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Introduction   Introduction to Fungi


Non-Technical Introduction to the World of Fungi and Mycology

Fungi are plant-like organisms that lack chlorophyll. Fungi are one of the five kingdoms of life. Many fungi are good and useful (edible mushrooms would be an example of these) while some cause problems (some fungi can injure plants and people). There are over 100,000 species of fungi. Mycologists are the scientists who study fungus. Medical mycologists study drugs to cure fungal infections, while agricultural and research mycologists study the industrial uses of fungi.

Since they do not have chlorophyll, fungi must absorb food from others. Since they don't use light to make food, fungi can live in damp and dark places. Fungi are supposed to "eat" things when they are dead but sometimes they start eating when the organism is still alive. That is when mycologists come in to figure out what to give to the infected patient or plant to get rid of the fungus.

Good fungus can help with many things to make the world a better place. Out of the many kinds of fungi, the ones we love to eat are mushrooms. We put them on pizza, burgers, salads, and more. During Lent, for those who give up meat, restaurants serve mushroom balls instead of meatballs on spaghetti. Fungi can even make some big things happen in food. For example, a yeast fungus called Saccharomyces cereviseae is used to make the alcohol in beer. This same fungus is used when we make bread--without its help, we would have flat bread. Without fungi, we would have piles of trash everywhere because fungi get food from our trash. They eat the trash and make it into soil. That is why we do not live in a landfill! For more on this, you might also enjoy Tom Volk's notes on fungi that are required for a Merry Christmas.

Bad fungus is just good fungus trying to do its job way too early to an organism. Most commonly, fungi cause something to happen on the skin of animals or people. This is sometimes called Ringworm, but there is no worm involved! Ringworm can also be called Tinea or Dermatomycosis. Ringworm can be found all over the world [1274]. It mostly forms on the foot and scalp. Some Ringworm is Anthropophilic. Anthropophilic means human (anthro- think of anthropology) loving (-philic), and you catch this fungus from other people. Ringworm can also be Zoophilic or Geophilic. Zoophilic means animal (zoo- just think of going to a real zoo) loving, and this is a fungus you may catch from your pet. Geophilic means earth (geo- as in geology, or the earth) loving, of course you get this one from the soil.

Ringworm is the kind of fungus that gets on the body, but some fungus just irritates the body. Fungus irritates the nose and causes allergies. Over 37 million people have allergies and many of them are caused by fungus. Buildings can also get sick. Buildings can get some fungi known as Penicillium and Stachybotrys. They float in the air and can cause watery eyes and breathing problems.

We also have smut fungi. These fungi live in the soil and are plant parasites. The name "smut" refers to the ripe galls filled with dark sooty spores that are formed when the fungus infests a plant. The most well-known smut fungus is the corn smut, Ustilago maydis. Among others are Microbotryum violaceum (formerly known as Ustilago violacea) that infects Caryophyllaceae including Silene species, and Tilletia caries that infects wheat.

The growing parts of the corn, including the base of the internodes, the base and the midrib of leaves, and young ears are susceptible to be infected by the smut fungus. Eventually, the fungus produces tumor-like masses on the infected plant which are covered with silvery-white or greenish-white layer. These masses are filled with powdery, darkened spores. These darkened spores, also known as teliospores, are resting spores and help the fungus to resist dry climates and low temperatures. They are either splashed by rain or blown by heavy winds. The teliospores germinate in spring and produce basidiospores which are the actual infective particles.

The smut fungus is not all bad! While it is a remarkable hazard for the farmers, it is consumed as a tasty food in some parts of the world! Smut fungus is sold canned in Mexico and America and is known as "cuitlacoche" or "huitlacoche" in Mexico.

You may also want to visit other websites for more information on smut fungi:

A discussion from whyfiles.com, including a recipe for smut soup!
A discussion of smuts from Tom Volk's website
A teaching example for the National Association of Biology Teachers

To cure fungal infections, mycologists use a drug from one of these families of drugs: Allylamines, antimetabolites, azoles, glucan synthesis inhibitors, polyenes, and others.

