Of nitrifying bacteria. The importance of nitrifying bacteria

Kind of all known living organisms are divided into two broad types: hetero - and autotrophs. A distinctive feature of the latter is their ability to independently build new elements of carbonic acid and other inorganic substances.

Sources of energy that support their livelihoods and determine their division into fotoaparaty (source-light) and chemoautotraphs (source – minerals). And depending on the name of the substrate, which oxidize chemoautotrophy, they split into hydrogen and nitrifying bacteria, and sulphur and iron bacteria.

This article will focus on the most common among them the group – nitrolicious bacteria.

History

Back in the mid-19th century by German scientists it was proven that the process of nitrification is the biological. Empirically, they showed that when added to the sewer water of chloroform stayed the oxidation of ammonia. But to explain why this is so, they could not.

It was done a few years later the Russian scientist Vinogradsky. He identified two groups of bacteria, which gradually took part in the nitrification process. So, one group was provided the oxidation of ammonium to nitric acid, and the second group of bacteria were responsible for its transformation into nitric. All involved in this process, nitrifying bacteria are gram-negative.

Oxidation

The formation of nitrite through the oxidation of ammonium has several stages, during which the formation of nitrogen-containing compounds with different degree of oxidation of the NH group.

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The First product of the oxidation of ammonia is hydroxylamine. Most likely, it is formed because of the inclusion of molecular oxygen in the group of NH₄, although finally this process has not been proven and remains controversial.

Next, the hydroxylamine becomes nitrite. Presumably, the process is carried out through the formation of NOH (hyponatremia) with the release of nitrous oxide. In this case, scientists believe the production of nitrous oxide is only a by-product of the synthesis, due to the recovery of the nitrite.

In addition to the production of chemical elements in the course of denitrification a large amount of energy. Like what is happening with heterotrophic aerobic organisms, in this case the synthesis of ATP molecules associated with redox processes, in which oxygen is transferred to the electrons.

The oxidation of nitrite plays a big role in the process of reverse electron transport. The inclusion of electrons in a circuit is directly in cytochromes (C-type and/or A-type), and this requires a fairly large expenditure of energy. As a result, chemoautotrophic nitrifying bacteria to be fully provided with necessary amount of energy, which is used to build processes and assimilation of carbon dioxide.

Types of nitrifying bacteria

In the first phase of nitrification taking part four of a kind nitrobacteria:

• Nitrosomonas;
• Microcystis;
• Nitrosolobus;
• Nitrosospira.

Kstati on the proposed picture, you can see nitrifying bacteria (photo taken under microscope).

Experimentally among them is quite difficult, and often impossible to highlight one of the cultures, therefore the consideration mainly complex. All of these microorganisms have a size of up to 2-2. 5 µm, mostly oval or round in shape (except for nitrospira that sticks). They are capable of binary fission and directed movement due to flagella.

In the second stage of nitrification take part:

• Rod nitrobacter;
• Rod nitrospina;
• Nitrococcus.

The Most studied strain of bacteria of the genus nitrobacter having the name in honor of its discoverer Vinogradsky. These bacteria are nitrifying pear-shaped cells, reproduce by budding, with the formation of moving (flagella) daughter cells.

Structure of bacteria

The Investigated nitrifiers bacteria have similar cell structure with other gram-negative organisms. Some of them have a well developed system of internal membranes that form a stack in the center of the cell, whereas in others they are located more on the periphery or form a structure in the form of bowls, consisting of several sheets. Apparently, these formations are associated enzymes that are involved in the oxidation process by nitrifying specific substrates.

Type of food nitrifying bacteria

Nitrobacteria belong to the obligate autotrophs, as are not able to use exogenous organic matter. However, experimentally still shown the ability of some strains of nitrifying bacteria to use certain organic compounds.

It Was found that the substrate containing yeast yeast, serine and glutamate at low concentrations, stimulating way affect the growth of nitrobaktery. It occurs in the presence of nitrite, and in his absence in the nutrient medium, although the process proceeds much slower. Conversely, in the presence of nitrite the oxidation of acetatesuppressed, but a significant increase in the inclusion of carbon in protein, various amino acids and other cellular components.

As a result of multiple experiments, data were obtained that nitrifying bacteria can switch to heterotrophic nutrition, but how well and how long they can exist in such conditions, remains to be seen. While the data is controversial enough to draw final conclusions on this issue.

Habitat and the importance of nitrifying bacteria

Nitrifying bacteria are chemoautotraphs and have a wide distribution in nature. They are found everywhere: in soil, various substrates and reservoirs. The process of their activity makes a significant contribution to the overall nitrogen cycle in nature and in fact, can reach enormous proportions.

For Example, a microorganism like Microcystis okeanus, isolated from the Atlantic ocean, refers to obligate halophilism. It can only exist in sea water or substrates that contain it. For these microorganisms are not only important habitat, but also constants such as pH and temperature.

