possess membrane-bound nuclei (containing chromosomes) and a range of membrane-bound cytoplasmic organelles (e.g. mitochondria, vacuoles, endoplasmic reticulum). • 2. Most are filamentous Composed of individual microscopic filaments called hyphae, which exhibit apical growth and which branch to form a network of hyphae called a mycelium. • 3. Some are unicellular e.g. yeasts. • 4. Protoplasm of a hypha or cell is surrounded by a rigid wall Composed primarily of chitin and glucans, although the walls of some species contain cellulose. • 5. Many reproduce both sexually and asexually Both sexual and asexual reproduction often result in the production of spores. • 6. Their nuclei are typically haploid and hyphal compartments are often multinucleate Although the Oomycota and some yeasts possess diploid nuclei. • 7. All are achlorophyllous They lack chlorophyll pigments and are incapable of photosynthesis. • 8. All are chemoheterotrophic (chemo-organotrophic) They utilise pre-existing organic sources of carbon in their environment and the energy from chemical reactions to sythesise the organic compounds they require for growth and energy. • 9. Possess characteristic range of storage compounds e.g. trehalose, glycogen, sugar alcohols and lipids. • 10. May be free-living or may form intimate relationships with other organisms i.e. may be free-living, parasitic or mutualistic (symbiotic).

4. Modes of nutrition • Fungi=absorptive heterotrophs • Animals=phagotrophic heterotroph • Heterotroph (chemo-organotrophs): an organism incapable of synthesizing carbohydrates from inorganic sources; requires preformed organic compounds produced by other organisms • Plants=autotrophs

5. Hyphae (singular, hypha) • Cylindrical, branching filaments composed of a tubular cell wall filled with cytoplasm and organelles • Most fungal hyphae are 2-10 m diameter

7. Septa • Septa—regular cross-walls formed in hyphae. Hyphae with septa are septate, those lacking septa are aseptateor coenocytic. • primary septa are formed as a process of hyphal extension and generally have a septal pore, which allows for cytoplasmic and organelle movement. • Secondary or adventitious septa are imperforate, formed to wall off ageing parts of the mycelium.

8. Fungi as model organisms • Small genome relative to other eukaryotes • Many fungal genes are homologous to those in other eukaryotes • Easy to grow, short life cycles • Haploid genomes amenable to mutation • Sexual stage for analysis of segregation and recombination of genes; all products of meiosis can be retrieved in haploid spores • Asexual (clonal) reproduction

9. Fungal Reproduction • Many fungi have the ability to reproduce by asexual and sexual means

10. Kingdom Fungi • Phyla: • Chytridiomycota • Form motile spores called zoospores • Meiosis occurs in resting sporangium • Glomeromycota • Form spores containing hundreds of nuclei; no known sexual reproduction • Zygomycota • Form asexual spores called sporangiospores • Meiosis occurs in zygospore • Ascomycota (including Deuteromycetes) • Form asexual spores called conidia • Meiosis occurs in ascus • Basidiomycota • Meiosis occurs in basidium

11. Fungal life cycles • The vegetative thallus predominates in the life cycle of a fungus • The thallus may be haploid (1n), dikaryotic (n+n) or diploid (2n) in different groups of fungi • Ploidy of thallus is determined by the timing of these events in the life cycle: • Plasmogamy (cell fusion) • Karyogamy (nuclear fusion) • Meiosis (reduction division)

12. What are the 3 stages during the life cycle of the fungus?