Almost all living organisms on Earth need a breathing process. Oxygen is one of the most common oxidizing agents in the respiratory chain of animals, plants, protists, and many bacteria. However, not everyone knows how much our body differs in complexity of structure from small cells of microorganisms. The question arises: how do bacteria breathe? Is their way of getting energy different from ours?
Do all bacteria breathe oxygen?
Not everyone knows that oxygen is not always an essential component in the respiratory chain. First of all, it plays the role of an electron acceptor; therefore, this gas oxidizes well and interacts with hydrogen protons. ATP is the reason all living organisms breathe. However, many types of bacteria do without oxygen, and still receive such a treasured source of energy as adenosine triphosphate. How do bacteria of this type breathe?
The process of respiration in our body proceeds in two stages. The first of these, anaerobic, does not require oxygen in the cell, and it only needs carbon sources and acceptors of hydrogen protons. The second stage - aerobic - proceeds exclusively in the presence of oxygen and is characterized by a large number of phased reactions.
In bacteria that do not absorb oxygen and do not use it for respiration, only the anaerobic stage proceeds. At its end, microorganisms also receive ATP, but its amount is very different from what we get after passing through two stages of respiration. It turns out that not all bacteria breathe oxygen.
ATP - a universal source of energy
It is important for any organism to maintain its vital functions. Therefore, it was necessary in the process of evolution to find energy sources that, when used, can provide enough resources for all the necessary reactions in the cell to occur. First, fermentation appeared in bacteria: the so-called stage of glycolysis or anaerobic stage of respiration of prokaryotes. And only then did the devices of more advanced multicellular organisms develop, thanks to which, with the participation of atmospheric oxygen, respiratory efficiency significantly increased. So the aerobic stage of cellular respiration appeared.
How do bacteria breathe? Grade 6 of the school biology course shows that for any organism it is important to receive a certain proportion of energy. In the process of evolution, it began to stock up in specially synthesized molecules for this, called adenosine triphosphate.
ATP is a macroergic substance, the basis of which is a pentose carbon ring, a nitrogenous base (adenosine). Phosphorus residues depart from it, between which high-energy bonds are formed. When one of them is destroyed, an average of about 40 kJ is released, and one ATP molecule is able to store a maximum of three phosphorus residues. So, if ATP breaks down to ADP (adenoside diphosphate), then the cell receives 40 kJ of energy during dephosphorylation. Conversely, storage occurs by phosphorylation of ADP to ATP with energy expenditure.
Glycolysis gives the bacterial cell 2 molecules of adenosine triphosphate, when the aerobic phase of respiration, upon completion, can supply the cell with 36 molecules of this substance immediately. Therefore, the question "How do bacteria breathe?" The answer can be given as follows: the breathing process for many prokaryotes consists in the formation of ATP without the presence and consumption of oxygen.
How do bacteria breathe? Types of breathing
With respect to oxygen, all prokaryotes are divided into several groups. Among them:
- Obligatory anaerobes.
- Optional anaerobes.
- Obligatory aerobes.
The first group consists only of those bacteria that cannot live in conditions of access of oxygen. O2 is toxic to them and leads to cell death. Examples of such bacteria are purely symbiotic prokaryotes that live inside another organism in the absence of oxygen.
The second group combines such types of prokaryotes that actively multiply and grow in the absence of oxygen, however, its small percentage in the environment does not lead to fatal consequences. These bacteria include saprophytes and some parasites.
How do bacteria of the third group breathe? These prokaryotes are distinguished by the fact that they can live only in conditions of good aerolization. If there is not enough oxygen in the air, such cells die quickly, because they need O2 to breathe.
How is fermentation different from oxygen breathing?
Bacterial fermentation is the same glycolysis process that can produce different reaction products in different types of prokaryotes. For example, lactic acid fermentation leads to the formation of a by-product of lactic acid, alcoholic fermentation - ethanol and carbon dioxide, butyric acid - butyric (butanoic) acid, etc.
Oxygen respiration is a complete chain of processes that begin with the stage of glycolysis with the formation of pyruvic acid, and end with the release of CO2, H2O and energy. The latter reactions take place under conditions of oxygen.
How do bacteria breathe? Biology (Grade 6) of the school course of microbiology
At school, they gave us only the simplest knowledge about how the process of breathing prokaryotes occurs. These microorganisms do not have mitochondria, however, there are mesosomes - protrusion of the cytoplasmic membrane into the cell. But these structures do not play the most key role in the respiration of bacteria.
Since fermentation is a type of glycolysis, it proceeds in the cytoplasm of prokaryotes. There are also numerous enzymes necessary for carrying out the entire chain of reactions. All bacteria, without exception, first form two molecules of pyruvic acid, as in humans. And only then they turn into other by-products, which depend on the type of fermentation.
Conclusion
The world of prokaryotes, despite the apparent simplicity of cellular organization, is full of complex and sometimes inexplicable moments. Now there is an answer to how bacteria actually breathe, because not all of them need oxygen. On the contrary, most have adapted to use another, less practical way of generating energy - fermentation.