Microbiology and Immunology

Fungicides WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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reproduce asexually by cell division, budding, fragmentation,

or spores, although some reproduce sexually.

The main groups of fungi are chytrids, water molds,

zygosporangium-forming fungi, sac fungi, and club fungi.

Chyrids live in muddy or aquatic habitats and feed on decay-

ing plants, though some live as parasites on living plants, ani-

mals, and other fungi. Water molds, distantly related to other

fungi, play an important role as decomposers in aquatic habi-

tats. Some, however, live as parasites on aquatic animals and

terrestrial plants, including potato plants that can be destroyed

by certain types of water molds. Zygosporangium-forming

fungi also can be either saprobes, such as the well-known

black bread mold, or parasites on insects, such as houseflies.

Sac fungi, of which more than 30,000 species are known,

include the yeast used to leaven bread and alcoholic bever-

ages. However, many of these fungi also cause diseases in

plants. Club fungi, numbering more than 25,000 species,

include mushrooms, stinkhorns, and puffballs. While some

fingi are edible, others produce deadly poisons.

See alsoCandidiasis; Chitin; Fermentation; Fungal genetics;

History of the development of antibiotics; Lichens;

Winemaking

FFungicidesUNGICIDES

Fungicides are chemicals that inhibit the growth of fungi.

Fungi can attack agricultural crops, garden plants, wood and

wood products (dry rot in particular is a major problem), and

many other items of use to humans. Fungicides usually kill

the fungus that is causing the damage. Sulfur, sulfur-contain-

ing compounds, organic salts of iron, and heavy metals are all

used as fungicides. Other fungicide types include carbamates

or thiocarbamates such as benomyl and ziram, thiozoles such

as etridiazole, triazines such as anilazine, and substituted

organics such as chlorothalonil. Many non-drug fungicides

have low mammalian tolerance for toxicity, and have been

shown to cause cancer or reproductive toxicity in experimen-

tal animal studies.

Fungicides operate in different ways depending upon

the species that they are designed to combat. Many are poisons

and their application must be undertaken carefully or over-

application may kill other plants in the area. Some fungicides

disrupt some of the metabolic pathways of fungi by inhibiting

energy production or biosynthesis, and others disrupt the fun-

gal cell wall, which is made of chitin, as opposed to the cellu-

lose of plant cell walls. Chitin is a structural polysaccharide

and is composed of chains of N-acetyl-D-glucosamine units.

Fungal pathogens come from two main groups of fungi, the

ascomycetes (rusts and smuts) and the basidiomycetes (the

higher fungi—mushrooms, toadstools, and bracket fungi).

Human fungal infections, such as athlete’s foot, can be

treated by fungicides normally referred to as antifungal agents

or antimycotics. Compounds such as fluconazole, clotrima-

zole, and nystatin are used to treat human fungal infections.

See alsoCandidiasis; Mycology

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