A microorganism (from the Antonie van Leeuwenhoek, using a microscope of his own design.
Microorganisms are very diverse and include all the
.... That spike in nickel allowed methanogens to take off.
There are no conditions where all microorganisms would grow, and therefore often several methods are needed. For example, a food sample might be analyzed on three different nutrient mediums designed to indicate the presence of "total" bacteria (conditions where many, but not all, bacteria grow), molds (conditions where the growth of bacteria is prevented by, e.g., antibiotics) and coliform bacteria (these indicate a sewage contamination).
There are several methods for investigating the level of hygiene in a sample of food, drinking water, equipment, etc. Water samples can be filtrated through an extremely fine filter. This filter is then placed in a selective media or polymerase chain reaction, can then be used for detection. The hygiene of hard surfaces, such as cooking pots, can be tested by touching them with a solid piece of nutrient medium and then allowing the microorganisms to grow on it.
In food preparation microorganisms are reduced by preservation methods (such as the addition of vinegar), clean utensils used in preparation, short storage periods, or by cool temperatures. If complete sterility is needed, the two most common methods are irradiation and the use of an autoclave, which resembles a pressure cooker.
Hygiene is the avoidance of viruses. A good example of this is a hypodermic needle.
Microorganisms are critical to the processes of decomposition required to cycle nitrogen and other elements in the natural environment.
Importance in ecology
.periodontal disease although a relationship has been proposed between the presence of some archaean methanogens and human  Microorganisms are the cause of many infectious diseases. The organisms involved include
Diseases caused by microbes
Importance in human health
In the Middle Ages, diseased corpses were thrown into castles during sieges using catapults or other siege engines. Individuals near the corpses were exposed to the pathogen and were likely to spread that pathogen to others.
Use in warfare
Microorganisms are essential tools in fuel cells, and as a solution for pollution.
Use in science
- Streptokinase produced by the bacterium Streptococcus and modified by genetic engineering is used as a clot buster for removing clots from the blood vessels of patients who have undergone myocardial infarctions leading to heart attack.
- organ transplantation
- Statins produced by the yeast Monascus purpureus are commercialised as blood cholesterol lowering agents which act by competitively inhibiting the enzyme responsible for synthesis of cholesterol.
Microorganisms are used for preparation of bioactive molecules and enzymes.
- Acetic acid: Produced by the bacterium Acetobacter aceti and other acetic acid bacteria (AAB)
- Butyric acid (butanoic acid): Produced by the bacterium Clostridium butyricum
- Lactic acid: Lactobacillus and others commonly called as lactic acid bacteria (LAB)
- Citric acid: Produced by the fungus Aspergillus niger
Microorganisms are used for many commercial and industrial production of chemicals, enzymes and other bioactive molecules.
Examples of organic acid produced include
Use in production of chemicals, enzymes etc.
Microorganisms are used in fermentation to produce ethanol, and in biogas reactors to produce methane. Scientists are researching the use of algae to produce liquid fuels, and bacteria to convert various forms of agricultural and urban waste into usable fuels.
Use in energy
 The majority of all oxidative sewage treatment processes rely on a large range of microorganisms to oxidise organic constituents which are not amenable to sedimentation or flotation. Anaerobic microorganisms are also used to reduce sludge solids producing methane gas (amongst other gases) and a sterile mineralised residue. In
Use in water treatment
 They are also used to control the
Use in food production
The morphology of the intestine of germ-free animals differs considerably from normal animals - villi of the small intestine are remarkably regular, the rate of epithelial cell renew is reduced and, as one would expect, the number and size of Peyer's patches is reduced. The cecum of germ-free rats is roughly 10 times the size of that in a conventional rat. Bacteria in the intestinal lumen metabolize a variety of sterols and steroids. For example, bacteria convert the bile salt cholic acid to deoxycholic acid. Small intestinal bacteria also have an important role in sex steroid metabolism. Finally, bacterial populations in the large intestine digest carbohydrates, proteins and lipids that escape digestion and absorption in small intestine. This fermentation, particularly of cellulose, is of critical importance to herbivores like cattle and horses which make a living by consuming plants. However, it seems that even species like humans and rodents derive significant benefit from the nutrients liberated by intestinal microorganisms.
It is also clear that microbial populations exert a profound effect on structure and function of the digestive tract. For example:
The gastrointestinal tract is sterile at birth, but colonization typically begins within a few hours of birth, starting in the small intestine and progressing caudally over a period of several days. In most circumstances, a "mature" microbial flora is established by 3 to 4 weeks of age.
