How are bacteria that chemosynthesize various substances arranged and carry out vital processes? To answer these questions, you need to deal with a number of biological concepts.
The characteristic features of bacteria
First, find out who the bacteria are. This is the whole Kingdom of wildlife. They are unicellular organisms of microscopic dimensions that are devoid of nucleus. But this does not mean that bacteria generally do not have structures responsible for the transmission of hereditary information. She 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 considered 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 chloroplast plastids allows them to carry out the process of photosynthesis. Its essence lies in the formation of glucose carbohydrate from inorganic substances - water and carbon dioxide. Another product of this chemical reaction is oxygen. Bacteria are also autotrophs. But they do not need sunlight to receive energy. They carry out another 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. In this case, energy is released, 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, the range of their distribution is quite wide. For example, serobacteria can live at great depths, sometimes being the only representatives of living creatures there. The habitat of these prokaryotes is most often the soil, wastewater and substrates rich in certain chemical compounds.
Iron bacteria
Chemosynthetic bacteria include prokaryotes that alter 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 salty water bodies. In nature, they circulate iron in nature, and in industry they 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.
Serobacteria
Bacteria, chemosynthetic substances from sulfur compounds, can exist separately at the bottom of water bodies or form a symbiosis with mollusks and marine invertebrates. As a source of oxidation, they use hydrogen sulfide, sulfides, thionic acids or molecular sulfur. This type of bacteria was the main object in the discovery and study of the chemosynthesis process. This group of prokaryotes also includes some phototrophic prokaryotes. For example, such as purple or green sulfur bacteria.
Nitrifying bacteria
On the roots of legumes, nitrifying bacteria settle. Chemosynthetic prokaryotes of this group oxidize ammonia to nitric acid. This reaction is carried out in several stages with the formation of intermediate substances. Nitrogen-fixing bacteria are also found in the soil . They settle on the roots of legumes. Intruding into the tissues of the underground organ, they form characteristic thickenings. A favorable environment for the progress of chemosynthesis is created inside such formations. The symbiosis of plants with nodule bacteria is mutually beneficial. The former provide prokaryotes with organics obtained during photosynthesis. Bacteria are able to fix atmospheric nitrogen and translate it into a form available for plants.
Why is this process so important? Indeed, in the atmosphere the nitrogen concentration is quite high and amounts to 78%. But in this form, plants can not absorb this substance. And nitrogen is necessary for plants to develop the root system. In this situation, nodule bacteria come to the rescue , which turn it into a nitrate and ammonium form.
Thionic bacteria
Chemosynthetic bacteria are thionic prokaryotes. Their source of energy are various sulfur compounds. This type of bacteria restores them to sulfuric acid. This reaction is accompanied by a significant decrease in the pH of the medium. Thionic bacteria are part of the acidophilus group. These include organisms that can survive in conditions of high acidity. Such conditions are characteristic of swamps. Together with the thian ones, this group consists 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 maintain viability at high temperatures, the rate of 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.
The role of chemosynthetic bacteria
Chemotrophs play a major role in the complex processes of transformation and cycling of the corresponding chemicals in nature. Since hydrogen sulfide and ammonia are quite toxic substances, there is a need to neutralize them. Chemotrophic bacteria also do this. In the course of chemical transformations, substances necessary for other organisms are formed, which makes possible their normal growth and development. 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 his activities. For example, with the help of sulfur bacteria they treat sewage from hydrogen sulfide, protect metal and concrete pipes from corrosion, and soil from acidification.
So, chemosynthetic bacteria are special prokaryotes capable of carrying out the corresponding 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 vital processes. The main ones are iron, sulfur and nitrogen-fixing bacteria. They live in both aquatic and soil environments. Chemotrophs are an indispensable link in the cycle of substances, provide living organisms with necessary substances and are widely used by humans in their economic and industrial activities.