Probably, in nature there are no organisms more tenacious and adapted to the environment than bacteria. These single-celled life forms are capable of withstanding enormous changes in temperature, pressure, and acidity. In a drought, they can do without water for a long time, and when favorable environmental factors occur, they can return to normal life again. How can bacteria survive where other organisms die?
What is a cyst in biology
Bacteria are able to survive adverse conditions by encysting. The essence of this process is that the bacterial cell is surrounded by a thick shell. In fact, this is the reason why microorganisms are not afraid of drought or temperature changes.
Cyst is a form of existence of bacteria, with the help of which they are able to survive under the influence of adverse factors. This protective and adaptive structure is characteristic not only for prokaryotic organisms, but also for some protists.
Features of a resting cell
A cyst is a very specifica form of bacteria that causes some transformation within the cell. These features depend on the type of encystation, but there are some general characteristics of this process. First, a thick protective shell is formed around the cell, which is a barrier to adverse environmental factors.
At the same time, encystation completely or partially blocks the connection of the cell with the environment, so microorganisms must prepare for the formation of a dense shell. First, the bacteria store essential substances and enzymes that will work even under conditions of encystation. Then the cell loses some of its structures in order to temporarily remove unnecessary energy costs at the moment.
Cyst is one of the stages in the life cycle of many microorganisms. Accordingly, the encystation process is periodic. Some cysts are able to remain viable after 5 or even 10 years. There is evidence that protist cysts can live up to 16 years. This gives the right to call microorganisms the most tenacious on the planet.
Factors contributing to encystation
Study of bacteria in laboratory conditions shows that the cyst is the best adaptation for survival of adverse conditions. Determination of encysted cells on Petri dishes under the influence of various factors shows the importance of a dense cell wall. What factors cause cyst formation?
1. Temperature fluctuations.
2. Concentration changesolutes in a given medium.
3. Evaporation of water (drainage of reservoirs).
4. Lack or excess of oxygen.
5. Lack of food resources.
The last item is a common cause of encystation of microorganisms. If a colony of bacteria is grown on a Petri dish, then after the food supply runs out, most of the cells turn into a cyst. If the environment is rich in nutrients, the chance of encysting is minimal.
In some groups of organisms, the cyst is formed under other circumstances. For example, in ciliates, this process is necessary for the rearrangement of the nuclear apparatus inside the cell. The encystation of parasitic eukaryotic cells occurs in order to leave the environment of the host organism and enter an uninhabitable habitat. Some prokaryotes and eukaryotes use cysts to reproduce.
Types of encystation
For what purposes do microorganisms pass into the cyst stage? Here are a few types of encystation that are most common in nature.
1. Resting cysts.
These forms of bacteria and protists are a typical example of encystation, in which the cell survives adverse environmental conditions.
2. Reproductive cysts.
This type is typical for many representatives of ciliates. In this case, the cysts form a fairly thin shell, and the cell begins to divide many times. As a result, the cyst bursts, and a large number of copies of the mother's organism come out.
3. Digestive cysts.
Such forms of cells are quite rare in a few species of microorganisms. Here the cyst is a device for the efficient digestion of food. This type of encystation is typical for predator organisms, which, after “eating” their prey, form a shell and begin to actively digest the prey.