In sharp contrast to the stomach and small intestine, the contents of the colon literally teem with bacteria, predominantly strict anaerobes (bacteria that survive only in environments virtually devoid of oxygen). Between these two extremes is a transitional zone, usually in the ileum, where moderate numbers of both aerobic and anaerobic bacteria are found.
The number and type of bacteria in the gastrointestinal tract vary dramatically by region. In healthy individuals the stomach and proximal small intestine contain few microorganisms, largely a result of the bacteriocidal activity of gastric acid; those that are present are aerobes and facultative anaerobes. One interesting testimony to the ability of gastric acid to suppress bacterial populations is seen in patients with achlorhydria, a genetic condition which prevents secretion of gastric acid. Such patients, which are otherwise healthy, may have as many as 10,000 to 100,000,000 microorganisms per ml of stomach contents.
The gastrointestinal tract contains an immensely complex ecology of microorganisms. A typical person harbors more than 500 distinct species of bacteria, representing dozens of different lifestyles and capabilities. The composition and distribution of this menagerie varies with age, state of health and diet.
Some forms of bacteria that live in animals' stomachs help in their digestion. For example, cows have a variety of different microorganisms in their stomachs that are essential in their digestion of grass and hay.
Use in digestion
 Microorganisms are vital to humans and the environment, as they participate in the
lichen. Certain fungi form mycorrhizal symbioses with trees that increase the supply of nutrients to the tree.
The nitrogen cycle in soils depends on the fixation of atmospheric nitrogen. One way this can occur is in the nodules in the roots of legumes that contain symbiotic bacteria of the genera Rhizobium, Mesorhizobium, Sinorhizobium, Bradyrhizobium, and Azorhizobium.
Extremophiles are significant in different ways. They extend terrestrial life into much of the Earth's hydrosphere, crust and atmosphere, their specific evolutionary adaptation mechanisms to their extreme environment can be exploited in bio-technology, and their very existence under such extreme conditions increases the potential for extraterrestrial life.
- Temperature: as high as 130 °C (266 °F), as low as −17 °C (1 °F)
- Acidity/alkalinity: less than pH 0, up to pH 11.5
- Salinity: up to saturation
- Pressure: up to 1,000-2,000 atm, down to 0 atm (e.g. vacuum of space)
- Radiation: up to 5kGy
Extremophiles are microorganisms that have adapted so that they can survive and even thrive in conditions that are normally fatal to most life-forms. For example, some species have been found in the following extreme environments:
Habitats and ecology
The fungi have several unicellular species, such as baker's yeast (Saccharomyces cerevisiae) and fission yeast (Schizosaccharomyces pombe). Some fungi, such as the pathogenic yeast Candida albicans, can undergo phenotypic switching and grow as single cells in some environments, and filamentous hyphae in others. Fungi reproduce both asexually, by budding or binary fission, as well by producing spores, which are called conidia when produced asexually, or basidiospores when produced sexually.
Some micro animals are multicellular but at least one animal group, Myxozoa, is unicellular in its adult form. Microscopic arthropods include dust mites and spider mites. Microscopic crustaceans include copepods, some cladocera and water bears. Many nematodes are also too small to be seen with the naked eye. A common group of microscopic animals are the rotifers, which are filter feeders that are usually found in fresh water. Some micro-animals reproduce both sexually and asexually and may reach new habitats by producing eggs which can survive harsh environments that would kill the adult animal. However, some simple animals, such as rotifers, tardigrades and nematodes, can dry out completely and remain dormant for long periods of time.
 The number of species of protists is unknown since we may have identified only a small portion. Studies from 2001-2004 have shown that a high degree of protist diversity exists in oceans, deep sea-vents, river sediment and an acidic river which suggests that a large number of eukaryotic microbial communities have yet to be discovered. have unique life cycles that involve switching between unicellular, colonial, and multicellular forms.slime molds protists, and multicellular are species algae Several  Of
Unicellular eukaryotes usually reproduce asexually by mitosis under favorable conditions. However, under stressful conditions such as nutrient limitations and other conditions associated with DNA damage, they tend to reproduce sexually by meiosis and syngamy.
Unicellular eukaryotes consist of a single cell nuclei.
Archaea were originally described in extreme environments, such as ammonia oxidation.
Archaea are also single-celled organisms that lack nuclei. In the past, the differences between bacteria and archaea were not recognised and archaea were classified with bacteria as part of the kingdom Monera. However, in 1990 the microbiologist Carl Woese proposed the three-domain system that divided living things into bacteria, archaea and eukaryotes. Archaea differ from bacteria in both their genetics and biochemistry. For example, while bacterial cell membranes are made from phosphoglycerides with ester bonds, archaean membranes are made of ether lipids.
