[01.26] General Concepts in Mycology V2

Mycology

What is the study of fungi called?

Eukaryotic

Fungi are characterized as what type of cells, similar to animal cells, possessing a nucleus and membrane-bound organelles?

Cell membrane

Fungi are protected by what in addition to a cell wall?

Chitins and glucans

The rigid cell wall of fungi is composed of what two main chemicals?

Ergosterol

What chemical is found in the cell membrane of fungi, which is important when discussing pharmacology and antifungals?

Chemoheterotroph

What term describes organisms that need an external source of carbon and are not photosynthetic, like fungi?

Saprophytes

What term describes most fungi, indicating they live off of decaying organic material?

Unicellular yeasts and multicellular molds

What are the two forms in which fungi exist?

Cell wall

During infection, which part of the fungal cell specifically exerts pathobiological properties?

Attachment to host cells

What do the surface components of the fungal cell wall mediate during infection?

Pattern recognition receptors (PRRs)

What do specific fungal cell wall moieties bind to on host cell membranes to stimulate innate immune responses?

Complement cascade

What host immune response can cell wall glucans and other polysaccharides activate?

Inflammatory reaction

What host response can be provoked by the activation of the complement cascade by fungal cell wall components?

Immunodominant antigens

What do fungal cell walls release that may elicit cellular immune responses and diagnostic antibodies?

Dematiaceous

What term describes some yeast and molds because their cell walls contain melanin?

Melanin

What pigment imparts a brown or black color to fungal colonies and protects fungi from host defenses?

Approximately 80,000

How many species of fungi have been described?

Approximately 400

How many fungal species are medically important?

Less than 50

How many fungal species are responsible for more than 90% of human and animal fungal infections?

Breaking down and recycling organic matter

Name one beneficial role of fungi in the environment.

Contributing to the production of food and spirits

Name a beneficial role of fungi related to human consumption.

Providing useful bioactive secondary metabolites (e.g., antibiotics like penicillin, immunosuppressive drugs like cyclosporine)

Name a beneficial role of fungi in medicine.

Single cells, usually spherical to ellipsoid in shape

Describe the basic morphology of yeast.

Budding

How do yeasts reproduce?

Multicellular organisms that have branching cylindrical tubules

Describe the basic morphology of molds.

Hyphae

What are the branching cylindrical tubules of molds called?

Dimorphic

What term describes fungi capable of growth as a yeast or mold depending on environmental conditions?

Temperature or available nutrients

What environmental conditions can influence a dimorphic fungus to grow as a yeast or a mold?

Yeast

In what form do dimorphic fungi grow in warm conditions?

Mold

In what form do dimorphic fungi grow in cold conditions?

"Molds during Cold"

What is the mnemonic for dimorphic fungi related to temperature?

Apical elongation at the hyphal tips

How do hyphae extend?

Mycelium

What is the mass of hyphae called?

Septate hyphae

What type of hyphae are divided into cells by cross walls or septum?

Coenocytic hyphae

What type of hyphae have no septum?

Vegetative hyphae

What type of hyphae serve as the anchor of the colony, similar to roots?

Aerial hyphae

What type of hyphae are projected above the surface of the mycelium and bear spores?

Appearance of spores, method of production, and appearance of the hyphae and mycelium

What three characteristics are used as a basis for identifying different species of fungi?

Sexually or asexually

What are the two ways molds can reproduce?

Anamorph

What is the mitotic or asexual reproductive state of a fungus called?

Mitospores

What are asexual fungal spores called?

Reproduction

What is the primary purpose of fungal spores, unlike bacterial spores?

Conidia and Sporangiospores

What are the two general types of mitospores?

Conidia (or Conidiospores)

What type of mitospores are exposed to the external environment and are not inside sacs or specialized cells?

Sporangiospores

What type of mitospores are produced inside specialized cells called sporangia and remain enclosed until maturity?

Phialoconidia

What subtype of conidia are produced by a vase-shaped conidiogenous cell called a phialide?

Microconidia

What term describes small conidia?

Macroconidia

What term describes large or multicellular conidia?

Arthroconidia (or Arthrospores)

What type of conidia result from the fragmentation of hyphal cells?

Chlamydospores (or Chlamydoconidia)

What type of conidia are large, thick-walled, usually spherical, and produced from terminal or intercalary hyphal cells?

Blastoconidia (or Blastospores)

What type of conidia are produced by budding?

