We deal with such questions in this article, which belongs to our field of biology. Many know bacteria only from diseases. People then go to the doctor and in some cases the doctor prescribes antibiotics to fight the annoying invaders called bacteria. However, bacteria do not only make people ill.
There are many useful in this world and without them human life would not even be possible.
They are protozoa, but can live together in colonies. Bacteria have no cell nucleus, in science this is called prokaryotes. Some bacteria can cause serious diseases such as plague and cholera. The size of most bacteria – based on the smaller diameter – is between 0.2 and 2 μm
Along with the eukaryotes and archaeae, bacteria form one of the three basic domains into which all living beings are divided. Like the archaeae, they are prokaryotes, which means that their DNA is not contained in a nucleus delimited from the cytoplasm by a double membrane as in eukaryotes, but in them, as in all prokaryotes, the DNA lies freely in the cytoplasm, compressed together in a narrow space, the nucleoid.
Forms and aggregates of bacteria
Apart from a few exceptions, individual bacteria cells cannot be seen by the naked eye because the resolution of the human eye is around 50 µm. Mycoplasmas are particularly small, the diameter of the smallest is about 0.3 µm. Many cyanobacteria are particularly large, their diameter usually lies between 2 and 8 µm.
Bacteria were first observed by Antoni van Leeuwenhoek with the help of a self-made microscope in water and human saliva and described by him in reports to the Royal Society of London in 1676. Until the end of the last century, the term “bacteria” was used in microbiology for all microscopically small, mostly unicellular organisms that do not have a real cell nucleus and therefore belong to the prokaryotes. However, this also applies to the archaeae, which have been assigned to a separate domain since about 1990. Today the two domains of the prokaryotes are called Bacteria and Archaea, the third domain is that of the eukaryotes.
This bacterium lacks essential genes that a bacterium needs for an independent life.