ch 12

Kingdom Fungi

• Nutritional Type: Chemoheterotroph

• Multicellularity: All fungi are multicellular except yeasts

• Cellular Arrangement: Can be unicellular, filamentous, or fleshy

• Food Acquisition Method: Absorptive

• Characteristic Features: Both sexual and asexual spores are present

• Embryo Formation: None

• Mycology: The study of fungi

Characteristics of Fungi

• Metabolism

  • Most fungi utilize aerobic respiration or fermentation for energy

  • Optimal growth occurs at a pH of approximately 5, lower than bacteria

• Osmotic Pressure Resistance: More resistant to high osmotic pressure compared to bacteria; able to grow in high sugar or salt environments

• Moisture Requirements: Can thrive in low moisture conditions

• Nitrogen Requirements: Require less nitrogen than bacteria

• Carbohydrate Metabolism: Capable of metabolizing complex carbohydrates, unlike bacteria

Types of Fungi

• Molds: Composed of a thallus with hyphae and spore structures; a mass of hyphae is termed mycelium.

• Yeasts: Unicellular fungi that can divide by:

  • Fission (symmetrical division)

  • Budding (asymmetrical division)

Economic Effects of Fungi

• Food Production:

  • Enzymes: E.g., cellulase used to remove cellulose in juice production

  • S. cerevisiae: Used in bread and wine making

• Medicine:

  • Antibiotics: E.g., Penicillium produces antibiotics

  • Cancer Treatment: E.g., Taxol from Taxomyces

• Agriculture:

  • Decomposers of organic materials

  • Involvement in many plant diseases

Mycotic Diseases

• Fungal infections in humans and animals are termed mycoses and are generally chronic, often opportunistic, causing disease when conditions allow.

Anti-fungal Agents Targets

• Targets include:

  • Membrane sterols (e.g., Amphotericin B)

  • Cell wall (e.g., Echinocandins)

  • RNA synthesis (e.g., Flucytosine)

  • Other (e.g., Griseofulvin, Tolnaftate)

Algae (A Super-phyla?)

• Characteristics:

  • Eukaryotic plant cells

  • Can be unicellular, filamentous, or multicellular

  • Primarily live in aquatic environments

  • Photoautotrophic

  • Form bodies called thallus, with structured components like holdfasts and blades

• Reproduction: All algae replicate asexually; some can reproduce sexually too.

Divisions of Algae

• Brown Algae: Kelp used for algin, a thickener

• Red Algae: Lives deep in oceans; produces agar

• Green Algae: Mostly microscopic

• Diatoms: Unicellular; have silica and pectin in cell walls

• Dinoflagellates: Unicellular plankton; some produce neurotoxins or experience 'red tides'.

Dinoflagellate Toxicity

• Example: Gambierdiscus toxicus produces ciguatoxin, harmful when concentrated in fish, affecting human neurological and gastrointestinal systems.

Oomycota (Water Molds)

• Multicellular, chemoheterotrophic, produce zoospores

• Notable historical relevance: caused the Great Irish Potato Famine (blight).

Lichens

• Mutualistic relationship between a green alga (or cyanobacteria) and fungus.

• Fungal hyphae provide protection and attachment, while algae produce carbohydrates for the fungus.

Slime Molds

• Amoeboid cells, showcasing characteristics of both fungi and protozoa.

  • Cellular Slime Molds:

  • Life cycle involves aggregation and spore formation under unfavorable conditions.

  • Acellular Slime Molds:

  • Exist as multinucleated plasmodium; when stressed, develop into stalked sporangia for spore formation.

Protozoa - Characteristics

• Unicellular animal-like cells, mostly found in water and soil.

• Nutritional Type: Chemoheterotroph

• Reproductive Modes: Primarily asexual; some can reproduce sexually.

• Cyst Formation: Some can form protective cysts during adverse conditions.

Types of Protozoa

• Archaezoa: Lack mitochondria; e.g., Giardia lamblia, Trichomonas vaginalis (most common STI).

• Amoebozoa: Move using pseudopodia; e.g., Entamoeba histolytica causes dysentery.

• Apicomplexa: Nonmotile intracellular parasites with complex life cycles; e.g., Plasmodium spp. (causes malaria), Cryptosporidium (causes water-borne enteric infections).

• Euglenozoa: Characterized by flagellar movement; e.g., Trypanosoma spp. causing Sleeping sickness and Chagas’ disease.

Antiprotozoan Drugs

• Anti-malarials: Quinine, chloroquine, mefloquine

• Giardiasis treatment: Quinacrine

• Other treatments: Metronidazole (Flagyl), Tinidazole (Fasigyn)