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Questions and Answers
What is mycology primarily concerned with?
What is mycology primarily concerned with?
All fungi are harmful to humans.
All fungi are harmful to humans.
False
Name one characteristic that is common to all fungi.
Name one characteristic that is common to all fungi.
Presence of chitin in the cell wall.
Fungi reproduce by means of spores, which can be formed ________ or ________.
Fungi reproduce by means of spores, which can be formed ________ or ________.
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Match the following types of fungi with their characteristics:
Match the following types of fungi with their characteristics:
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Which of the following is a feature of dimorphic fungi?
Which of the following is a feature of dimorphic fungi?
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Most fungi are obligate anaerobes.
Most fungi are obligate anaerobes.
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What is the main reason for the increased incidence of fungal infections worldwide?
What is the main reason for the increased incidence of fungal infections worldwide?
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More than __________ valid species of fungi have been identified.
More than __________ valid species of fungi have been identified.
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Which of the following best describes opportunistic pathogens?
Which of the following best describes opportunistic pathogens?
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What structure in molds is primarily responsible for asexual reproduction?
What structure in molds is primarily responsible for asexual reproduction?
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Yeasts reproduce predominantly through a process known as fission.
Yeasts reproduce predominantly through a process known as fission.
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What are the two morphological forms that dimorphic fungi can take based on environmental conditions?
What are the two morphological forms that dimorphic fungi can take based on environmental conditions?
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Molds possess a network of long strands known as _____.
Molds possess a network of long strands known as _____.
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Match the type of spores with their description:
Match the type of spores with their description:
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Which of the following characteristics is unique to phaeoid fungi?
Which of the following characteristics is unique to phaeoid fungi?
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Aerial mycelium is involved in nutrient absorption for molds.
Aerial mycelium is involved in nutrient absorption for molds.
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What structure produces phialoconidia in fungi?
What structure produces phialoconidia in fungi?
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Anamorphs are fungi that can only reproduce sexually.
Anamorphs are fungi that can only reproduce sexually.
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What temperature and condition does a dimorphic fungus typically grow as a yeast?
What temperature and condition does a dimorphic fungus typically grow as a yeast?
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In molds, the term _____ refers to the structures used for anchorage and nutrient absorption.
In molds, the term _____ refers to the structures used for anchorage and nutrient absorption.
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Name one example of a fungus in the Mucorales order.
Name one example of a fungus in the Mucorales order.
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Which term describes the ability of a single organism to exist in both yeast and mold forms?
Which term describes the ability of a single organism to exist in both yeast and mold forms?
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Fungi that reproduce via zygospores belong to the phylum ______.
Fungi that reproduce via zygospores belong to the phylum ______.
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Match the type of fungal reproduction with its respective structure.
Match the type of fungal reproduction with its respective structure.
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Which term refers to the name for amorphic strains when more than one anamorph is present for the same teleomorph?
Which term refers to the name for amorphic strains when more than one anamorph is present for the same teleomorph?
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Phylum Ascomycota is known for its asexual reproduction primarily through conidia.
Phylum Ascomycota is known for its asexual reproduction primarily through conidia.
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What is the primary characteristic of Mucorales fungi?
What is the primary characteristic of Mucorales fungi?
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The policy adopted in July 2011 regarding fungi is called ______.
The policy adopted in July 2011 regarding fungi is called ______.
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Which reproductive structure is produced by Annellides?
Which reproductive structure is produced by Annellides?
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Study Notes
Mycology
- Mycology is the study of fungi
- Key aspects include taxonomy, environmental impact, and genetic/biochemical properties
Medical Mycology
- Focuses on fungi and their relationship to human disease
- Encompasses single-celled yeasts and filamentous molds
- Includes agents causing superficial skin infections (cutaneous mycosis) and disseminated deep-seated visceral disease (systemic mycosis).
- True pathogens are historically pathogenic fungi—opportunistic.
- Pathogens—Saprophytic fungi
- Immunocompromised hosts (HIV/AIDS, immunosuppressive infections, high-dose cancer chemotherapy, solid organ transplant) are at risk.
