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Questions and Answers
What is the primary structural component of the fungal cell wall?
What is the primary structural component of the fungal cell wall?
Which group of fungi is noted to have chitin that is partially deacetylized?
Which group of fungi is noted to have chitin that is partially deacetylized?
What type of glycoproteins are primarily found in fungal cell walls?
What type of glycoproteins are primarily found in fungal cell walls?
What component of fungal membranes is primarily targeted by polyene antifungal drugs?
What component of fungal membranes is primarily targeted by polyene antifungal drugs?
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Which type of fungi lacks chitin in its cell wall and primarily contains cellulose?
Which type of fungi lacks chitin in its cell wall and primarily contains cellulose?
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What is the function of the special fungal sterols found in the cell membrane?
What is the function of the special fungal sterols found in the cell membrane?
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What happens to vacuoles in the hyphae of fungi as they age?
What happens to vacuoles in the hyphae of fungi as they age?
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Which of the following best describes the role of ergosterol in fungal cells?
Which of the following best describes the role of ergosterol in fungal cells?
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What structure bears sporangiospores?
What structure bears sporangiospores?
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Which type of spore is motile?
Which type of spore is motile?
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What is the term used for asexual non-motile spores produced externally?
What is the term used for asexual non-motile spores produced externally?
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How are conidia formed?
How are conidia formed?
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Which of the following structures is NOT a compound structure formed by conidiophores?
Which of the following structures is NOT a compound structure formed by conidiophores?
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What phase do fungi generally exhibit during their vegetative stage?
What phase do fungi generally exhibit during their vegetative stage?
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Which kingdom is known for producing motile spores?
Which kingdom is known for producing motile spores?
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Which of the following correctly describes the process of sexual reproduction in fungi as mentioned?
Which of the following correctly describes the process of sexual reproduction in fungi as mentioned?
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What type of heterotrophic life involves living at the expense of dead organic matter?
What type of heterotrophic life involves living at the expense of dead organic matter?
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In the context of parasitic fungi, what is the difference between biotrophic and necrotrophic relationships?
In the context of parasitic fungi, what is the difference between biotrophic and necrotrophic relationships?
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What are fungi living on the exterior of their hosts called?
What are fungi living on the exterior of their hosts called?
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Which of the following is NOT a method for isolating fungal tissue samples?
Which of the following is NOT a method for isolating fungal tissue samples?
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In lichen, what is the term for the fungal partner?
In lichen, what is the term for the fungal partner?
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Which factor makes lichens intolerant of industrial pollutants?
Which factor makes lichens intolerant of industrial pollutants?
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What key benefit does the photobiont provide to the mycobiont in a lichen?
What key benefit does the photobiont provide to the mycobiont in a lichen?
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Which of the following advantages is NOT provided to the photobiont by the mycobiont?
Which of the following advantages is NOT provided to the photobiont by the mycobiont?
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What role do mycorrhizae play in arid environments?
What role do mycorrhizae play in arid environments?
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What are mycorrhization helper bacteria primarily involved in?
What are mycorrhization helper bacteria primarily involved in?
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Which statement accurately reflects the role of fungi in soil?
Which statement accurately reflects the role of fungi in soil?
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What is the primary purpose of the dilution plate technique in soil fungi isolation?
What is the primary purpose of the dilution plate technique in soil fungi isolation?
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In what form do fungi primarily exist in the soil?
In what form do fungi primarily exist in the soil?
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Which concentration is recommended for the dilution when performing the dilution plate technique?
Which concentration is recommended for the dilution when performing the dilution plate technique?
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What is the characteristic of most fungi found in the soil?
What is the characteristic of most fungi found in the soil?
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What characteristic is true for mycorrhizal fungi during their life cycle?
What characteristic is true for mycorrhizal fungi during their life cycle?
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What is one major limitation of using the dilution plate technique with larger soil particles?
What is one major limitation of using the dilution plate technique with larger soil particles?
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Which technique is specifically designed for the selective isolation of dermatophytes?
Which technique is specifically designed for the selective isolation of dermatophytes?
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What is the main purpose of the washing techniques developed for soil fungi isolation?
What is the main purpose of the washing techniques developed for soil fungi isolation?
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Which of the following is a preferred substrate for isolating aquatic fungi?
Which of the following is a preferred substrate for isolating aquatic fungi?
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Why are zoospores significant in the study of aquatic fungi?
Why are zoospores significant in the study of aquatic fungi?
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What kind of fungi does the soil washing technique primarily benefit?
What kind of fungi does the soil washing technique primarily benefit?
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How are cellulolytic fungi typically isolated from the soil?
How are cellulolytic fungi typically isolated from the soil?
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What components are included in the procedure for preparing Warcup's soil plates?
What components are included in the procedure for preparing Warcup's soil plates?
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What is the key difference between homothallic and heterothallic sexual reproduction?
What is the key difference between homothallic and heterothallic sexual reproduction?
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Which of the following describes the composition of mycelium in zygomycetes?
Which of the following describes the composition of mycelium in zygomycetes?
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Which family includes species characterized by collumelate sporangia?
Which family includes species characterized by collumelate sporangia?
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What type of asexual reproduction is primarily involved in zygomycetes?
What type of asexual reproduction is primarily involved in zygomycetes?
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What are chlamydospores?
What are chlamydospores?
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What distinguishes the teleomorphic phase in zygomycetes?
What distinguishes the teleomorphic phase in zygomycetes?
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Which characteristic does NOT apply to mucoraceous fungi?
Which characteristic does NOT apply to mucoraceous fungi?
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In terms of sporangial morphology, which family is known for having a single sporangium that discharges violently?
In terms of sporangial morphology, which family is known for having a single sporangium that discharges violently?
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Study Notes
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.
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