The division of organisms considered here as algae is very diverse and does not represent a single taxon. These organisms are heterogeneous in their structure and origin.

Algae are autotrophic plants; their cells contain various modifications of chlorophyll and other pigments that provide photosynthesis. Algae live in fresh and marine, as well as on land, on the surface and in the thickness of the soil, on the bark of trees, stones and other substrates.

Algae belong to 10 divisions from two kingdoms: 1) Blue-green, 2) Red, 3) Pyrophytes, 4) Golden, 5) Diatoms, 6) Yellow-green, 7) Brown, 8) Euglenoids, 9) Greens and 10 ) Charovye. The first section belongs to the kingdom of Prokaryotes, the rest - to the kingdom of Plants.

Department of Blue-green algae, or Cyanobacteria (Cyanophyta)

There are about 2 thousand species, united in about 150 genera. These are the oldest organisms, traces of which were found in Precambrian deposits, their age is about 3 billion years.

Among blue-green algae there are unicellular forms, but most species are colonial and filamentous organisms. They differ from other algae in that their cells do not have a formed nucleus. They lack mitochondria, vacuoles with cell sap, no formed plastids, and the pigments with which photosynthesis is carried out are located in photosynthetic plates - lamellae. The pigments of blue-green algae are very diverse: chlorophyll, carotenes, xanthophylls, as well as specific pigments from the phycobilin group - blue phycocyanin and red phycoerythrin, which, in addition to cyanobacteria, are found only in red algae. The color of these organisms is most often blue-green. However, depending on the quantitative ratio of various pigments, the color of these algae can be not only blue-green, but also purple, reddish, yellow, pale blue or almost black.

Blue-green algae are distributed throughout the globe and are found in a wide variety of environments. They are able to exist even in extreme living conditions. These organisms endure prolonged darkening and anaerobiosis, can live in caves, in different soils, in layers of natural silt rich in hydrogen sulfide, in thermal waters, etc.

Mucous sheaths are formed around the cells of colonial and filamentous algae, which serve as a protective wrapper that protects the cells from drying out and is a light filter.

Many filamentous blue-green algae have peculiar cells - heterocysts. These cells have a well-defined two-layer membrane, and they look empty. But these are living cells filled with transparent contents. Blue-green algae with heterocysts are able to fix atmospheric nitrogen. Some types of blue-green algae are components of lichens. They can be found as symbionts in the tissues and organs of higher plants. Their ability to fix atmospheric nitrogen is used by higher plants.

The massive development of blue-green algae in water bodies can have negative consequences. Increased water pollution and organic substances cause the so-called "water bloom". This makes the water unfit for human consumption. Some freshwater cyanobacteria are toxic to humans and animals.

Reproduction of blue-green algae is very primitive. Unicellular and many colonial forms reproduce only by dividing cells in half. Most filamentous forms reproduce by hormogonia (these are short sections that have separated from the maternal filament and grow into adults). Reproduction can also be carried out with the help of spores - overgrown thick-walled cells that can survive adverse conditions and then grow into new threads.

Department Red algae (or Bagryanka) (Rhodophyta)

Red algae () - a large (about 3800 species from more than 600 genera) group of mainly marine life. Their sizes vary from microscopic to 1-2 m. Outwardly, red algae are very diverse: there are filamentous, lamellar, coral-like forms, dissected and branched to varying degrees.

Red algae have a peculiar set of pigments: in addition to chlorophyll a and b, there is chlorophyll d, known only for this group of plants, there are carotenes, xanthophylls, as well as pigments from the phycobilin group: blue pigment - phycocyanin, red - phycoerythrin. A different combination of these pigments determines the color of algae - from bright red to bluish-green and yellow.

Red algae reproduce vegetatively, asexually and sexually. Vegetative reproduction is typical only for the most poorly organized crimson (unicellular and colonial forms). In highly organized multicellular forms, torn off sections of the thallus die. Various types of spores are used for asexual reproduction.

The sexual process is oogamous. On the gametophyte plant, male and female germ cells (gametes) are formed, devoid of flagella. During fertilization, female gametes do not enter the environment, but remain on the plant; male gametes are thrown out and passively carried by currents of water.

Diploid plants - sporophytes - have the same appearance as gametophytes (haploid plants). This is an isomorphic change of generations. Organs of asexual reproduction are formed on sporophytes.

Many red algae are widely used by humans, they are edible and beneficial. In the food and medical industry, polysaccharide agar obtained from different types of crimson (about 30) is widely used.

Department Pyrophyta (or Dinophyta) algae (Pyrrophyta (Dinophyta))

The department includes about 1200 species from 120 genera, uniting eukaryotic unicellular (including biflagellate), coccoid and filamentous forms. The group combines the features of plants and animals: some species have tentacles, pseudopodia and stinging cells; some have a type of nutrition characteristic of animals, provided by the pharynx. Many have a stigma, or peephole. Cells are often covered with a hard shell. Chromatophores are brownish and reddish, contain chlorophylls a and c, as well as carotenes, xanthophylls (sometimes phycocyanin and phycoerythrin). Starch is deposited as reserve substances, sometimes oil. Flagellated cells have distinct dorsal and ventral sides. There are grooves on the surface of the cell and in the pharynx.

They reproduce by division in a mobile or immobile state (vegetatively), by zoospores and autospores. Sexual reproduction is known in few forms; it takes place in the form of fusion of isogametes.

Pyrophytic algae are common inhabitants of polluted water bodies: ponds, settling ponds, some reservoirs and lakes. Many form phytoplankton in the seas. Under unfavorable conditions, they form cysts with thick cellulose membranes.

The genus Cryptomonad (Cryptomonas) is the most widespread and rich in species.

Division Golden algae (Chrysophyta)

Microscopic or small (up to 2 cm long) golden yellow organisms that live in salt and fresh water bodies around the globe. There are unicellular, colonial and multicellular forms. About 300 species from 70 genera are known in Russia. Chromatophores are usually golden yellow or brown. They contain chlorophylls a and c, as well as carotenoids and fucoxanthin. Chrysolaminarine and oil are deposited as spare substances. Some species are heterotrophic. Most forms have 1-2 flagella and are therefore mobile. They reproduce mainly asexually - by division or zoospores; the sexual process is known only in a few species. Usually found in clean fresh waters(acidic waters of sphagnum bogs), less often - in the seas and in soils. Typical phytoplankton.

Division Diatoms (Bacillariophyta (Diatomea))

Diatoms (diatoms) number about 10 thousand species belonging to about 300 genera. These are microscopic organisms that live mainly in water bodies. Diatoms are a special group of single-celled organisms, distinct from other algae. Diatomaceous cells are covered with a silica shell. The cell contains vacuoles with cell sap. The nucleus is located in the center. Chromatophores are large. Their color has various shades of yellow-brown, since carotenes and xanthophylls, which have yellow and brown hues, and masking chlorophylls a and c predominate among the pigments.

The shells of diatoms are characterized by the geometric regularity of the structure and big variety outlines. The shell consists of two halves. The larger one, the epithecus, covers the smaller one, the hypotheca, just like a lid covers a box.

Most diatoms with bilateral symmetry are able to move on the surface of the substrate. The movement is carried out using the so-called seam. The seam is a gap that cuts through the wall of the sash. The movement of the cytoplasm into the gaps and its friction against the substrate ensure the movement of the cell. Diatom cells with radial symmetry are incapable of locomotion.

Diatoms usually reproduce by dividing the cell into two halves. The protoplast increases in volume, as a result of which the epithecus and hypothecus diverge. The protoplast divides into two equal parts, the nucleus divides mitotically. In each half of the divided cell, the shell plays the role of an epitheca and completes the missing half of the shell, always a hypotheca. As a result of numerous divisions, a gradual decrease in cell size occurs in part of the population. Some cells are about three times smaller than the original ones. Reaching minimum dimensions, cells develop auxospores ("growing spores"). The formation of auxospores is associated with the sexual process.

Cells of diatoms in the vegetative state are diploid. Before sexual reproduction, the reduction division of the nucleus (meiosis) occurs. Two diatom cells approach each other, the valves move apart, the haploid (after meiosis) nuclei merge in pairs, and one or two auxospores are formed. The auxospore grows for some time, and then develops a shell and turns into a vegetative individual.

Among diatoms, there are light-loving and shade-loving species; they live in water bodies at different depths. Diatoms can also live in soils, especially wet and swampy ones. Along with other algae, diatoms can cause snow blooms.

Diatoms play a large role in the economy of nature. They serve as a permanent food base and the initial link in the food chain for many aquatic organisms. Many fish feed on them, especially juveniles.

The shells of diatoms, settling to the bottom for millions of years, form a sedimentary geological rock - diatomite. It is widely used as a building material with high heat and sound insulation properties, as filters in the food, chemical, and medical industries.