All known nitrifying bacteria belong to obligate aerobes. In order to oxidize the ammonia to nitrous acid, and nitrous acid in nitric, they need oxygen.

Habitat

Another important moment, which showed the scientists was that the place where you live nitrifying bacteria, must not contain organic substances. Put forward the theory that these microorganisms are, in principle, can not use organic compounds from the outside. They even called obligate autotrophs.

In the subsequent it has been proven the detrimental effect of glucose, urea, peptone, glycerol and other organic matter on the nitrifying bacteria, but the experiments don't stop.

The Importance of nitrifying bacteria to the soil

Until recently it was believed that the nitrifying microorganisms have a beneficial effect on the soil, increasing its fertility through the breakdown of ammonium to nitrate. The latter not only are absorbed by plants, but in and of themselves increase the solubility of some minerals.

However, in recent years, scientific views are changing. Revealed the negative effect of the described microorganisms on soil fertility. Nitrifying bacteria, forming nitrate, acidified environment, which is not always a positive thing, and to a greater extent provoke the saturation of soil ammonium than nitrate. Moreover, the nitrates have the ability to recover up to N₂ (in the process denitrification), which in turn leads to the impoverishment of the soil with nitrogen.

What is the danger of nitrifying bacteria?

Some strains of nitrobaktery in the presence of organic substrate can oxidize the ammonia to form hydroxylamine, and subsequently nitrites and nitrates. Also as a result of such reactions can occur hydroxamate acid. Moreover, a number of bacteria responsible for the process of nitrification of different compounds, which include nitrogen (oxime, amines, amides, hydroxamates and other nitro compounds).

The Extent of heterotrophic nitrification under certain conditions can be not only huge, but also very harmful. The danger lies in the fact that in the course of such reactions is the formation of toxic substances, mutagens and carcinogens. So scientists are working closely on the study of the topic.

Biological filter, which is always at hand

Nitrifying bacteria - it is not an abstract concept, but a very common form of life. Moreover, they are often used by man.

For Example, in the biological filters for aquariums include these bacteria. This type of cleaning is less expensive and not as labor-intensive as mechanical cleaning, but at the same time requires adherence to certain conditions to ensure the growth and activity of nitrifying bacteria.

The Most favorable climate for them is the ambient temperature (in this case water) of about 25-26 degrees Celsius, a constant supply of oxygen and the presence of aquatic plants.

Nitrifying bacteria in agriculture

In order to increase the yield, farmers use various fertilizers containing nitrifying bacteria.

Power of the soil in this case is provided by the nitrobaktery and azotobacteria. These bacteria recovered from soil and water is necessary substances that are in the process of oxidation to form a sufficiently large amount of energy. This so-called process of chemosynthesis when the energy goes to the formation of complex organic molecules from carbon dioxide and water.

For these organisms do not have the nutrients from their environment - they can produce their own. Thus, if green plants which are also autotrophs, need sunlight for nitrifying bacteria is not a requirement.

Self-cleaning soil

The Soil – is an ideal substrate for growth and reproduction not only of plants but also of many living organisms. Therefore, it is importantits normal and balanced composition.

It Should be remembered that biological treatment of soil provide including nitrifying bacteria. They are in the soil, water or humus, convert ammonia, which is extracted other microorganisms and waste organic materials, nitrates (to be more precise, the salts of nitric acid). The whole process consists of two steps:

1. The Oxidation of ammonia to nitrite.
2. The Oxidation of nitrite to nitrate.

In addition, each stage is provided by certain types of microorganisms.

The So-called vicious circle

The Circulation of energy and the maintenance of life on Earth is possible through the observance of certain laws of existence of all living things. At first glance it is difficult to understand what was going on, but it is actually quite simple.

Let's imagine the following picture from a school textbook.

1. Inorganic substances are metabolized by the microorganisms and thereby creates favorable conditions in soil for growth and plant nutrition.
2. They, in turn, are an indispensable source of energy for most herbivores.
3. The Following chain of this vital link are predators, the energy for which are, respectively, their herbivore counterparts.
4. People are known, belong to the top predators, and this means that we can obtain energy from the plant world and the animal.
5. The remains of our own life, as well as those of plants and animals, serve as nutrient substrate for microorganisms.

Thus, a vicious circle, continuously-functioning and life-supporting of all living things on Earth. Knowing these principles is not difficult to imagine how multi-faceted and actually boundless power of nature and all living things.

Conclusion

In this article we tried to answer the question, what is nitrifying bacteria in biology. As you can see, despite the overwhelming evidence of life, functioning and impact of these microorganisms, there are still many controversial issues that require further experimental studies.

Nitrifying bacteria belong to the hemotrofy. Source of energy for them are different minerals. Despite their microscopic size, these organisms have a huge impact on the world around them.

As you know, hemotrofy can't metabolize organic compounds that are in the substrate (soil or water). On the contrary, they produce a building material for creating living and functioning cells.