topic 7B: fungi Flashcards
what are the two types of fungi?
(1) unicellular: such as yeasts (e.g. Saccharomyces cerevisiae)
(2) multicellular: e.g. mushrooms and molds
mushrooms and molds are types of?
multicellular fungi
regarding fungal morphology; what does the cell wall consist of?
chitin
some fungal species experience dimorphism, which is?
some fungi can grow both as filaments (multicellular) or yeasts (unicellular)
(depending on their environmental conditions, e.g. Blastomyces)
describe unicellular fungi (yeasts)
- usually form multicellular colonies
- reproduce by sexual or asexual reproduction (e.g. budding)
- example: Saccharomyces cerevisiae
describe multicellular fungi
- have a filamentous structure: consists of mycelia
- have filaments: called hyphae
what is mycelia? what function does it have?
- networks of branched hyphae (filaments)
- function: aids in nutrient absorption
the hyphae of most fungi are divided into cells by internal walls called?
septa
what are the types of hyphae?
(1) septate = with septa
- most fungi have hyphae divided into cells by septa
- pores allow cell-to-cell movement of organelles
(2) coenocytic fungi = aseptate
- lack septa
- have a continuous cytoplasmic mass with hundreds/thousands of nuclei
what are septa?
rings of hyphae cell walls
(function: divide hyphae into cells)
what are the ways asexual reproduction of fungi takes place?
(1) simple cell division (binary fission)
(2) budding: a new organism develops from an outgrowth (bud) that separates from the parental cell
what are sporangia?
spore-producing structures
describe sexual reproduction of fungi
production of diploid zygote (2n) from the fusion of 2 haploid (n) fungi (hyphae)
describe fungi reproduction
fungi reproduce by sexual or asexual reproduction by producing spores
the haploid (n) spores can be produced in 2 ways:
sexually or asexually
describe how haploid (n) spores can be produced sexually?
sexual reproduction:
- from the zygote by meiosis
- called sexual spores
- zygote (2n) => meiosis => spores (n)
describe how haploid (n) spores can be produced asexually?
asexual reproduction:
- by mitosis
- called asexual spores
- spore (n) => mitosis => spore (n)
(haploid spores produce even more haploid spores through mitosis)
what is the difference between haploid spores produced by sexual and asexual reproduction?
they are the same spores, just produced differently
what is another type of reproduction that fungi can undergo?
germination
what is germination?
- when, under favorable conditions, spores grow back to the vegetative cell (fungal cell)
- spore => germination => vegetative cell
which of the two is ALWAYS sporogenic: fungi or bacteria?
- ALL fungi is sporogenic
- only some bacteria is sporogenic
describe the fungal life cycle, undergoing sexual reproduction
(1) a mycelium fuses with another mycelium with the process of plasmogamy (cytoplasmic fusion) initially
(2) after the cytoplasms fuse, it goes through a heterokaryotic stage (2 different haploid nuclei that do not fuse right away)
(3) then the nuclei fuse together to cause karyogamy (nuclear fission) to create the diploid zygote
(4) the diploid zygote undergoes meiosis to produce haploid spores (called sexual spores as they are produced by sexual reproduction - meiosis)
(5) these spores undergo germination when found in optimum conditions (such as in the human body) to create mycelium
(6) these mycelia can fuse together to repeat the process
describe the fungal life cycle, undergoing asexual reproduction
(1) haploid mycelium can itself undergo mitosis (asexual reproduction) and produce in the sporangia even more haploid cells
(2) again, through germination can lead to formation of mycelium (process repeats)
2 haploid mycelia fuse together to create a diploid zygote
sexual reproduction of fungi
the process of producing a haploid cell through mitosis is ONLY present in?
only plants, protists, and fungi, and NOT IN ANIMALS
fungi nuclei are normally _____?
haploid
what do we have instead of genders in fungi?
- different mating types
sexual reproduction = fusion of hyphae from different mating types
what are the sexual signaling molecules fungi use to communicate their mating type?
pheromones
what is plasmogamy?
the union of cytoplasm from two parent mycelia
what is a heterokaryon?
the mycelium in which the haploid nuclei from each parent co-exist (they do not fuse right away)
what is karyogamy?
fusion of the haploid nuclei => production of diploid cells (the zygote)
which type of fungi prefers asexual reproduction?
yeasts and molds
describe the reproduction of yeasts and molds
- yeasts: reproduce mostly by asexually by simple cell division and budding
- molds: produce haploid spores by mitosis (e.g. conidia) => form mycelia
what are molds and yeasts are called?
deuteromycetes (imperfect fungi)
what is conidia?
a type of asexual reproductive spore of fungi
what supergroup does fungi belong to?
Opisthokonts, Unikonts
what forms the Opisthokonts?
fungi, animals, and their protist relatives
what are the 5 fungal phyla?
