How are the life processes of bacteria that chemosynthesize various substances arranged and carried out? To answer these questions, you need to understand a number of biological concepts.
Characteristic features of bacteria
First, let's find out who the bacteria are. This is the whole kingdom of wildlife. They are single-celled organisms of microscopic size that lack a nucleus. But this does not mean that bacteria generally do not have structures responsible for the transmission of hereditary information. It just has a more primitive organization. These are circular DNA molecules that are concentrated in a specific part of the cytoplasm called the nucleoid.
The essence of autotrophic nutrition
Chemosynthetic bacteria, examples of which will be discussed in our article, independently produce organic substances. They are autotrophs, like plants. However, the latter use the energy of sunlight for this. The presence of green plastids of chloroplasts allows them to carry out the process of photosynthesis. Its essence lies in the formation of glucose carbohydrate frominorganic substances - water and carbon dioxide. Another product of this chemical reaction is oxygen. Bacteria are also autotrophs. But they don't need sunlight to get energy. They carry out a different process - chemosynthesis.
What is chemosynthesis
Chemosynthesis is the process of formation of organic substances due to the occurrence of redox reactions. It is carried out in nature only by prokaryotes. Chemosynthetic bacteria can use sulfur, nitrogen, and iron compounds to synthesize organic substances. This releases energy, which is first accumulated in ATP bonds, after which it can be used by bacterial cells.
Chemosynthetic bacteria: habitat
Since the life of chemotrophs does not depend on the presence of sunlight, their distribution area is quite wide. For example, sulfur bacteria can live at great depths, sometimes being the only representatives of living beings there. The habitat of these prokaryotes is most often soil, wastewater and substrates rich in certain chemical compounds.
Iron bacteria
Chemosynthetic bacteria include prokaryotes that change the composition of iron compounds. They were discovered by the outstanding Russian microbiologist Sergei Nikolaevich Vinogradsky in 1950. This type of bacteria during the oxidation reaction changes the oxidation state of iron, making it trivalent. They live in fresh and s alt waters. In nature, they carry out the cycle of iron innature, and in industry are used to produce pure copper. This type of bacteria also belongs to lithoautotrophs, capable of synthesizing some elements of their cells from carbonic acid.
Sulfur bacteria
Bacteria, chemosynthesizing substances from sulfur compounds, can exist separately at the bottom of water bodies or form a symbiosis with mollusks and marine invertebrates. They use hydrogen sulfide, sulfides, thionic acids or molecular sulfur as the source of oxidation. This type of bacteria was the main object in the discovery and study of the process of chemosynthesis. This group of prokaryotes also includes some phototrophic prokaryotes. For example, such as purple or green sulfur bacteria.
Nitrifying bacteria
Nitrifying bacteria settle on the roots of leguminous plants. Chemosynthetic prokaryotes of this group oxidize ammonia to nitric acid. This reaction is carried out in several stages with the formation of intermediate substances. There are also nitrogen-fixing bacteria in the soil. They live on the roots of leguminous plants. Penetrating into the tissues of the underground organ, they form characteristic thickenings. Inside such formations, a favorable environment is created for the flow of chemosynthesis. The symbiosis of plants with nodule bacteria is mutually beneficial. The first provide prokaryotes with organic matter obtained during photosynthesis. Bacteria, on the other hand, are able to fix atmospheric nitrogen and convert it into a form accessible toplants.
Why is this process so important? Indeed, in the atmosphere, the concentration of nitrogen is quite high and amounts to 78%. But in this form, plants cannot absorb this substance. Plants need nitrogen for root development. In this situation, nodule bacteria come to the rescue, which turn it into a nitrate and ammonium form.
Thion bacteria
Thion prokaryotes are also chemosynthetic bacteria. Their energy source is various sulfur compounds. This type of bacteria reduces them to sulfuric acid. This reaction is accompanied by a significant decrease in the pH of the medium. Thionic bacteria belong to the group of acidophiles. These include organisms that can survive in conditions of high acidity. Such conditions are typical for swamps. Together with the thianaceae, this group is made up of lactic and acetic acid bacteria, flagellates and rotifers.
Hydrogen bacteria
These types of prokaryotes are soil inhabitants. They oxidize molecular hydrogen to water with the release of energy. Such bacteria are also included in the group of thermophiles. This means that they are able to survive at high temperatures, which can reach 50 degrees Celsius. This ability of hydrogen bacteria is due to the fact that they secrete special enzymes that function even in such conditions.
Rolechemosynthetic bacteria
Chemotrophs play a major role in the complex processes of transformation and circulation of the corresponding chemicals in nature. Since hydrogen sulfide and ammonia are quite toxic substances, there is a need to neutralize them. This is also carried out by chemotrophic bacteria. In the course of chemical transformations, substances necessary for other organisms are formed, which makes their normal growth and development possible. Large deposits of iron and manganese ores at the bottom of the seas and swamps arise due to the activity of chemotrophs. Namely, iron bacteria.
Man has learned to use the unique properties of chemotrophs in their activities. For example, with the help of sulfur bacteria they clean wastewater from hydrogen sulfide, protect metal and concrete pipes from corrosion, and soils from acidification.
So, chemosynthetic bacteria are special prokaryotes capable of carrying out appropriate chemical reactions under anaerobic conditions. These organisms oxidize substances. The energy that is released in this case is first stored in ATP bonds, and then used to carry out life processes. The main ones are iron-, sulfur- and nitrogen-fixing bacteria. They live in both water and soil environments. Chemotrophs are an indispensable link in the cycle of substances, provide living organisms with the necessary substances and are widely used by humans in their economic and industrial activities.
