BOTANY WITH BASICS OF HYDROBOTANY - 2010

8. FUNGI

8.1. General characteristics of Fungi

There are about 100 thousand species of fungi. This is an ancient group of living organisms, which is still undergoing active speciation today.

Fungi are a distinct group of cellular eukaryotic organisms that share similarities with both plants (reproduction via spores, absorption of nutrients driven by osmotic pressure differences, etc.) and animals (heterotrophic Nutrition, metabolic features). The science that studies the Structure, reproduction patterns, and diversity of fungi is known as mycology.

The body of most fungi consists of a mycelium, or thallus, made up of fine, tubular filaments called hyphae. The mycelium can be unicellular (non-septate) or divided by partitions into many Cells (septate). There are pores within these septa. Fungal cells have Cell walls composed mostly of Polysaccharides and Chitin, except for oomycetes, whose walls are made of Cellulose. The cells contain Cytoplasm, vacuoles, and one or more nuclei. Reserve nutrients include volutin, Lipids, Glycogen, and Proteins. Fungi lack Plastids. In some species, pigments are present in the cytoplasm, vacuoles, or cell walls. Fungi contain A wide variety of Enzymes.

Fungi reproduce via vegetative, asexual, and sexual means. Vegetative Reproduction occurs through fragments of the mycelium, budding, sclerotia, oidia, and chlamydospores; asexual reproduction occurs via spores, zoospores, sporangiospores, and conidia; sexual reproduction occurs through isogamy, heterogamy, oogamy, zygogamy, gametangiogamy, and somatogamy. During sexual reproduction, some fungi form fruiting bodies—interwoven networks of hyphae (plectenchyma). In everyday language, these fruiting bodies are what we call "mushrooms," although in reality, they are merely a part of the fungal Organism that forms at a specific developmental stage, and they are not present in all species. The rest of the fungus remains embedded in the substrate on which it grows.

Fungi feed on preformed organic matter, absorbing it from dead remains (saprotrophic fungi) or living organisms (parasitic fungi). Fungi inhabit soil and Water, plants and animals, and a wide variety of organic nutrient substrates. In addition to nutrients, fungi require moisture and warmth (1...40°C) to survive normally. With few exceptions, they are aerobic organisms.

By mineralizing the organic remains of dead organisms, fungi perform a vital function by participating in the global cycling of nutrients. At the same time, parasitic fungi infect plants and animals, causing diseases that inflict significant damage on agriculture and, in particular, fish farming. Lower vertebrates—such as fish, amphibians, and reptiles—are primarily parasitized by lower fungi, including chytrids and basidiobolids, which cause superficial lesions and affect the respiratory and digestive systems. Species such as Saprolegnia, Achlya, Aphanomyces, Pythium, Leptomitus, and Allomyces infect adult fish. Fish weakened by other stress factors are the most susceptible to infection.

Some fungi produce edible fruiting bodies—these are the lamellar and tubular Basidiomycetes.

8.2. Classification of Fungi

Fungi are divided into six classes: Chytridiomycetes, Oomycetes, Zygomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes. The first three classes, characterized by The formation of a plasmodium or a non-septate mycelium, are grouped together as Lower Fungi. The remaining three classes make up the group of Higher Fungi, which are characterized by a septate mycelium.

The Class Oomycetes includes the order Saprolegniales. These are freshwater and marine fungi that live either as saprotrophs on animal carcasses and other organic substrates, or as parasites of Algae, aquatic fungi, fish roe, fry, and weakened fish (Fig. 8.1). Some species inhabit damp soil.

In Representatives of the genera Saprolegnia and Achlya, the mycelium is well developed. Finer, branching hyphae anchor into the substrate, while the bulk of the thicker, sparsely branched hyphae grow freely outward from the substrate.

In bodies of water with weak currents and insufficient aeration, saprolegnian fungi infect fish eggs as well as weakened and injured fish. The colonization of a fish's body by the fungus is typically preceded by a sharp Temperature change or its gradual drop below the tolerance limit for that particular fish species. Diseased fish rub against objects and become sluggish. A light white coating then appears on their body, which, as it grows, develops into fluffy fungal tufts.

The primary method of controlling saprolegniasis is ensuring adequate water aeration and cleanliness.

The class Zygomycetes includes mucoraceous Molds, whose mycelium consists of well-developed, branching hyphae. Mucor fungi frequently grow on various feeds and food products, causing them to spoil (Fig. 8.2).

The class Ascomycetes includes Yeasts (brewer's, wine, baker's yeasts, etc.), which carry out Fermentation and are used in food production (Fig. 8.3). The ascomycetes also include Claviceps purpurea, a parasite of flowering plants known as ergot.

Basidiomycetes are higher fungi with a multicellular mycelium. This group includes plant parasites, soil saprotrophs, cap fungi, mycorrhizal fungi, and wood-destroying fungi.

The order Holobasidiales includes the wood-destroying tinder fungus (Fomes fomentarius), as well as edible species such as the golden chanterelle (Cantharellus cibarius), penny bun (Boletus edulis), cultivated mushroom (genus Agaricus), slippery jack (Suillus luteus), bay bolete (Xerocomus badius), orange-cap bolete (Leccinum quercinum), and others.

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Fig. 8.1. Saprolegnia:

1 — zoosporangium, 2 — release of zoospores,

3 — proliferation of zoosporangia,

4 — Fertilization, 5 — oogonium,

6 — antheridium,

7 - fish infected with Saprolegnia

Fig. 8.2. Mucor: a - mycelium with sporangiophores and sporangia, b - sporangium, c - sexual process (zygogamy), d - mature zygospote and its germination

Fig. 8.3. Yeasts:

a - budding Yeast cells; b - ascus with ascospores

Poisonous mushrooms (such as the Devil's bolete, or satanic bolete) cau

se digestive disorders and even death.

Smut fungi (Ustilago avenae, U. hordei, U. nuda, U. maydis, Tilletia tritici) attack cereal crops and cause severe agricultural damage, reducing yields in certain years by 20–30% or more. Consuming infected plant parts can cause poisoning in humans and animals. Rust fungi parasitize ferns, gymnosperms, and angiosperms. Infected plant parts typically exhibit rusty-brown stripes or spots. The CAUSATIVE AGENT OF cereal stem rust, the fungus Puccinia graminis, begins its life cycle on barberry before its spores spread

to cereal crops.

Deuteromycetes (imperfect fungi) include Penicillium molds (Penicillium notatum, P. chrysogenum), which produce the antibiotic penicillin. Penicillins were the first fungal Antibiotics to

be produced on an industrial scale. Other fungal antibiotics used in human and veterinary medicine are now also known (such as griseofulvin, fumagillin, etc.).

METABOLISM/35.html">Selection/41.html">Review Questions and Tasks

1. What is the STRUCTURE OF FUNGI? How do fungi reproduce?

2. How are fungi classified? Name the most important representatives of the classes.

3. Describe The Role of fungi in nature and human life.