Department of yellow-green algae (Xanthophyta)

This group of algae has about 550 species. They are mainly inhabitants of fresh waters, less often found in the seas and on moist soil. Among them there are unicellular and multicellular forms, flagella, coccoid, filamentous and lamellar, as well as siphonal organisms. These algae are characterized by a yellow-green color, which gave the name to the whole group. Chloroplasts are disc-shaped. Characteristic pigments are chlorophylls a and c, a and b carotenoids, xanthophylls. Spare substances - glucan,. Sexual reproduction is oogamous and isogamous. Vegetatively reproduce by division; asexual reproduction is carried out by specialized mobile or immobile cells - zoo- and aplanospores.

Division Brown algae (Phaeophyta)

Brown algae are highly organized multicellular organisms that live in the seas. There are about 1500 species from about 250 genera. The largest of the brown algae reach several tens of meters (up to 60 m) in length. However, microscopic species are also found in this group. The shape of the thalli can be very diverse.

A common feature of all algae belonging to this group is a yellowish-brown color. It is caused by the pigments carotene and xanthophyll (fucoxanthin, etc.), which mask green color chlorophylls a and c. The cell membrane is cellulose with an outer pectin layer capable of strong mucus.

In brown algae, all forms of reproduction are found: vegetative, asexual and sexual. Vegetative propagation occurs by separated parts of the thallus. Asexual reproduction is carried out with the help of zoospores (mobile spores due to flagella). The sexual process in brown algae is represented by isogamy (less often, anisogamy and oogamy).

In many brown algae, the gametophyte and sporophyte differ in shape, size, and structure. In brown algae, there is an alternation of generations, or a change in nuclear phases in the development cycle. Brown algae are found in all the seas of the world. In the thickets of brown algae near the coast, numerous coastal animals find shelter, breeding and feeding places. Brown algae are widely used by man. Alginates (salts of alginic acid) are obtained from them, which are used as stabilizers for solutions and suspensions in the food industry. They are used in the manufacture of plastics, lubricants, etc. Some brown algae (kelp, alaria, etc.) are used in food.

Division Euglenophyta (Euglenophyta)

This group contains about 900 species from about 40 genera. These are unicellular flagellar organisms, mainly inhabitants of fresh waters. Chloroplasts contain chlorophylls a and b and a large group of auxiliary pigments from the group of carotenoids. Photosynthesis occurs in these algae in the light, and in the dark they switch to heterotrophic nutrition.

Reproduction of these algae occurs only due to mitotic cell division. Mitosis in them differs from this process in other groups of organisms.

Division Green algae (Chlorophyta)

Green algae is the largest division of algae, numbering, according to various estimates, from 13 to 20 thousand species from about 400 genera. These algae are characterized by a purely green color, like in higher plants, since chlorophyll predominates among the pigments. In chloroplasts (chromatophores) there are two modifications of chlorophyll a and b, as in higher plants, as well as other pigments - carotenes and xanthophylls.

Rigid cell walls of green algae are formed by cellulose and pectin substances. Spare substances - starch, less often oil. Many features of the structure and life of green algae indicate their relationship with higher plants. Green algae are distinguished by the greatest diversity compared to other departments. They can be unicellular, colonial, multicellular. This group represents the whole variety of morphological differentiation of the body, known for algae - monadic, coccoid, palmelloid, filamentous, lamellar, non-cellular (siphonal). The range of their sizes is great - from microscopic single cells to large multicellular forms tens of centimeters long. Reproduction is vegetative, asexual and sexual. All the main types of change in the forms of development are encountered.

Green algae live more often in fresh water bodies, but there are many brackish and marine forms, as well as out-of-water terrestrial and soil species.

The Volvox class includes the most primitive representatives of green algae. Usually these are unicellular organisms with flagella, sometimes united in colonies. They are mobile throughout life. Distributed in shallow freshwater bodies, swamps, in the soil. From single-celled species of the genus Chlamydomonas are widely represented. Spherical or ellipsoidal cells of chlamydomonas are covered with a membrane consisting of hemicellulose and pectin substances. There are two flagella at the anterior end of the cell. All inner part The cell is occupied by a cup-shaped chloroplast. In the cytoplasm that fills the cup-shaped chloroplast, the nucleus is located. At the base of the flagella there are two pulsating vacuoles.

Asexual reproduction occurs with the help of biflagellate zoospores. During sexual reproduction in the cells of chlamydomonas, biflagellated gametes are formed (after meiosis).

Chlamydomonas species are characterized by iso-, hetero- and oogamy. On the onset adverse conditions(drying of the reservoir), chlamydomonas cells lose their flagella, become covered with a mucous membrane and multiply by division. When favorable conditions occur, they form flagella and move to a mobile lifestyle.

Along with the autotrophic method of nutrition (photosynthesis), chlamydomonas cells are able to absorb organic substances dissolved in water through the membrane, which contributes to the processes of self-purification of polluted waters.

Cells of colonial forms (pandorina, volvox) are built according to the type of chlamydomonas.

In the Protococcal class, the main form of the vegetative body is immobile cells with a dense membrane and colonies of such cells. Chlorococcus and chlorella are examples of unicellular protococci. Asexual reproduction of Chlorococcus is carried out with the help of biflagellated motile zoospores, and the sexual process is a fusion of mobile biflagellated isogametes (isogamy). Chlorella does not have mobile stages during asexual reproduction, there is no sexual process.

The Ulotrix class combines filamentous and lamellar forms that live in fresh and marine waters. Ulothrix is ​​a thread up to 10 cm long, attached to underwater objects. The filament cells are identical, short-cylindrical with lamellar parietal chloroplasts (chromatophores). Asexual reproduction is carried out by zoospores (mobile cells with four flagella).

The sexual process is isogamous. Gametes are motile due to the presence of two flagella in each gamete.

The class Conjugates (couplings) combines unicellular and filamentous forms with a peculiar type of sexual process - conjugation. Chloroplasts (chromatophores) in the cells of these algae are lamellar and very diverse in shape. In ponds and slow-flowing water bodies, the main mass of green mud is formed by filamentous forms (spirogyra, zignema, etc.).

When conjugated from opposite cells of two adjacent threads, processes grow that form a channel. The contents of the two cells merge, and a zygote is formed, covered with a thick membrane. After a dormant period, the zygote germinates, giving rise to new filamentous organisms.

The Siphon class includes algae with a non-cellular structure of the thallus (thallus), with its rather large sizes and complex division. The siphon seaweed caulerpa outwardly resembles a leafy plant: its size is about 0.5 m, it is attached to the ground by rhizoids, its thalli creep along the ground, and vertical formations resembling leaves contain chloroplasts. It easily reproduces vegetatively by parts of the thallus. There are no cell walls in the body of the alga, it has a continuous protoplasm with numerous nuclei, chloroplasts are located near the walls.

Department Charovye algae (Charophyta)

These are the most complex algae: their body is differentiated into nodes and internodes, in the nodes there are whorls of short branches resembling leaves. The size of plants is from 20-30 cm to 1-2 m. They form continuous thickets in fresh or slightly saline water bodies, attaching to the ground with rhizoids. Outwardly, they resemble higher plants. However, these algae do not have a real division into root, stem, and leaves. There are about 300 species of charophytes belonging to 7 genera. They have similarities with green algae in terms of pigment composition, cell structure, and reproduction characteristics. There is also a similarity with higher plants in the features of reproduction (oogamy), etc. The noted similarity indicates the presence of a common ancestor in characeae and higher plants.

Vegetative reproduction of characeae is carried out by special structures, the so-called nodules, formed on rhizoids and on the lower parts of the stems. Each of the nodules germinates easily, forming a protonema, and then a whole plant.

The whole department of algae, after the first acquaintance with it, is very difficult to grasp mentally and give each department its correct place in the system. The system of algae did not develop in science soon and only after many unsuccessful attempts. At the present time, we impose on any system the basic requirement that it be phylogenetic. At first it was thought that such a system could be very simple; imagined it as a single genealogical tree, albeit with many side branches. Now we are building it in no other way than in the form of many genealogical lines that developed in parallel. The matter is further complicated by the fact that, along with progressive changes, regressive ones are also observed, setting a difficult task for resolution - in the absence of one or another sign or organ, to decide that it has not yet appeared or has already disappeared?

For a long time, the system given to Ville in the 236th issue of the main work on the descriptive taxonomy of plants, published under the editorship of A. Engler, was considered the most perfect. Flagellates or Flagellata are recognized as the main group here.

This scheme covers only the main group of green algae. For the rest, we will take Rosen's scheme, changing only the names of the groups, in accordance with those adopted above when describing them.

1

Efimova M.V., Efimov A.A.

The article presents and analyzes the data of some authors on the systematics of blue-green algae (cyanobacteria). The results of determination of cyanobacteria species of some hot springs of Kamchatka are presented.