Common Terms in Medical Mycology (Table of Terms)
- (A comprehensive list of terms and related definitions)
Overview of Fungi
- Diverse group of organisms, including molds (filamentous) and yeasts (moist)
- Categorization includes classic pathogens and environmental saprobes (living on nonliving material)
- Can cause a range of signs and symptoms, from mild to life-threatening, significant in immunocompromised patients
General Characteristics
- Eukaryotic organisms
- Most fungi are saprophytic (live on dead organic matter)
- Fungi can be yeasts (moist) or molds (filamentous).
- Dimorphic organisms can exist in both yeast and mold forms, often dependent on temperature.
- Polymorphic fungi have more than one form or stage.
- Fungi have thick cell walls made of chitin.
- Mostly obligate aerobes (require oxygen)
- Prefer neutral pH.
Shared Characteristics
- Contain chitin in the cell wall
- Ergosterol in the cell membrane
- Reproduce via spores (sexually or asexually)
- Lack chlorophyll
- Lack susceptibility to antibacterial agents
Epidemiology
- Increased fungal infections worldwide, particularly in immunocompromised individuals.
Yeasts
- Single vegetative cells
- Form a smooth, creamy, bacterial-like colony without aerial hyphae
- Identification relies on biochemical testing and molecular diagnostic methods
- Reproduction via budding or fission
Molds
- Filamentous mycelium (long strands of tubelike structures called hyphae)
- Reproduction by spores (asexually or sexually)
- Vegetative mycelium composed of arthrospores, chlamydospores, blastospores, and rhizoids
- Aerial mycelium composed of conidia and sporangia
Mold Morphology
- Hyphae can be diverse in shape, including antler, racquet, spiral, or rhizoid shapes.
- Septate hyphae have frequent perpendicular cross-walls
- Sparsely septate hyphae have frequent perpendicular cross-walls
Hyaline Versus Phaeoid
- Hyaline fungi are nonpigmented or lightly pigmented
- Phaeoid (dematiaceous) fungi have darkly pigmented cell walls due to melanin production
Dimorphism and Polymorphism
- Dimorphism is the ability to exist in two forms based on growth conditions (mold phase at room temperature/ yeast phase at 37C with increased CO2)
- Polymorphism is an ability to form both yeast and mold forms in the same culture.
Asexual Reproduction
- Asexual reproduction involves conidia (conidium) formation following mitosis
- Types include phialoconidia (produced in fruiting structures or phialides), annellides (produced in structures called annellides), and arthroconidia (formed by fragmentation of specialized hyphae.)
Sexual Reproduction
- Sexual Reproduction involves the teleomorph stage.
- Some fungi can reproduce asexually as occasionally observed.
- Synanamorphs are a name given to strains that display more than one anamorph (form) in the same teleomorph.
Zygospore Formation
- Sexual reproduction involving the fusion of hyphae and nuclei
Taxonomy Nomenclature
- Historically, fungi had multiple names associated with reproductive forms
- Current practice uses a "one fungus, one name policy". (International Codes of Nomenclature for Algae, Fungi, and Plants)
Taxonomy of Clinically Significant Fungi
- Four groups of fungi cause clinical infections including Phylum Ascomycota, Basidiomycota, Mucoromycotina, and Entomophthoromycotina.
Mucorales
- Rapid-growing fungi often causing opportunistic infections.
- Characterized by a gray to white aerial mycelium with hyaline, sparsely septate hyphae.
- Reproduce asexually.
- Results in zygospores (not commonly seen in clinical labs).
Ascomycota
- Sexual spores are ascospores.
- Ascospores are contained within sac-like structures (asci).
- Common species include Microsporum, Trichophyton, and Scedosporium.
Basidiomycota
- Filobasidiella neoformans is a significant pathogen (causing cryptococcosis).
- Other genera associated with human infections are Malassezia and Trichosporon.
- Identification involves clamp connections at septations.
Fungi Imperfecti
- Category applied when mode of sexual reproduction is not known.
- Identified based on characteristic asexual reproductive structures.
- Examples: Ulocladium and Alternaria tenuis.
Parafungal Organisms
- Resemble yeast and protozoans
- Remain unculturable
- Atypical agents of human infections.
Macroconidia
- Larger conidia produced by some molds
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Description
This quiz covers the key aspects of medical mycology, focusing on the relationship between fungi and human diseases. Learn about different types of fungal infections, key terms, and the impact of immunocompromised hosts on susceptibility to fungal pathogens.
