Rucete ✏ Campbell Biology In a Nutshell
Unit 5 THE EVOLUTIONARY HISTORY OF BIOLOGICAL DIVERSITY — Concept 31.5 Fungi Play Key Roles in Nutrient Cycling, Ecological Interactions, and Human Welfare
Fungi have far-reaching impacts on ecosystems and human life. As decomposers, mutualists, and pathogens, fungi influence nutrient cycles, plant productivity, and health. They also provide important benefits through medicine, food, and biotechnology.
Fungi as Decomposers
- Essential decomposers that break down:
- Lignin and cellulose in plant cell walls
- Almost any carbon-based material (e.g., paint, fuel)
- Recycle carbon and nitrogen otherwise trapped in dead matter
- Fungal recycling maintains nutrient availability for plants
Fungi as Mutualists
Fungus-Plant Mutualism
- Endophytes live in plant tissues:
- Mostly ascomycetes, some mucoromycetes
- Increase plant tolerance to heat, drought, toxins
- Produce toxins that deter herbivores
- Example: Endophyte-infected cacao trees had less Phytophthora damage
Fungus-Animal Mutualism
- Fungi help animals digest cellulose (especially herbivores)
- Leaf-cutter ants grow fungi on chewed leaves:
- Ants eat nutrient-rich hyphal tips
- Fungi detoxify plant chemicals
- Symbiosis has lasted 50+ million years
Lichens
- Symbiosis between fungi and photosynthetic organisms (algae/cyanobacteria)
- Colonize rocks, trees, and soils—important for ecosystem succession
- Fungus provides structure; alga gives carbon, cyanobacteria fix nitrogen
- Reproduce via soredia (clumps of hyphae + algae)
- Contribute to soil formation and mineral absorption
Fungi as Pathogens
- About 30% of fungi are parasites or pathogens, mostly on plants
- Plant pathogens:
- Cryphonectria parasitica: chestnut blight
- Fusarium: threats to pine forests
- Claviceps purpurea: causes ergotism (hallucinations, death)
- Animal pathogens (Mycoses):
- Skin infections: ringworm, athlete’s foot (Candida, Trichophyton)
- Systemic mycoses: deadly fungal infections in lungs/organs
- Batrachochytrium: chytrid fungus killing amphibians globally
- Candida auris: drug-resistant human pathogen in hospitals
Practical Uses of Fungi
- Food:
- Mushrooms, truffles, morels
- Yeast in bread, beer, wine fermentation
- Fungi ripen blue cheeses (e.g., Roquefort)
- Medicine:
- Penicillium: source of penicillin
- Ergots yield drugs for blood pressure and childbirth
- Fungi produce cholesterol-lowering and immunosuppressant drugs (e.g., cyclosporine)
- Biotech & Research:
- Saccharomyces cerevisiae used in genetic research
- Fungi engineered to produce human glycoproteins
- Gliocladium roseum produces biofuel-like hydrocarbons
In a Nutshell
Fungi drive nutrient recycling, form crucial symbiotic relationships with plants and animals, and play key roles in health, agriculture, and biotechnology. While some are deadly pathogens, many fungi offer immense benefits—from life-saving medicines to sustainable fuel production. Understanding and preserving fungal diversity is vital to both ecosystems and human well-being.