BSC 1011 - Unit 2 9/11/2025 Lecture: Fungi Life Cycles

Fungi Characteristics

• Eukaryotic

• Structure:

  • Cell Wall: Chitin

  • Hyphae: Thready

  • Fruiting body: Thallus or mycelium (ex. mushroom)

• Multicellular (except yeast)

• Heterotrophic

Fungi basic life requirements

• Obtain energy: Extracellular Digestion

  • Heterotrophic: Extracellular digestion+absorption of nutrients

• Obtain+retain water: Grow in moist dark cool places

• Reproduce: Sporic life cycle

Fungi Symbiotic roles

1. Decomposers (saprobes)

2. Parasites/ pathogens (for plants+animals)

   1. Pathogenic ex: Spores can grow in lungs

3. Mutualists

   1. Ex. Lichens (green algae+fungus mutualism). Fungus protects algal cell out of water. Algae produces sugar, fungus produces environment for algae to grow in

   2. Ex. mycorrhizae: Fungus growing on root (outside - ectomycorrhizae produces protective chemicals, inside - endomycorrhizae breaks down nutrients for root to digest).

4. Predaceous (rarer)

Symbiotic relationship

Two organisms living togetherM

Mutualism

2+ species all benefit

Commensalism + fungi example

One benefits, other not affected

• Trichomycetes live in hindgut of arthropods to break down cellulose

Parasitism + fungi example

One harmed, other benefits

• Ex. Athlete’s foot, penicillium

• Plant disease ex. corn smut, tar spots, ergots (on rye)

Histoplasmosis

Grows in tissues (usually lungs).

Aspergillus + how does it cause health issues?

Causes allergies by producing mycotoxins

Commercial uses of fungi

• Food

• Yeasts

• Antibiotics: -cillum

Fruiting body

Spores produced here. Has:

• reproductive structure

• Spore forming structure

Hyphae

Thread Structure

Mycelium/Thallus

Grouping of hyphae

Structure of multicellular fungi

• Cell wall: Chitin

• Hyphae: Thread

  • Septate hypha: Each cell separated by cell wall and communicate through pores

  • Coenocytic hypha: Large cell with many nuclei.

  • Haustorium: Hyphae inserted inside host cell. Ex. nematode with hyphae

Heterokaryotic hyphae (n+n)

• Fusion of two haploid hyphae.

• Two separate nuclei, will eventually fuse into diploid

• No other organisms has this stage that lasts as long as in fungi.

• Could be multiple n+n’s

Asexual fungi life cycle

1. Mycelium (n)

2. Spore producing structures: Produces spores through mitosis (cloning fungal body)

3. Germination: To myclelium

Sexual fungi life cycle

1. Plasmogamy: One mycelium cell fuses with other mycelium cell

2. Heterokaryotic Stage: n+n stage can last long time

3. Karyogamy: Fusion of nuclei to produce zygote (2n)

4. Meiosis: Forms spore producing structure+spores.

5. Germination: Produces another mycelium

Dikaryon hyphae: 2 nuclei in each cell. Subtype of heterokaryon