Ch. 24.4 Fungal Parasites and Pathogens

BSC2011

What is parasitism?

A symbiotic relationship where one organism benefits at the expense of the other (the host).

What is the difference between a parasite and a pathogen?

Pathogens cause disease and damage host tissues/physiology; parasites usually harm the host by competing for nutrients/resources but don't necessarily cause disease.

What is commensalism?

A relationship where one organism benefits while the other is unaffected.

Why are fungal plant pathogens important to humans?

They can destroy crops, reduce agricultural yields, spoil stored food, and cause famine.

How do fungal pathogens damage plants?

They can destroy plant tissues directly and/or produce toxins that damage or kill the plant.

What is ergot?

A disease of cereal crops, especially rye, caused by the fungus Claviceps purpurea.

What is ergotism?

The disease caused by consuming ergot toxins, producing symptoms such as convulsions, hallucinations, gangrene, and loss of milk in cattle.

What is lysergic acid?

An active compound produced by ergot that is a precursor of LSD.

Name common fungal pathogens that affect crops.

Smuts, rusts, powdery mildew, downy mildew, and gray rot.

What is Botrytis cinerea?

A fungus that causes gray rot in grapes and other crops.

What is noble rot?

A controlled infection by Botrytis that can produce highly prized dessert wines.

What is a mycosis?

A fungal disease caused by infection and direct damage from fungal growth and infiltration.

What is mycotoxicosis?

Poisoning caused by eating food contaminated with fungal toxins (mycotoxins).

What is mycetismus?

Poisoning from eating poisonous mushrooms containing preformed toxins.

Mycosis =

fungus infects you

Mycotoxicosis =

fugal toxin in food

Mycetismus =

poisonous mushroon eatenresulting in illness.

Why are fungal infections difficult to treat?

Fungi are eukaryotes, like humans. Drugs that kill fungi can also damage the host’s cells.

Why dont antibiotics generally work against fungi?

Antibiotics primarily target prokaryotic cells (bacteria), while fungi are eukaryotic.

What are superficial fungal infections?

Infections that occur primarily on surface tissues, such as the skin.

What are cutaneous mycoses?

Fungal infections of the skin, hair, and nails.

What are dermatophytes?

Fungi that infect skin, hair, and nails by digesting keratin.

What is another common name for dermatophyte infections?

Ringworm

Why can dermatophytes infect skin, hair, and nails?

They produce enzymes that break down keratin, a protein found in those tissues.

What are examples of superficial fungal infections?

Athlete's foot and jock itch.

What are systemic mycoses?

Fungal infections that spread to internal organs, often entering through the respiratory system.

What is coccidioidomycosis?

A systemic fungal infection also called Valley fever, caused by inhaling fungal spores from soil/dust.

Where is Valley fever commonly found?

The southwestern United States.

How does Valley fever enter the body?

Inhalation of fungal spores.

What is histoplasmosis?

A fungal disease caused by the dimorphic fungus Histoplasma capsulatum.

What form does Histoplasma take inside humans?

It grows as a yeast in the human host.

What does Histoplasma commonly infect?

The lungs/respiratory system, causing pulmonary infection.

What are opportunistic mycoses?

Fungal infections that mainly affect people with a weakened or compromised immune system.

Why can Candida cause opportunistic infections?

Candida can normally live as part of the body's natural microbiota, but it can grow uncontrollably when immune defenses, pH, or normal bacteria are disrupted.

What infections can Candida cause?

Vaginal infections and oral thrush, among others.

Who is particularly vulnerable to opportunistic mycoses?

People with compromised immune systems, including patients with advanced AIDS.

What fungus contributes to the decline of frog populations?

Batrachochytrium dendrobatidis, a chytrid fungus.

How does Batrachochytrium dendrobatidis harm frogs?

It infects the skin, interfering with the skin's essential functions, including gas exchange.

What causes white-nose syndrome in bats?

The cold-loving fungus Pseudogymnoascus destructans.

Where does Pseudogymnoascus destructans spread?

In caves where bats hibernate.

What causes mycetismus?

Eating poisonous mushrooms containing preformed toxins.

Why is mushroom identification important?

Poisonous mushrooms can resemble edible mushrooms, and eating them can cause serious illness or death.

Pathogen vs. parasite?

Pathogens cause disease; parasites benefit at the host's expense and may harm the host without necessarily causing disease.