Blue-green algae number up to 1500 species. In different literary sources, they are referred to by different authors under different names: cyanides, cyanobionts, cyanophytes, cyanobacteria, cyanella, blue-green algae, blue-green algae, cyanophycea. The development of research leads some authors to change their views on the nature of these organisms and, accordingly, to change the name. So, for example, back in 2001, V.N. Nikitina classified them as algae and called them cyanophytes, and in 2003 already identified them as cyanoprokaryotes. Basically, the name is chosen in accordance with the classification preferred by this or that author.

What is the reason for the presence of so many names in organisms of one group, and such names as cyanobacteria and blue-green algae contradict each other? By the absence of a nucleus, they are close to bacteria, and by the presence of chlorophyll a and the ability to synthesize molecular oxygen - with plants. According to E.G. Kukka, "an extremely peculiar structure of cells, colonies and filaments, interesting biology, a large phylogenetic age - all these features ... provide the basis for many interpretations of the taxonomy of this group of organisms." Kukk gives such names as blue-green algae ( Cyanophyta), phycochrome pellets ( Schizophyceae), slime algae ( Myxophyceae) .

Systematics is one of the main approaches to the study of the world. Its purpose is to search for unity in the visible diversity of natural phenomena. The problem of classification in biology has always occupied and occupies a special position, which is associated with the gigantic diversity, complexity and constant variability of the biological forms of living organisms. Cyanobacteria are the clearest example of polysystemicity.

The first attempts to build a blue-green system date back to the 19th century. (Agard - 1824, Kützing - 1843, 1849, Thure - 1875). Further development of the system was continued by Kirchner (1900). Since 1914, a significant revision of the system began, and a number of new systems were published. Cyanophyta(Elenkin - 1916, 1923, 1936; Borzi - 1914, 1916, 1917; Geytler - 1925, 1932). The system of A.A. was recognized as the most successful. Elenkin, published in 1936. This classification has survived to the present, as it has proven to be convenient for hydrobiologists and micropaleontologists.

The scheme of the Key to Freshwater Algae of the USSR was based on the Elenkin system, to which minor changes were made. In accordance with the scheme of the Determinant, blue-greens were assigned to the type Cyanophyta, divided into three classes ( Chroococceae, Chamaesiphoneae, Hormogoneae). Classes are divided into orders, orders - into families. This scheme determined the position of blue-greens in the plant system.

According to the classification of algae by Parker (1982), blue-greens belong to the kingdom Procaryota, department Cyanophycota, class Cyanophyceae .

The International Code of Botanical Nomenclature was once recognized as unacceptable for prokaryotes, and the current International Code of Nomenclature of Bacteria (International Code of Nomenclature of Bacteria) was developed on its basis. However, cyanobacteria are regarded as "dual membership" organisms and can be described under the rules of both the ICNS and the Botanical Code. In 1978, the Subcommittee on Phototrophic Bacteria of the International Committee for Systematic Bacteriology proposed to subordinate the nomenclature Cyanophyta the rules of the "International Code of Nomenclature of Bacteria" and until 1985 to publish lists of newly approved names of these organisms. N.V. Kondratieva in the article conducted a critical analysis of this proposal. The author believes that the proposal of bacteriologists "is erroneous and may have harmful consequences for the development of science." The article presents the classification of prokaryotes adopted by the author. According to this classification, blue-greens belong to the super-kingdom Procaryota, kingdom Photoprocaryota, subkingdom Procaryophycobionta, department Cyanophyta.

S.A. Balandin and co-authors, characterizing the plant kingdom, assign the department Bacteria ( Bacteriophyta) to lower plants, and the department Blue-green algae ( Cyanophyta- and not otherwise) - to algae. At the same time, it remains unclear what kind of taxonomic group Algae is, perhaps a subkingdom. At the same time, describing the department of Bacteria, the authors point out: "When classifying bacteria, several classes are distinguished: true bacteria (eubacteria), myxobacteria, ... cyanobacteria (blue-green algae)" . Probably, the taxonomic affiliation of cyanobacteria is an open question for the authors.

There are many classifications in the literature, which are based on the division into groups according to phenotypic signs. Different taxonomists estimate the rank of cyanobacteria (or blue-green?) in different ways - from a class to an independent kingdom of organisms. So, according to the three-kingdom system of Heckel (1894), all bacteria belong to the kingdom Protista. Whittaker's (1969) five-kingdom system assigns cyanobacteria to the kingdom Monera. According to the system of organisms of Takhtadzhyan (1973), they belong to the super-kingdom Procaryota, kingdom Bacteriobiota. However, in 1977 A.L. Takhtajyan refers them to the kingdom of Drobyanka ( Mychota), the sub-kingdom of Cyanea, or Blue-green algae ( Cyanobionta), department Cyanophyta. At the same time, the author points out that many to designate the kingdom instead of Mychota"use an unfortunate name Monera, proposed by E. Haeckel for a supposedly nuclear-free "genus" Protamoeba, which turned out to be just a nuclear-free fragment of an ordinary amoeba. In accordance with the rules of the ICNB, blue-green algae are included in the super-kingdom Prokaryota, kingdom Mychota, subkingdom Oxyphotobacteriobionta as a department cyanobacteria. The five kingdom classification system according to Margelis and Schwartz assigns cyanobacteria to the kingdom Prokariotae. The six-regal taxonomy of Cavalier-Smith refers the phylum cyanobacteria to the empire Procaryota, kingdom bacteria, subkingdom Negibacteria .

In the modern classification of microorganisms, the following hierarchy of taxa is adopted: domain, phylum, class, order, family, genus, species. The taxon of the domain has been proposed as higher in relation to the kingdom, in order to emphasize the importance of dividing the living world into three parts - Archaea, bacteria and Eukarya. In accordance with this hierarchy, cyanobacteria are assigned to the domain bacteria, phylum B10 cyanobacteria, which, in turn, is divided into five subsections.

The National Center for Biotechnology Information (NCBI) Taxonomy Browser scheme (2004) defines them as a phylum and assigns them to a kingdom Monera.

In the 70s. of the last century K. Woese was developed phylogenetic classification, which is based on the comparison of all organisms according to one small rRNA gene. According to this classification, cyanobacteria constitute a separate branch of the 16S-rRNA tree and belong to the kingdom Eubacteria. Later (1990) Woese defined this realm as bacteria dividing all organisms into three kingdoms - bacteria, Archaea and Eukarya.

The taxonomic schemes of cyanobacteria considered in the article are summarized in Table 1 for clarity.

Table 1. Taxonomic schemes of cyanobacteria

			Sub-realm
Haeckel, 1894		Protista
Hollerbach	Procaryota		plants	Cyano-
Whittaker,					Cyano- bacteria
Takhtajyan, 1974	Procaryota		Cyanobionta		Cyanophyta
Kondratieva, 1975	Procaryota	Photo-procaryota	Procaryo-phycobionta		Cyanophyta
		Eubacteria		Cyano- bacteria
International Code of Nomenclature for Bacteria, 1978	Procaryota		Oxyphoto- bacteria- bionta		Cyano- bacteria
Parker, 1982		Procaryota			Cyanophycota	Cyano- phyceae
Margelis & Schwartz, 1982		Prokariotae	Prokaryotae		cyanobacteria
Determinant bacteria Burgi, 1984-1989		Procaryotae			Gracilicutes	Oxyphoto- bacteria
		bacteria		Cyano- bacteria
Determinant bacteria Burgi, 1997		Procaryotae			Gracilicutes	Oxyphoto- bacteria
Cavalier-Smith,	Praboutcaryota	bacteria	Negibacteria		cyanobacteria
NCBI Taxonomy Browser, 2004				Cyano- bacteria
Balandin		Plants	Seaweed?		Cyanophyta
		Plants	plants?		Bacteriophyta	Cyano- bacteria

The classification of cyanobacteria is under development and, in fact, all genera and species given at present should be considered as temporary and subject to significant modification.

The basic principle of classification is still phenotypic. However, this classification is convenient, since it allows you to determine the samples in a fairly simple way.

The most popular taxonomic scheme is Bergey's Key to Bacteria, which also divides bacteria into groups according to phenotypic characters.

According to the edition of Burgey's Guide to the Systematics of Bacteria, all pre-nuclear organisms were united in the kingdom Procaryotae which was divided into four sections. Cyanobacteria are assigned to division 1 - Gracilicutes, which includes all bacteria that have a gram-negative type of cell wall, class 3 - Oxyphotobacteria, order Cyanobacteriales .

