Fungi and fungal diseases

Fungi are diverse microorganisms with great biological and medical significance – they perform important functions, but can also cause serious diseases.

Fungi
Fungi (Mycophyta) are eukaryotic microorganisms with a rigid cell wall and a classic cell nucleus. They are immobile, contain no photosynthetic pigments and feed heterotrophically on organic substances.

Of the more than 100,000 known species of fungi, only about 300 have been identified as pathogens in humans, and less than a dozen of these cause over 90% of all fungal infections – mostly in people with weakened immune systems.

Basic forms of fungi

There are two main forms:

• Hypha: Tubular, branched structure (2–10 µm); basic element of filamentous fungi.
• Mycelium: network of hyphae.
• Fungal thallus: entirety of the mycelium; also referred to as a fungal colony.
• Yeast: round or oval cells (Ø 3–10 µm); basic form of unicellular fungi.

Reproduction and metabolism
Fungi form special reproductive organs, known as reproductive organs or fruiting bodies. There are both sexual and asexual fruiting bodies.

Since fungi depend on organic carbon sources, their metabolic processes play an important role in industry and the environment. They are used positively, for example, in the production of cheese, beer, bread, and antibiotics. On the other hand, fungi can also cause damage to food, wood, textiles, and plants.

Fungal diseases
Fungal diseases in humans mainly include fungal allergies, fungal poisoning (mycotoxicosis), and fungal infections (mycoses).

Fungal allergies
Fungal spores in the air we breathe can contain allergens that cause excessive reactions in sensitive individuals, such as allergic rhinitis, bronchial asthma, or pneumonia. Many of these diseases are occupational, e.g. in the case of “farmer's lung”.

Fungal toxicosis
Some molds, such as Aspergillus species, produce mycotoxins (e.g. aflatoxins), which are ingested through moldy food. Aflatoxins may be linked to certain types of liver cancer.

Mycoses
Mycoses are fungal infections and are divided into the following classes:

• Primary mycoses: Spores enter the lungs via inhaled dust and cause primary pulmonary mycoses – rare and not widespread in Central Europe.
• Opportunistic mycoses: Occur in immunocompromised individuals and affect the skin, mucous membranes, or internal organs. Caused by yeasts and molds.
• Subcutaneous mycoses: Fungi from the soil enter the connective tissue through skin lesions. Occur mainly in tropical and subtropical regions.
• Cutaneous mycoses: Affect the skin, hair, or nails.