Mycology Lecture 1 Flashcards
Fungi are completely ____ from plants.
distinct
True or false: of the 2-4 million fungal species that have been described by taxonomists, a large portion are clinically relevant.
False - only about 200 fungal species are known to cause human disease
Fungi are a part of which domain of life?
Eukarya
Good fungi are a part of our ___, such as:
food; chocolate, bread, beer, cheese, edible mushrooms and truffles
Besides food, how else are fungi beneficial? (5)
they are commercially and medically useful:
- some fungi convert corn sugars to ethanols for food, and
- we have extracted penicillin (antibiotic) from fungal species
- can be used for biodegradable packaging
- can play a role in cleaning up pollution
- fight cancer
Great Potato Famine in Ireland was caused by:
Phytophthora infestans
Saint Anthony’s Fire (more common in Middle Ages) is caused by:
Claviceps
Symptoms of Saint Anthony’s Fire
Hallucinations, confusions, gangrenous limbs, skin sores, convulsions
Derivatives of the toxin produced by ____ is now used in medications, such as migraine meds.
Claviceps
About __ fungal species are known to cause human disease. About __% of all human infections are caused by __ ___ species of fungi.
200; 90%; a few dozen
True or false: fungal pathogens cause a wide range of infections, such as superficial, cutaneous, subcutaneous, and systemic
True
True or false: when a fungal pathogen becomes systemic, often it is easy to cure the infection solely by using antifungal drugs.
False - at that stage, the fungi can erode through layers of skin and tissue. The only way to remove the infection is through surgical excision/debridement. In other words, fungal meds on their own will likely not be enough
Fungi are ___ and contain ____
eukaryotic; organelles
Fungi are like animals in the sense that they are _____
heterotrophs
Fungi require organic compounds for ____ and ____ ____
energy and carbon sources
True or false: first fungi ingest their food source and then digest them
False - first digest externally, then ingest nutrients
In addition to being heterotrophs, fungi are _____
osmiotrophs
A unique biosynthetic pathway found in fungi
lysine synthesis
Fungi take on what three morphological forms?
- yeast
- hyphae
- both
What is one way that fungi are completely distinct from plants?
No chlorophyll
True or false: fungal cell membrane is primarily made of chitin
False - cell wall contains chitin
Chitin is useful for providing ___ to fungal cells
rigidity
Chitin is similar to ____ ___ in humans
hyaluronic acid
Fungal cell wall contains:
chitin, glucans, mannans
Fungal cell membranes contain:
ergosterol
___ ____ RNA is used in fungal diagnosis
18S ribosomal (18S rRNA)
True or false: Fungi are largely anaerobic
False - mainly aerobic (limited anaerobic capabilities)
Name 3 fungal “nutritional modes”
- saprobes
- parasites
- mutualists
Saprobe
lives on dead materials; decomposers found in the environment
Parasites
live on living organisms; pathogens that cause harm to host
mutualists
live on host but provide benefits to the host
A commonly known parasitic fungus called ____ causes “zombie ants”
Cordyceps
Cordyceps pathogenesis in ant
- invades brain of ant
- forces ant to walk up to a high point on vegetation
- kills ant by sprouting from its body (long hyphae type structure)
- spores are released (aerosolized) to spread to other ants
Fungi are non-____, which means the have to reproduce via ____ dissemination of ___
non-motile; passive dissemination; spores
True or false: some fungi can produce both asexual and sexual spores
True
What are some means of spore dissemination?
wind, gardening, construction, lawn mower, etc.
Hyphae
microscopic, long, branching filaments
True or false: hyphae are the same thing as yeasts
False (they are distinct from each other!!)
Mycelium
tangled mass of hyphae that can grow to huge proportions
Armillaria species (honey fungus) is well known because:
it has grown over 2000 acres underground in Oregon; largest organism on Earth
___ are asexual spores
Conidia
True or false: fungi are everywhere, and infections are common, but only a very small percentage of all fungi cause human disease
True
Yeasts are ____, ___ or ____
unicellular, oval or round
2 asexual reproductive modes of yeast
- cell budding (asymmetrical)
2. fission (symmetrical)
True or false: yeast cells can sometimes form chains, and when this happens, they become multicellular
False - they are still unicellular since there is no connection or cell-to-cell communication between chained cells
Yeast sexual form of reproduction is called:
conjugation
Yeast asexual forms of reproduction (2)
a and alpha
True or false: Yeast life cycle can change how pathogenic they are
True
Moulds form ____, which undergo ___ growth
hyphae; apical
True or false: all hyphae are septate
false; can be septate or non-septate
How many nuclei can molds have in their hyphae?
one or more (uni or multi-nucleate)
When moulds branch, they can form what kinds of angles?
