Microbio Kingdom Fungi

Fungi

General Characteristics

  • Nutrition:

    • Saprophytic: Live on and feed from decaying matter.

    • Parasitic: Live inside a living host and obtain food from the host.

  • Kingdom:Belong to the 5 kingdom system.

    • Fungi. They cannot move and cannot make their own food.

      • Example: Yeast.

      • Example: Molds.

Fungal Cell Structure

  • Hyphae: Tubular cell parts of fungi.

  • Cytoplasm: Jelly-like fluid inside the cell, holding the organelles.

    • Cell wall is made of chitin (cellulose counterpart).

      • Present in exoskeleton.

      • Provides strength and immune interaction.

      • Offers structural support and protection.

      • Triggers immune system response.

  • Needs decaying matter to absorb nutrients.

  • Septa:

    • Cross-walls that divide hyphae into cells.

Hyphae Types

  • Aerial Hyphae (Reproductive Hyphae):

    • Extend above the surface of the growing medium.

    • Involved in spore formation (sexual or asexual reproduction).

  • Surface Hyphae (Vegetative Hyphae):

    • Attached or anchored to the ground and beneath the surface.

Classification of Fungi

Yeast

  • Unicellular organisms.

  • Live in environments with a temperature of 37 degrees Celsius (body temperature).

  • Larger than bacteria.

  • Oval to round shape cells microscopically.

  • Reproduction: Budding (asexual reproduction).

  • Economic Importance:

    • Fermentation of beer and bread (Saccharomyces cerevisiae - "brewer's yeast/baker's yeast").

    • Ethanol production.

    • Wastewater treatment: Mixed cultures of yeasts like Candida lipolytica, Candida tropicalis, and Yarrowia lipolytica grown on hydrocarbons or gas oil.

Yeast Reproduction by Budding

  • The parent cell forms a protuberance (bud) on its outer surface.

  • As the bud elongates, the parent cell's nucleus divides, and one nucleus migrates into the bud.

  • Cell wall material is laid down between the bud and parent cell, and the bud eventually breaks away.

  • Yeast reproduce rapidly; one yeast cell can produce up to 24 daughter cells by budding.

Pseudohypha

  • Some yeasts produce buds that fail to detach, forming a short chain of cells called a pseudohypha.

  • Example: Candida Albicans

    • Attaches to human epithelial cells as a yeast but usually requires a pseudohypha to invade deeper tissues.

    • Lives in environments with a temperature of 37 degrees Celsius.

Molds/Filamentous Fungi

  • Multicellular with hyphae/mycelium.

  • Live in environments with a temperature of 25 degrees Celsius (room temperature).

  • Cottony-spreading growth.

  • Reproduction: Asexual & Sexual.

Dimorphic Fungi

  • Exhibit dimorphism - two forms of growth (mold or yeast).

  • Can shift from yeast form to mold form and vice versa.

  • Many fungal pathogens exist in the body in the yeast form but revert to the mold form in the laboratory when cultivated.

  • Mold-like forms produce vegetative and aerial hyphae; yeast-like forms reproduce by budding.

Reproduction of Fungi

Spores

  • One way fungi reproduce is by spore production.

  • Asexual and Sexual spores.

  • Non-motile.

  • Spores are for REPRODUCTION and not survival.

  • Ensures that species will dispersed to new location.

  • Dispersed by wind.

Fungal Spores vs Bacterial Endospores

  • Fungal spores are quite different from endospores.

  • Bacterial endospores allow a bacterial cell to survive adverse environmental conditions.

  • A single vegetative bacterial cell forms one endospore, which eventually germinates to produce a single vegetative bacterial cell.

  • The process is not reproduction since it does not increase the total number of bacterial cells.

    • When a mold forms a spore, the spore detaches from the parent and germinates into a new mold.

    • Unlike bacterial endospores, this is a true reproductive spore; a second organism grows from the spore.

    • Although fungal spores can survive for extended periods in dry or hot environments, most do not exhibit the extreme tolerance and longevity of bacterial endospores.

Asexual Reproduction

  • Anamorph: Asexual form of fungus.

