VJ - Bad Fungi Flashcards
Why are some mushrooms poisonous?
As a defence against being eaten
What are some common toxins found in poisonous mushrooms?
Muscimol, ibotenic acid – activates neurotransmitters to produce sedative/hypnotic, depressant and hallucinogenic effects
What are some effects of amatoxins found in certain mushroom species?
Amatoxins, found in mushrooms like Amanita, cause perforations in plasma membranes and inhibit RNA polymerase II
- Leading to cell death and symptoms like headache, dizziness, nausea, and gastrointestinal disturbances
How are toxic moulds like Claviceps purpurea harmful to humans?
Produce alkaloids such as ergotamine, affecting the:
1. The nervous system - spasms, fever, hallucinations, nausea, seizures, vomiting, unconsciousness, death
2. The vascular system- (vasoconstriction) violent burning (‘fire’), absent peripheral pulses, shooting pains in fingers and toes, gangrene, loss of limbs….death?
What is the treatment for ergot poisoning? Then vs Now
- Then = wine with vasodilating herbs + topical balms
- Now = vasodilators e.g., Na nitroprusside or nitroglycerine
What are the effects of high exposure and chronic low exposure moulds on food?
High exposure = acute hepatic necrosis, later cirrhosis, liver cancer
Chronic low exposure = liver and gall-bladder cancer. In children also stunting, delayed development
Treatment of mould on food infection?
Treatment: none (better to avoid)
What are Rusts and Smuts including treatment? (5)
Plant pathogens (all Basidiomycota)
- Smuts typically have one host
- Rusts typically have two hosts
Don’t normally kill the plant, but cause severe drop in yield
Treatment: fungicides, breed from resistant genotypes
What occurs from tree pathogens? (4)
Dutch Elm Disease due to Ophiostoma ulmi spread by acolytes beetles
- Fungus overwinters as mycelium in bark and dead wood
- Conidiophores develop sticky conidia that are spread by vectors moving through their tunnels
- Mycelia spread rapidly later winter & spring, secreting enzymes to breakdown cell walls and allow entry to the xylem tissue
- Fungal growth blocks the trees vascular system leading to wilting and branch death
Dutch Elm Disease fightback (4)
- Destroy diseased trees
- Target bark beetles
- ‘Vaccinate’ trees with weaker fungus strain
- Breed from resistance genotypes
What are 2 other major fungal tree pathogens?
Ash dieback, Hymenoscyphus fraxineus (‘A’)
- Since 2012 in UK, up to 85% mortality
Honey fungus, Armillaria mellea (‘B’)
- Long-lived, forming huge networks (largest living fungus)
Brown rot vs White rot
Brown rot attacks cellulose & hemicellulose (leaving brown)
- Produced H2O2 diffuses out and causes cubical fractures
White rot, as above + degrades lignin, which leaves cellulose crystals and hence the white colour
Treatments for wood-decaying fungi? (4)
- Environmental (lower humidity, increase ventilation)
- Fungicides
- Heat
- Biological Control (competing fungus species)
What are 6 examples of fungi pathogenic to humans?
- Candidiasis
- Dermatophytosis
- Aspergillosis
- Cryptococcosis
- Fungal allergies
- Microsporidia
What are features of Candidiasis (3) and what is the treatment?
Candida albicans and other spp
- Thrush (oral and genital)
- Dimorphic: grows as yeast and filaments
- Filaments form with Chlamydospores on Corn Meal Agar (was the diagnostic test)
Ability to filament vital for virulence – thus much research into this switch in cell morphology
Treatment: antifungals
What is Dermatophytosis how is it caused and what reduces the risk of it?
Athletes foot, ringworm, fungal nail
Trichophyton, Microsporum, Epidempphyton
Infection through:
Spores in the environment (spores viable for 1.5 yr +)
Risk factors:
Public showers, contact sports, sweating, contact with animals, obesity, and poor immunity
Reduce risks by: staying at home, getting rid of your pets and not exerting yourself !
Treatment: antifungal medications
What is Aspergillosis caused by and how can it be treated?
Caused by inhaling spores of Aspergillus spp (‘A’)
- Range of effects on lungs, sinuses, and beyond (blood stream)
- Aspergilloma: fungus ball developing in a body cavity – often the paranasal sinus. Might not show symptoms for some time
Treatment: antifungal medications
What is the Cryptococcosis caused by and how can it be treated?
Caused by inhaling the spores of Cryptococcus spp (‘B’)
- Spores found in soil, etc., and bird droppings (urea and creatine allow fungus to develop)
- Infects lungs > CNS
- Meningitis, Meningoencephalitis
Reduce risk by managing pigeons
Treatment: antifungal medications
What are fungal allergies caused by and what are features and treatments?
Caused by inhaling spores of moulds and mildew
- Wide range of species
- Everyone breaths in fungal spores
- Allergic reactions, asthma
Treatment: antihistamines, steroids
What is Opportunistic mycosis ? (5)
Many fungal infections cause no problem to healthy individuals
Resistance to fungal infection based on:
- Physical exclusion i.e., by intact skin
- Effective immune response
Thus, fungi can become a problem cases of damage, surgery or in individuals with weaker immune systems (HIV, chemotherapy, transplant, very old/young)
Examples of Saccharomyces cerevisiae in liver, heart, lungs, etc.
