The monera kingdom is formed by bacteria, cyanobacteria and archaebacteria (also called archeas), all very simple, unicellular beings with prokaryotic cells (no differentiated nucleus). These microscopic beings are usually smaller than 8 micrometers (1µm = 0.001 mm).
Note: The term "monera" in the current classification is obsolete. Its members were divided among the kingdoms Bacterium and Archaea. The kingdom Bacterium represents the largest number of species as it encompasses bacteria and cyanobacteria. Already the kingdom Archaea covers a small number of species. Archaea are prokaryote organisms, but they are no longer classified with bacteria because they have characteristics that make them also close to eukaryotes.
Despite this new classification, as the term "monera" is still adopted in textbooks, we continue to present its definition here.
The bacteria (from the Greek bakteria: 'rod') are found in all of Earth's ecosystems and are of great importance to health, the environment and the economy. Bacteria are found in any type of environment: sea, freshwater, soil, air, and even within many living things.
Examples of the importance of bacteria:
- at decomposition of dead organic matter. This process is performed both aerobically and anaerobically;
- agents that provoke disease in man;
- in industrial processes, such as lactobacilli, used in the curdling industry;
- at the nitrogen cycle, in which they act in several phases, making the atmospheric nitrogen can be used by plants;
- in Genetic Engineering and Biotechnology for the synthesis of various substances, including insulin and growth hormone.
Bacteria are unicellular microorganisms, prokaryotes, and can live in isolation or build colonial clusters of various shapes. The bacterial cell contains the four fundamental components of any cell: plasma membrane, hyaloplasma, ribosomes and chromatin, in this case a circular DNA molecule, which is the only bacterial chromosome.
The region occupied by the bacterial chromosome is usually called nucleoid. Outside the plasma membrane there is a cell wall (skeletal membrane of bacterial specific chemical composition).
it is common to have plasmids - DNA molecules not bound to the bacterial chromosome - scattered throughout the hyaloplasma. Plasmids usually contain genes for antibiotic resistance.
Some species of bacteria have, outside the skeletal membrane, another mucilaginous envelope called capsule. This is the case of pneumococci (pneumonia-causing bacteria). The dangerousness of these bacteria was found to reside in the capsule in one experiment, where rats infected with capsule-free pneumococcus had the disease but did not die, while capsulated pneumococci caused lethal pneumonia.
The bacterial cell wall, also known as the skeletal membrane, coats the plasma membrane externally, and is made up of a bacterial-only chemical known as murein (n-acetyl muramic acid).