MICRO EXAM 4-FUNGI

mycology

study of fungi

Fungi Characteristics

• Diverse

• Chemoheterotrophs

• Saprophytes (Decompose dead organic matter)

• Aerobic or facultative anaerobic

• Unicellular or multicellular

Nutritional Adaptations

• Prefer pH of 5

• Resistant to osmotic pressure

• Can grow in low moisture content

• Requires less N

• Can metabolize complex carbohydrates

Fungi Terms, Characteristics

• Asexual or sexual reproduction

• Molds, mushrooms, yeasts

• Teleomorphic fungi: Produce sexual and asexual spores

• Some are anamorphic: Lost ability to sexually reproduce

• Some are pathogenic, some beneficial

Mold and mushroom structure

• The fungal thallus (body)

• hyphae filaments

• mycelium: a mass of hyphae

différent types of hyphae

• Septate hyphae: contain cross-walls

• Coenocytic (aseptic) hyphae: do not contain septa

• Vegetative hyphae = for nutrients

• aerial hyphae = reproduction

Yeasts

• Nonfilamentous and unicellular

• Budding yeasts divide unevenly

• Fission yeasts divide evenly

• Dimorphic fungi: Yeast like at 37°-C and mold like at 25°-C

Fungi Cell Walls

• Composed of glucans, mannans, glycoproteins, trehalose, chitin

Asexual Reproduction

• Asexual spores: mitosis, cell division, form hyphae

1. Mitosis while budding (smaller daughter cell)

2. form new cell wall between 2 daughter cells

Types of asexual spores:

• Conidiospore: not enclosed in a sac

• Arthroconidia: fragmentation of septate hyphae

• Blastoconidia: buds of the parent cell

• Chlamydoconidium: spore within a hyphal segment

• Sporangiospore: enclosed in a sac

Sexual Reproduction spores

• Sexual spores

• Homothallic: self-fertile, sexually reproduce in a culture derived from a single spore or cell vs heterothallic: self-sterile, need another individual

• Three phases of sexual reproduction:

• Plasmogamy: haploid donor cell nucleus (+) penetrates cytoplasm of recipient cell (−)

• Karyogamy: + and − nuclei fuse and form diploid zygote

• Meiosis: diploid nucleus produces haploid nuclei (sexual spores)

Terms for Fungal Diseases

• Mycosis: fungal infection

• Superficial mycoses: localized (e.g., hair shafts)

• Cutaneous mycoses: affect hair, skin, and nails

• Subcutaneous mycoses: beneath the skin

• Systemic mycoses: deep within the body

• Opportunistic mycoses: fungi harmless in normal habitat but pathogenic in a compromised host

All fungi evolved from

flagellated ancestor, most lost flagella for spore dispersal

Medically Important Fungi

• Microsporidia
• Zygomycota (Murcomycota)
• Ascomycota
• Basidiomycota

Microsporidia

• No sexual reproduction hasbeen observed to date

• No mitochondria, peroxisomes,centrioles

• Obligate intracellular parasites

• Enterocytozoon bieneusi (diarrhea, pneumonia)

• Encephalitozoon cuniculi (encephalitis, nephritis)

• immunocompromised

Zygomycota (Mucoromycota)

• Rhizopus species

• Coenocytic hyphae(continuous)

• Produced asexually: sporangiospore

• Produced sexually: zygospore: Forms when nuclei of two similar cells fuse

• Free-living saprophytes

• Food industry, food spoilage (Black bread mold)

• Mucurmycosis (immunocompromised)

Mucormycota:

Mucormycosis

• Black fungus

• Serious, rare

• Immunocompromised

• Sinus/lungs; skin injury

• Spores inhaled, contaminated food, or open wounds contaminated

• COVID-19 associated mucormycosis

Ascomycota

• Sac fungi; septatehyphae

• Produced asexually:conidiospore

•Produced sexually: ascospore: Nuclei morphologically similar or dissimilar fuse in a sac like ascus

Ascomycota: Claviceps purpurea

• C. purpurea parasite of rye, grasses

• Ergot, ergotism

• Toxic to humans that eatgrain infected with C.purpurea

• St. Anthony's fire

• Speculated associatedwith Salem witch trials

• Active ingredient is lysergic acid diethylamide (LSD)

• Severe vasoconstriction(gangrene); convulsions,delusions, reprod. issues

Ascomycota: Aspergillus fumitagus

• Ubiquitous in homes/work

• Inhalation, in respiratory tract

• Allergic responses, severe asthma

• Aspergillosis: May form "fungalballs" in lungs

• Invasive if pulmonary disease spreads

Ascomycota: C. albicans

• Pseudohyphae, incomplete budding

• Normal inhabitants of microbiotain GI tract, respiratory tract,vagina

• Opportunistic (immunocompromised, antibiotics lead to overgrowth)

• Thrush, yeast infections

• Produce toxin candidalysin (permeabilize cell membrane of host)

Ascomycota: Coccidioidomycosis immitis

• Causes coccidioidomycosis (Valley Fever)

• Immunocompromised, inhaling spores

• Soil in SW USA, Mexico, S. America

• Forms spherules in humans

• May be asymptomatic

• Fever, cough, tiredness, chills, night sweats, red/spotty rash on lowe rlegs

• Could take months to recover

Ascomycota: Tinea

• Direct contact with infected humans, animals

• Fomite (indirect contact)

• Several species in Epidermophyton, Microsporum, Trichophyton

• Tinea corporis (ringworm)

• Tinea pedis (athlete's foot)

Ascomycota: Pneumocystis pneumonia

• Pneumocysis jiroveci

• Found in wide variety of mammals

• Most humans exposed by age 3,4

• PCP: pneumocystis pneumonia

Basidiomycota

• Club fungi; septatehyphae

• Produced asexually:conidiospores

• Produced sexually:basidiospores: Formed externally on a base pedestal calleda basidium

Basidiomycota: Cryptococcus gattii, C.neoformans

• Causes Cryptococcosis

• Grow as budding yeasts in humans

• Saprophytes across world

• Birds may/may not be reservoirs

• Pneumonia, meningitis

• Enter by respiratory tract, usually cleared (if healthy)

• Immunocompromised

Antifungal mechanism of action

1. ergostral inhibition 2. Beta-glucansynthase 3. DNA/RNA synthesis, fluropyrimidine 4. Mitosis inhibition, griseofulvin

Economic Effects of Fungi: Therapies

• Ascomycota Saccharomy cescerevisiae: model organism for study

• hepatitis B vaccine

• Organic acids (citric)

• Drugs (ergometrine, cortisone,cyclosporine)

• Antibiotics (penicillin,griseofulvin)

Economic Effects of Fungi: food industry

• Saccharomyces cerevisiae:

• Fermentation (bread, wine, cheese, soy sauce)

• Diseases in plants (lose crops); important relationship with vascular roots (mycorrhizae)\

• Food spoilage (fruits, grains, veggies)

• Control pests