Q6: Parasitism & Medical Mycology Flashcards
Parasitism.
A symbiosis where one partner is benefitted while the other is negatively impacted.
Pathogen.
A parasite that causes perceptible damage to its host.
Mutualism.
A symbiosis where both partners benefit.
The three broad categories of parasites.
Necrotrophs, biotrophs, and hemibiotrophs.
Necrotroph.
A parasite that kills the cells of a living host and uses the remains for food. Many can live as saprobes and may not require living hosts.
A parasite that kills the cells of a living host and uses the remains for food. Many can live as saprobes and may not require living hosts.
Necrotroph.
(T/F) Necrotrophs require a living host.
False; many can live as saprobes without a living host.
Biotroph.
A parasite that derives nutrition only from living cells, often not killing the host or its cells. Often obligate.
A parasite that derives nutrition only from living cells, often not killing the host or its cells. Often obligate.
Biotroph.
(T/F) Biotrophs require a living host.
True; often an obligate symbiosis.
Hemibiotroph.
A parasite that requires a living host to initiate infection, but then can live as a necrotroph.
A parasite that requires a living host to initiate infection, but then can live as a necrotroph.
Hemibiotroph.
Ecological roles of parasites.
Population regulation and community structure mediation.
(T/F) Hemibiotrophs require a living host.
True; required to initiate infection.
The ecological role of Phellinus weirii.
A wood decay fungus that rots the roots of mountain hemlock and eventually kills individual trees, opening large gaps in the forest. Within these gaps, pine and fir trees regenerate.
Approximately _____% of plant pathogens are fungi.
75%
The three elements that interact in the disease triangle to produce a disease.
The parasite, a susceptible host, and a conducive environment.
In most cases, the pathogen evolution is geared towards (increased/reduced) virulence.
Reduced.
What has caused the increased mortality of rubber trees due to rubber leaf blight?
Plantation planting; monoculture.
Exotic pathogen species.
A new pathogen that has not co-evolved with a host.
Important North American examples of exotic pathogens.
Chestnut blight, white pine blister rust, and Dutch elm disease.
Necrotrophs often require _____ to enter a plant.
Wounds.
Specialized structures that biotrophs often use to acquire nutrients from host cells.
Haustoria.
Hemibiotrophs can be seen as _______.
Obligate necrotrophs.
(T/F) Hemibiotrophs can have a free living saprobic stage.
False (or if they do they are not efficient).
(T/F) Necrotrophs can have a free-living saprobic stage.
True.
Hemibiotrophs penetrate a living plant like a ______ but then grow like a ______.
Biotroph; necrotroph
Phytophthora species are well known ______.
Hemibiotrophs.
Common mechanisms that some fungi use to capture microanimals.
Constricting rings, adhesive hyphae, and projectiles.
Many fungi that feed on animals are primarily ______.
Saprobes, receiving only supplemental nutrition from predation.
Oyster mushrooms parasitize _______.
Nematodes.
Entomophthora spp. are _______.
Insect parasites.
Cordyceps spp. are ______.
Obligate biotrophs of insects.
(T/F) Fungal biological control agents have proven generally efficiency in controlling agricultural pests.
False; infection is very dependent on environmental factors that differ from natural settings.
The exotic oomycete Aphanomyces astaci has devastated populations of _____ in Europe.
Crayfish.
A disease caused by Aspergillus sydowii has significantly reduced ______ populations.
Coral.
A terrestrial fungus that has become the cause of a major marine coral disease.
Aspergillus sydowii.
Many vertebrate pathogens are _____ and are primarily ______, while others are ______.
Facultative; saprobes; obligate commensals.
Candida albicans is primarily _______ but can become ______.
An obligate commensal; parasitic.
Batrachochytridium dendrobatides has been associated with massive die-offs of ______.
Frogs.
Batrachochytridium dendrobatides kills frogs by _______.
Disruption of osmoregulation on the skin.
Chitinases.
Enzymes produced by necrotrophic mycoparasites to attack fungi.
Enzymes produced by necrotrophic mycoparasites to attack fungi.
Chitinases.
Rozella is an example of a ______ parasite of chytrids.
Biotrophic.
The three main barriers to fungal infection in the human body.
Skin, body temperature, and immune system.
As a result of the major barriers to fungal infection of the human body, most human pathogenic fungi have developed one of these three features.
Ability to use keratin as a nutrient source, ability to grow at 37C, and dimorphic growth (switch to yeast growth at 37C).
The two main reasons there are few therapeutic options for fungal infection in humans.
Difficult to find drugs that impact fungi without strong side-effects (humans more closely related to fungi compared to bacteria/viruses), and there has been little incentive for pharmaceutical companies to develop antifungal drugs due to how rare fungal infections have been until very recently.
The leading causes of the increased prevalence of human fungal infections.
AIDS, cancer treatments, organ transplants, diabetes, and antibiotics.
Around ___-___% of childhood airway allergies are due to fungi.
8-25%.
Common fungi responsible for human allergies include:
Alternaria, Cladosporium, Aspergillus, and Penicillium.
