Mycology Overview and Its Importance

Mycology

• Mycology is the study of fungi, including yeasts and molds.
• It examines their genetic and biochemical properties.
• It analyzes their taxonomy and human uses (e.g., tinder, medicine, food like beer, wine, cheese, mushrooms, and entheogens).
• It investigates fungal dangers like poisoning and infection.

Fungal Characteristics and Roles

• Many fungi produce toxins, antibiotics, and other secondary metabolites (not essential for survival). Examples include antibiotics and pigments.
• Fungi are crucial for life on Earth as symbionts, like in mycorrhizae, insect symbionts, and lichens.
• Many fungi break down complex organic biomolecules, such as lignin (a wood component), xenobiotics, petroleum, and polycyclic aromatic hydrocarbons.
• This decomposition plays a critical role in the global carbon cycle.

Fungal Impacts and Classifications

• Fungi, and some organisms formerly classified as fungi (oomycetes and slime molds), are important economically and socially, causing diseases in animals (like histoplasmosis) and plants (like elm disease and rice blast).
• Some fungi cause diseases in humans and other organisms.
• The study of pathogenic fungi is termed medical mycology.
• Actinomycetes are a large group of prokaryotic organisms resembling fungi, but are bacteria, with threadlike cells (hyphae) forming branching networks (mycelia).

Fungal Structure

• The main body of most fungi is made up of branching, colorless threads called hyphae.
• Vast numbers of hyphae intertwine to form a tangled web called a mycelium.
• Fruiting bodies (such as mushrooms) are thick hyphae collections.
• Fruiting bodies vary in size from tiny to large and eye-catching structures.
• They are usually produced at the surface of the food source to allow spores to be shed and dispersed by wind, water, or animals.

Pathogenic Fungi Examples

• Candida species are important human pathogens, often causing opportunistic infections in immunocompromised hosts (e.g., transplant patients, AIDS sufferers, cancer patients).
• Candidiasis infections are difficult to treat and can be life-threatening (30-40% mortality rate).
• Aspergillus spores are common in the environment.
• Aspergillus fumigatus and Aspergillus clavatus can cause allergic disease.
• Some Aspergillus species cause disease in grain crops (especially maize), producing mycotoxins like aflatoxin.
• Aspergillosis is a group of diseases caused by Aspergillus. Symptoms include fever, cough, chest pain, and breathlessness. Typically only those with weakened immune systems or other lung conditions are affected.

More Pathogenic Fungi Examples

• Cryptococcus neoformans can cause severe meningitis and meningoencephalitis in HIV-infected and AIDS patients.
• Most Cryptococcus species live in the soil and rarely affect humans.
• Histoplasma capsulatum causes histoplasmosis (mostly lung disease) in humans, dogs, and cats.
• Histoplasma is most prevalent in the Americas, India, and Southeast Asia. Infections are typically from inhaling contaminated air.
• Pneumocystis jirovecii causes pneumonia in people with weakened immune systems (e.g., premature babies, the elderly, and AIDS patients).