Most often, bacteria are in the form of rods, the thickness of which is 0.5–1 µm, and the length is 2–3 µm. Giants are bacteria whose body is 30–100 microns in length.
Bacterial cells are surrounded by a dense membrane (cell wall), which performs protective and supporting functions, and also gives the bacteria a permanent, characteristic shape. In terms of composition and structure, the cell walls of bacteria differ significantly from plants and animals.
The cell membrane of the bacterium is permeable: through it, nutrients freely pass into the cell, and metabolic products are released into the environment. Often, bacteria develop an additional protective layer of mucus on top of the cell wall – a capsule. The capsule prevents the bacteria from drying out. The thickness of the capsule can be many times the diameter of the cell itself, but it can be very small.
On the surface of some bacteria there are long flagella (one, two or many) or short thin villi. The length of the flagella can be many times the size of the bacterial body. With the help of flagella and villi, bacteria move.
Inside the bacterial cell is a dense, immobile cytoplasm, which contains various proteins (enzymes) and reserve nutrients.
Unlike other unicellular organisms, bacteria do not have a formed nucleus: their nuclear substance is not separated from the cytoplasm by a membrane and is distributed in the cytoplasm.
Bacterial cells are called non-nuclear. On this basis (and a number of others) bacteria are classified as prokaryotes (prenuclear organisms) and are distinguished from organisms that have a formed nucleus with a nuclear envelope – eukaryotes.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.