  • Produce Asexual spores

  • Methods:

    • Thallic Reproduction (Nuclear Fission).

    • Budding: produces Blastoconidia or Blastospore.

      • Germ type: becomes a pseudohyphae

Examples of Asexual Spores

  • Sporangiospores: Asexual propagules that form inside a sporangium (spherical or cylindrical) through cleavage of the cytoplasm; enclosed in a sac.

  • Conidiospores: Asexual spores (multiple or single-spore) formed at the end of the aerial hyphae; not enclosed in a sac.

  • Chlamydospores: Enlarged, thick-walled vegetative cells with varied forms and condensed cytoplasm that form within hyphae or at hyphal tips.

  • Blastospores: Asexual fungal spore produced by budding; also known as a blastoconidium.

  • Arthrospores: Primitive spore type formed by the breaking up or disarticulation of fungal mycelia. ex) Geotricum and Trichosporon.

Sexual Reproduction

  • Fusion/Union of gametes.

  • Meiosis

  • Sexual Spore

  • Gametangia: Sex organs of fungi

    • Antheridium - male sex organ

    • Oogonium - female sex organ

    • Ascus

    • Basidium

    • Monoecious/Hermaphroditic - male and female sex organ in same thallus (body)

    • Dioecious - male and female sex organ in separate thallus

Classification of Fungi

  • Kingdom Mycota

    • Primitive Fungi

      • Oomycota (Aseptate Mycelium)

        • Class Zygomycetes (Conjugation fungi)

          • Rhizopus sp.

          • Mucor sp.

          • Absidia sp.

            • Sexual spore: Zygospores

    • Advanced Fungi

      • Eumycota (Septate Mycelium)

        • Ascomycetes (Sac fungi)

          • Aspergillus sp.

          • Penicillium sp.

            • Sexual spore: Ascospores

        • Basidiomycetes

          • Sexual spore: Basidiospores

        • Deuteromycetes (Fungi Imperfecti)

          • Sexual Reproduction: Not Identified

          • Microsporum sp.

          • Trichophyton sp.

          • Epidermophyton sp.

Examples of Sexual Spores

  • Zygospores: Spores produced by the fusion of two haploid nuclei, resulting in gametangia; do not occur inside any enclosing structure; direct fusion of two hyphal protrusions.

    • Usually recognized as larger, nearly spherical, often dark brown or black, roughed-wall spore with two connecting hyphae.

  • Ascospores: Spore contained in an ascus; specific to ascomycetes (Ascomycota).

  • Basidiospores: Reproductive spore produced by Basidiomycete fungi; typically contain one haploid nucleus (product of meiosis) and produced by specialized fungal cells called basidia.

Importance of Fungi

  • Garbage disposers!

  • Nearly all plants depend on symbiotic fungi (mycorrhizae), which help their roots absorb minerals and water from the soil.

  • Food consumption and production.

  • Of more than 100,000 species of fungi, only about 200 are pathogenic to humans and animals.

  • Medicine: Miracle drug!

Fungal Infections of Humans

  • Mycoses - fungal infections (mycosis - singular)

    • Categorized as superficial, cutaneous, subcutaneous, or systematic mycoses.

Types of Mycoses

  • Superficial Mycoses:

    • Fungal infection of the outermost areas of the human body: hair, fingernails, toenails, and the dead outermost layer of the skin (epidermis).

  • Cutaneous Mycoses:

    • Fungal infections of the living layers of the skin (dermis).

    • Dermatophytes cause Tinea Infections (Ringworms).

      • Tinea Pedis - athlete's foot

      • Tinea Unguium - fingernails and toenails

      • Tinea Capitis - scalp

      • Tinea Barbae - face and neck

      • Tinea Corporis - trunk of the body

      • Tinea Cruris - groin area

  • Subcutaneous Mycoses:

    • Most severe types of mycoses.

    • Fungal infection of the dermis and underlying tissues.

      • Example: Madura Foot (a type of eukaryotic mycetoma).

  • Systematic Mycoses:

    • Fungal infection of the internal organs of the body, sometimes affecting two or more different organs.

      • Example: Blastomycosis