Mycotoxins.
Fungal-produced toxins that may be harmful to humans.
Mycotoxins are considered to be _______.
Secondary metabolites.
Secondary metabolites.
Metabolites not essential for growth in pure culture.
Secondary metabolite production tends to greatest at what stages of growth?
After growth rate slows and during a “stationary phase.”
The ecological role of secondary metabolites among saprobes.
Competition between saprobes; invading or protecting substrates.
It is estimates that as much as ____% of the world’s food supply is contaminated by mycotoxins.
25%
Aflatoxin is produced by ______.
Aspergillus flavus.
Aspergillus flavus produced which mycotoxin?
Aflatoxin.
Aspergillus flavus is associated with what types of crops?
Nuts, legumes, and grains.
Acute aflatoxin poisoning is rare in humans for what reason?
We tend to eat a varied diet that does not result in us consuming a large amount of aflatoxin at once. Generally only a major concern in poorer countries suffering through drought (food scarcity, forced to eat contaminated grain).
Chronic exposure to low levels of aflatoxin has been associated with _____.
Liver cancer.
Aflatoxin is primarily managed through ______.
Quality control during storage. Sorting, managing moisture levels below 12%.
Stachybotrys chartarum is known as the ______.
Toxic mold.
The toxic mold.
Stachybotrys chartarum.
Stachybotrys chartarum grows primarily on ____ and has been associated with mold in ______.
Cellulose; houses.
The two main types of mycotoxins produced by Stachybotrys chartarum.
Trichothecenes and cyclosporins.
Trichothecenes.
A type of mycotoxin produced by Stachybotrys chartarum associated with sore throat, fatigue, and dermatitis.
Cyclosporins.
A type of mycotoxin produced by Stachybotrys chartarum associated with immune system suppression.
A type of mycotoxin produced by Stachybotrys chartarum associated with sore throat, fatigue, and dermatitis.
Trichothecenes
A type of mycotoxin produced by Stachybotrys chartarum associated with immune system suppression.
Cyclosporins
Stachybotrys chartarum is a part of a broader condition known as ______.
Sick building syndrome.
The most well-characterized mushroom toxins are found in the genus _____.
Amanita.
____% of all mushroom-related deaths are associated with Amanita phalloides.
95%.
95% of all mushroom-related deaths are associated with what species?
Amanita phalloides.
The two types of mycotoxins produced by deadly Amanita species.
Amatoxins and phallotoxins.
In contrast to other toxic mushrooms, what is unique about the symptoms of Amanita poisoning?
6-12 hour delay, stopping after a few hours to return after 24-36 hours. May cause jaundice or liver damage/failure.
Mycoses.
Fungal diseases in which the fungus invades human cells to cause disease.
Fungal diseases in which the fungus invades human cells to cause disease.
Mycoses.
Superficial mycoses.
Mycoses that tend to be found on the outer part of the body on skin, hair, or nails.
Mycoses that tend to be found on the outer part of the body on skin, hair, or nails.
Superficial mycoses.
Subcutaneous mycoses.
Mycoses that involve the subcutaneous tissues, muscle, and fascia, often resulting from a piercing trauma to the skin.
Mycoses that involve the subcutaneous tissues, muscle, and fascia, often resulting from a piercing trauma to the skin.
Subcutaneous mycoses.
Systemic (invasive) mycoses.
Mycoses in which fungi invade internal parts of the body such as lungs, liver, lymph systems, or other organs, often growing as yeasts.
Mycoses in which fungi invade internal parts of the body such as lungs, liver, lymph systems, or other organs, often growing as yeasts.
Systemic (invasive) mycoses.
Dermatophytes.
Fungi that cause superficial infections of the skin, hair, and nails.
Fungi that cause superficial infections of the skin, hair, and nails.
Dermatophytes.
Common dermatophytes include:
Aspergillus spp., Candida spp., and Trichophyton spp.
What fungi cause the skin infection Tinea?
Trichophyton spp.
Yeast infections are associated with ______.
Candida albicans.
Candida albicans is associated with what common disease?
Yeast infections. Also thrush.
Thrush.
An infection of the mucus membranes of the oral cavity caused by Candida albicans.
An infection of the mucus membranes of the oral cavity caused by Candida albicans.
Thrush.
Pneumocystis carnii is the cause of what disease?
Pneumonia.
Pneumonia is caused by _____.
Pneumocystis carnii.
The large rise in pneumonia cases in the last century has been associated with _____.
AIDS/HIV
Valley fever is caused by ______.
Coccidioides immitis.
Coccidioides immitis causes what disease?
Valley fever.
Histoplasma capsulatum.
A thermally dimorphic fungus that infects the lungs with airborne spores before growing as a yeast. Severe infections are often mistaken for tuberculosis. Systemic dissemination is often fatal.
A thermally dimorphic fungus that infects the lungs with airborne spores before growing as a yeast. Severe infections are often mistaken for tuberculosis. Systemic dissemination is often fatal.
Histoplasma capsulatum.
