Interactions with Fungi

Fungal Interactions

Fungi and Decomposition

• Decomposers: break down dead organics into usable minerals
• Most fungi break down plant lignin
• Important, lignin is hard to break down
• Important for CO2 and nutrient cycle
• Release C and N trapped in dead matter

Soil Formation

• Lichens: symbiotic relationship between fungal hyphae and photosynthetic algae
• Fungus gets protection and nutrients
• Algae gets more nutrients
• Colonize disturbed habitat
• Aided colonization of land plants
• Most symbionts are in Ascomycota and Basidiomycota

Plant Mutualism

• Mycorrhiza: Mutualistic Symbiosis between plant roots and fungus
• Fungus gets sugars
• Plant gets nutrients (N)
• Fueled the colonization of land plants
• Obligate: both must occur together, can't survive independently

Animal Mutualism

• Exist in herbivore guts, aid in digestion
• Leaf-cutter ants farm fungus

Fungi as Parasites

Fungi and Plants

• 2nd biggest threat to plants (insects first)
• Necroses: fungi digests living plant tissue Examples: blight, cankers, scab
• Wilt: Plants loose their structure
• Powdery Mildew: Fungi coats leaves and fruit, hyphae penetrates surface cells Example: Dutch Elm Disease
• caused by fungus Ophiostoma ulmi
• Disease spread via Black Beetles

Fungi and Invertebrates

• Invertebrate Parasites
• Fungi that infect insects and arachnids
• Spores produced inside of host
• Sometimes produces fruiting body to burst out of host
• Invertebrate Predators
• Some fungi function like predators Example: Nematode traps
• Catches another organism and strangles it to death

Fungi and Vertebrates

• Vertebrate Parasites
• Mycosis: fungal disease in vertebrates (humans)
• infects terrestrial and aquatic vertebrates
• Cutaneous Infection: infects outer layers of skin Example: Ringworm
• Causes a ring of hyphae around infection
• Localized Subcutaneous Infection: infects wounds
• Spores in environment colonize open wound
• Systemic Infection: Whole body is infected
• Opportunistic Fungal Disease
• Typically harmless fungi infect other parts of body Example: Yeast
• Common in gut and moist skin
• Can infect other skin when moist = diaper rash
• Can infect mucous membrane (if normal microflora / chemical conditions change)
• Other Human Fungal Diseases
• Histoplasmosis: common systemic mycosis
• Inhale from bird / bat droppings
• Can also be cutaneous
• Fungi transitions from hyphae to yeast
• Yeast can invade host cells
• Results in systemic infection => death
• Especially dangerous for immune compromised individuals