What are Bacteria?
Bacteria are microorganisms, very small living beings with dimensions in the order of a thousandth of a millimeter.
Even if we can't see them with the naked eye, bacteria are everywhere, in our body and in the whole environment around us; some of them even live in the most inhospitable environments, such as the ocean floor or glaciers. In addition to being omnipresent, bacteria are also among the most widespread living forms on Earth, so much so that in a single spoonful of soil up to 10, 000 billion can be found.
Often, bacteria are associated with dirt or certain diseases, but in reality many of them are particularly useful to humans ; think, for example, of the bacteria that allow the production of yogurt or those that make up the intestinal symbiont flora.
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Bacteria: General characteristics
Type of organization
Prokaryotes, usually single-celled.
dimensions
They are in the order of the micrometer, which is the millionth part of the meter; generally they vary between 0.2 and 10 µm;
Form
The shape of the bacteria varies according to the type of bacteria considered:
- coconut: spherical
- bacillus: rod-shaped
- vibrios: comma (they have a curvature)
- spirilli: spiral (large pitch helix cylindrical shape)
- spirochete: corkscrew (very short pitch sinusoids)
DIPLOCOCCHI: bacteria associated two by two |  |
STREPTOCOCCHI: chain | |
TETRADI: groups of four cells | |
| SHELL: eight cube-shaped cocci | |
| STAFILOCOCCHI: cluster |
Examples of bacteria from different forms
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Generally asexual, by simple division (or binary splitting); each bacterium (mother cell) splits into two units, giving rise to two daughter cells identical to the original. During this process bacterial aggregates can be formed, from which colonies consist of cells different in number and position:
Bacterial reproduction takes place in two distinct phases:
- increase in the size of the bacterium, which synthesizes and develops the various cellular structures;
- division of the mother cell to originate two daughter cells.
The growth of the bacterial population follows a characteristic trend, which makes it divided into four phases:
- DI LATENZA: bacteria synthesize the substances necessary to prepare for division and do not increase in number; its duration varies from species to species and in relation to environmental conditions.
- OF EXPONENTIAL GROWTH: every 10 - 60 minutes the number of bacteria doubles (logarithmic development).
- STATIONARY PHASE: nutrients are scarce and the number of new cells equals the number of dead bacteria.
- DEATH: the drastic drop in nutrients leads to the death of a higher number of bacteria than that of cells that are still able to reproduce.
