Fundamentals of microbiology: classification of fungi and their structure

Science 2023

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Fundamentals of microbiology: classification of fungi and their structure
Fundamentals of microbiology: classification of fungi and their structure
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Phylogeny and classification of fungi microbiology has been changing and revising for many years, since the 19th century. The objects of research are really unusual and will be studied for a long time.

Mushrooms that grow all their lives, like plants, but at the same time crawl and devour other organisms - is this possible? Yes, modern studies of the ultrastructure of the cell, its biochemistry and physiological characteristics allow us to conclude that fungi have an intermediate position, which have the characteristics of animals and plants.

Sign

Mushrooms

Animals

Plants

Number of cores in a cell

Many, rarely one

One

One

Cell wall

Present and may contain chitin, cellulose, chitosan, glucan

No

Present and contains cellulose

The end product of nitrogen metabolism

Carbamide

(urea)

Carbamide

(urea)

Asparagine, glutamine

Carbohydrates (reserve)

Glycogen, sugar alcohols

Glycogen

Starch

Lifestyle

Fixed and loose

Free

Stocked

How mushrooms became a separate kingdom

During the time of Carl Linnaeus (early 18th century), mushrooms were considered plants. In the 20th century (in the 1940s), B. M. Kozopolyansky proposed to split the plant kingdom into sub-kingdoms:

  • Schizophyta Schizophyta (shotguns) - bacteria were referred to them.
  • Nomophyta Nomophyta (real plants) are the main representatives of the flora.
  • Mycophyta Mycophyta (mushrooms and slime molds).

In the 50s of the twentieth century, changes in the taxonomy of fungi continued: publications appeared in microbiology, or rather in the relevant literature, where the evolution of cellular microstructures was analyzed. Based on this material, Whittaker created in 1969 his own system of the world, where all life can be divided into 5 kingdoms. One of them was given to mushrooms.

A. L. Takhtadzhyan (works of 1973 and 1976) insisted on four kingdoms in the organic world, and the fourth was assigned to mushrooms. Both scientists had the highest authority inscientific circles. The issue of a separate kingdom for mushrooms was resolved. But then this taxon began to “spread.”

mushroom colony

Mushrooms of mysterious origin

The group of fungi is interesting because their historical development (phylogeny) is heterogeneous.

They differ, as it was recently found out, in biochemical composition, structure of cell membranes and genome. Since the end of the 20th century (1998), three stems of fungi have been distinguished that are evolutionarily different from each other. Each corresponds to a separate class (Cavalier-Smith):

  • Protozoa.
  • Chromists.
  • Fungi.

Protozoa and Chromists belong to the lower mushrooms, the Fungi class - to the higher ones.

Higher and lower - what's the difference

Mushroom of any rank is represented by mycelium (mycelium). The mycelium of lower fungi is non-cellular, that is, not divided by partitions into small sectors. Higher fungi have partitions (septa), but they are not solid, but have holes, so the contents of the protoplasm can move from sector to sector.

Another difference between the lower mushrooms and the higher ones is the impossibility of forming large and dense fruiting bodies. No one has yet found fruiting bodies in primitive non-cellular fungi (or mushroom-like organisms). This does not detract from their nutritional function - small soil animals eat microscopic mycelium very willingly.

mushroom dna

Mushroom monsters

In the classification of fungi in microbiology, the Fungi kingdom is always considered, and sometimes the other two kingdoms (Protozoa and Chromists)not mentioned. This is because Protozoa are fungus-like organisms rather than fungi.

They are unique in that they are capable of independent amoeboid movement. Their body is a multinucleated extensive protoplast (plasmodium that does not form hyphae), and in the development cycle there is a flagellar moving stage.

Chromista is also very unusual. The kingdom unites a rather motley group of organisms related to algae (brown, golden, diatoms, etc.) and organisms similar to fungi.

Mushroom-like chromists lose their color for the second time, are equipped with flagella, and instead of chitin, cell walls may contain cellulose. Often there are no cell walls at all. Then the body of the fungus is represented by a protoplast, that is, it is surrounded only by a membrane. They are close in origin to algae (yellow-green).

Luminescence, mushroom

More about Protozoa

Protozoa contains departments:

  • Mixomycetes (Myxomycota)
  • Plasmodiophoromycetes (Plasmodiophoromycota)
  • Dictyosteliomycetes (Dictyosteliomycota)

Representatives of the Myxomycota department are also called slime molds. They combine the features inherent in both mushrooms and animals. They can crawl along the substrate like amoeba, passively absorb nutrients from the entire surface or actively capture and digest bacteria. React to light or accumulation of food. They usually live on forest soils, rotting wood.

