Mycology Flashcards
Sterol of fungi
ergosterol
Rigid cell wall of fungi contain?
Chitin (N-acetylglucosamine) and glucan
Main difference of fungi from plants
Fungi are nonphotosynthetic. They do not form chlorophyll.
True or false. Less than 50 species cause more than 90% of the fungal infection.
True
Overall, fungi exert their greatest economic impact as?
Phytopathogens
- the agricultural industry
sustains huge crop losses every year as a result of fungal diseases of rice, corn, grains, and other plants
True or false. Most fungi are obligate or facultative aerobes.
True.
Fungi secrete enzymes
that degrade a wide variety of organic substrates into soluble
nutrients which are then passively absorbed or taken into the cell by active transport. This property is termed?
Chemotrophic
Fungal infections are called?
Mycoses
Most pathogenic fungi
are exogenous, their natural habitats being water, soil, and organic debris. True or false?
True.
Th e mycoses with the highest incidence?
candidiasis dermatophytosis
Immune response of most patients who develop mycosis?
cellular and humoral immune responses to the fungal antigens
Asexual reproductive structures (mitospores)
produced either from the transformation of a vegetative
yeast or hyphal cell or from a specialized conidiogenous
cell.
Conidia
Conidia may be formed on specialized hyphae,
termed?
conidiophores
Conidia that result from
the fragmentation of hyphal cells.
Arthroconidia (arthrospores)
Conidial formation through a budding process (eg, yeasts: Candida, cryptococcus)
Blastoconidia (blastospores)
If blastoconidia continue to elongate and fail to pinch off, they are called?
pseudohyphae (yeast-like)
Large, thick-walled,
usually spherical conidia produced from terminal
or intercalary hyphal cells
Chlamydospores (chlamydoconidia)
Conidia that are produced by a “vase-shaped”
conidiogenous cell termed a phialide (eg,
Aspergillus fumigatus)
Phialoconidia
Fungi whose cell walls contain
melanin, which imparts a brown to black pigment.
Dematiaceous fungi
Fungi that have two growth forms, such
as a mold and a yeast, which develop under different growth conditions (eg, Blastomyces dermatitidis forms hyphae in vitro and yeasts in tissue)
Dimorphic fungi
Tubular, branching filaments (2–10 μm in width) of fungal cells, the mold form of growth.
Hyphae
Most hyphal
cells are separated by porous cross-walls called?
Septa
Aseptate hyphae (lack crosswalls) are also called?
coenocytic
Hyphae which grow within the surface of the medium (agar)
Vegetative hyphae
Hyphae which extend above the surface
Aerial hyphae
Septa formed as a process of hyphal extension and generally have a septal pore.
Primary septa
Function of primary septa
allows for cytoplasmic and organelle movement
Imperforate septa formed to wall off aging parts of the mycelium.
Secondary or adventitiopus septa
Mucor fungi have what type of septa?
Aseptate
3 structural components of fungi cell wall
- Chitin microfibrils (N-acetylglucosamine)
- Chitosan (glucosamine)
- B-linked glucans
Gel-like components of fungi cell wall
mannoproteins
Dark brown to black pigments on fungi cell wall
melanins
Function of melanins in fungi cell wall (3)
- Confer resistance to enzyme lysis
- Confer mechanical strength
- Protect cells from UV light, solar radiation and desiccation
Aromatic polymer found in spore walls of some fungi that confers properties similar to melanin
sporopollenin
Permeability of fungi cell wall
semi-permeable
An allergic reaction to molds and spores
hypersensitivity
Poisoning of man and animals by feeds and food products contaminated by fungi which produce toxins from the grain substrate.
Mycotoxicoses
Ingestion of pre-formed toxin (mushroom poisoning)
Mycetismus
Yeasts may be gram positive and are much larger than bacteria. True or false?
True
Cylindrical, branching filaments composed of a tubular cell wall filled with cytoplasm and organelles
HYPHAE (MYCELIUM)
Unicellular organism
Round or oval fungi that bud or pinch off
yeasts
Size of most fungal hyphae
2-10 μm diameter
A mass of hyphae is called?
mycelia
Fungi that are characteristically
sparsely septate.
zygomycetous hyphae
Vegetative or substrate hyphae anchor the colony and?
absorb nutrients
Aerial hyphae project
above the colony and bear the?
reproductive structures
Fungi that lack sexual reproduction; they are represented only by an anamorph, the mitotic or asexual reproductive state.
Imperfect fungi
asexual reproductive state of imperfect fungi
anamorph
Hyphal or mycelial colony or form of growth
mold
Mass or mat of hyphae, mold colony
mycelium
Fungi that are capable of sexual reproduction, which is the teleomorph.
perfect fungi
Sexual reproductive state of perfect fungi
teleomorph
Chains of elongated buds or blastoconidia
Pseudohyphae
Hyphal cross-wall, typically perforated
septum
Asexual structures characteristic of the Order Mucorales; they are mitotic spores produced within an enclosed sporangium, often supported by one sporangiophore
sporangiospores
A specialized propagule with enhanced survival
value, such as resistance to adverse conditions or
structural features that promote dispersion
spore
During sexual reproduction, haploid
cells of compatible strains mate through a process of?
plasmogamy, karyogamy, and meiosis
In the Phylum Ascomycota, following
meiosis, four to eight meiospores form within an ascus
ascospores
In the Phylum Basidiomycota, following
meiosis, four meiospores usually form on the surface of a specialized structure, a club-shaped basidium
Basidiospores
In the Order Mucorales, following meiosis, a
large, thick-walled called ___ develops.
zygospores
Unicellular, spherical to ellipsoid (3–15 μm) fungal
cells that usually reproduce by budding.
yeasts
Pathogenic fungi do not
produce potent toxins. True or false.
