Bacteria

Bacteria are a widespread group of unicellular microorganisms with a primitive cellular organization. They were first discovered in the 17th century by the Dutch scientist A. Leeuwenhoek. Intensive study of the biological properties of bacteria and their role in the biosphere began in the mid-19th century thanks to the work of the French scientist L. Pasteur, the German scientist R. Koch and the English scientist D. Lister.

Most bacteria lack chlorophyll and do not use solar energy, but obtain it from chemical transformations of inorganic and organic compounds. Bacteria are widespread in nature: in soil, water, plants, in the body of humans and animals. They are able to exist in a wide variety of conditions and play an important role in the cycle of substances.

Among bacteria there are a small number of species that cause diseases in humans, animals and plants. Their ability to cause infectious diseases is called pathogenicity.

Based on their shape, bacteria are divided into spherical (cocci), rod-shaped (bacteria and bacilli) and convoluted (vibrios, spirilla). The dimensions of the rod-shaped forms are from 1 to 10 microns in length and from 0.5 to 2 microns in width.

The main structures of a bacterial cell: cytoplasmic membrane, cell wall, cytoplasm with ribosomes and nucleoid (circular DNA). Many bacteria have flagella, a capsule, and are capable of forming spores.

Bacteria reproduce by dividing cells in half. The rate of division under favorable conditions is very high. The genetic material of bacteria is circular DNA. Bacteria are capable of transferring genetic material to each other and causing mutations.

The pathogenicity of bacteria is determined by the ability to produce toxins, the presence of a capsule and other factors. To combat bacteria, antiseptics, antibiotics, sterilization and disinfection are used.