Cyanobacterium is ... Cyanobacteria: structure, general information

Among existing organisms there are those whose belonging to a certain wildlife kingdom is constantly disputed. This is what happens with creatures called cyanobacteria. Although they do not even have the exact names. Too many synonyms:

• Blue-green algae;
• Cyanobionts;
• Phycochrome crushers;
• Cyanine;
• Mucus algae and others.

So it turns out that cyanobacterium is a very small, but at the same time, a complex and contradictory organism that requires careful study and consideration of its structure in order to determine the exact taxonomic affiliation.

History of existence and discovery

Judging by the fossil remains, the history of the existence of blue-green algae has its roots far back in the past, several million years ago. Such conclusions allowed to make researches of scientists-paleontologists who analyzed rocks (their sites) of those far times.

On the surface of the samples were found cyanobacteria, the structure of which was no different from that of modern forms. This indicates a high degree of fitness of these creatures to different habitat conditions, to their extreme endurance and survival. Obviously, over millions of years, there have been many changes in the temperature and gas composition of the planet. However, nothing has affected the viability of cyanide.

In modern times, cyanobacterium is a unicellular organism that was discovered simultaneously with other forms of bacterial cells. That is Antonio Van Leuvengueck, Louis Pasteur and other researchers in the XVIII-XIX centuries.

They were subjected to a more detailed study later, with the development of electron microscopy and modernized methods and methods of investigation. The peculiarities of cyanobacteria have been revealed. The structure of the cell includes a number of new structures that are not found in other beings.

Classification

The question of determining their taxonomic affiliation remains open. So far, only one thing is known: cyanobacteria are prokaryotes. This is confirmed by such features as:

• Absence of nucleus, mitochondria, chloroplasts;
• Presence in the cell wall of murein;
• Molecule of S-ribosomes in the cell.

Nevertheless, cyanobacteria are prokaryotes, numbering about 1500 thousand varieties. All of them were classified and combined into 5 large morphological groupings.

1. Chromococcal. A fairly large group, uniting single or colonial forms. High concentrations of organisms are retained together due to the general mucus secreted by the cell wall of each individual. The shape of this group includes rod-shaped and globular structures.
2. Pleurocapsids. Very similar to the previous forms, but there is a feature in the form of the formation of the bocytes (more on this phenomenon later). Included in this cyanobacteria belong to three main classes: Pleurokapsy, Dermokapsy, Mixoksartsiny.
3. Oxillatoria. The main feature of this group is that all cells combine into a common mucus structure called trichoma. The division occurs, without going beyond this thread, inside. Oscillatoria include only vegetative cells that divide asexually in half.
4. Nostokovye. Interesting for their cryophility. Capable of living on open ice deserts, forming on them colored raids. The so-called phenomenon of "flowering ice deserts". The forms of these organisms are also filamentous in the form of trichomes, but reproduction is sexual, with the help of specialized cells - heterocyst. You can bring here the following representatives: Anaben, Nostoki, Kalotriksy.
5. Stingone. Very similar to the previous group. The main difference in the method of reproduction is that they are able to divide multiply within a single cell. The most popular representative of this association is Fisherella.

Thus, cyanides are also classified according to the morphological criterion, since there are many questions on the rest and confusion is obtained. Botany and microbiologists to the common denominator in the taxonomy of cyanobacteria can not yet come.

Habitat

Thanks to the availability of special devices (heterocyst, beotsites, unusual tillacoids, gas vacuoles, ability to fix molecular nitrogen and others), these organisms have spread everywhere. They are able to survive even in the most extreme conditions, in which no living organism can exist at all. For example, hot thermophilic sources, anaerobic conditions with an atmosphere of hydrogen sulfide, an acidic medium with a pH of less than 4.

Cyanobacterium is an organism that quietly survives on sea sand and rocky protrusions, ice blocks and hot deserts. To know and determine the presence of cyanide can be by the characteristic color coating, which form their colonies. Color can be different, from blue-black to pink and purple.

They are called blue-green because they often form a blue-green mucus film on the surface of ordinary fresh or saline water. This phenomenon was called the "flowering of water". It can be seen almost on any lake, which begins to overgrow and swam.

Features of the structure of the cell

Cyanobacteria structure is common for prokaryotic organisms, but there are also some features.

The overall plan of the cell structure is as follows:

• Cell wall of polysaccharides and murein;
• Plasma membrane of bilipid structure;
• Cytoplasm with freely distributed genetic material in the form of a DNA molecule;
• Tillakoidy, performing the function of photosynthesis and containing pigments (chlorophylls, xanthophylls, carotenoids).

The special parts of the cell will be considered further.

Types of specialized structures

First of all, these are heterocysts. These structures are not parts, but the cells themselves in the composition of the trichome (a common colonial thread, combined with mucus). They differ when viewed in a microscope by their composition, since their main function is the production of an enzyme that allows fixing molecular nitrogen from the air. Therefore, there are practically no pigments in heterocysts, but there is a lot of nitrogen.

Secondly, this is gormogonii - plots, torn from trichomes. Served as breeding sites.

The beots are the original daughter cells, which in many cases are made up of one parent. Sometimes their number reaches one thousand during one division period. Dermocapses and other Pleurocapsodia are capable of such a feature.

Akinets are special cells that are at rest and are included in the trichomes. They differ more massive, polysaccharide-rich cell wall. Their role is similar to heterocysts.

Gas vacuoles - all cyanobacteria have them. The structure of the cell initially implies their presence. Their role is involved in the flowering of water. Another name for such structures is the carboxysome.

Cell inclusions. They certainly exist in plant, animal, and bacterial cells. However, in blue-green algae, these inclusions are somewhat different. These include:

• glycogen;
• Granules of polyphosphate;
• Cyanofen - a special substance consisting of aspartate, arginine. Serves for the accumulation of nitrogen, since these inclusions are in heterocysts.

This is what cyanobacterium possesses. The main parts and specialized cells and organoids are what allows cyanines to carry out photosynthesis, but at the same time treat bacteria.

Reproduction

This process is not particularly difficult, since it is the same as that of ordinary bacteria. Cyanobacteria can divide vegetatively, trichomatically, in a conventional cell in two, or carry out the sexual process.

Often in these processes specialized cells are heterocysts, akinets, and beotsites.

Ways of movement

The cell of the cyanobacterium is covered externally with a cell wall, and sometimes also with a layer of a special polysaccharide, capable of forming a mucus capsule around it. It is thanks to this feature and the movement of cyanide.

Flagellum or special outgrowths. Movement can only be carried out on a hard surface with mucus, with short cuts. Some Oscillatoria have a very unusual way of moving - they spin around their axis and simultaneously cause the rotation of the entire trichome. This is how the surface moves.

Ability to fix nitrogen

This feature has almost every cyanobacter. This is possible due to the presence of a nitrogenase enzyme capable of fixing molecular nitrogen and converting it into a digestible form of compounds. This occurs in the structures of heterocysts. Consequently, those species that do not have them, fix nitrogen from the air are not capable.

In general, this process makes cyanobacteria very important creatures for plant life. Settling in the soil, cyanides help the representatives of the flora to absorb the bound nitrogen and lead a normal life.

Anaerobic species

Some forms of blue-green algae (for example, Oscillilla) are able to live in completely anaerobic conditions and hydrogen sulphide atmosphere. In this case, the compound is processed inside the body and as a result, molecular sulfur is formed, which is released into the environment.