Soil is a product of the vital activity of the organisms that inhabit it. They influence the process of its formation, self-purification and circulation of useful elements. The soil microflora determines its qualitative composition and the possibility of using it for agricultural purposes. Today, many different methods have been developed for studying the composition of soil and controlling it.
Species and quantitative composition
There are quite a lot of species of bacteria living in the soil, which are divided according to their functions, habitat, feeding habits and other parameters. Rotting bacteria, parasites, and symbionts are found in the soil. Moreover, the relationships between different types of microorganisms differ significantly.
There are 12 varieties of single-celled organisms that form spores. They are divided according to the criterion of preference for the environment. For example, only high temperature parameters are suitable for thermophiles. Under the influence of unicellular organisms, many substances are transformed into elements that are characteristic of plant development.
Soil contamination with feces leads to the appearance of pathogenic flora. These microorganisms can enter the soil from plants or the intestines of animals. This provokes the development of decay processes. The main representatives of pathogenic bacteria are coliform prokaryotes. These single-celled microorganisms can live in the soil for a long time, provided it is well heated and not exposed to direct sunlight.
Coliform bacteria are considered the most dangerous. They penetrate into the soil from the intestines of animals. Also very dangerous are microorganisms that produce toxic enzymes.
According to the shape of the cell walls
The division of microorganisms depending on the shape of the cell walls is based on the results of genomic studies. This principle allows us to distinguish several types of unicellular organisms:
- cocci - have cells in the form of spheres;
- bacilli - their cells differ in the shape of the rod;
- spirilla - these microorganisms have a spiral shape.
There are also soil organisms that have a complex structure. This group includes actinomycetes, which have many branches.
In relation to oxygen
Depending on the way they use oxygen to carry out life activities, the following types of bacteria are distinguished:
- aerobic - they require oxygen to exist;
- anaerobic - die if oxygen is present in some layer of the soil.
According to the ability to stain using the Gram method
The essence of this method lies in the presence of an outer shell, which has protective functions. It can allow or, conversely, prevent the antibacterial component and dye from entering the bacterial structure.
In most cases, the following gram-negative organisms are found in the soil:
- pseudomonads are small, solitary bacteria that do not cause spore formation;
- budding bacteria - this group includes nitrifying organisms;
- nodule unicellular;
- enterobacteria - can be mobile or immobile and are considered pathogenic for plants;
- Azotobacteria are large, mobile, free-living rods;
- myxobacteria and cytophages - these microorganisms produce mucus and strands with a dense structure.
Gram-positive bacteria include the following varieties:
- spore-forming;
- bacilli - these include rod-shaped bacteria that live in colonies and are highly mobile;
- large anaerobic organisms that take part in the processes of decay, fermentation of pectin, carbohydrates, starch;
- coryne-like bacteria - live in litter, soil, and plant substrate.
By food type
Depending on the type of nutrition, bacterial microorganisms that live in the soil are autotrophic and heterotrophic. The first group extracts organic substances to carry out life activities independently, the second group uses ready-made organic matter.
By function
Organisms present in the soil are required for the destruction of organic matter. During their life activities, single-celled organisms saturate the soil with important elements. Nodule bacteria are responsible for nitrogen fixation near the roots. Nitrifying microorganisms are required to increase soil fertility.
Also, depending on their functions, there are the following categories of unicellular organisms:
- Destructors - absorb carbohydrates and various substances presented in the form of living or dead organic matter.
- Mutualists - such bacteria coexist on favorable terms. An example is nodule bacteria.
- Chemoautotrophs - obtain energy from inorganic elements without carbon.
How to study soil microflora
The soil is examined through a full or brief analysis. Full control is carried out in the following situations:
- detailed and in-depth characteristics of the sanitary condition of the soil;
- assessing the suitability of the soil for placing various buildings;
- epidemiological studies.
A short study is required to carry out routine sanitary control. It helps determine the total number of saprophytic and thermophilic bacteria, clostridia and other organisms.
A complete sanitary and bacteriological analysis additionally includes an assessment of the number of fungi, actinomycetes, Shigella, and Salmonella. In addition, it helps to identify and determine the number of causative agents of botulism, tetanus, brucellosis, and anthrax.
Control Features
To neutralize soil that is contaminated with harmful microorganisms, mechanical treatment is carried out and various plants are planted. The use of chemicals provokes a decrease in soil fertility.
To normalize soil microflora, it is permissible to use various biological fertilizers. With their help, it is possible to saturate the soil with valuable substances, reduce the activity of pathogenic bacteria, and make the substrate more fertile.
Thanks to this, substances significantly increase the yield parameters of cultivated plants and help cope with the influence of unfavorable factors. In addition, they significantly reduce the amount of nitrates and heavy elements in the soil structure.
Soil microflora is an important indicator that is often used in agriculture. The soil contains many pathogenic and beneficial microorganisms that affect the development of cultivated plants.
