Intro Lecture Flashcards
What are the 3 fungal lifestyles?
Saprophytic
Parasitic
Mutualistic/Sybiotix
What is saprophytic lifestyle?
Decomposition of organic matter.
What is mutualistic/symbiotic lifestyle?
Non-pathogenic, obligatory associations with other microorganisms
What fungal lifestyle is of veterinary importance?
Parasitic
Are yeasts unicellular or multicellular?
Unicellular
Are moulds unicellular or multicellular?
Multicellular
What are three structural features of fungi?
Capsules, Cell Wall, Cytoplasmic Membrane
What does a capsule provide?
Protection against phagocytosis. May possess antigens - stimulate an immune response in the host.
What is a capsule made up of?
Slime = loose polysaccharide gelatinous sheath deposited around the cell wall.
What is the cell wall made up of?
Net of polysaccharide microfibrils (chitin, glucan, mannan and cellulose). Cross linked by proteins/glycoproteins.
What does the Fungi’s cell wall determine?
Morphology
What is the cytoplasmic membrane?
Bilayered membrane containing sterols. Dissimilar to bacterial membranes, similar to other eukaryotes.
What is mycelia?
A feeding system of colourless tubules.
What are mycelium components of?
Thallus
What is hypha?
A single branch of the mycelium. (Individual filament of the filamentous structure)
What are vegetative mycelia?
Hyphae and mycelia embedded for support and nutrition in the surface of the substrate (soil, bread, skin) on which the fungus grows.
What are aerial hyphae or conidiophores?
Fungal hyphae that grow above the the surface where the terminal portions often differentiate into reproductive spore-bearing structures.
What are ascospores?
Spores produced as a result of sexual reproduction and are enclosed in microscopic sacs called asci.
What are conidiospores or conidia?
Asexually produced spores that are produced at the tips of the hyphae often in chains or sticky masses.
What shape are yeasts?
Oval/spherical
What are the two modes of fungal replication?
Asexual and sexual.
What occurs during sexual replication?
Fusion of 2 hyphal nuclei - followed by meiotic division. Resulting haploid spore (meiospores) = sexual spore.
What is the sexual stage of replication referred to as?
Teleomorphic or perfect state.
What occurs during asexual replication?
Mitosis of a single parent nucleus (spores or conidia). Sporulation or germinations, budding of yeast cells, fragmentation of hyphae. Conidia arise by budding off from a conidiophore or by differentiation of preformed hyphae. Asexual spores are commonly formed by cleavage of a sporangium.
What are the 3 morphological types fungi are classified into?
Yeasts, moulds, dimorphic.
What are the 3 main mechanisms of fungal disease in animals?
Tissue invasion, toxin production, induction of hypersensitivity.
What are the general features of tissue invasion?
Superficial mycoses, subcutaneous mycoses and tumour like granulomas.
What are the general features of toxin production?
Mycotoxicosis
What are the general features of induction of hypersensitivity?
Immune complex induced tissue injury.
What are the routes of entry of fungal diseases?
Endogenous commensals and exogenous fungal spores.
What are endogenous commensals?
Already present on host in low numbers.
How do exogenous fungal spores get into the host?
Deposited onto host, inhaled by host, ingested by host. Wounds, mucosa, macerated skin.
What are the two laboratory test for diagnosis and identification of fungal infections?
SDA- Sabouraud’s Dextrose Agar
DTM- Dermatophyte Test Medium
What are the features of SDA?
pH 5.6 -slightly acidic pH helps to inhibit bacterial growth. Antimicrobials may be included.
What are the features of DTM?
SDA with a pH indicator. Red colour change with dermatophytes.
How do you grow fungi in the lab?
Culture two plates. One at 25C and one at 37C. Slow growers- will take a few days (yeast) and up to 3-6 weeks (dermatophytes). Examine two times a week.
Are fungi eukaryotes?
Yes- they have a true nucleus
How do fungi obtain energy?
No chlorophyll - obtain energy by breakdown of dead or living organic matter.
Heterotrophic
Where will fungal disease often be present?
In immune compromised animals.
What is a dispersal spore?
Produced in large numbers and separate completely from parent mycelium. Launched by specialist hyphae. Germinate readily in available nutrients.
What are survival spores?
May not completely separate from mycelium. Tend to be large. Retain substantial nutrient reserves. Germination only occurs after slow waning of dormancy or in response to a specific stimulus.
How do yeasts reproduce?
Budding (blastospores)
Are moulds strict aerobes?
Yes
How do moulds grow?
Apical growth occurring at the tip of the hyphae. “Extension Zone” allows fungus to utilise distant food sources.
What are the three zones of a mature mould colony?
Peripheral extension zone, fruiting/sporing zone and central aged zone.
How can dimorphic fungi exist?
In hyphal/filamentous form or yeast form.
What is the temperature dependent morphology of yeasts and moulds?
Yeast = 37C (body temperature) Moulds = 25C (room temperature)
