Among the organisms existing today, there are constant debates about their belonging to any kingdom of wildlife . This happens with creatures called cyanobacteria. Although they don’t even have an exact name. Too many synonyms:
- blue-green algae;
- cyanobionts;
- phytochrome granules;
- cyanoes;
- mucus algae and others.
So it turns out that cyanobacteria is a completely small, but at the same time such 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 time, several (3.5) billion years ago. Such conclusions allowed the research of paleontologists who analyzed the rocks (their sections) of those distant times.
Cyanobacteria were found on the surface of the samples, the structure of which was no different from that of modern forms. This indicates a high degree of fitness of these creatures to various living 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 affected the viability of cyanide.
In modern times, cyanobacteria is a unicellular organism that has been discovered simultaneously with other forms of bacterial cells. That is, Antonio Van Levenguk, Louis Pasteur and other researchers in the XVIII-XIX centuries.
They underwent a more thorough study later, with the development of electron microscopy and modernized research methods and methods. The features that possess cyanobacteria were identified. The structure of the cell includes a number of new structures not found in other creatures.
Classification
The question of determining their taxonomic affiliation remains open. So far, only one thing is known: cyanobacteria are prokaryotes. Confirmation of this are features such as:
- lack of nucleus, mitochondria, chloroplasts;
- the presence of murein in the cell wall;
- S-ribosome molecules in the cell.
Nevertheless, cyanobacteria are prokaryotes, numbering about 1,500 thousand species. All of them were classified and combined into 5 large morphological groups.
- Chroococcal. A fairly large group that combines single or colonial forms. High concentrations of organisms are held together due to the common mucus secreted by the cell wall of each individual. In shape, rod-shaped and spherical structures belong to this group.
- Pleurocaps. Very similar to previous forms, however, a feature appears in the form of formation of beocytes (more on this phenomenon later). The cyanobacteria included here belong to three main classes: Pleurocapses, Dermocapses, Mixosarcinos.
- Oxyllatoria. The main feature of this group is that all cells are combined into a common mucus structure called trichome. The division occurs without going beyond the limits of this thread, inside. Oscillatoria include exclusively vegetative cells that divide in asexually in half.
- Nostokovye. Interesting for their cryophilicity. Able to inhabit open ice deserts, forming colored raids on them. The so-called phenomenon of "flowering icy deserts." The forms of these organisms are also filamentous in the form of trichomes, however, sexual reproduction, with the help of specialized cells, is heterocysts. The following representatives can be attributed here: Anaben, Nostoki, Kalotriksy.
- Stigonemovye. Very similar to the previous group. The main difference in the method of reproduction is that they are able to divide multiple times within the same cell. The most popular representative of this association is Fischerella.
Thus, cyanides are classified according to the morphological criterion, since for the rest many questions arise and confusion arises. Botanists and microbiologists cannot yet come to a common denominator in the taxonomy of cyanobacteria.
Habitat
Due to the presence of special devices (heterocysts, beocytes, unusual thillakoids, gas vacuoles, the ability to fix molecular nitrogen and others), these organisms settled 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 environment with a pH of less than 4.
Cyanobacteria is an organism that survives quietly on sea sand and rocky ledges, blocks of ice and hot deserts. One can recognize and determine the presence of cyanides by the characteristic color coating that their colonies form. Color can vary from blue-black to pink and purple.
They are called blue-green because often they form a blue-green mucus film on the surface of ordinary fresh or salt waters. This phenomenon is called "flowering water." It can be seen on almost any lake that begins to overgrow and swamp.
Cell structure features
The structure of cyanobacteria is common for prokaryotic organisms, however, there are some features.
The general plan of the cell structure is as follows:
- cell wall of polysaccharides and murein;
- bilipid plasma membrane ;
- cytoplasm with freely distributed genetic material in the form of a DNA molecule;
- thillakoids that perform the function of photosynthesis and contain pigments (chlorophylls, xanthophylls, carotenoids).
We will consider the special parts of the cell below.
Types of specialized structures
First of all, these are heterocysts. These structures are not parts, but the cells themselves as part of trichomes (a common colonial thread combined by mucus). When viewed under a microscope, they differ in their composition, since their main function is to produce an enzyme that allows molecular nitrogen to be fixed from the air. Therefore, there are practically no pigments in heterocysts, but there is quite a lot of nitrogen.
Secondly, these are hormone hormones - plots torn from trichomes. Serve as breeding sites.
Beocytes are a kind of daughter cells, in the majority endowed from one mother. Sometimes their number reaches one thousand in one division period. Dermocapses and other pleurocapsodium ones are capable of such a feature.
Akinets are special cells that are at rest and included in the composition of trichomes. They differ in a 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 to take part in the processes of flowering water. Another name for such structures is carboxysomes.
Cellular inclusions. Of course, they are found in plant, animal, and bacterial cells. However, in blue-green algae, these inclusions are somewhat different. These include:
- glycogen;
- polyphosphate granules;
- cyanocin is a special substance consisting of aspartate, arginine. Serves for the accumulation of nitrogen, since these inclusions are located in heterocysts.
This is what cyanobacteria have. The main parts and specialized cells and organelles - this is what allows cyanide to carry out photosynthesis, but at the same time relate to bacteria.
Breeding
This process is not particularly difficult, since it is the same as ordinary bacteria have. Cyanobacteria can divide vegetatively, in parts of trichomes, an ordinary cell in two, or carry out the sexual process.
Often, specialized cells heterocysts, akinets, and beocytes participate in these processes.
Ways of movement
A cell of cyanobacteria is covered on the outside 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 that cyanide movement is carried out.
No flagella or special outgrowths. Movement can be carried out only on a hard surface with the help of mucus, in short contractions. Some Oscillatoria have a very unusual way of moving - they spin around their axis and at the same time cause the rotation of the entire trichome. So there is movement on the surface.
Nitrogen fixation ability
Almost every cyanobacteria possesses this feature. This is possible due to the presence of the enzyme nitrogenase, which is able to fix molecular nitrogen and translate it into a digestible form of compounds. This happens in heterocyst structures. Therefore, those species that do not have them are not capable of fixing nitrogen from the air.
In general, this process makes cyanobacteria very important creatures for plant life. Settling in the soil, cyanides help representatives of the flora to absorb bound nitrogen and lead a normal lifestyle.
Anaerobic species
Some forms of blue-green algae (for example, Oscillatoria) are able to live in completely anaerobic conditions and an atmosphere of hydrogen sulfide. In this case, the compound is processed inside the body and, as a result, molecular sulfur forms, which enters the environment.