VJ - Bad Fungi

Question 1

Why are some mushrooms poisonous?

Answer 1

As a defence against being eaten

Question 2

What are some common toxins found in poisonous mushrooms?

Answer 2

Muscimol, ibotenic acid – activates neurotransmitters to produce sedative/hypnotic, depressant and hallucinogenic effects

Question 3

What are some effects of amatoxins found in certain mushroom species?

Answer 3

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

Question 4

How are toxic moulds like Claviceps purpurea harmful to humans?

Answer 4

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?

Question 5

What is the treatment for ergot poisoning? Then vs Now

Answer 5

• Then = wine with vasodilating herbs + topical balms
• Now = vasodilators e.g., Na nitroprusside or nitroglycerine

Question 6

What are the effects of high exposure and chronic low exposure moulds on food?

Answer 6

High exposure = acute hepatic necrosis, later cirrhosis, liver cancer

Chronic low exposure = liver and gall-bladder cancer. In children also stunting, delayed development

Question 7

Treatment of mould on food infection?

Answer 7

Treatment: none (better to avoid)

Question 8

What are Rusts and Smuts including treatment? (5)

Answer 8

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

Question 9

What occurs from tree pathogens? (4)

Answer 9

Dutch Elm Disease due to Ophiostoma ulmi spread by acolytes beetles

1. Fungus overwinters as mycelium in bark and dead wood
2. Conidiophores develop sticky conidia that are spread by vectors moving through their tunnels
3. Mycelia spread rapidly later winter & spring, secreting enzymes to breakdown cell walls and allow entry to the xylem tissue
4. Fungal growth blocks the trees vascular system leading to wilting and branch death

Question 10

Dutch Elm Disease fightback (4)

Answer 10

• Destroy diseased trees
• Target bark beetles
• ‘Vaccinate’ trees with weaker fungus strain
• Breed from resistance genotypes

Question 11

What are 2 other major fungal tree pathogens?

Answer 11

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)

Question 12

Brown rot vs White rot

Answer 12

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

Question 13

Treatments for wood-decaying fungi? (4)

Answer 13

• Environmental (lower humidity, increase ventilation)
• Fungicides
• Heat
• Biological Control (competing fungus species)

Question 14

What are 6 examples of fungi pathogenic to humans?

Answer 14

1. Candidiasis
2. Dermatophytosis
3. Aspergillosis
4. Cryptococcosis
5. Fungal allergies
6. Microsporidia

Question 15

What are features of Candidiasis (3) and what is the treatment?

Answer 15

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

Question 16

What is Dermatophytosis how is it caused and what reduces the risk of it?

Answer 16

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

Question 17

What is Aspergillosis caused by and how can it be treated?

Answer 17

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

Question 18

What is the Cryptococcosis caused by and how can it be treated?

Answer 18

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

Question 19

What are fungal allergies caused by and what are features and treatments?

Answer 19

Caused by inhaling spores of moulds and mildew

• Wide range of species
• Everyone breaths in fungal spores
• Allergic reactions, asthma

Treatment: antihistamines, steroids

Question 20

What is Opportunistic mycosis ? (5)

Answer 20

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.