The ninth edition of Burgey's Key to Bacteria defines divisions as categories, each subdivided into groups that have no taxonomic status. It is curious that some authors interpret the classification of the same edition of Burgey's Bacteria Key differently. For example, G.A. Zavarzin - clearly in accordance with the division into groups given in the publication itself: cyanobacteria are included in group 11 - oxygenic phototrophic bacteria. M.V. Gusev and L.A. Mineev, all groups of bacteria up to the ninth inclusive are characterized in accordance with the Key, and then radical discrepancies follow. So, in group 11, the authors include endosymbionts of protozoa, fungi, and invertebrates, and oxyphotobacteria are assigned to group 19.

According to the latest edition of Burgey's manual, cyanobacteria are included in the domain bacteria .

The taxonomic scheme of Burgey's Key to Bacteria is based on several classifications: Rippka, Drouet, Heitler, a classification created as a result of a critical reassessment of the Heitler system, the classification of Anagnostidis and Komarek.

The Drouet system is based mainly on the morphology of organisms from herbarium specimens, which makes it unacceptable for practice. The complex Heitler system is based almost exclusively on the morphological features of organisms from natural specimens. By critically reassessing the Heitler genera, another system based on morphological characters and modes of reproduction has been created. As a result of a critical reassessment of the Heitler genera, a system based primarily on morphological characters and the mode of reproduction of cyanobacteria has been created. By carrying out a complex modification of the Heitler system, taking into account data on morphology, ultrastructure, methods of reproduction, and variability, a modern extended system of Anagnostidis and Komarek was created. The simplest Rippk system, given in Burgey's Key to Bacteria, is based almost exclusively on the study of only those cyanobacteria that are present in cultures. This system uses morphological characters, mode of reproduction, cell ultrastructure, physiological characteristics, chemical composition and sometimes genetic data. This system, like the system of Anagnostidis and Komarek, is transitional, as it approaches partly the genotypic classification, i.e. reflects phylogeny and genetic relationship.

According to the taxonomic scheme of Burgey's Guide to Bacteria, cyanobacteria are divided into five subgroups. Subgroups I and II include unicellular forms or non-filamentous cell colonies united by outer layers of the cell wall or a gel-like matrix. Bacteria of each subgroup differ in the way of reproduction. Subgroups III, IV and V include filamentous organisms. Bacteria of each subgroup differ from each other in the way of cell division and, as a result, in the form of trichomes (branched or unbranched, single-row or multi-row). Each subgroup includes several genera of cyanobacteria, and also, along with genera, the so-called "groups of cultures", or "supergenera", which in the future, as expected, can be divided into a number of additional genera.

So, for example, "a group of cultures" Cyanothece(subgroup I) includes seven studied strains isolated from different habitats. In general, the first subgroup includes nine genera ( Chamaesiphon, Cyanothece, Gloeobacter, Microcystis, Gloeocapsa, Gloeothece, Myxobaktron, Synechococcus, Synechocystis). Subgroup II includes six genera ( Chroococcidiopsis, Dermocarpa, Dermocarpella, Myxosarcina, Pleurocapsa, Xenococcus). Subgroup III includes nine genera ( Arthrospira, Crinalium, Lyngbya, Microcoleus, Oscillatoria, Pseudanabaena, Spirulina, Starria, Trichodesmium). Subgroup IV contains seven genera ( Anabaena, Aphanizomenon, Cylindrospermum, Nodularia, Nostoc, Scytonema, Calothrix). Subgroup V includes eleven genera of potentially filamentous cyanobacteria, distinguished by a high degree morphological complexity and differentiation (multi-row threads). It's kind Chlorogloeopsis, Fisherella, Geitleria, Stigonema, Cyanobotrys, Loriella, Nostochopsis, Mastigocladopsis, Mastigocoleus, Westiella, Hapalosiphon.

Some authors, based on the analysis of the 16S pRNA gene, refer to cyanobacteria and prochlorophytes (order Prochlorales), a relatively recently discovered group of prokaryotes that, like cyanobacteria, perform oxygenic photosynthesis. Prochlorophytes are in many ways similar to cyanobacteria, however, unlike them, along with chlorophyll a contain chlorophyll b do not contain phycobilin pigments.

There is still a lot of uncertainty in the taxonomy of cyanobacteria, and great disagreements arise at every level of their study. But, according to Kukk, the blue-green algae themselves are “guilty” of such a fate.

The work was supported by a grant fundamental research FEB RAS for 2006-2008 "Microorganisms of the Russian Far East: systematics, ecology, biotechnological potential".

BIBLIOGRAPHY:

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Bibliographic link

Efimova M.V., Efimov A.A. BLUE-GREEN ALGAE OR CYANOBACTERIA? QUESTIONS OF SYSTEMATICS // Contemporary Issues science and education. - 2007. - No. 6-1 .;
URL: http://science-education.ru/ru/article/view?id=710 (date of access: 02/01/2020). We bring to your attention the journals published by the publishing house "Academy of Natural History"

Cyanobacteria (blue-green) - a department of the kingdom of prokaryotes (shotguns). Represented by autotrophic phototrophs. Life forms - unicellular, colonial, multicellular organisms. Their cell is covered with a layer of pectin located on top of the cell membrane. The nucleus is not expressed, the chromosomes are located in the central part of the cytoplasm, forming the centroplasm. Of the organelles, there are ribosomes and parachromatophores (photosynthetic membranes) containing chlorophyll, carotenoids, phycocyan and phycoerythrin. Vacuoles are only gas, cell juice does not accumulate. Spare substances are represented by grains of glycogen. Cyanobacteria reproduce only vegetatively - by parts of the thallus or by special sections of the thread - hormogonia. Representatives: oscillatoria, lingbia, anabaena, nostoc. They live in water, on soil, in snow, in hot springs, on the bark of trees, on rocks, and are part of the body of some lichens.

blue green algae, cyanide (Cyanophyta), algae department; belong to prokaryotes. In blue green algae, as in bacteria, the nuclear material is not delimited by a membrane from the rest of the cell contents; the inner layer of the cell membrane consists of murein and is sensitive to the action of the enzyme lysozyme. Blue-green algae are characterized by a blue-green color, but pink and almost black are found, which is associated with the presence of pigments: chlorophyll a, phycobilins (blue - phycocyan and red - phycoerythrin) and carotenoids. Among the blue-greenalgae, there are unicellular, colonial and multicellular (filamentous) organisms, usually microscopic, less often forming balls, crusts and bushes up to 10 cm in size. Some filamentous blue-green algae are able to move by sliding. The protoplast of blue-green algae consists of an outer colored layer - chromatoplasm - and a colorless inner part - centroplasm. In the chromatoplasm there are lamellae (plates) that carry out photosynthesis; they are arranged in concentric layers along the shell. The centroplasm contains a nuclear substance, ribosomes, reserve substances (volutin granules, cyanophycin grains with lipoproteins) and bodies consisting of glycoproteins; plantain species have gas vacuoles. Chloroplasts and mitochondria are absent in blue-green algae. The transverse partitions of filamentous blue-green algae are equipped with plasmodesmata. Some filamentous blue-green algae have heterocysts - colorless cells, isolatedfrom vegetative cells by "plugs" in plasmodesmata. Blue-green algae reproduce by division (unicellular) and by hormogonia - sections of filaments (multicellular). In addition, the following are used for reproduction: akinetes - immobile resting spores, formed entirely from vegetative cells; endospores that arise several times in the mother cell; exospores, detached from the outer side of the cells, and nanocytes - small cells that appear in the mass during the rapid division of the contents of the mother cell. There is no sexual process in blue-green algae, however, there are cases of recombination of hereditary traits through transformation. 150 genera uniting about 2000 species; in countries former USSR- 120 genera (over 1000 species). Blue-green algae are part of the plankton and benthos of fresh waters and seas, live on the surface of the soil, in hot springs with water temperatures up to 80 ° C, on snow - in the polar regions and in the mountains; a number of species live in a calcareous substrate (“drilling algae”), some blue-green algae are components of lichens and symbionts of protozoa and terrestrial plants (bryophytes and cycads). Blue-green algae develop in the greatest quantities in fresh waters, sometimes causing water blooms in reservoirs, which leads to the death of fish. Under certain conditions, the mass development of blue-green algae contributes to the formation of therapeutic mud. In some countries (China, the Republic of Chad), a number of species of blue-green algae (nostoc, spirulina, etc.) are used for food. Attempts are being made to mass-scale cultivation of blue-green algae to obtain fodder and food protein (spirulina). Some blue-green algae absorb molecular nitrogen, enriching the soil with it. In the fossil state, blue-green algae have been known since the Precambrian.

blue green algae(Cyanophyta), shotguns, more precisely, phycochrome pellets(Schizophyceae), slime algae (Myxophyceae) - how many different names this group of ancient autotrophic plants received from researchers! Passions have not subsided to this day. There are many such scientists who are ready to exclude blue-greens from among the algae, and some from the plant kingdom altogether. And not so, "with a light hand", but with full confidence that they are doing it on a serious basis. scientific basis. Blue-green algae themselves are “guilty” of such a fate. The extremely peculiar structure of cells, colonies and filaments, interesting biology, great phylogenetic age - all these features separately and taken together provide the basis for many interpretations of the taxonomy of this group of organisms.

