Fungi

Fungal Structures

First and foremost, fungi are interesting in that they can be both unicellular and multicellular. Most fungi, including molds and mushrooms are multicellular, but yeasts happen to be unicellular, possibly having evolved from multicellular ancestors. Fungi are known as “saprophyte heterotrophs,” meaning that the acquire and process carbon from an outside, organic source, specifically dead or decaying matter. Fungi are distinct in that they can be unicellular, multicellular, or dimorphic (unicellular or multicellular depending upon the conditions). Key structural components of fungi include:

○ Mycelium – Milky mass of branching, threadlike hyphae, often underground.
○ Hyphae – A long, branching, filamentous structure of a fungus that is the main mode of vegetative growth
○ Glucan – Any polymer of glucose
○ Chitin – complex polysaccharide that can also be found in the exoskeletons of arthropods; thought to be responsible for some forms of athsma in humans
○ Thallus – Vegetative body of a fungus
○ Pileus – The “cap” of a fungus most associated with mushrooms

Mechanisms of pathogenesis (how does it cause disease)

The general way that fungi cause disease in humans, is when those fungi become parasitic to the human, and sustaining infection. Interestingly, fungi rarely cause disease in healthy, immuno-competent hosts. It appears that disease results when fungi accidentally penetrate host barriers or when immunologic defects or other debilitating conditions exist that favor fungal entry and growth. Host barriers include previously uncompromised bodily systems, etc. Multiplication within the host is facilitated by virulence mechanisms (ability to grow at up to 37 degree C temperatures, capsule shape) and morphological forms (yeast, sclerotic bodes, spherules). Resistance to fungi are largely based on an innate ability to ward fungi off due to cutaneous and mucosal physical barriers. The fungi cause internal infection, which often result in aspergillosis most commonly affects the lungs, but sometimes infects other organs, cryptococcus’s which is uncommon, but can cause meningitis, and histoplasmosis

Treatment options and how they relate to the biology of the organism

The most common infections come from the fungal group tinea to which ringworm (tinea corporis), ringworm of the scalp (tinea capitis), athlete’s foot (tinea pedis) all belong. Many of the fungi are treated by damaging the cell wall of the fungus, which causes the fungal cell to die. The cell wall, which is integral to the survival of the fungus. Because people generally have a natural resistance to fungi, people are usually only given anti-fungal medication if they are very ill or have a persistent autoimmune deffiviency.

Diseases caused by fungi include:

  • Candida
  • Athlete’s Foot
  • Fungal Meningitis
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