Topic 7B: Fungi ✅ Flashcards
What are fungi?
Eukaryotic microorganisms
Fungal types
Unicellular: Yeasts (eg Saccharomyces cerevisiae)
Multicellular (eg mushrooms, molds)
Multicellular fungi characteristics
Non-motile
Usually live in moist, humid or aquatic environments
Growth temperature: 2-20 degrees
Heterotrophs: absorb nutrients from their external environment
*some are saprophtes (decomposers): obtain their nutrients from dead organic matter
Fungal morphology
Cell wall made of chitin
Body structures:
-Multicellular filaments
-Unicellular fungi
Dimorphism: some fungal species (eg Blastomyces) can grow both as filaments or yeasts depending on environmental conditions
Yeasts
Unicellular fungi
-usually form multicellular colonies
-reproduce using asexual reproduction (e.g. budding)
Eg Saccharomyces cerevisiae
Multicellular fungi
Filamentous structure: consist of mycelia
-filaments = hyphae (Septate, Coenocytic fungi [lack septa])
Mycelia: forma of branched hyphae => aid nutrient absorption and then become sporangia to produce spores
Fungal reproduction overview
By either sexual or asexual by producing spores
Asexual:
-simple cell decision (aka binary fission)
-Budding: new organism develops from outgrowth (bud) that separates from parent cell
Sexual reproduction:
-production of diploid zygote (2n) by fusion of haploid (n) fungi (hyphae)
How can haploid (n) sported be produced?
Sexually or asexually
Sexual: zygote (2n) —meiosis—> spores (n)
-called sexual spores
Asexual: spore (n) —mitosis—> spores (n)
Germination
Under favourable conditions, spores grow back to the vegetative cell (fungal cell)
Spore —germination—> vegetative cell
Fungal life cycle
SEXUAL REPRODUCTION
Plasmogamy (cytoplasmic fusion) (n)
-> Heterokaryotic stage (non-fused nuclei from 2 different parents)
-> Karyogamy (nuclear fusion), zygote (2n)
-> Meiosis, spores (n)
-> Germination
Through mycelium
Repeat
ASEXUAL
Through mycelium (n)
-> Spore producing structures
-> Spores
-> Germination
Repeat
Asexual reproduction
Yeasts: reproduce mostly asexually by simple cell division and budding
Molds- produce haploid spores by mitosis (e.g. conidia)
-> form mycelia
What are molds and yeasts called?
Deuteromycetes
-imperfect fungi
What is the origination of Fungi?
Fungi, animals and their protist relative form the Opisthokonts clade (part of the Uniconts Supergroups)
- Chytrids
Phylum Chytridiomycota
Characterized by zoospores: flagellated spores
Have hyphae
- Zygomycetes
Phylum Zygomycota
Named after characteristic zygosporangia (e.g. black bread mold)
Spore-producing structures=
-Sporangia: produce spores by asexual
-Zygosporangia:
contain sexually produced spores (by karyogamy and meiosis)
Resist drying and freezing => can survive unfavorable conditions
- Glomeromycetes
Phylum Glomeromycota
Mychoerrhizae: Mutualistic relationship between fungi and plant roots
Arbuscular mycorrhizal fungi: have specialized hyphae (called haustoria) that pentraate the cell walls of root cells
Mutualistic relationship: mycorrhizae fungi deliver phosphate ions and minerals to plants
What is Arbuscular mycorrhizae formed by?