There is no doubt that blue-green algae are the oldest group among autotrophic organisms and among organisms in general. The remains of organisms similar to them are found among stromatolites (calcareous formations with a tuberculous surface and a concentrically layered internal structure from Precambrian deposits), which were about three billion years old. Chemical analysis found in these residues decomposition products of chlorophyll. The second serious evidence of the antiquity of blue-green algae is the structure of their cells. Together with bacteria, they are united in one group called pre-nuclear organisms(Procaryota). Different taxonomists estimate the rank of this group differently - from a class to an independent kingdom of organisms, depending on the importance they attach to individual characters or the level of cellular structure. There is still much unclear in the taxonomy of blue-green algae, great disagreements arise at every level of their study.

Blue-green algae are found in all kinds of and almost impossible habitats, on all continents and water bodies of the Earth.

Cell structure. According to the shape of vegetative cells, blue-green algae can be divided into two main groups:

1) species with more or less spherical cells (spherical, broadly ellipsoid, pear- and ovoid);

2) species with cells strongly elongated (or compressed) in one direction (elongated-ellipsoidal, fusiform, cylindrical - from short-cylindrical and barrel-shaped to elongated-cylindrical). Cells live separately, and sometimes join in colonies or form threads (the latter can also live separately or form tufts or gelatinous colonies).

Cells have fairly thick walls. In essence, the protoplast is surrounded here by four shell layers: a two-layer cell membrane is covered on top with an outer wavy membrane, and between the protoplast and the shell there is also an inner cell membrane. In the formation of a transverse partition between cells in the threads, only the inner layer of the membrane and the inner membrane are involved; the outer membrane and the outer layer of the shell do not go there.

The structure of the cell wall and other microstructures of blue-green algae cells were studied using an electron microscope (Fig. 49).

Although the cell membrane contains cellulose, the main role is played by pectin substances and mucus polysaccharides. In some species, the cell membranes are well mucilaginous and even contain pigments; in others, a special mucous sheath is formed around the cells, sometimes independent around each cell, but more often merging into a common sheath surrounding a group or the entire series of cells, called in filamentous forms by a special term - trichomes. In many blue-green algae, trichomes are surrounded by true sheaths - sheaths. Both cellular and true sheaths are composed of thin, intertwining fibers. They can be homogeneous or layered: the layering of threads with separate bases and apex is parallel or oblique, sometimes even funnel-shaped. True sheaths grow by stacking new layers of mucus on top of each other or inserting new layers between old ones. Some nostalgic(Nostoc, Anabaena) cell sheaths are formed by secretion of mucus through pores in the membranes.

The protoplast of blue-green algae is devoid of a formed nucleus and was previously considered diffuse, divided only into a colored peripheral part - chromatoplasm - and a colorless central part - ceptroplasm. However, various methods of microscopy and cytochemistry, as well as ultracentrifugation, have shown that such a separation can only be conditional. The cells of blue-green algae contain well-defined structural elements, and their different arrangement causes differences between the centroplasm and chromatoplasm. Some authors now distinguish three components in the protoplast of blue-green algae:

1) nucleoplasm;

2) photosynthetic plates (lamellae);

3) ribosomes and other cytoplasmic granules.

But since the nucleoplasm occupies the region of the centroplasm, and the lamellae and other constituents are located in the region of the chromatoplasm containing pigments, the old, classical distinction (ribosomes are found in both parts of the protoplast) cannot be considered a mistake either.

Pigments concentrated in the peripheral part of the protoplast are localized in lamellar formations - lamellae, which are located in the chromatoplasm in different ways: randomly, they are packed into granules or oriented radially. Such systems of lamellae are now often referred to as parachromatophores.

In the chromatoplasm, in addition to lamellae and ribosomes, there are also ectoplasts (cyanophycin grains consisting of lipoproteins) and various kinds of crystals. Depending on the physiological state and age of the cells, all these structural elements can change greatly up to complete disappearance.

The centroplasm of blue-green algae cells consists of hyaloplasm and various rods, fibrils and granules. The latter are chromatin elements that are stained with nuclear dyes. Hyaloplasm and chromatin elements in general can be considered an analogue of the nucleus, since these elements contain DNA; during cell division, they divide longitudinally, and the halves are equally distributed among the daughter cells. But, unlike a typical nucleus, in the cells of blue-green algae around the chromatin elements it is never possible to detect the nuclear envelope and nucleoli. It is a nucleus-like formation in the cell and is called a nucleoid. It also contains ribosomes containing RNA, vacuoles and polyphosphate granules.

It has been established that filamentous forms have plasmodesmata between cells. Sometimes the systems of lamellae of neighboring cells are also interconnected. The transverse partitions in the trichome should by no means be considered pieces of dead matter. It's alive component a cell that is constantly involved in its life processes like the periplast of flagellated organisms.

The protoplasm of blue-green algae is denser than that of other groups of plants; it is immobile and very rarely contains vacuoles filled with cell sap. Vacuoles appear only in old cells, and their occurrence always leads to cell death. But in the cells of blue-green algae, gas vacuoles (pseudo-vacuoles) are often found. These are cavities in the protoplasm filled with nitrogen and giving the cell a black-brown or almost black color in the transmitted light of a microscope. They are found in some species almost constantly, but there are also species in which they are not found. Their presence or absence is often considered a taxonomically important feature, but, of course, we still do not know everything about gas vacuoles. Most often they are found in cells in species that lead a planktonic lifestyle (representatives of the genera Anabaena, Aphanizomenon, Rivularia, Microcystis, etc., Fig. 50, 58.1).

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There is no doubt that the gas vacuoles in these algae serve as a kind of adaptation to a decrease in specific gravity, i.e., to an improvement in “floating” in the water column. And yet their presence is not at all necessary, and even in such typical plankters as Microcystis aeruginosa and M. flosaquae one can observe (especially in autumn) the almost complete disappearance of gas vacuoles. In some species, they appear and disappear suddenly, often for unknown reasons. At nostoca plumiformis(Nostoc pruniforme, pl. 3, 9), large colonies of which always live at the bottom of water bodies; they appear in natural conditions in spring, shortly after the ice melts. The usually greenish-brown colonies then acquire a greyish, sometimes even milky, tinge and completely blur within a few days. Microscopic examination of the alga at this stage shows that all nostoc cells are packed with gas vacuoles (Fig. 50) and become blackish-brown, similar to planktonic anaben cells. Depending on conditions, gas vacuoles persist for up to ten days, but eventually disappear; the formation of a mucous membrane around the cells and their intensive division begins. Each thread or even a piece of thread gives rise to a new organism (colony). A similar picture can also be observed during the germination of spores of epiphytic or planktonic species of gleotrichia. Sometimes gas vacuoles appear only in some cells of the trichome, for example, in the meristem zone, where intensive cell division occurs and hormogonies can occur, the release of which gas vacuoles somehow help.

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Gas vacuoles are formed at the border of the chromato- and centroplasm and are completely irregular in outline. In some species living in the upper layers of bottom silt (in sapropel), in particular in species oscillator, large gas vacuoles are located in the cells on the sides of the transverse partitions. It has been experimentally established that the appearance of such vacuoles is caused by a decrease in the amount of dissolved oxygen in the medium, with the addition of hydrogen sulfide fermentation products to the medium. It can be assumed that such vacuoles arise as storages or places of deposition of gases that are released during enzymatic processes occurring in the cell.

The composition of the pigment apparatus in blue-green algae is very variegated; about 30 different intracellular pigments have been found in them. They belong to four groups - chlorophylls, carotenes, xanthophylls and biliproteins. Of the chlorophylls, the presence of chlorophyll a has been reliably proven so far; from carotenoids - α, β and ε-carotenes; from xanthophylls - echineone, zeaxanthin, cryptoxaitin, mixoxanthophyll, etc., and from biliproteins - c-phycocyanin, c-phycoerythrin and allophycocyanin. Very characteristic of blue-green algae is the presence of the last group of pigments (still found in crimson and some cryptomonads) and the absence of chlorophyll b. The latter once again indicates that blue-green algae are an ancient group that separated and followed an independent path of development even before the appearance of chlorophyll b in the course of evolution, the participation of which in the photochemical reactions of photosynthesis gives the highest efficiency.

The diversity and peculiar composition of photoassimilating pigment systems explains the resistance of blue-green algae to the effects of prolonged darkening and anaerobiosis. This also partly explains their existence in extreme living conditions - in caves, layers of bottom silt rich in hydrogen sulfide, in mineral springs.

