Nitrogen-fixing bacteria: what are they and the main classes, importance in the economy
Nitrogen is considered one of the most important chemical elements that affects the development of agricultural plants. This substance affects the process of photosynthesis and the amount of chlorophyll in cultures. At the same time, nitrogen fixation is an important agricultural process. However, the application of nitrogen in the form of fertilizers is not considered the only solution. A very effective option is the use of nitrogen-fixing bacteria.
What are bacteria
This term refers to representatives of the kingdom of wildlife, which are a category of prokaryotes.They are organisms whose cells do not contain a nucleus. However, this does not mean that such organisms are completely devoid of hereditary information. DNA molecules are freely located in the cell cytoplasm. In addition, a shell surrounds them.
Bacteria are microscopic in size, and therefore they are studied by microbiology. Researchers have determined that prokaryotes are single-celled or unite in colonies. They are characterized by a very primitive structure. In addition to the nucleus, bacteria lack all types of plastids, mitochondria, and lysosomes. However, in any case, their cells are capable of carrying out a variety of vital processes. They are characterized by anaerobic respiration without the use of oxygen, asexual reproduction, the formation of cysts in adverse conditions.
Main classes
The classification is based on various features, one of which is the shape of the cells. Cocci are round in shape, vibrios are comma-shaped, spirilli are spiral-shaped, and bacilli are rod-shaped.
In addition, the classification of bacteria is carried out taking into account the peculiarities of the cellular structure. True species can form a slimy capsule around their cell. In addition, they have flagella. Cyanobacteria have a process of photosynthesis and belong to lichens.
Many varieties of bacterial microorganisms are prone to symbiosis, which is a mutually beneficial cohabitation. Nitrogen-fixing bacteria settle on the roots of legumes and form nodules. These microorganisms transform atmospheric nitrogen, which is important for the full development of crops.
Eating Methods
Prokaryotes are organisms that can eat in any way. For example, purple and green bacteria are distinguished by an autotrophic type of nutrition - thanks to the use of solar energy. Due to the presence of plastids, they differ in different shades, but they necessarily include chlorophyll.
It is important to consider that the process of photosynthesis in bacteria and plants is significantly different. In the first case, water is not a mandatory reagent. Hydrogen or hydrogen sulfide can act as an electron supplier. Therefore, oxygen is not released during such a process.
A significant category of bacterial microorganisms is distinguished by a heterotrophic type of nutrition. This means that they use ready-made organic elements. To saturate the necessary substances, bacteria use the remains of dead organisms. At the same time, putrefactive microorganisms can lead to the decomposition of any organic matter. They are also called saprotrophs.
Individual plant bacteria are able to enter into symbiosis with other organisms. So, together with fungi, they are part of lichens. At the same time, nitrogen-fixing nodule bacteria are capable of mutually beneficial coexistence with the root system of legumes.
Who are chemotrophs
An important category that stands out by the type of absorption of nutrients are chemotrophs. They are microorganisms that are considered one of the types of autotrophs. At the same time, instead of solar energy, these bacteria use the energy of the chemical relationship of various elements. Chemotrophs include nitrogen-fixing bacteria. They cause the oxidation of a number of inorganic compounds and at the same time provide themselves with the necessary amount of energy.
Habitat for nitrogen-fixing bacteria
In general, bacteria are ubiquitous. At the same time, nitrogen-fixing varieties live in the soil, or more precisely, on the roots of legumes.
Body structure
The functions of nodule bacteria are related to their structure. These microorganisms can be seen with the naked eye. They settle on the root system of legumes and cereals and penetrate into plants. In this case, thickenings are formed in which metabolic processes are observed.
Expert opinionZarechny Maxim ValerievichAgronomist with 12 years of experience. Our best gardening expert.Ask a QuestionIt should be noted that nitrogen-fixing bacteria belong to the category of mutualists. This means that their coexistence with other microorganisms is considered to be mutually beneficial. In the process of photosynthesis, the plant produces glucose, which is needed for life processes. Bacterial microorganisms are not capable of this, because they receive sugar from legumes in finished form.Plants need nitrogen for normal life. Nature contains a sufficient amount of this element. For example, in the air its amount reaches 78%. However, cultures cannot absorb this substance in this form. Nitrogen-fixing microorganisms are able to absorb nitrogen from the atmosphere. Then they transform this substance into a form that is available to crops.
Performance
To better understand the function of nitrogen-fixing microorganisms, consider the example of a chemotrophic bacterium called azospirillum.This organism lives on the root system of cereal plants - wheat or barley. It rightfully occupies a leading position among nitrogen producers. For 1 hectare of sown area, this organism gives up to 60 kilograms of this substance.
Nitrogen-fixing bacteria in legumes include rhizobitums, synorhysobiums and others. They are also high performance. Such plants are capable of producing up to 390 kilograms of nitrogen per 1 hectare of land. On perennial legumes, bacteria are formed that are characterized by maximum productivity. This parameter reaches 560 kilograms per 1 hectare of sown area.
Features of life
Depending on the characteristics of life processes, all nitrogen-fixing microorganisms can be combined into two categories. The first group is considered nitrifying. In this case, metabolic processes consist in a chain of chemical transformations.In this case, ammonium is converted into nitrites, which are s alts of nitric acid. In turn, nitrites are converted to nitrates. They are also s alts of this compound. In this form, nitrogen is better absorbed by the roots of crops.
The second group is called denitrifiers. They do the reverse process. At the same time, nitrates that are present in the soil are transformed into gaseous nitrogen. As a result, the cycle of this substance in nature is observed.
Among the life processes, it is also worth highlighting reproduction. It is carried out by cell division in two. Much less often, this occurs by budding. Also, bacterial microorganisms can reproduce sexually. This method is called conjugation, during which genetic information is exchanged.
Since the roots of the culture secrete a large number of valuable elements, a lot of bacteria settle on them. They transform plant residues into substances that plants can absorb.As a result, the layer of soil around is endowed with special characteristics. They call it the rhizosphere.
How bacteria get into the root
There are several options for introducing bacterial cells into root tissues. This happens as a result of damage to the integumentary tissues or in areas of accumulation of young root cells. Also, chemotrophs can penetrate into cultures in the zone of root hairs. Then they become infected.
As a result of active division of bacterial cells, nodules are formed. After that, infectious threads appear, which continue to penetrate into plant tissues. Over time, a special substance is formed here, which is called legoglobin. At the stage of the appearance of optimal activity, the nodules turn pink. This is due to the presence of pigment.
Value in the household
People have long been able to establish that if you dig legumes with soil, plant yields will improve.However, the essence is not in the process of plowing. Such soil is better saturated with nitrogen, which is important for the development of crops. That is why nitrogen-fixing bacteria are called the nitrate factory.
Nitrogen-fixing bacteria are important microorganisms that are actively used in agriculture. This is due to their ability to obtain nitrogen from the air and transform it into a form available to plants.