True
Because fungi are eukaryotes, they share numerous homologous genes, gene products, and pathways with their
human hosts. True or false?
True
Growth in the mold form occurs by the production of multicellular filamentous colonies called?
hyphae
The mass of intertwined
hyphae that accumulates during active growth is a?
mycelium
When a mold is
isolated from a clinical specimen, its _____, _____ and _____ are usually
sufficient to determine its genus and species.
growth rate, macroscopic
appearance, and microscopic morphology
The most helpful
phenotypic features are the ontogeny and morphology of the asexual reproductive spores, or conidia. True or false?
True
Cell wall component that activate the complement cascade and provoke an inflammatory reaction.
Cell wall glucans and other polysaccharides
Usually detected component of fungi cell wall voa special histologic stains
cell wall polysaccharides since they are poorly degraded by the host
Fungi that impart a brown or black pigment
dematiaceous fungi
The medical fungi produce two major types of asexial spores which are?
- Conidia (from most pathogenic fungi)
2. Sporangiospores (Order Mucorales)
The lower fungi were assigned
to the Phylum?
Phylum Zygomycota
Phylum Zygomycota, shown to be polyphyletic, has been replaced by?
Phylum
Glomerulomycota and four subphyla
Under Phylum Glomerulomycota contains the orders of zoopathogenic molds which are?
Mucorales and
the Entomophthorales
Two largest phyla of fungi
Ascomycota and Basidiomycota
Phylum which include more than 60% of the known fungi and about 85% of the human pathogens.
Phylum Ascomycota (or ascomycetes)
In Phylum Glomerulomycta, Order Mucorales, sexula reproduction results in ____ and asexual reproduction occurs via _____.
Sexual - zygospore
Asexual - sporangia
Rhizopus, Lichtheimia, Mucor, Cunninghamella are under which phylum?
Phylum Glomerulomycta, Order Mucorales
In Phylum Ascomycota (Ascomycetes)
Sexual reproduction involves a sac or ____ in which karyogamy and meiosis occur.
sac or ascus
Asexual reproduction in Phylum Ascomycota (Ascomycetes) is via?
conidia
Ascomycetous molds have what type of hyphae?
septate hyphae
(Saccharomyces,
Candida) and molds (Coccidioides, Blastomyces, Trichophyton)
Phylum Ascomycota (Ascomycetes)
In Phylum Basidiomycota (Basidomycetes)
Sexual reproduction results in _____ and four progeny
basidiospores supported by a club-shaped basidium.
dikaryotic hyphae
Type of hyphae of Phylum Basidiomycota (Basidomycetes)
complex septa
Mushrooms, Cryptococcus
Phylum Basidiomycota (Basidomycetes)
Most fungi occur in nature and grow readily on simple
sources of?
N and CHO
The traditional mycological
medium, _______, which contains glucose
and modified peptone (pH 7.0), has been used because it
does not readily support the growth of bacteria.
Sabouraud’s agar
Content of Sabouraud’s agar
glucose
and modified peptone (pH 7.0)
Sabouraud’s agar i sused for?
ID of morphologic characteritsics of fungi
agar that facilitates the
recovery of fungi from clinical specimens
inhibitory mold agar
To culture medical fungi from non-sterile specimens, these are added to the media to inhibit bacteria and saprobic molds.
antibacterial antibiotics
(eg, gentamicin, chloramphenicol) and cycloheximide
antibacterial antibiotics in culture of medical fungi ate used to inhibit?
bacteria
cycloheximide in culture of medical fungi is used to inhibit growth of?
saprobic molds
Stain that binds
to cellulose and chitin in the cell walls of fungi and fluoresces under long-wavelength ultraviolet light. It may demonstrate morphology that is diagnostic of the species (eg,
spherules with endospores in Coccidioides immitis infection).
calcofluor white
Pneumocystis jirovecii cysts are identified morphologically in?
silver-stained specimens
used to stain tissue sections
when fungal infection is suspected
PAS
After primary isolation
of fungi, stains such as _____are used to distinguish fungal growth and to identify organisms by their
morphology.
lactophenol cotton blue
Specimens to be examined for fungi can be examined
unstained after treatment with a solution of ______, which breaks down the tissue surrounding
the fungal mycelia to allow a better view of the hyphal
forms.
10% potassium
hydroxide
used for specimens such as surveillance cultures and cultures of urine
chromogenic agars
agars that incorporate antibiotics and chromogenic enzyme
substrates that impart color to specific organisms of interest
FACTORS AFFECTING ESTABLISHMENT OF MYCOSIS
- Inoculum size
- Resistance of the host
- Severity of disease in mycotic infections depends more on the host immune system than on the virulence of the fungus
multiplication of an organism at a given site without harm to the host
colonization
invasion and multiplication of organisms in body tissue resulting in local cellular injury
true infection