Exam 1: Lec 1 Flashcards
What are Fungi?
Classified in this kingdom because
- Absorb food directly through their cell walls
- Reproduce sexually and asexually
- None conduct photosynthesis
- Absorptive Heterotrophs
- Saprobic, parasitic, or mutualistic:
- Digestive enzymes are secreted outside of the cell(s) to break down large molecules in the enviroment
What are Fungi?
Absorbative Heterotrophs
- Organism utilized complex material from the evironment for energy source
- Good recyclers:
- Decompose dead organisms and waste
- Also decompose cellulose, lignin and keratin
What are Fungi?
Saprobes:
Absorb nutrients from dead organic matter
What are Fungi?
Parasities
Absorb nutrients from living hosts
What are Fungi?
Mutualists
Derive nutrients from other organisms in a way that benefits both partners
Fungi are also called
Thallophytes - considered lower plants
- One cell or a relatively undifferentiated mass of cells called a thallus instead of having an organized plant body
Medical Mycology
5 things about the mycology
- Aerobic
- Eukaryotic with membrane-bound nucleus
- Cell wall of chitin
- Cell membrane
- Require carbon source
Medical Mycology
Cell wall of chitin
- 5-10% protein witn 50-60% carbohydrate polymer
- Responsible for alkai resistance
- Resist osmotic pressure
- Provides strength
Medical Mycology
Cell membrane
-Ergosterol (provitamin D2) or zymosterol (unsturated sterol, resembles ergosterol, intermediate in the synthesis of cholesterol)
Fungal Morphology
Yeast Morphology
- Unicellular
- Individual oval to round cells
- Bud to form daughter cells = Blastoconidia or blastospores
- Following mitosis, one daughter nucleus is sequestered in a small bleb outgrowth of cytoplasm that is isolated from the parent cell by the formation a a new wall
Fungal Morphology
Mold Morphology
- Multicellular
- Hyphae - long strand of cells
- With crosswalls = septate
- Without crosswalls = aseptate/ nonseptate or coenocytic
- Mass/ group of hyphae = mycelium
- Pseudohyphae (false hyphae) - Elongated blastoconidia, constriced at their point of attachment, true hyphae are not constricted
- Rapidly grow, and may be able to produce spores in fruiting structures
Mold Morphology
Hyphae
Long strand of cells,
Mycelium
Mold Morphology
Hyphae with crosswalls
Septate
Mold morphology
Hyphae without crosswalls
Aseptate/ Nonseptate or coenocytic
Mold Morphology
Mass/ group of hyphae
Mycelium
Mold Morphology
Pseudohyphae (false hyphae)
Elongated blastoconidia, constricted at their point of attachment, true hyphae are not constricted
Dimorphic fungi
- Two shaped fungi
- Fungal isolate that in response to temperature or CO2 concentration some isolates can switch between yeast morphologies and mold morphologies
- Human pathogenic isolates demonstrate different morphologies based upon temperature, thermally dimorphic
- Yeast (tissue phase) 35-37℃
- Mold (hyphal) 25-30℃
Fungal Morphology
Spores
- Single celled, reproductive structures
- Can be produce sexually or asexually reproduction
- Extremely small and easily spread:
- May cause infection upon inhalation or entry into skin abrasion
Fungal Reproduction
Asexual reproduction
- Generally faster, but less genetic diversity
- Most common - asexual spores
- Produced by one one parent only (through mitosis)
- Genetically identical to that parent
- Released from the parent hypha
Fungal Reproduction
Sexual reproduction
- Slower but greater genetic diversity
- Occurs in response to adverse environmental conditions
- Fungal mating types “+” and “-“ not male and female as hyphae are morphologically indistinguishable
- Both mating types present in the mycelium = homothallic or self-fertile
- Heterothallic mycelia require two different, but compatible, mycelia to reproduce sexually
Fungal Reproduction
Genetic diversity
Increases the probability that some members of the species have traits that will allow those individuals to survive some kind of selective pressure. Thus, making it more likely the species will prevail
Types of Infection
Intoxication
- Accidental or recreational ingestion of fungal metabolities: alkaloids, psychotropic chemicals, aflatoxin, other toxin substances
- Mycotoxicosis -
- Mycetismus- mushroom poisoning resulting from eating mycotoxins found within the intact mushroom
Types of Infection
Hypersensitivity disease
- Allergic disease
- Type 1 hypersensitivity - fungal spore exposure
- Inhalation - asthma
- Skin - eczema
- Eye/ sinus ( nasal mucous membrane) - rhinitis, hay fever
Types of Infection
Colonization
- Yeast isolates are commonly identified as normal microbiota of skin and mucous membranes
Types of Infection
Infection
- Mild and self- limiting or severe life threatening
- Opportunistic or true-pathogenic isolates regardleess of immune status
Four categories of infection
Superfical & Cutaneous
- Dermatophytes
- Affecting superficial layer of skin, hair, and nails
- Cause little or no inflammation
- Example: Trichophyton sp.
Four catergories of infection
Subcutaneous mycoses
- Localized infections of subcutaneous tissue following the traumatic implantation of the aetiologic agent
- Results in significant inflammation
- Example: Sporothrix schenckii
Four catergories of infection
Systemic mycosis
- Deep tissue and organ infection resulting from dissemination of from other area (lung, skin, tramatic injury)
- Example: Blastomyces, Cryptococcus sp.
Four catergories of infection
Opportunistic
- Immunocompromised
- Example: Aspergillus, Zygomycetes, Candida sp.
