BacteriaBacteria (bækˈtɪəriə; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the fixation of nitrogen from the atmosphere.
Pathogenic bacteriaPathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of these pathogenic species in humans is estimated to be fewer than a hundred. By contrast, several thousand species are part of the gut flora present in the digestive tract.
Acid-fastnessAcid-fastness is a physical property of certain bacterial and eukaryotic cells, as well as some sub-cellular structures, specifically their resistance to decolorization by acids during laboratory staining procedures. Once stained as part of a sample, these organisms can resist the acid and/or ethanol-based decolorization procedures common in many staining protocols, hence the name acid-fast. The mechanisms of acid-fastness vary by species, although the most well-known example is in the genus Mycobacterium, which includes the species responsible for tuberculosis and leprosy.
LeprosyLeprosy, also known as Hansen's disease (HD), is a long-term infection by the bacteria Mycobacterium leprae or Mycobacterium lepromatosis. Infection can lead to damage of the nerves, respiratory tract, skin, and eyes. This nerve damage may result in a lack of ability to feel pain, which can lead to the loss of parts of a person's extremities from repeated injuries or infection through unnoticed wounds. An infected person may also experience muscle weakness and poor eyesight.
Mycolic acidMycolic acids are long fatty acids found in the cell walls of the Mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of mycolata species. Despite their name, mycolic acids have no biological link to fungi; the name arises from the filamentous appearance their presence gives mycolata under high magnification. The presence of mycolic acids in the cell wall also gives mycolata a distinct gross morphological trait known as "cording".