But they reproduce like mushrooms by spores. There is also a sexual process. Slime molds can bemicroscopic, but they grow all their lives. Some slime molds, such as fuligo, grow up to several tens of centimeters.

Biochemical test tubes

Amazing Chromists

Kingdom Chromists (Chromista) unites departments:

  • Hyphochytriomycetes (Hyphochytriomycota).
  • Oomycetes (Oomycot).
  • Labyrinthulomycetes (Labyrinthulomycota).

Among the Chromists, one can consider a labyrinthula as an example. These are small marine mushroom-like creatures. The body of the "mushroom" is a plasmodium, which is covered on top with a mesh of mucous ectoplasm, dressed in a membrane. The mesh facilitates attachment to the substrate or movement towards the food source. It even protects against desiccation if Plasmodium crawls onto land.

Reproduction, like most fungi, is carried out with the help of spores, but under certain conditions, the sexual process is activated. In marine food chains, labyrinthulae are given a place of honor - amoebas, planktonic species, and small crustaceans feed on them. Labyrinthules, along with bacteria, successfully colonize inorganic debris - glass, glass wool, plastic. Secondary garbage colonizers may already be, for example, sea acorns.

Chromists algal

About real mushrooms

Real mushrooms in human understanding are primarily macromycetes. The fruiting bodies of macromycetes are so valuable as food objects that a separate industry has appeared in the industry - the cultivation of mushrooms in specially created conditions.

Kingdom of Fungi (Fungi,Mycota) is divided into four divisions. Among them:

  • Chytridiomycetes (Chytridiomycota).
  • Zygomycota.
  • Ascomycetes (Ascomycota).
  • Basidiomycetes (Basidiomycota).

Of these, the first two departments include representatives of lower fungi (micromycetes), and the second two - higher ones (mainly macromycetes). Micromycetes cannot be seen with the naked eye. Rarely, motile flagellar stages occur in the life cycle. There are many parasites among the representatives. Macromycetes include representatives that form fruiting bodies. These are mainly tinder fungi and cap mushrooms.

Sometimes Deuteromycetes (Deuteromycóta) are indicated as the fifth department. In building a classification of fungi, microbiology attaches great importance to the methods of reproduction. Representatives of deuteromycetes are called imperfect fungi. The reason is that they have completely lost the ability to reproduce sexually.

mushroom plasmodium

Yeast - unicellular fungi

According to the modern classification of fungi, microbiology assigns yeast to the kingdom of Fungi, department of Ascomycetes. These are higher mushrooms, despite the fact that their body is unicellular. Yeast ancestors were multicellular, but the evolutionary direction of their development has shifted towards the loss of mycelium.

A distinctive feature of the department is two-layer cell membranes. Macromycetes, mold fungi, and yeasts also have them. Yeast shells contain polysaccharides glucans and mannans.

Yeast - a class of fungi Hemiascomycetes (Hemiascomycetes), order Saccharomycetales.There is an opinion that yeast is a group of organisms that does not have its own taxon. It includes representatives of the departments Ascomycetes and Basidiomycetes.

Yeast reproduces by budding, less often by cell division in half, and in unfavorable conditions, a sexual process is possible. Part of the yeast forms spores, which allows them to be divided into two large groups - sporogenic and asporogenic.

Yeast photography

Mold mushrooms

Found in almost all large taxa. There are higher and lower molds: unlike lower fungi, in higher mold micromycetes, the mycelium is divided by partitions into fragments (cells). They feed by releasing enzymes on the substrate that decompose substances into simple components. For example, you can find molds and yeast on the same piece of bread, but the substances they consume will be different. Yeast feeds on sugar, while proteins and fats are food substrates for mold fungi.

Molds are found in all taxonomic groups of the Kingdom of Fungi:

  • Chytridiomycetes. Synchytrium endobioticum is a potato parasite that causes tuber rot.
  • Zygomycetes. The representative of mukor is a saprophyte (settles on an inanimate substrate), causes bread mold.
  • Ascomycetes. The representative of black mold is a saprophyte, which is used for the industrial production of citric acid. The strongest allergen in humans causes a disease such as aspergillosis. This also includes penicilli used to make cheese and antibiotics.
  • Basidiomycetes. Cause diseasescereals (rust and smut parasites).
  • Mold in a petri dish

There are molds even in the Chromist kingdom, among oomycetes:

  • Phytophthora, a parasite that causes rot in tomatoes and potatoes.
  • Plasmopara (Plasmopara viticola) parasitizes vines and fruits. Plant disease - powdery mildew.

Thus, mushrooms remain one of the most poorly studied groups of organic nature. Modern methods of studying the microstructures and biochemistry of the cell make it possible to make new discoveries, on the basis of which the classification of fungi continues to change.

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