- chytrids
- zygomycetes
- glomeromycetes
- ascomycetes
- basidiomycetes
what is the type of spores in chytrids?
zoospores (flagellated spores)
zygomycetes are named after their characteristic?
zygosporangia
what is an example of a zygomycete?
black bread mold
what are the spore-producing structures in zygomycetes?
- sporangia
- zygosporangia
describe the spore-producing structures in zygomycetes
(1) sporangia:
- produce spores by asexual reproduction (by mitosis)
(2) zygosporangia:
- contain sexually produced spores (by karyogamy and meiosis)
- resistant to freezing and drying => can survive under unfavorable conditions
how is zygosporangia produced/structured?
- 2 different mycelia share one sporangium between them
- these mycelia fuse to produce zygosporangia
what are the ways ascomycetes can produce spores?
both sexually and asexually
what are the spore-producing structures in ascomycetes?
(1) asci
- produce sexual spores (ascospores) by meiosis
- located in the ascocarps (fruiting body)
(2) conidiophores
- specialized hyphae that produce asexual spores (conidia)
what is the fruiting body?
multicellular structure (reproductive structure) which contains the spore-producing structures
what are examples of ascomycetes?
bread mold Neurospora crassa, morels and truffles
what are basidiomycetes characterized as?
club fungi: characterized by a clublike structure called basidium
what are the spore-producing structures in basidiomycetes?
basidia
what do basidia produce?
produce sexual spores (basidiospores)
what is basidiocarp?
the fruiting body, has numerous basidia
what are examples of basidiocarp?
mushrooms (the fruiting body = reproductive structure of basidiomycetes
which of the 5 fungal phyla is the only type that does not produce asexual spores?
basidiomycetes, only produce sexual spores
fungi have several interactions with other organisms:
- decomposers
- mutualists
- parasites
what are the examples of plant pathogenic fungi?
(1) pathogenic zygomycetes
(2) pathogenic ascomycetes
(3) pathogenic basidiomycetes
describe pathogenic zygomycetes
- ex: genera Mucor, Rhizopus, Absidia
- cause skin and ear infections, bronchitis-pneumonia
describe pathogenic ascomycetes
(A) Aspergillus flavus:
- produces mycotoxins such as aflatoxins
- infects peanuts and wheat
- causes Aflatoxin B1: which causes liver cancer due to p53 mutations
(B) Claviceps purpurea:
- infects cereals (e.g. rye)
- produces ergotamine and lysergic acid (precursors for LSD synthesis)
=> psychotropic effects (hallucinations, temporary insanity), convulsions, gangrene
describe pathogenic basidiomycetes
(A) Amanita phalloides
- poisonous mushrooms
- contain lethal toxins (e.g. phalloidin, amanitin)
(1) α-amanitin: inhibits eukaryotic RNA polymerase II
(2) phalloidin: inhibits F-actin poymerization
(B) Amanita muscaria ands Psilocybe cubensis
- magic mushrooms
- psychoactive mushrooms => cause hallucinations (psychotropic effects)
what effect does the lethal toxin α-amanitin have?
inhibits transcription of mRNA, which inhibits gene expression (death)
what effect does the lethal toxin phalloidin have?
inhibits many cell functions, and the polymerization/depolymerization of actin
what are mycoses?
human fungal infections
what are the major types of human mycoses?
- superficial-cutaneous mycoses (IMP)
- subcutaneous mycoses
- systemic mycoses
- opportunistic mycoses (IMP)
describe superficial-cutaneous mycoses
fungal infections of hair, nails, and skin
what are the examples of superficial-cutaneous mycoses?
(1) Microsporum furfur
- ascomycete that causes ringworm
(2) Ascomycete genera Trichophyton and Epidermophyton
- causes athlete’s foot (ringworm of the foot
describe 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
what are the examples of opportunistic mycoses?
yeast Candida albicans
- causes candidiasis
=> mouth infection (thrush), skin infection, vaginal infection
what are some industrial and therapeutic applications of fungi?
- production of antibiotics
- production of alcoholic beverages, bread and cheeses
- genetic engineering
what are the examples of fungi production of antibiotics?
ascomycetes of genus penicillin
(1) penicillium chrysogenum
- produces penicillin (anti-bacterial antibiotic)
(2) penicillium griseofulvum
- produces griseofulvin (anti-fungal antibiotic)
what are the examples of fungi production of alcoholic beverages, bread and cheeses?
ex: the yeast Saccharomyces cerevisiae:
- production of enzymes used for alcohol fermentation => production of beer, wine, etc
- also used as baking yeast
what are the examples of fungi in genetic engineering?
- ex: insulin-like growth factor (IGF) can be produced in the fungus Saccharomyces cerevisiae
- study of genes involved in human diseases