The product of photosynthesis in the cells of vulture green algae is a glycoprotein, which occurs in the chromatoplasm and is deposited there. Glycoprotein is similar to glycogen - from a solution of iodine in potassium iodide, it becomes brown. Polysaccharide grains were found between photosynthetic lamellae. Cyanophycin grains in the outer layer of chromatoplasm are composed of lipoproteins. Volutin grains in the centroplasm are reserve substances of protein origin. Sulfur grains appear in the plasma of the inhabitants of sulfur reservoirs.

The variegation of the pigment composition can also explain the diversity of the color of the cells and trichomes of blue-green algae. Their color varies from pure blue-green to purple or reddish, sometimes to purple or brownish-red, from yellow to pale blue or almost black. The color of the protoplast depends on the systematic position of the species, as well as on the age of the cells and the conditions of existence. Very often it is masked by the color of the mucous membranes of the vagina or colonial mucus. Pigments are also found in mucus and give the filaments or colonies a yellow, brown, reddish, purple or blue tint. The color of mucus, in turn, depends on environmental conditions - on light, chemistry and pH of the environment, on the amount of moisture in the air (for aerophytes).

Thread structure. A few blue-green algae grow as single cells, most tend to form colonies or multicellular filaments. In turn, the filaments can either form pseudo-parenchymal colonies, in which they are closely closed, and the cells retain their physiological independence, or have a hormonal structure, in which the cells are connected in a row, making up the so-called trichomes. In a trichome, the protoplasts of neighboring cells are connected by plasmodesmata. A trichome surrounded by a mucous sheath is called a filament.

Filamentous forms can be simple and branched. Branching in blue-green algae is twofold - real and false (Fig. 51). Such branching is called real when a side branch arises as a result of the division of one cell perpendicular to the main thread (the order of Stigonematales). False branching is the formation of a side branch by breaking the trichome and breaking it through the vagina to the side with one or both ends. In the first case, they talk about a single, in the second - about a double (or paired) false branch. Loop-like branching, which is characteristic of the Scytonemataceae family, and the rare V-shaped branching, which is the result of repeated division and growth of two adjacent trichome cells in two mutually opposite directions with respect to the long axis of the filament, can also be considered false branching.

Very many filamentous blue-green algae have peculiar cells called heterocysts. They have a well-defined two-layer shell, and the contents are always devoid of assimilation pigments (it is colorless, bluish or yellowish), gas vacuoles and grains of reserve substances. They are formed from vegetative cells in different places of the trichome, depending on the systematic position of the alga: on one (Rivularia, Calothrix, Gloeotrichia) and both (Anabaenopsis, Cylindrospermum) ends of the trichome - basal and terminal; in the trichome between vegetative cells, i.e. intercalary (Nostoc, Anabaena, Nodularia) or on the side of the trichome - laterally (in some Stigonematales). Heterocysts occur singly or several (2-10) in a row. Depending on the location, one (in terminal and lateral heterocysts) or two, occasionally even three (in intercalary) plugs appear in each heterocyst, which clog the pores between the heterocyst and neighboring vegetative cells from the inside (Fig. 5, 2).

Heterocysts are called a botanical mystery. In a light microscope, they look as if they were empty, but sometimes, much to the surprise of the researchers, they suddenly germinated, giving rise to new trichomes. In false branching and during filament separation, the trichomes most often rupture near the heterocysts, as if they were restricting the growth of the trichomes. Because of this, they used to be called border cells. Threads with basal and terminal heterocysts are attached to the substrate with the help of heterocysts. In some species, the formation of resting cells - spores - is associated with heterocysts: they are located next to the heterocyst one by one (in Sulindrospermum, Gloeotrichia, Anabaenopsis raciborskii) or on both sides (in some Anabaena). It is possible that heterocysts are repositories of some reserve substances or enzymes. It is curious to note that all types of blue-green algae capable of fixing atmospheric nitrogen have heterocysts.

Reproduction. The most common type of reproduction in blue-green algae is cell division in two. For unicellular forms, this method is the only one; in colonies and filaments, it leads to the growth of a filament or colony.

A trichome is formed when cells dividing in the same direction do not move away from each other. If the linear arrangement is violated, a colony with randomly arranged cells appears. When dividing in two perpendicular directions in one plane, a lamellar colony is formed with the correct arrangement of cells in the form of tetrads (Merismopedia). Volumetric accumulations in the form of packets occur when cells divide in three planes (Eucapsis).

Representatives of some genera (Gloeocapsa, Microcystis) are also characterized by rapid division with the formation of many small cells - nanocytes - in the mother cell.

Blue-green algae reproduce in other ways - by the formation of spores (resting cells), exo- and endospores, hormogoniums, hormospores, gonidia, cocci and planococci. One of the most common types of reproduction of filamentous forms is the formation of hormogonia. This method of reproduction is so characteristic of a part of blue-green algae that it served as the name of a whole class. hormogonian(Hormogoniophyceae). Hormogonia are called fragments of the trichome, into which the latter breaks up. The formation of hormogonia is not simply the mechanical separation of a group of two, three, or more cells. Hormogonia are isolated due to the death of some necroidal cells, then, with the help of mucus secretion, they slip out of the vagina (if any) and, making oscillatory movements, move in water or along the substrate. Each hormogony can give rise to a new individual. If a group of cells similar to hormogonia is dressed in a thick shell, it is called a hormospore (hormocyst), which simultaneously performs the functions of both reproduction and the transfer of adverse conditions.

In some species, unicellular fragments are separated from the thallus, which are called gonidia, cocci or planococci. The gonidia retain a mucous membrane; cocci lack clearly defined membranes; planococci are also naked, but, like hormogonia, they have the ability to actively move.

The reasons for the movement of hormogonia, planococci, and whole trichomes (in Oscillatoriaceae) are still far from clear. They slide along the longitudinal axis, oscillating from side to side, or rotate around it. driving force consider the secretion of mucus, contraction of trichomes in the direction of the longitudinal axis, contractions of the outer wavy membrane, as well as electrokinetic phenomena.

Quite common reproductive organs are spores, especially in algae from the order Nostocales. They are unicellular, usually larger than vegetative cells and arise from them, more often from one. However, in representatives of some genera (Gloeotrichia, Anabaena), they are formed as a result of the fusion of several vegetative cells, and the length of such spores can reach 0.5 mm. It is possible that recombination also occurs in the process of such a merger, but so far there are no exact data on this.

The spores are covered with a thick, two-layer membrane, the inner layer of which is called the endosporium, and the outer one is called the exospore. The shells are smooth or dotted with papillae, colorless, yellow or brownish. Due to thick shells and physiological changes in the protoplast (accumulation of reserve substances, disappearance of assimilation pigments, sometimes an increase in the number of cyanophycin grains), spores can remain viable for a long time under adverse conditions and under various strong influences (at low and high temperatures, during drying and strong irradiation) . Under favorable conditions, the spore germinates, its contents are divided into cells - sporohormogonies are formed, the shell becomes slimy, torn or opens with a lid and the hormogonies come out.

Endo- and exospores are found mainly in representatives chamesiphon class(Chamaesiphonophyceae). Endospores are formed in enlarged mother cells in large numbers (over a hundred). Their formation occurs successively (as a result of a series of successive divisions of the protoplast of the mother cell) or simultaneously (by simultaneous disintegration of the mother cell into many small cells). Exospores, as they form, detach from the protoplast of the mother cell and go outside. Sometimes they do not separate from the mother cell, but form chains on it (for example, in some species of Chamaesiphon).

Sexual reproduction in blue-green algae is completely absent.

Ways of nutrition and ecology. It is known that the majority of blue-green algae are able to synthesize all the substances of their cells due to the energy of light. The photosynthetic processes occurring in the cells of blue-green algae are close in their concept to the processes that take place in other chlorophyll-containing organisms.

The photoautotrophic type of nutrition is the main one for them, but not the only one. In addition to true photosynthesis, blue-green algae are capable of photoreduction, photoheterotrophy, autoheterotrophy, heteroautotrophy, and even complete heterotrophy. If present in the environment organic matter they also use them as additional sources of energy. Due to the ability to mixed (mixotrophic) nutrition, they can be active even in extreme conditions for photoautotrophic life. In such habitats, competition is almost completely absent, and blue-green algae occupy a dominant place.

In conditions of poor illumination (in caves, in the deep horizons of reservoirs), the pigment composition in the cells of blue-green algae changes. This phenomenon, called chromatic adaptation, is an adaptive change in the color of algae under the influence of a change in the spectral composition of light due to an increase in the number of pigments that have a color that is complementary to the color of the incident rays. Changes in cell color (chlorosis) also occur in the case of a lack of certain components in the environment, in the presence of toxic substances, and also during the transition to a heterotrophic type of nutrition.

