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MICR2209 > 21 - Intro to Mycology and Fungal Diseases > Flashcards

21 - Intro to Mycology and Fungal Diseases Flashcards

1
Q

Three domains of life

A

Bacteria, Archaea, Eukarya

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2
Q

What is the universal phylogenetic tree based on

A

16s rRNA sequences

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3
Q

Fungi

A

Describes a diverse group of eukaryotic organisms that are spore bearing, have absorptive nutrition, do not photosynthesise, and reproduce both sexually and asexually

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4
Q

Characteristics of fungi

A
  1. Eukaryotic (nucleus, mitochondria, etc)
  2. Have cell walls
  3. Heterotrophic, osmotrophic, and saprophytic nutrition
  4. Basic unit is hyphae
  5. Have simple to complex life cycles involving asexual and sexual reproduction, and spore production
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5
Q

Heterotrophic

A

Use reduced, preformed organic molecules as carbon source

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6
Q

Osmotrophic

A

Soluble nutrients are absorbed through the cytoplasmic membrane

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7
Q

Saprophytic

A

Derive nutrition from degradation of dead organic matter

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8
Q

Hypha (pl. hyphae)

A
  • Tubular branching filament
  • A mass of branching hyphae = mycelium
  • Mycelium is a type of thallus (body or vegetative structure of fungus)
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9
Q

Aseptate (coenocytic) hyphae

A

Multinucleate protoplasm streams through the hyphae

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10
Q

Septate hyphae

A

have septa (cross walls) with pores to allow streaming of protoplasm

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11
Q

Yeasts

A

Fungi but typically are unicellular, bud, and do not have a mycelial stage

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12
Q

Mould

A

Term used for fungi producing filamentous growth

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13
Q

Dimorphic fungi

A
  • Mycelial form outside host
  • Yeast form in host
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14
Q

Thermally dimorphic fungi

A

Cell shape changes, composition of the cell wall differs, presence of antigens differs, and virulence increases/decreases

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15
Q

Asexual reproduction

A
  • Elongation of hyphae, or budding of yeast cells to form a smaller daughter cell
  • Often accompanied by formation of asexual spores
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16
Q

Sexual reproduction

A
  • Fusion of nuclei, meiosis, mitosis
  • Produces sexual spores
17
Q

Sexual fungi spores

A
  • Enable fungi to survive
    drying, heating, starvation, some chemicals
  • Both sexual and asexual
    spores can germinate to form new hyphae
18
Q

Types of asexual spores

A
  • Sporangiospores
  • Conidiospores:
  • Arthrospores (arthroconidia)
19
Q

Sporangiospores

A

produced in a membrane enclosed structure termed a ‘sporangium’

20
Q

Conidiospores

A

Pores born on tips or sides of ‘conidiophores’ – not enclosed in a membrane

21
Q

Arthrospores

A

formed when hyphae fragment

22
Q

Basidiospores

A

Sexual spores produced on the end of a club shaped structure or “basidium”

23
Q

Mycoses

A

Fungal diseases

24
Q

Systemic mycoses

A
  • Most acquired by an air-borne route
  • Spores are inhaled from the soil where the free-living fungi are found
  • The fungal pathogens are often thermally dimorphic
25
Q

Types of systemic mycoses

A
  • Coccidioidomycosis
  • Cryptococcosis
  • Histoplasmosis
26
Q

Coccidioidomycosis

A
  • aka Valley fever
  • Coccidioides immitis
  • Thermally dimorphic fungus
27
Q

Coccidioidomycosis in soul and on culture media

A

Grows as a filamentous mould that forms arthroconidia at the tips of hyphae

28
Q

Coccidioidomycosis in humans

A

Grows as a thick-walled spherule filled with spores

29
Q

Coccidioidomycosis life cycle

A
  1. Arthroconidium germinates into tubular hypa
  2. Hypha begins to segment into arthroconidia
  3. Airborne arthroconidium is inhaled
  4. Inhaled arthroconidium enlarges and begins to develop into a spherule
  5. Endospores develop within spherule
  6. Spherule releases endospores which spread in tissue (each developing into new spherule)
30
Q

Coccidioidomycosis clinical features

A
  • Flu like symptoms, most recover
  • Pneumonia
  • Chronic, progressive lung disease, may be fatal
31
Q

Cryptococcosis

A
  • Geographically ubiquitous organism
  • In host, and isolated in lab, as large spherical yeast cells
  • Can be mycelial in environment or smaller yeast cells
  • Infection by inhalation of basidiospores
  • C. gatti causes disease in immunocompromised
  • C. neoformans infects people with HIV
32
Q

Clinical features of Cryptococcosis

A
  • Meningoencephalitis
  • Pneumonia
  • Skin lesions
33
Q

Cryptococcosis diagnosis

A
  • Direct Microscopy (India Ink stain)
  • Yeast cells have capsules which exclude ink particles, so cell appears surrounded by clear area
  • Culture is used to tell if a cryptococcal infection is C. neoformans or gattii
34
Q

Histoplasmosis

A
  • Soil & bat/bird droppings link
  • Histoplasma capsulatum thermally dimorphic
  • Survival and multiplication in phagocytes
  • Microconidia become air borne and are inhaled
  • Disease of lungs
  • May disseminate to many organs via infected macrophages
35
Q

Categories of mycoses

A
  • Superficial
  • Cutaneous
  • Subcutaneous
  • Systemic
  • Opportunistic

MICR2209 (26 decks)

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