Untitled Quiz

Mycology

• Mycology is the study of fungi.
• Myco = fungus
• Logy = study

General Characters

• Fungi are eukaryotic organisms.
• Fungi are non-motile, except in some cases.
• Fungal vegetative bodies can be unicellular (e.g., yeast fungi) or filamentous.
• Filamentous fungi can be non-septated (coenocytic) or septated.
• Fungi, like plants, have an alternation of generations.
• Fungal cell walls are similar in structure to plant cell walls but contain different chemical compositions (e.g., cellulose + lignin in plants, chitin in fungi).
• Food storage of fungi is glycogen, whereas plants store food as starch.
• Fungal cell membranes contain ergosterol, whereas animal cell membranes contain cholesterol.
• Fungi grow by apical elongation of hyphal tips.
• Fungi are heterotrophic organisms (lack chlorophyll).

Economic Importance

• Beneficial: Fungi have several industrial uses, for example in baking and brewing (yeast), antibiotics production (penicillin), steroid and hormone production, and cheese making. Fungi are also a source of food (mushrooms), enzymes, acids, biofuels, and vitamins (e.g., B-complex).
• Harmful: Fungi can cause diseases in humans, animals, and plants, directly through toxins or indirectly with their decay of foods and other products.

Nutrition

• Saprophytes—utilize non-living organic materials; crucial for nutrient recycling.
• Parasites—use living organisms and cause diseases; have varied hosts (diatoms, fungi, plants, animals, and humans).
• Symbiotic—fungi with a beneficial relationship with other organisms (e.g., mycorrhizae, lichens).

Reproduction

• Sexual Reproduction: Involves two compatible nuclei fusing and subsequent meiotic division.
• Key stages in sexual fungal life cycles:
  • Plasmogamy (cell fusion).
  • Karyogamy (nuclear fusion).
  • Meiosis (formation of haploid spores).
• Asexual Reproduction:
  • Fragmentation (filamentous fungi).
  • Fission (unicellular fungi).
  • Budding (unicellular fungi).
  • Spore formation (sporangiospores and conidia).
• Sporangiospores—formed internally in a sac-like structure (sporangium).
  • Can be motile (zoospores) or non-motile (planospores).
• Conidia—formed externally on a specialized hypha (conidiophore).
  • Occur singly or in chains.
• Conidiophores can form compound structures like acervulus, pycnidium, and sporodochium.

General Fungi Reproduction Cycles:

• All sexual fungal life cycles have plasmogamy, then karyogamy, then meiosis, reducing 2n to 1n.

Fungal Classification

• Kingdom Protozoa: (Slime molds)
  • Vegetative phase is plasmodium (ameoboid structure)
• Kingdom Chromista:
  • Produce motile spores (zoospores)
  • Vegetative body is mycelium
• Kingdom Eumycota: (True molds)
  • Produce non-motile spores (aplanospores)
  • Vegetative body is mycelium
• Subdivided into Zygomycota, Ascomycota, and Basidiomycota based on sexual characteristics

Fungal Cell Structure

• Fungi are eukaryotes with complex cellular organization.
• Fungal cells have a membrane-bound nucleus where DNA wraps around histone proteins.
• The fungal cell wall has a unique structure and composition, primarily composed of chitin.

Cytoplasmic Inclusions

• Vacuoles: Found in older hyphae cells; primary storage sites for small molecules and precursors.
• Endoplasmic Reticulum (ER): Involved in protein folding, modification, and assembly.

Other Organelles

• Nucleus: Contains one to multiple globose or spherical nuclei within the cytoplasm (1-3 µm in diameter).
• Mitochondria: Involved in cellular respiration, converting glucose to ATP for energy, protein regulation, and cell division control.
• Golgi Apparatus: Involved in protein packaging and secretion.

Ecological Groups

• Saprobic: Fungi that obtain nutrition from dead organic matter.
• Parasitic: Fungi that obtain nutrition from living organisms, often causing diseases. Biotrophic species colonize hosts while they are alive; necrotrophic fungi kill hosts before colonizing.
• Symbiotic: Fungi living in a mutually beneficial relationship with another organism, e.g., mycorrhizae and lichens.

Mycorrhizae

• Symbiotic association of a fungus and roots of vascular plants.
• Over 95% of vascular plants have mycorrhizae.
• Types: ectomycorrhizae, ectendomycorrhizae, vesicular-arbuscular mycorrhizae (VAM), ericoid, and orchid endomycorrhizae.
• Functions: Increase plant competitiveness, improve nutrient availability, and enhance water uptake, particularly in arid environments.

Isolation Techniques

• Dilution plate technique: Used for isolating soil fungi.
  • Soil is diluted with sterile water to disperse the organisms.
  • Dilutions are plated onto media, and colonies are selected.
• Warcup's soil plates: Ideal for isolating fungi with large hyphal complexes.
• Larger soil particles sediment more rapidly, preserving these types of fungi from loss.

Soil Fungi, Water Molds, and Fungi on Seeds

• Many soil fungi are saprotrophs, decomposing plant matter; they dominate soil biomass.
• Aquatic fungi (water molds) are associated with motile spores and gametes found in water environments.
• Isolation techniques for aquatic fungi involve baits such as hemp seeds placed onto a thin layer of water in a Petri dish.
• Seed fungi can be discovered by placing seeds on water agar to form colonies.

Fungi on Dung

• Coprophilous fungi are unique fungi that thrive on dung.
• The isolation technique involves placing dung on moist filter papers placed in Petri dishes.

Fungicolous, Entomogenous, and Thermophilic Fungi

• Fungicolous fungi are parasites, commensals, or saprobes living on other fungi.
• Entomogenous fungi parasitize arthropods.
• Thermophilic and thermotolerant fungi thrive in areas with high temperatures, like compost piles.

Oligotrophic Fungi

• Oligotrophic fungi thrive in environments with low nutrient concentration like drinking water and on rocks.
• Isolation of oligotrophic fungi requires extended time periods due to their small biomass.

Lichens

• Lichens are a symbiosis between a fungus (mycobiont) and an alga or cyanobacterium (photobiont).
• Structure: Usually stratified with an upper and/or lower cortex layers, a medulla (fungal layer), and an algal layer near the surface.
• Worldwide distribution in extreme environments like arctic, Antarctic, and deserts.
• Often used in dyes, essential oils, food, and for nesting/bedding material.
• Also used in some medicinal applications.
• Reproduction: Sporangia and conidia; sexual spores (ascospores and basidiospores).
  • Stratified lichen: algal cells are not distributed throughout the lichen.
  • Non-stratified lichen: algal cells are distributed throughout the lichen.