Mycology Definition

Mycology is the study of fungi. This term was proposed by Pier Antonio Micheli in the 18th century. Fungi are organisms that lack chlorophyll and, unlike higher plants, they don’t have structures such as roots, stems, leaves, or vascular systems. Fungi can have either a single-celled or multi-celled structure. Their body is made up of numerous threads called hyphae or mycelium. They reproduce sexually or asexually, with asexual reproduction being more common. In this section, samples of skin, hair, and bodily secretions are examined microscopically and cultured to detect the presence of dermatophytes (skin fungi) and visceral fungi. We have also decided to introduce fungi to you in very simple language.

What is Mycology?

Mycology is the study of fungi, a group that includes molds and yeasts. Many fungi are beneficial in medicine and industry. Mycological research has led to the development of antibiotic drugs such as penicillin, streptomycin, and tetracycline, as well as other medications including statins (cholesterol-lowering drugs). Mycology has undoubtedly influenced your life. Whether it’s the penicillin you took to recover from illness or the mushrooms you had for dinner, you have mycology to thank. Mycologists are scientists who devote their careers to studying fungi.

Surprisingly, mycology is not a widely popular field. Most universities do not offer programs in mycology, and this trend doesn’t seem to be changing. Fungal pathogens infect over a billion people worldwide and destroy one-third of global food production. So why aren’t there more mycologists working in these areas? On the other hand, humans benefit from many species of fungi, including those we eat and use as medicines.

General Characteristics of Fungi

The key characteristics of fungi include:

– They are eukaryotic.
– They lack chlorophyll and vascular tissues.
– They have cell walls.
– They reproduce sexually and asexually.
– The fungal body can be single-celled or multi-celled.
– Fungi obtain their nutrients through absorption, while plants obtain theirs through photosynthesis, and animals acquire food by ingestion.
– Fungi are immobile, distinguishing them from animals and making them more similar to plants. A few fungi, like amoeboid fungi, move by creating pseudopodia over food surfaces. Fungal spores have flagella that allow movement, and cytoplasmic movement within cells also counts as a form of motion.

Cellular and Chemical Structure of Fungi

A large percentage of a fungal cell’s weight is water, especially in young cells, where water makes up 90% of the fresh weight of mycelium. Spores also contain a high water content (40-44%). Carbon, minerals (2-5%), phosphorus, potassium, silicon, and aluminum are among the inorganic compounds found in fungi. Nitrogen compounds (2-7%) include proteins, nucleic acids, and urea. Most of the carbon fungi absorb is used to build cell walls.

Fungal cell walls contain a high percentage of chitin. Studies on fungi have shown that chitin content varies between 2.6% and 26.2% of the dry weight of the fungus. Single-celled fungi like yeasts produce minimal chitin. The main components of fungal cell walls are glucans and mannans. Other cell wall materials include cellulose, lignin, callose, and chitosan. Some heteropolysaccharides, proteins, fats, and minerals like Mg and Ca are also common in the cell wall structure.

Modes of Fungal Nutrition

Fungi can live as saprophytes on decaying material or as parasites on other living organisms. The organism attacked by fungi is called the host. Fungi are different from plants in that they cannot produce their own food.

When given sugars such as glucose, sucrose, and maltose, fungi can use organic compounds to synthesize their required proteins. Thiamine and biotin are vitamins essential for fungi. Fungi can survive at temperatures between 0 and 30 degrees Celsius, with 20 to 30 degrees Celsius being the ideal range. The optimal pH for fungal growth is around 6, although the pH range can vary from 2 to 12.

Fungal Cytology

Fungal cells have cell walls. The nuclei are small and visible under a light microscope, with a double-layered nuclear membrane containing pores. During mitosis, the nuclear membrane does not disappear, and nucleoli remain intact, although during meiosis, the nuclear membrane and nucleoli disintegrate. The endoplasmic reticulum in fungi is composed of two parallel membranes, prominent in young cells but sparse and sometimes invisible in older cells. Ribosomes are present and scattered within the cell cytoplasm. Mitochondria are also found in fungal cells, and the Golgi apparatus, composed of dictyosome units, is present. Vacuoles are numerous in young cells but become fewer and larger in older cells. Fungal storage materials are mainly glycogen and fat.

Morphology of Fungi

Single-celled fungi consist of one cell, or their body can exist as a plasmodium—a multinucleated mass of cytoplasm without a cell wall. In most fungi, the vegetative structure is tubular and known as hyphae or mycelium. Hyphae are transparent, microscopic, and vary in diameter, growing in multiple directions, primarily from their tips. A collection of hyphae is called mycelium. Hyphae with internal walls are known as septate hyphae, while those without are called non-septate hyphae. The internal wall, known as septum, may be porous or incomplete.

Types of Vegetative Structures in Fungi

1. Prosenchyma: Consists of parallel hyphae, forming a loose connective tissue.
2. Pseudoparenchyma: Tissue with hyphae of similar width and length, forming a structure resembling plant parenchyma.
3. Stroma: A mattress-like structure with a prosenchyma structure on or within which reproductive structures develop.
4. Sclerotium: Another structure with pseudoparenchyma tissue, formed in unfavorable conditions and capable of regrowth when conditions improve.
5. Rhizomorph: A structure that forms in unfavorable conditions, commonly seen in basidiomycetes. It consists of long, parallel hyphae with a meristematic tip. The outer hyphae undergo changes in their cell walls and contents, becoming more opaque. Rhizomorphs can regrow when conditions become favorable.

Fungal Nutrition Mechanisms

– Prototrophic fungi: Fungi capable of synthesizing their required vitamins from available organic compounds.
– Auxotrophic fungi: Fungi that require pre-synthesized vitamins.
– Saprophytic fungi: Fungi that live on decaying materials. Hyphae come into direct contact with food sources, breaking them down and absorbing nutrients via diffusion. Parasitic fungi acquire nutrients either by growing on the host or by penetrating host tissues.