Pseudohyphae

What are chains of elongated buds or blastoconidia called, which show constrictions unlike true hyphae?

Conidiospore and Sporangiospores

What two types of asexual spores do medical fungi produce?

Phialides

Most pathogenic fungi produce conidiospores on what finger-like projections?

Aerial hyphae (conidiophore)

Conidia are born externally in chains on what structure?

Penicillium

What is a common household mold and frequent food contaminant that produces phialoconidia?

Aspergillus

What genus contains fungi with short phialides that produce conidia?

Sporangium

Where are sporangiospores produced?

Sporangiophore

What is the aerial hyphae that bears the sporangium called?

Vegetative hyphae with rhizoids

What is the anchoring structure for molds that produce sporangiospores?

Rhizopus

What is an example of a genus that produces sporangiospores, is usually non-pathogenic but can cause opportunistic infections, and can reproduce sexually?

Teleomorph

What is the sexual reproductive state of a fungus called?

Zygospore

What is the sexual spore produced during sexual reproduction when the nuclei of hyphal tips fuse?

Sporangiospores

What gives rise to a new sporangium during sexual reproduction, resulting in recombination of parent strain DNA?

Anamorph

What term refers to the asexual reproductive state of a fungus?

Mitospore

What term refers to an asexual spore (e.g., Conidia and Sporangiospore)?

Teleomorph

What term refers to the sexual reproductive state of a fungus?

Zygospore

What term refers to a sexual spore?

Unicellular, spherical to ellipsoid in shape

Describe the morphology of yeast.

Budding

How do yeasts reproduce asexually?

Candida albicans

What dimorphic Candida species can switch from a yeast form to a filamentous hyphal form and form true hyphae?

Constrictions

What morphological feature differentiates pseudohyphae from true hyphae?

37°C (body temperature)

At what temperature do thermally dimorphic fungi typically grow in their yeast phase?

22-25°C

At what temperature do thermally dimorphic fungi typically grow in their hyphae/mold phase?

Upregulate genes involved with subverting host immune defenses

What do thermally dimorphic fungi do in their yeast phase to aid in infection?

Coccidioides immitis and posadasii

What fungi cause Coccidioidomycosis?

Histoplasma capsulatum

What fungus causes Histoplasmosis?

Blastomyces dermatitidis and gilchristi

What fungi cause Blastomycosis?

Paracoccidioides brasiliensis and lutzii

What fungi cause Paracoccidioidomycosis?

Sporothrix schenckii

What fungus causes Sporotrichosis?

Talaromyces marneffei

What fungus causes Penicilliosis?

"Can Have Both Prominent Shapes"

What is the mnemonic for the most relevant dimorphic fungi (Coccidioides, Histoplasma, Blastomyces, Paracoccidioides, Sporothrix)?

Mycoses

What is the general term for infections caused by fungi?

Superficial, Cutaneous, Subcutaneous, Systemic

What are the four classifications of mycoses?

Primary pathogens (endemic or geographically restricted agents) and Secondary opportunistic pathogens (ubiquitous)

What are the two types of systemic mycoses?

Stratum corneum

What is the most superficial layer of the skin infected by superficial mycoses?

Malassezia species

What is the best example of a fungus causing superficial mycoses, commonly associated with dandruff?

Living skin

Cutaneous mycoses pertain to infections of what?

Dermatophytes

What group of fungi causes cutaneous mycoses?

Ringworm, athlete's foot, jock itch

Give two examples of cutaneous mycoses.

Inoculation into subcutaneous tissue, usually by cuts or injuries

How do subcutaneous mycoses typically occur?

Coccidioidomycosis, Histoplasmosis, Blastomycosis, Paracoccidioidomycosis

What are the four primary systemic mycoses?

Geographically restricted to specific areas of endemicity

How are endemic mycoses distributed?

Dimorphic fungi

What type of fungi cause all four endemic mycoses?

Immunocompetent individuals

In what type of individuals do over 90% of endemic mycoses infections occur?

60-95%

What percentage of endemic mycoses infections are asymptomatic and self-limited or latent?

Immunocompromised patients, including those with HIV/AIDS

In what patient population does symptomatic endemic mycosis disease occur frequently?

C. posadasii or C. immitis

What two species cause Coccidioidomycosis?

Semiarid regions of the southwestern United States, Central America, and South America

Where is Coccidioidomycosis endemic?

Filipinos and Blacks

In which two ethnic groups is the risk of dissemination or progressing pulmonary disease for Coccidioidomycosis higher?