Glomeromycetes
Ascomycetes
Phylum Ascomycetes
Sac fungi
Can produce spores by both sexual and asexual
Spore producing structures:
- Asci: -produced sexual spores (ascospores)
-located in ascocarps (fruiting body) - Conidiophores: specialized hyphae that produce asexual spores (conidia)
Eg bread mold Neurospora crasse, Morchella esculenta (tasty morel) and Tuubor melanosporum (truffle)
Fruiting body
Multicellular
Reproductive structure
Contains spore-producing structures
- Basidiomycetes
Phylum Basidiomycota
Club bacteria: characterized by a clublike structure called a basidium (transient diploid stage)
Basidia: spore-producing structures (only produce sexual spores [basidiospores])
Basidiocarp: fruiting body, has numerous basidia)
E.g. mushrooms
Fungi function roles
- As decomposers:
-Nutrient recycling between living and non-living - As mutualists:
-fungi -> animals: in the digestive system - Pathogenic fungi
Pathogenic Fungi
- Pathogenic Zygomycetes
E.g. genera Mucor, Rhizopus, Absidia
- causes skin and ear infections, bronchitis - pneumonia - Pathogenic Ascomycetes
I: Aspergillus flavus
-produces mycotoxins such as aflatoxins
-infects peanuts and wheat
-Aflatoxin B1: liver cancer (due to p53 mutations)
II: Claviceps purpurea
-infects cereals (eg rye)
-produces ergotamine and lysergique acid (precursors fro LSD synthesis)
-> psychotropic effects (hallucinations, temporary insanity), convulsions, gangrene
- Pathogenic Basidiomycetes
Amanita phalloides: poisonous mushrooms
-contain lethal toxins (eg phalloidin, amanitin)
Amanita muscaria and Psilocybe cubensis aka magic mushrooms
-psychoactive mushrooms => causes hallucinations (psychotropic effects)
Mycoses
Human fungal infections
Major types of human mycoses:
- Superficial: Cutaneous mycoses
- Subcutaneous mycoses
- Systematic mycoses
- Opportunistic mycoses
- Superficial and cutaneous mycoses
More common
Fungal infections of hair, nails and skin
-Microsporum furfur: ascomycete that causes ringworm
-Ascomycete genera Trichophyton and Epidermophyton: causes athlete’s foot (ringworm of foot)
- Subcutaneous mycoses
Subcutaneous fungal infection due to trauma
-Chromomycosis: caused by the fungi Hormodendrum pedrosoi, Hormodendrum compactum, Phialophora verrucosa
-Sporotrichosis: caused by fungus Sporotrichum schenckii
-Mycetoma: caused by fungi of the Aspergillus genus
- Systemic mycoses
Fungal infection spread through blood stream to various sites/ organs of the body
Commonly cause respiratory infections initially, then spread to other organs
-Coccidioidmycosis: caused by Coccidioides immitis -> produces TB-like symptoms
-Histoplasmosis: caused by Histoplasma capsulatum
-Cryptococcosis: caused by Cryptococcus neoformans
-Blastomycosis: caused by Blastomyces dermatitidis
-Geotrichosis: caused by Geotrichum candidum
- Opportunistic mycoses
More common
Caused by fungi that are part of our normal flora (saliva, skin, digestive system)
Normally non-pathogenic
Become pathogenic and cause infections only in immunosuppressed individus
-yeast Candida albicans: causes candidiasis
-> mouth infection (thrush), skin & vaginal infections
Industrial and Therapeutic Applications of Fungi
Penicillium chrysogenum: produces penicillin (anti-bacterial anti-biotic)
-Penicillium griseofulvum: produces griseofulvin (anti-fungal antibiotic)
Production of alcoholic beverages, bread and cheeses
Genetic engineering
Antibiotic production by fungi: Ascomycetes of genus Penicillium
Production of alcoholic beverages, bread and chees
Yeast Saccharomyces cerevisae
-production of enzymes used for alcohol fermentation
=> production of beer, wine etc
Also used for baking yeast (CO2 production)
Genetic engineering and fungi
Insulin-like growth factor (IGF) can be produced by the fungus Saccharomyces cerevisae
Study of genes involved in human diseases
Antibiotic production by fungi
Ascomycetes of genus Penicillium
The fungus Penicillium chrysogenum produces penicillin which kills Staphylococcus
=> produces zone of inhibition of Staphylococcus growth around its colonies on nutrient agar
Septate
Hyphae type
With septa
Most fungi have hyphae divided into cells by septa
Septa= rings of hyphae cell walls
-pores allow cell-to-cell movement of organelles
Coenocytic fungi
Aseptate
Hyphae type
Lack septa
Have continuous cytoplasmic mass with hundreds/thousands of nuclei
What are fungal nuclei normally?
