FUNGI

1. FUNGI

2. Fungus • Fungi • MYCOLOGY

3. Eukaryotic spore-bearing protists, lacking chlorophyll • Fungi • Molds: Filamentous and multicellular • Yeasts: Mostly, unicellular

4. Fungi are heterotrophic: • Chemoorganotrophic • Require organic compounds for nutrition. • Saprophytic: • If they feed on dead organic matter. • Important in industrial fermentations – for brewing of beer, wine making & production of antibiotics as penicillin. • Parasitic:

5. Dimorphic Fungi: • Exist in 2 forms. • Human/animal pathogenic fungi: • Have unicellular & yeastlike form in host • Under saprophytic conditions, have a filamentous mold form • Plant pathogens • In Taphrina, smuts • Mycelial form occurs in host • Unicellular yeastlike form occurs in lab culture.

6. MORPHOLOGY • Size range: • 1 to 5 μm in width; • 5 to 30 μm or more in length. • Shape: • Egg-shaped or spherical. • Depends on age and environment • No organelles of locomotion.

7. Thallus (pl. thalli) • Body of a fungus • Consists of a single cell as in yeasts • Consists of branched filaments, as in molds, 5 to 10 μm across • Surrounded by a true cell wall • Exception: In slime molds. • Thallus has a naked mass of protoplasm.

8. Thallus of a mold has 2 parts: • Mycelium (pl, mycelia) and • Spores (resistant, resting, or dormant cells).

9. A complex of several filaments - Hypha (pl, hyphae) • A spore, on germination, puts out a germ tube(s) • Germ tubes elongate and branch to form hyphae. • A complex of several hyphae - Mycelium

10. HYPHA • Composed of an outer tubelike wall surrounding a cavity, the LUMEN, which is filled / lined by protoplasm. • Between the protoplasm and the wall is the PLASMALEMMA, a double-layered membrane • Hyphal wall consists of microfibrils composed for the most part of hemicelluloses or chitin • True cellulose - Only in the walls of lower fungi.

11. Growth of a hypha is distal, near the tip. • New hypha is divided into cells by crosswalls which are formed by centripetal invagination from the existing cell wall. • Crosswalls constrict the plasmalemma • Grow inward to form an incomplete septum (pl, septa) • Septum has a central pore to allow protoplasmic streaming.

12. Hyphae occur in three forms • Nonseptate / Coenocytic: No septa. • Septate with uninucleate cells. • Septate with multinucleate cells • Each cell has > 1 nucleus.

13. Types of hyphae:(A) Nonseptate (coenocytic), (B) septatewith uninucleate cells, (C) septate with multinucleate cells.

14. REPRODUCTION • Asexual / Somatic / Vegetative • Sexual

15. Asexual Reproduction • Fission of somatic cells yielding 2 similar daughter cells; • Budding of somatic cells or spores • Each bud, a small outgrowth of parent cell • Fragmentation of the hyphal cells • Each fragment becomes a new organism • Spore formation. • Many types.

16. Types of Spores • Sporangiospores: Single-celled spores, formed within sacs called sporangia at the end of hyphae – sporangiophore • Aplanospores: Nonmotile sporangiospores • Zoospores: Motile sporangiospores, motility due to flagella. • Conidiospores or conidia: Formed at the tip or side of a hypha • Microconidia: Small, single-celled • Macroconidia: Large, multicelled

17. Arthrospores or Oidia: Single-celled spores, formed by disjointing of hyphal cells • ChIamydospores: Thick-walled, single-celled, highly resistant. • Blastospores: Spores formed by budding.

19. Sexual Reproduction • Joining of two cells • Fusion of protoplasts (Plasmogamy) • Fusion of haploid nuclei of 2 mating types (Karyogamy) • Formation of a diploid nucleus • Meiosis to reduce the number of chromosomes to haploid no. • Gametangia: • Sex organelles of fungi • Forms differentiated sex cells (gametes) • May have one or more gamete nuclei. • Male gametangium – Antheridium • Female gametangium – Oogonium

20. Methods of sexual reproduction in fungi

21. Gametic copulation: • Fusion of gametes. • Gamete-gametangial copulation: • 2 gametangia come into contact without fusion; • Male nucleus migrates through pore or fertilization tube into female gametangium. • Gametangial copulation: • 2 gametangia or their protoplasts fuse • A zygote forms & develops into a resting spore. • Somatic copulation: • Fusion of somatic or vegetative cells. • Spermatization: • Spermatia uniting with receptive hyphae of compatible female strain. • Spermatium empties its contents into the latter during plasmogamy.

22. Sexual spores: • Produced by the fusion of 2 nuclei • Occur in smaller numbers than asexual spores. • These single-celled spores are produced in a sac called ASCUS • Usually has 8 ascospores in each ascus.

23. Ascospores. • Nuclear fusion occurs in the ascus. • Diploid zygote nucleus divides by meiosis • 4 haploid nuclei are produced • Haploid nuclei divide by mitosis • Forms 8 ascospores, typically in each ascus.

24. Basidiospores • Single-celled spores, borne on a club-shaped structure called a basidium • A basidium begins with one nucleus from each parent. • Nuclear fusion & meiosis occurs in basidium • Basidium assumes a species-specific shape & produces tapering projections: Sterigmata. • Basidiospores are formed in Sterigmata • The nuclei produced after nuclear fission from meiosis move towards sterigmata

25. Zygospores • Large, thick-walled spores • Formed when the tips of two sexually compatible hyphae or gametangia of certain fungi fuse together

26. Oospores • Formed within a special female structure: Oogonium. • Male gametes formed in an antheridium • Fertilization of the eggs (Oospheres) results in Oospores.

27. Cultivation of Fungi • Almost all of them grow aerobically • At temperatures from 20 to 30°C • Good to use a medium that favors their growth but is not optimal for the growth of bacteria. • Acidic (pH 5.6) media that incorporates a relatively high conc. of sugar are tolerated by molds but are inhibitory to many bacteria.

28. Sabouraud Media • contains maltose and peptone as important components • Glucose • For the isolation of molds and certain yeasts • Selective action is due to the high sugar conc and low pH.