The structure of the bacterial cell: features. What is the structure of a bacterial cell?
We cannot even imagine how many microorganisms constantly surround us. Having taken hold of the rail in the bus, you have already planted about a hundred thousand bacteria in your hand, by going to the public toilet, again, you rewarded yourself with these microorganisms. Bacteria always and everywhere accompany a person. But it is not necessary to react negatively to this word, because bacteria are not only pathogenic, but also beneficial to the body.
Scientists were very surprised when they realized that some bacteria retained their appearance for about a billion years. Such microorganisms were even compared with a Volkswagen car - the appearance of one of their models has not changed for 40 years, having an ideal shape.
Bacteria appeared on the Earth one of the first, so they deservedly be called long-livers.Interesting is the fact that these cells do not have a formed nucleus, so to this day they attract a lot of attention to their structure.
What are bacteria?
Bacteria are microscopic organisms of plant origin. The structure of the bacterial cell (table, diagrams exist for clarity of understanding the types of these cells) depends on its purpose.
These cells are distributed everywhere, as they are able to multiply rapidly. There is scientific evidence that literally in six hours a single cell can give offspring of 250 thousand bacteria. These single-celled organisms have many varieties that differ in shape.
Bacteria are very tenacious organisms, their spores can maintain the ability to live for 30-40 years. These disputes are transferred with the wind blow, water flow and in other ways. Viability is maintained up to a temperature of 100 degrees and with a slight frost. And yet, what is the structure of a bacterial cell? The table describes the main components of the bacteria, the functions of other organelles are outlined below.
|Name of cell components||Functions of the elements of bacteria|
|Capsule||Cell protection and hydration|
|Cytoplasm||Preservation of communication between cellular organelles|
|Nuclear matter||Preservation and transfer of hereditary material|
|Cell wall||Ensuring the protection and preservation of the shape of bacteria|
Spherical (cocci) bacteria
By nature, they are pathogenic. Cocci are divided into groups depending on their location to each other:
- Micrococci (small). The division occurs in the same plane. Arrangement in a chaotic solitary order. They feed on ready-made organic compounds, but do not depend on other organisms (saprophytes).
- Diplococci (double). They share in the same plane as micrococci, but form paired cells. They look like beans or lancelet.
- Streptococci (in the form of a chain). The division is the same, but the cells are interconnected and look like beads.
- Staphylococcus (bunch of grapes). This species is divided in several planes, with the formation of clusters of cells similar to grapes.
- Tetrakokki (four). Cells divide in two perpendicular planes, forming tetrads.
- Sarcins (bundle). Such cells are divided in three planes, which are mutually perpendicular to each other.At the same time, they look like bags or bales, consisting of many individuals of an even number.
Cylindrical (sticks) bacteria
The sticks that form the spores are divided into clostridia and bacilli. In size, these bacteria are short and very short. The end sections of the sticks are rounded, thickened or trimmed. Depending on the location of the bacteria, several groups are distinguished: mono-, diploo, and streptobacteria.
Spiral (twisted) bacteria
These microscopic cells are of two types:
- Vibrioes (with a single bend or generally straight).
- Spirilla (large in size, but few curls).
Threadlike bacteria. There are two groups of such forms:
- Temporary threads.
- Permanent threads.
The structural features of the bacterial cell consist in the fact that in the course of its existence it is capable of changing forms, but at the same time, polymorphism is not inherited. Various factors act on the cell in the process of metabolism in the body, as a result of which quantitative changes in its appearance are observed. But as soon as the action from the outside stops, the cell will take on the old image.What are the structural features of a bacterial cell can be identified when viewed with a microscope.
The structure of the bacterial cell, the shell
The shell gives and maintains the shape of the cell, protects the internal components from damage. Due to incomplete permeability, not all substances can enter the cell, which facilitates the exchange of low and high molecular structures between the external environment and the cell itself. Various chemical reactions also occur in the wall. Using an electron microscope, it is easy to examine what kind of detailed structure a bacterial cell has.
The base of the shell contains polymer murein. Gram-positive bacteria have a single-layer skeleton consisting of murein. Here are the polysaccharide and lipoprotein complexes, phosphates. In gram-negative cells, the mouraine skeleton has many layers. The outer layer adjacent to the cell wall is the cytoplasmic membrane. It also has certain layers containing proteins with lipids. The main function of the cytoplasmic membrane is to control the penetration of substances into the cell and their removal (osmotic barrier).This is a very important function for cells, as it helps to protect cells.
The composition of the cytoplasm
The living semi-liquid substance that fills the cell cavity is called the cytoplasm. A large amount of protein, a supply of nutrients (fats and fat-like substances) contains a bacterial cell. A photo taken during a microscopic examination clearly shows the constituent parts inside the cytoplasm. The main part consists of ribosomes, which are located in a chaotic manner and a large number. Also in the composition are mesosomes containing redox enzymes. Due to them, the cell draws energy. The nucleus is represented as a nuclear substance in chromatin bodies.
Functions of ribosomes in cells
Ribosomes are made up of subunits (2) and are nucleoproteins. Combining with each other, these constituent elements form polysomes or polyribosomes. The main objective of these inclusions is protein synthesis, which occurs on the basis of genetic information. Sedimentation rate of 70s.
Features of the nucleus of bacteria
Genetic material (DNA) is in the unformed nucleus (nucleoid).This nucleus is located in several places of the cytoplasm, being a loose shell. Bacteria with such a nucleus are called prokaryotes. The apparatus of the nucleus is devoid of the membrane, the nucleolus and the set of chromosomes. And deoxyribonucleic acid is located in it by fibril bundles. The scheme of the structure of the bacterial cell in detail demonstrates the structure of the nuclear apparatus.
Under some conditions, bacteria may cause an oeze of the membranes. This results in the formation of a capsule. If the mucus is very strong, then the bacteria turn into a zoogly (total mucous mass).
Bacterial cell capsule
The structure of the bacterial cell has a feature - the presence of a protective capsule consisting of polysaccharides or glycoproteins. Sometimes these capsules are made of polypeptides or fiber. It is located on top of the cell wall. The thickness of the capsule can be both thick and thin. Its formation occurs due to the conditions in which the cell falls. The main property of the capsule is to protect the bacteria from drying out.
In addition to the protective capsule, the structure of the bacterial cell provides for its motor ability.
Flagella on bacterial cells
Flagella are additional elements that move the cell. They are presented in the form of filaments of different lengths, which consist of flagellin. It is a protein that has the ability to shrink.
The composition of the flagellum is three-component (thread, hook, basal body). Depending on the attachment and location, several groups of motile bacteria were identified:
- Monotrichi (these cells have 1 flagellum located polar).
- Lofotrichi (flagella in the form of a bundle at one end of the cell).
- Amphitrich (bundles from both ends).
There are many interesting facts about bacteria. So, it has long been proven that the mobile phone contains a huge number of these cells, even on the toilet seat there are fewer of them. Other bacteria allow us to live a quality life - to eat, to carry out certain activities, to free our body from the decay products of nutrients without any problems. Bacteria are truly diverse, their functions are multifaceted, but we should not forget about their pathological effects on the body, so it is important to monitor their own hygiene and cleanliness around us.