The cultural properties of bacteria: the definition, description, features and functions

Microbiology is a vast modern science that studies the biochemical and physical properties, morphology and systematics of bacteria. The world of prokaryotes is rich in a huge number of different species. To investigate all the parameters of these microorganisms, work is carried out with their cultures on special nutrient media under sterile conditions. The cultural properties of bacteria is one of the most important ways to determine and study prokaryotes.

What is a colony of bacteria?

It's not a secret that prokaryotes are unicellular organisms. They easily and quickly multiply, doubling their number, according to some data, every 20-30 minutes. It's easy to guess that we have a geometric progression of culture growth.

The colony is the offspring of a single cell, a visible accumulation of a huge number of microorganisms on a nutrient medium. The size of the colony, its color and other morphological features in the laboratory determine the cultural properties of bacteria.

To study the parameters of a separate congestion of prokaryotic cells, a special nutrient medium is used. On it, microorganisms are able to multiply rapidly, because the substance includes substances important for the metabolism of bacteria. As a result, after 4-5 days (a period of time can vary), the Petri dish shows visible visible points, with which the work is carried out.

A bacterial sample obtained from a medium is preliminarily diluted to reduce the number of bacteria per unit volume. This procedure is carried out for a comfortable work in the future, since with excessive seeding of microorganisms, the nutrient medium can be covered with a continuous layer of colonies (the so-called "lawn"). Then the individual points are hardly distinguishable, and many procedures become impossible to conduct.

The concept of the cultural properties of bacteria

How is the colony of microorganisms analyzed? What parameters should be considered in the study?

The characteristics of a colony of bacteria on a nutrient medium are compiled according to several criteria. These include the morphological, biochemical, physiological properties of microorganisms, and all these parameters are determined in the laboratory in stages. For example, the visual differences of colonies of a given bacterium can be registered immediately after their cultivation. The remaining signs are studied already with the help of special equipment (microscope) or certain methods of working with analyte substances metabolites, pigments, enzymes and other prokaryotic prod- ucts.

Some cultural properties of bacteria are given below.

1. The size of the colony. It can be very shallow, shallow, medium and large. The diameter is measured in millimeters and can be in the range of 0.1 to 5 or more. Colonies not exceeding 1 mm in diameter are called point colonies.

2. Color, as well as the ability to release the pigment to the environment.

3. Surface. Here it is determined whether it is smooth, rough, bumpy or completely folded.

4. Colony profile: crater-shaped, convex, conical or flat.

5. Structure of the colony. It can be homogeneous, streamy, coarse-grained or fine-grained.

6. Optical properties: transparent, translucent, opaque, fluorescent, matte or shiny;

7. Consistency. The colony can be viscous or liquid, doughy or filmy, oily or brittle.

8. Cry colonies: flat, lobed, rhizoid, wavy, dentate, etc.

If the work is done with small groups of cells, a microscope is used. With a small increase, you can see the edge of the colony, and its profile, and the surface. Some signs are examined with the help of chemicals. Consistency can be recognized by touching a sterilized loop or pipette to the colony. Thus, the cultural and biochemical properties of bacteria are determined.

The nutrient medium

To ensure that bacteria actively multiply in the laboratory, nutrient media are used. They can be of vegetable or animal origin, and in consistence - solid or liquid. Important parameters in the manufacture of such mixtures are constant acidity, osmotic pressure and, of course, the presence of enzymes, vitamins, micro- and macroelements. Do not forget about the sources of carbon, nitrogen and hydrogen.

The nutrient medium must be transparent or translucent, so that it is possible to determine the cultural properties of bacteria without errors. Agar is most often used as a starting material for manufacturing such media. It can be in the liquid (molten) state, but it is mostly immediately poured into the Petri dish and freezes.

Liquid nutrient media are also used in laboratory conditions, but, in connection with the aggregate state of the physiology of microorganisms, the cultural properties of bacteria are studied a little differently. Parameters such as the degree of turbidity of water, surface, near-wall or bottom growth are important here. A granular precipitate, homogeneous or in the form of flakes, and other signs that can be observed only in a liquid medium.

Tools for work

Manipulations with bacterial cells require the use of sterilized laboratory instruments. Sowing and studying the cultural properties of microorganisms requires the presence of a bacterial loop or a Pasteur pipette. Both tools should be sterilized in the flame of the spirit lamp, and the pipette tip is pre-cut.

These simple adaptations will help when working with crops in the laboratory both on a solid nutrient medium and in a liquid medium.

3 stages of isolation of isolated colonies

The starting material, as a rule, contains a mixture of various bacteria. Isolation of isolated colonies of the necessary group of cells is a scrupulous and demanding process. It is conditionally divided into three stages:

1. Allocating a storage culture of bacteria, among which is necessary for us to study.

2. Isolation of isolated pure colonies by means of special selective methods.

3. Growing and multiplication of bacterial cells, work with them.

Of course, to "extract" the right bacteria, one should look for places of their greatest concentration in the external environment, and in the case of pathogenic or conditionally pathogenic prokaryotes, a biological method of investigation can be used at all. The essence of the latter is that an organism that is sensitive to a given bacterium is selected. That multiplies in the experimental animal, and as a result, in the blood sample, you can find many necessary for the work of prokaryotic cells.

Isolation of isolated colonies

The cultural properties of bacteria can be investigated only in isolated and pure colonies. To obtain those of several tens of extraneous bacterial species on a Petri dish, use the Koch method. Its essence lies in the fact that on 3 different and microorganism-free cups with a nutrient medium they place the necessary bacteria. And this is done by the same loop or pipette according to the residual principle, i.e., do not scrape off additional bacterial cells after carrying out the first and second cups through the nutrient medium. So, already on the third the quantity of bacteria will decrease and it will be possible to calmly find the necessary colony for research.

Cultural properties - the basis of microbiology

The study of bacterial cells always begins with an analysis of their colony. A certain list of parameters describes a group of microorganisms on a petri dish, and then a fixed smear is made and a preparation is prepared in this way. He is treated with a microscope and already describes the individual cells of the colony. Both actions are needed to identify bacteria: whether they are pathogenic or not, to which systematic group, etc., belong.

Where can I find bacteria?

Almost everywhere. They live in the air, and in the earth's crust, and in water, and in such extreme conditions as geysers, volcanoes or, conversely, arctic glaciers. Billions of bacteria are found in our human body, and among them are both useful and pathogenic species.

A smear from any surface, if it has not been previously sterilized, on the Petri dish will give several different kinds of colonies. A bacterial cell sprouts or not, depends on the composition of the nutrient substrate, which is often used when growing the necessary microorganisms. Thus, an electoral environment is prepared in advance, on which only certain types of bacteria can live.

For the systematization or identification, the cultural properties of bacteria are actively used. Microbiology often meets with problems such as seeding and growth of colonies, their selection, sterilization of equipment and scrupulous work on the flame of the spirit lamp.

Conclusion

In many biological laboratories, bacterial cells of various origins are being studied. These are diagnostic centers and scientific associations. The cultural properties of bacteria is one of the ways to determine microorganisms, which helps when working with "cocktails" from various types of prokaryotes. Also, knowledge of which systematic group this or that cell belongs to allows one more time to check the correctness of the progress of the study of the material used.