Among the blue-green algae, there is also such a group of species, similar to which there are few among other organisms. These algae are able to fix atmospheric nitrogen, and this property is combined with photosynthesis. About a hundred such species are now known. As already mentioned, this ability is characteristic only of algae that have heterocysts, and not all of them.

Most blue-green algae-nitrogen fixers are confined to terrestrial habitats. It is possible that it is their relative food independence as atmospheric nitrogen fixers that allows them to populate uninhabited, without the slightest traces of soil, rocks, as was observed on the island of Krakatau in 1883: three years after the volcanic eruption, slimy accumulations were found on the ashes and tuffs , consisting of representatives of the genera Anabaena, Gloeocapsa, Nostoc, Calothrix, Phormidium, and others. The first settlers of Surcey Island, which arose as a result of an underwater volcano eruption in 1963 near the southern coast of Iceland, were also nitrogen fixers. Among them were some widespread planktonic species that cause “blooming” of water (Anabaena circinalis, A. cylindrica, A. flos-aquae, A. lemmermannii, A. scheremetievii, A. spiroides, Anabaenopsis circularis, Gloeotrichia echinulata).

The maximum temperature for the existence of a living and assimilating cell is +65°C, but this is not the limit for blue-green algae (see essay on hot spring algae). Thermophilic blue-green algae tolerate such a high temperature due to the peculiar colloidal state of protoplasm, which coagulates very slowly at high temperatures. The most common thermophiles are cosmopolitans Mastigocladus laminosus, Phormidium laminosum. Blue-green algae are able to withstand low temperatures. Some species were stored without damage for a week at liquid air temperature (-190°C). In nature, there is no such temperature, but in Antarctica at a temperature of -83 ° C, blue-green algae (nostoks) were found in large numbers.

In Antarctica and in the highlands, in addition to low temperatures, algae are also affected by high temperatures. solar radiation. To reduce the harmful effects of short-wave radiation, blue-green algae have acquired a number of adaptations in the course of evolution. The most important of these is the secretion of mucus around the cells. The mucus of the colonies and the mucous membranes of the filamentous forms of the vagina are a good protective wrapper that protects the cells from drying out and at the same time acts as a filter that eliminates the harmful effects of radiation. Depending on the intensity of light, more or less pigment is deposited in the mucus, and it is colored throughout its thickness or in layers.

The ability of mucus to quickly absorb and retain water for a long time allows blue-green algae normally vegetate in desert areas. Mucus absorbs the maximum amount of night or morning moisture, the colonies swell, and assimilation begins in the cells. By noon, gelatinous colonies or clusters of cells dry out and turn into black crispy crusts. In this state, they keep until the next night, when the absorption of moisture begins again.

For an active life, vaporous water is quite enough for them.

Blue-green algae are very common in the soil and in ground communities, they are also found in damp habitats, as well as on the bark of trees, on stones, etc. All these habitats are often not constantly provided with moisture and are unevenly lit (for more details, see the essays about terrestrial and soil algae).

Blue-green algae are also found in cryophilic communities - on ice and snow. Photosynthesis is possible, of course, only when the cells are surrounded by a layer of liquid water, which happens here in the bright sunlight of snow and ice.

Solar radiation on glaciers and snowfields is very intense, a significant part of it is short-wave radiation, which causes protective adaptations in algae. The group of cryobionts includes a number of species of blue-green algae, but still, in general, representatives of this division prefer habitats with elevated temperatures (for more details, see the essay on snow and ice algae).

Blue-green algae predominate in the plankton of eutrophic (nutrient-rich) water bodies, where their mass development often causes water "bloom". The planktonic way of life of these algae is facilitated by gas vacuoles in the cells, although not all pathogens of "blooming" have them (Table 4). Live secretions and post-mortem decomposition products of some of these blue-green algae are poisonous. The mass development of most planktonic blue-green algae begins at high temperatures, i.e., in the second half of spring, summer and early autumn. It has been established that for most freshwater blue-green algae, the optimum temperature is around +30°C. There are also exceptions. Some types of oscillatoria cause water to “bloom” under ice, that is, at a temperature of about 0 ° C. Colorless and hydrogen sulfide-loving species develop in mass quantities in the deep layers of lakes. Some pathogens of "flowering" clearly go beyond the boundaries of their range due to human activity. Thus, species of the genus Anabaenopsis were not encountered for a long time outside the tropical and subtropical regions, but then they were found in the southern regions of the temperate zone, and a few years ago they developed already in the Helsinki Bay. Suitable temperatures and increased eutrophication (organic pollution) allowed this organism to develop in large numbers north of the 60th parallel.

The "bloom" of water in general, and that caused by blue-green algae in particular, is considered a natural disaster, since the water becomes almost useless. At the same time, secondary pollution and silting of the reservoir significantly increase, since the biomass of algae in the "blooming" reservoir reaches significant values ​​(average biomass - up to 200 g / m3, maximum - up to 450-500 g / m3), and among blue-greens there is very little species that would be eaten by other organisms.

The relationship between blue-green algae and other organisms is multilateral. Species from the genera Gloeocapsa, Nostoc, Scytonema, Stigonema, Rivularia and Calothrix are phycobionts in lichens. Some blue-green algae live in other organisms as assimilators. Anabaena and Nostoc species live in the air chambers of Anthoceros and Blasia mosses. Anabaena azollae lives in the leaves of the water fern Azolla americana, and in the intercellular spaces of Cycas and Zamia-Nostoc punctiforme (for more details, see the essay on the symbiosis of algae with other organisms).

Thus, blue-green algae are found on all continents and in all kinds of habitats - in water and on land, in fresh and salt water, everywhere and everywhere.

Many authors are of the opinion that all blue-green algae are ubiquitous and cosmopolitan, but this is far from being the case. We have already mentioned the geographical distribution of the genus Anabaenopsis. Detailed studies have shown that even such a common species as Nostoc pruniforme is not cosmopolitan. Some genera (for example, Nostochopsis, Camptylonemopsis, Raphidiopsis) are entirely confined to zones of hot or warm climates, Nostoc flagelliforme - to arid regions, many species of the genus Chamaesiphon - to cold and clean rivers and streams of mountainous countries.

The department of blue-green algae is considered the oldest group of autotrophic plants on Earth. The primitive structure of the cell, the absence of sexual reproduction and flagellar stages are all serious evidence of their antiquity. By cytology, blue-greens are similar to bacteria, and some of their pigments (biliproteins) are also found in red algae. However, taking into account the whole complex of features characteristic of the department, it can be assumed that blue-green algae are an independent branch of evolution. Over three billion years ago, they departed from the main trunk of plant evolution and formed a dead end branch.

Speaking about the economic importance of blue-greens, their role as causative agents of the “blooming” of water should be put in the first place. This, unfortunately, is a negative one. Their positive value lies primarily in the ability to absorb free nitrogen. In eastern countries, blue-green algae are even used for food, and in last years some of them have found their way into mass culture basins for the industrial production of organic matter.

The taxonomy of blue-green algae is still far from perfect. The comparative simplicity of morphology, the relatively small number of characters valuable from the point of view of systematics and the wide variability of some of them, as well as the different interpretations of the same characters, have led to the fact that almost all existing systems are subjective to some extent and far from natural. There is no good, reasonable distinction between the view as a whole and the scope of the view in different systems is understood differently. Total species in the department is determined in 1500-2000. According to the system adopted by us, the department of blue-green algae is divided into 3 classes, several orders and many families.

Biological Encyclopedia

SYSTEMATICS AND ITS OBJECTIVES A special branch of biology called systematics deals with the classification of organisms and the elucidation of their evolutionary relationships. Some biologists call systematics the science of diversity (diversity ... ... Biological Encyclopedia

Symbiosis, or the cohabitation of two organisms, is one of the most interesting and still largely mysterious phenomena in biology, although the study of this issue has almost a century of history. The phenomenon of symbiosis was first discovered by the Swiss… Biological Encyclopedia

Kingdom of Drobyanka
This kingdom includes bacteria and blue-green algae. These are prokaryotic organisms: their cells lack a nucleus and membrane organelles, the genetic material is represented by a circular DNA molecule. They are also characterized by the presence of mesosomes (an invagination of the membrane into the cell), which perform the function of mitochondria, and small ribosomes.

bacteria
Bacteria are single-celled organisms. They occupy all environments of life and are widespread in nature. According to the shape of the cells, bacteria are:
1. globular: cocci - they can combine and form structures of two cells (diplococci), in the form of chains (streptococci), clusters (staphylococci), etc.;
2. rod-shaped: bacilli (dysentery bacillus, hay bacillus, plague bacillus);
3. curved: vibrios - the form of a comma (cholera vibrio), spirilla - weakly spiralized, spirochetes - strongly twisted (causative agents of syphilis, relapsing fever).