Acute + right angles
True or false: molds form different types of hyphae
True
Characteristics of hyphae (how are they different/distinct)?
- septate vs aseptate
- hyaline vs dematiaceous (clear vs pigmented)
- branching or non-branching
- angle of branching (acute or not)
Fungi can have an organelle called _____ which allows for apical growth of hyphae
Spitzenkorper
Vegetative hyphae
form that gathers nutrients
aerial hyphae
reproductive form
True or false: hyphae can be very distinctive looking and can be diagnostic
True
All sexual fungal life cycles consist of _____ and is followed by _____.
plasmogamy; karyogamy
True or false: the transition between plasmogamy and karyogamy is usually rapid
False - it can be, or it can take up to years. Depends heavily on the right environmental conditions for karyogamy to follow
Molds can have what kind of life cycles?
both sexual and asexual
Describe the asexual life cycle of molds
- conidia (asexual spores) undergo swelling and apical growth to form a germling
- germling elongates and branches to form hyphae
- hyphae continue to form and tangles to form mycelium
- conidiophore can form within mycelium and disperse more conidia thru wind or disruption of soil
What are dimorphic fungi?
Fungi that can occur as yeast and mycelial forms
Dimorphic fungi are usually ____ dimorphic
thermally
Why is it important to study dimorphic fungi?
A lot of them are clinically relevant. Yeast form survives better at body temperature (37ºC)
True or false: sexual and asexual stages of same fungus have different names
True
Name commonly used for naming the species of fungus for clinical purposes
Anamorph (according to asexual reprod.)
____ ____ are often critical diagnostic importance
Asexual structures
Most human pathogenic fungi produce _____ ____ as the reproductive and infectious propagule
asexual conidia
Major fungal phyla were traditionally based on ____ ____ ____. Now, it’s mainly ___.
sexual reproductive structures; genetics
Three major fungal phyla:
- Ascomycetes
- Basidiomycetes
- Zygomycetes (group that contains mucormycota)
Ascomycetes
8 sexual spores inside ascus
Basidiomycetes
4 sexual spores externally on basidium
Basidium
little pedestal
Ascus
sac
True or false: basidiospores, ascospores, and zygospores are sexual propagules and do meiosis
True
Zygospore arises from ___ ___ and are ____
sexual conjugation; diploid
Conidiophore arises from ____
hyphae
Blastic conidia
parent cell enlarges first and then conidium is visible before the septum is laid down to separate parent and daughter cell
Thallic conidia
Septum is formed before differentiation into conidium occurs
Arthroconidia
Septa are laid down, become conidia, and then fragment into individualized cells
_-___ is often targeted by antifungals in Candida cell wall
Beta-glucan
Pathology of fungal cell wall
Can be irritants, can activate complement, immunogenic, allergenic, immunopathogenic, immunomodulatory
Pathogenesis of fungal cell wall
Signaling, morphogenesis, pathogenicity are altered in response to the host: can attach to host cells and form biofilms which increases resistance to antifungals
Diagnostics of fungal cell wall
staining properties, antigenicity that can indicate the type of fungus causing infection
True or false: ascomycetes, deuteromycetes, basidiomycetes, and zygomycetes all have chitin in their fibrillar layer and differ in whether they have glucans in fibrillar or matrix layer
True
____ are harder to treat because they lack some common drug targets
Zygomycetes
What antifungal targets are particularly sensitive in fungi?
ergosterol, unique polysaccharides like glucans
Major classes of antifungal drugs
- membrane function
- cell wall synthesis (echinocandins)
- ergosterol synthesis (azoles + allylamines)
- nucleic acid synthesis (pyrimidine analog)
Amphotericin B is a ____
polyene
Amphotericin B is both:
amphoteric and amphipathic
Amphotericin B works as an antifungal by:
forming a pore/channel which lyses fungal cell
True or false: spectrum of azoles depends greatly on the agent
True
Mechanism of azoles:
blocks synthesis of ergosterol in fungal membrane which causes accumulation of toxic sterol precursors in the cytoplasm
True or false: with azoles, you have to match the agent to the fungus
True
Echinocandins mechanism
non-competitively inhibits beta-1,3-glucan synthase enzyme complex, which prevents resistance against osmotic forces and causes cell lysis
Echinocandins spectrum
most yeast species but is not the best choice for Aspergillus (since it’s just fungistatic)