Haploid
Exception: transients diploid stages formed during the sexual life cycles
Sexual reproduction of fungi
Fusion of hyphae from different mating types
Use sexual signaling molecules (pheromones) to communicate their mating types
Plasmogamy
Union of cytoplasm from 2 parent mycelia
Heterokaryon
Mycelium in which the haploid nuclei from each parent coexist (don’t fuse right away)
Karyogamy
Fusion of haploid nuclei
=> production of diploid cells
What is Penicillium?
Common mold
Food decomposer
How many species of each type of fungal category are there?
Chytrids: 1,000
Zygomycetes: 1,000
Glomeromycetes: 160
Ascomycetes: 65,000
Basidiomycetes: 30,000
Mutualistic relationships examples
Fungi - plants: Mycorrhizae
Fungi - animals: in digestive system
Fungi - microorganisms: in lichens
Lichens
Symbiotic association between a photosynthetic microorganism (cyanobacterium/ green alga) and a fungus (eg an ascomycete)
Leaflike = foliose
Crustose = encrusting
Fruticose = shrublike
Pathogenic Ascomycetes
- Aspergillus flavus
- Claviceps purpurea
- Pathogenic Basidiomycetes
- Aspergillus flavus
-produces mycotoxins such as alfaltoxins
-infects peanuts and wheat
-Aflatoxin B1: liver cancer (due to p53 mutations)
- Claviceps purpurea
-infects cereals (eg rye)
-produces ergotamine and lysergique acid (precursors for LSD synthesis)
=>psychotropic effects (hallucinations, temporary insanity), convulsions, gangrene
- Pathogenic Basidiomycetes
-Amanita phalloides: poisonous mushrooms
-contain lethal toxins (eg phalloidin, amanitin)
=> alpha-amanitin: inhibits eukaryotic RNA pol II
=> Phalloidin: inhibits F-actin polymerisation
-Amanita muscaria and Psilocybe cubensis: magic mushrooms
=>psychoactive mushrooms -> cause hallucinations (psychotropic effects)
Mycoses
Human fungal infections
Major types of human mycoses
- Superficial-cutaneous mycoses
- Subcutaneous mycoses
- Systemic mycoses
- Opportunistic mycoses
Superficial and cutaneous mycoses
Fungal infections of hair, nails and skin
Microsporum furfur: ascomycete, causes ringworm
Ascomycete genera Tricophyton and Epidermophyton: causes athlete’s foot (ringworm of foot)
Opportunistic mycoses
Caused by fungi that are part of our normal flora (saliva, skin, digestive system) - normally non-pathogenic
Become pathogenic and cause infections only in immunosuppressed individuals
Eg Candida albicans: yeast, causes candidiasis
=> mouth infection (thrush), skin infection, vaginal infection etc
Industrial and Therapeutic applications of Fungi
Production of antibiotics: eg Ascomycetes of genus Penicillium
Production of alcoholic beverages, bread and cheeses: eg the yeast Saccharomyces cerevisiae
Genetic engineering: eg insulin-like growth factor (IGF) can be produced in the fungus Saccharomyces cerevisiae
Ascomycetes of genus Penicillium
-Penicillium chrysogenum: produces penicillin (anti-bacterial antibiotic)
-Penicillium griseopfulvum: produces griseofulvin (anti-fungal antibiotic)
Production of alcoholic beverages, bread and cheeses
Eg the yeast Saccharomyces cerevisiae
-production of enzymes used for alcohol fermentation
=>production of beer, wine etc
-also used in baking yeast (CO2 production)
Genetic engineering eg
Eg insulin-like growth factor (IGF) can be produced in the fungus Saccharomyces cerevisiae
Study of genes involved in human diseases
Penicillium chrysogenum
Produces penicillin => kills Staphylococcus
=>produces zone of inhibition of Staphylococcus growth around its colonies on nutrient agar
Which fungal phylum do mushrooms belong to?
Basidiomycetes