The structure of bacteria
Outside, the cell is covered with a cell wall, which includes murein. Many bacteria are able to form an outer capsule that provides additional protection. Under the shell is the plasma membrane, and inside the cell is the cytoplasm with inclusions, small ribosomes and genetic material in the form of circular DNA. The part of a bacterial cell that contains the genetic material is called the nucleoid. Many bacteria have flagella responsible for movement.

Bacteria are divided into two groups based on the structure of the cell wall: gram-positive(stained by Gram when preparing preparations for microscopy) and gram-negative (not stained by this method) bacteria (Fig. 4).

reproduction
It is carried out by division into two cells. First, DNA replication occurs, then a transverse septum appears in the cell. Under favorable conditions, one division occurs every 15-20 minutes. Bacteria are able to form colonies - an accumulation of thousands or more cells that are descendants of one original cell (colonies of bacteria rarely occur in nature; usually in artificial conditions growth medium).
Under adverse conditions, bacteria are able to form spores. The spores have a very dense outer shell that can withstand various external influences: boiling for several hours, almost complete dehydration. Spores remain viable for tens and hundreds of years. When favorable conditions occur, the spore germinates and forms a bacterial cell.

living conditions
1. Temperature - optimal from +4 to +40 ° С; if lower, then most bacteria form spores, higher - they die (therefore, medical instruments are boiled and not frozen). There is a small group of bacteria that prefer high temperatures - these are thermophiles that live in geysers.
2. In relation to oxygen, two groups of bacteria are distinguished:
aerobes - live in an oxygen environment;
anaerobes - live in an oxygen-free environment.
3. Neutral or alkaline environment. The acidic environment kills most bacteria; this is the basis for the application acetic acid when preserving.
4. No direct sunlight (they also kill most bacteria).

Importance of bacteria
positive
1. Lactic acid bacteria are used to produce lactic acid products (yogurt, curdled milk, kefir), cheeses; when pickling cabbage and pickling cucumbers; for the production of silage.
2. Symbiont bacteria are found in the digestive tract of many animals (termites, artiodactyls), participating in the digestion of fiber.
3. Production of drugs (antibiotic tetracycline, streptomycin), acetic and other organic acids; feed protein production.
4. They decompose the corpses of animals and dead plants, that is, they participate in the circulation of substances.
5. Nitrogen-fixing bacteria convert atmospheric nitrogen into compounds that are assimilated by plants.

negative
1. Food spoilage.
2. Cause human diseases (diphtheria, pneumonia, tonsillitis, dysentery, cholera, plague, tuberculosis). Treatment and prevention: vaccinations; antibiotics; hygiene; destruction of carriers.
3. Cause diseases of animals and plants.

Blue-green algae (cyanoea, cyanobacteria)
Blue-green algae live in aquatic environment and on the ground. Their cells have a structure typical of prokaryotes. Many of them contain vacuoles in the cytoplasm that support the buoyancy of the cell. Able to form spores to wait out adverse conditions.
Blue-green algae are autotrophs, contain chlorophyll and other pigments (carotene, xanthophyll, phycobilins); capable of photosynthesis. During photosynthesis, oxygen is released into the atmosphere (it is believed that it was their activity that led to the accumulation of free oxygen in the atmosphere).
Reproduction is carried out by crushing in unicellular forms and by the collapse of colonies (vegetative reproduction) in filamentous ones.
The value of blue-green algae: cause the "bloom" of water; bind atmospheric nitrogen, converting it into forms available to plants (thus, increasing the productivity of reservoirs and rice fields), are part of lichens.

reproduction
Fungi reproduce asexually and sexually. Asexual reproduction: budding; parts of the mycelium, with the help of spores. Spores are endogenous (formed inside sporangia) and exogenous or conidia (they are formed on the tops of special hyphae). Sexual reproduction in lower fungi is carried out by conjugation, when two gametes merge and a zygospore is formed. It then forms sporangia, where meiosis occurs, and haploid spores are formed, from which a new mycelium develops. In higher fungi, bags (asci) are formed, inside which haploid ascospores, or basidia, develop, to which basidiospores are attached from the outside.

mushroom classification
There are several departments, which are combined into two groups: higher and lower mushrooms. Separately, there are so-called. imperfect fungi, which include species of fungi whose sexual process has not yet been established.

Department of Zygomycetes
They belong to the lower mushrooms. The most common of these is the genus Mukor are fungi. They settle on food and dead organic residues (for example, on manure), i.e., they have a saprotrophic type of nutrition. Mucor has a well-developed haploid mycelium, hyphae are usually non-segmented, there is no fruiting body. The color of the mucor is white; when the spores ripen, it turns black. Asexual reproduction occurs with the help of spores that mature in sporangia (mitosis occurs during spore formation) developing at the ends of some hyphae. Sexual reproduction is relatively rare (with the help of zygospores).

Department of Ascomycetes
This is the largest group of mushrooms. It includes unicellular forms (yeast), species with fruit bodies (morels, truffles), various molds (penicillium, aspergillus).
Penicillium and Aspergillus. Found on food (citrus fruits, bread); in nature, they usually settle on fruits. The mycelium consists of segmented hyphae, separated by partitions (septa) into compartments. The mycelium is white at first, later it can acquire a green or bluish tint. Penicillium is able to synthesize antibiotics (penicillin discovered by A. Fleming in 1929).
Asexual reproduction occurs with the help of conidia, which are formed at the ends of special hyphae (conidiophores). During sexual reproduction, the fusion of haploid cells and the formation of a zygote, from which a bag (ask) is formed, occurs. Meiosis occurs in it, and ascospores are formed.

Yeast - These are unicellular fungi, characterized by the absence of mycelium and consisting of individual spherical cells. Yeast cells are rich in fat, contain one haploid nucleus, and have a vacuole. Asexual reproduction occurs by budding. Sexual process: cells fuse, a zygote is formed, in which meiosis occurs, and a bag with 4 haploid spores is formed. In nature, yeast is found on juicy fruits.

in fig. Division of yeast by budding

Department of Basidiomycetes
These are the higher mushrooms. The characteristic of this department is considered on the example of cap mushrooms. This department includes most edible mushrooms (champignon, porcini mushroom, butterdish); but there are also poisonous mushrooms (pale grebe, fly agaric).
The hyphae have an articulated structure. Mycelium perennial; fruiting bodies are formed on it. First, the fruiting body grows underground, then it comes to the surface, rapidly increasing in size. The fruit body is formed by hyphae tightly adjacent to each other; a hat and a leg are distinguished in it. The top layer of the cap is usually brightly colored. In the lower layer, sterile hyphae, large cells (protect the spore-bearing layer) and the basidia themselves are isolated. Plates are formed on the lower layer - these are agaric mushrooms (mushroom, chanterelle, mushroom) or tubules - these are tubular mushrooms (oil can, porcini mushroom, boletus). On the plates or on the walls of the tubules, basidia are formed, in which the nuclei merge to form a diploid nucleus. Basidiospores develop from it by meiosis, during the germination of which a haploid mycelium is formed. The segments of this mycelium merge, but the fusion of the nuclei does not occur - this is how the dicarionic mycelium is formed, which forms the fruiting body.

The meaning of mushrooms
1) Food - many mushrooms are eaten.
2) Cause plant diseases - ascomycetes, smut and rust fungi. These fungi infect cereals. Spores of rust fungi (bread rust) are carried by the wind and fall on cereals from intermediate hosts (barberry). Spores of smut fungi (smut) are carried by the wind, fall on the grains of cereals (from infected cereal plants), attach and overwinter together with the grain. When it germinates in the spring, the spore of the fungus also germinates and penetrates the inside of the plant. In the future, the hyphae of this fungus penetrate into the ear of cereal, forming black spores (hence the name). These mushrooms do serious damage. agriculture.
3) Cause human diseases (ringworm, aspergillosis).
4) Destroy wood (tinder fungus - settle on trees and wooden buildings). This is a double meaning: if a dead tree is destroyed, then it is positive, if it is alive or wooden buildings, then it is negative. The tinder fungus penetrates into a living tree through wounds on the surface, then mycelium develops in the wood, on which perennial fruiting bodies are formed. They produce spores that are dispersed by the wind. These fungi can cause the death of fruit trees.
5) Poisonous mushrooms can cause poisoning, sometimes quite severe (up to fatality).
6) Food spoilage (mold).
7) Receiving medicines.
They cause alcoholic fermentation (yeast), therefore they are used by humans in the baking and confectionery industries; in winemaking and brewing.
9) They are decomposers in communities.
10) Form a symbiosis with higher plants - mycorrhiza. In this case, the roots of the plant can digest the hyphae of the fungus, and the fungus can inhibit the plant. But, despite this, these relationships are considered mutually beneficial. In the presence of mycorrhiza, many plants develop much faster.