Finally, fungi can be helpful and not helpful, but they all are important and required in life. Fungi are one of the earth's big recyclers. Without them we could not live, and sometimes humans die because of them, but they are very important and required in life.

(Editorial note: The preceeding section was contributed by a 6th grader who prepared the text as an English class writing assignment. If you or your class prepare fungus-related materials that are suitable for the web and that might be of interest to others, please contact us. We'd love to discuss posting your work!)

Somewhat More Technical Introduction to the Fungi

All living things can be classified into one of five fundamental Kingdoms of life, and the term fungus refers generically to all members of the Kingdom Fungi. There are more than a million species of fungi, but only about 400 cause diseases relevant to man, animals, or plants. These organisms are the subject of this web site. The majority of the pathogenic species are classified within the Phyla Zygomycota, Basidiomycota, Ascomycota, or the form group Fungi Imperfecti. Fungi (the singular form is 'fungus'), including those pathogenic to humans and animals, are eukaryotic microorganisms.

Classically, there are two broad groups of fungi: yeasts and moulds. Note that mould is spelled with a 'u'. While not mutually exclusive, mould spores germinate to produce the branching filaments known as hyphae. Yeasts, on the other hand, are solitary rounded forms that reproduce by making more rounded forms through such mechanisms as budding or fission. For more details on fungal classification, see our discussion of Taxonomy and Nomenclature.

Typical yeast. Note the multiple solitary small rounded forms. These are yeast because these rounded forms are the actively dividing, growing, and metabolizing form of the fungus. Reproduction occurs via budding (or fission) and the colonies are typically moist and mucoid.
Typical mould. Note the interwoven filamentous forms known as hyphae. The mass of hyphae is called a mycelium. The hyphae grow by elongation at their tips. At the ends of some of these hyphae are rounded forms that could be confused with yeast, but that are instead called conidia or spores. These rounded fungal forms are relatively metabolically inactive. They can be likened to seeds--they are alive, but they're not doing much. Rather, they are looking for a good place to live.

The nuclei of all fungi, like that of other eukaryotic organisms, contains a nucleolus and several chromosomes that are bound by a nuclear membrane. Hyphal cells in septate hyphae may be uninucleate, binucleate, or multinucleate. For the most part, cellular and nuclear division are independent events, especially with respect to vegetative growth. As in other eukaryotic organisms, fungi have mitochondria, 80S ribosomes, and centrioles.

The cell wall of fungi consist of chitin, chitosan, glucan, mannan, other components in various combinations. Fungi are carbon heterotrophs, therefore they require preformed organic compounds as carbon sources. Fungi do not contain chlorophyll.

As an important contrast, the actinomycetes are prokaryotic gram positive filamentous bacteria. Historically, because of their microscopic morphology, some actinomycetes have been studied by medical mycologists. However, they are quite different from fungi. The actinomycetes serve as a host to bacteriophages, whereas fungi cannot serve as their host. These organisms are sensitive to antibacterial agents such as penicillin, but not to antimycotic agents such as amphotericin B, the opposite is true for fungi.

For more information about fungi, mycology, or medical mycology, please consult our:

 
Why do we spell mould with a 'u'?

We agree with Frank Odds' analysis of the etymology of these words. Mould is derived from the Norse mowlde, for fuzzy. Mold, on the other hand, is from the French molde, for shape or form. Thus, if you make gelatin in a mold, a mould might then grow on the gelatin in your mold.


The adjacent highway sign found in Wales is yet ANOTHER reason why mould is spelled with a "u." To go deeper into this issue, type "yr wyddgrug" into Google...




References

1274. Kwon-Chung, K. J., and J. E. Bennett. 1992. Medical Mycology. Lea & Febiger, Philadelphia.



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