, but for bacteria this is a mechanism for survival, not reproduction. Under optimal conditions bacteria can grow extremely rapidly and can double as quickly as every 20 minutes.spores Some species form extraordinarily resilient  In nature, the development of competence for transformation is usually associated with stressful environmental conditions, and seems to be an adaptation for facilitating repair of DNA damage in recipient cells.. However, many bacterial species can transfer DNA between individual cells by a process referred to as natural transformation.sexual reproduction meiotic, but do not undergo budding or sometimes by binary fission, which provides strength and rigidity to their cells. They reproduce by cell wall. Bacteria are surrounded by a bacterial conjugation. These plasmids can be transferred between cells through plasmids, although they can also harbor small pieces of DNA called DNA Their genome is usually a single loop of  Almost all bacteria are invisible to the naked eye, with a few extremely rare exceptions, such as
Consisting of two Earth and inhabit practically all environments where the temperature is below +140 °C. They are found in water, soil, air, animals' gastrointestinal tracts, hot springs and even deep beneath the Earth's crust in rocks. Practically all surfaces that have not been specially sterilized are covered by prokaryotes. The number of prokaryotes on Earth is estimated to be around five million trillion trillion, or 5 × 1030, accounting for at least half the biomass on Earth.
Prokaryotes are organisms that lack a myxobacteria can aggregate into complex structures as part of their life cycle.
Microorganisms can be found almost anywhere in the microbiology also encompasses the study of viruses.
Classification and structure
On 8 November 2013, scientists reported the discovery of what may be the earliest signs of life on Earth—the oldest complete fossils of a microbial mat (associated with sandstone in Western Australia) estimated to be 3.48 billion years old.
In 1876, Koch's postulates. Although these postulates cannot be applied in all cases, they do retain historical importance to the development of scientific thought and are still being used today.
spores on dust, rather than spontaneously generated within the broth. Thus, Pasteur dealt the death blow to the theory of spontaneous generation and supported germ theory.
Lazzaro Spallanzani (1729–1799) found that boiling broth would sterilise it, killing any microorganisms in it. He also found that new microorganisms could only settle in a broth if the broth was exposed to air.
from non-living substances during the process of spoilage. spontaneously appeared Leeuwenhoek's discovery, along with subsequent observations by Spallanzani and Pasteur, ended the long-held belief that life  Before Leeuwenhoek's discovery of microorganisms in 1675, it had been a mystery why
History of microorganisms' discovery
All these early claims about the existence of microorganisms were speculative and were not based on any data or science. Microorganisms were neither proven, observed, nor correctly and accurately described until the 17th century. The reason for this was that all these early studies lacked the microscope.
In 1546, Girolamo Fracastoro proposed that epidemic diseases were caused by transferable seedlike entities that could transmit infection by direct or indirect contact, or even without contact over long distances.
… and because there are bred certain minute creatures that cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and they cause serious diseases.
The possibility that microorganisms exist was discussed for many centuries before their discovery in the 17th century. The existence of unseen microbiological life was postulated by Roman scholar Marcus Terentius Varro in a 1st-century BC book titled On Agriculture in which he warns against locating a homestead near swamps:
Microorganisms tend to have a relatively fast rate of evolution. Most microorganisms can reproduce rapidly, and bacteria are also able to freely exchange genes through evolve (via natural selection) to survive in new environments and respond to environmental stresses. This rapid evolution is important in medicine, as it has led to the recent development of "super-bugs", pathogenic bacteria that are resistant to modern antibiotics.
Single-celled microorganisms were the Triassic period. The newly discovered biological role played by nickel, however — especially that engendered by volcanic eruptions from the Siberian Traps (site of the modern city of Norilsk) — is thought to have accelerated the evolution of methanogens towards the end of the Permian–Triassic extinction event.
- Evolution 1
- Pre-microbiology 2
- History of microorganisms' discovery 3
Classification and structure 4
- Bacteria 4.1.1
- Archaea 4.1.2
- Protists 4.2.1
- Animals 4.2.2
- Fungi 4.2.3
- Plants 4.2.4
- Prokaryotes 4.1
Habitats and ecology 5
- Extremophiles 5.1
- Soil microorganisms 5.2
- Symbiotic microorganisms 5.3
- Use in digestion 6.1
- Use in food production 6.2
- Use in water treatment 6.3
- Use in energy 6.4
- Use in production of chemicals, enzymes etc. 6.5
- Use in science 6.6
- Use in warfare 6.7
Importance in human health 7
- Human digestion 7.1
- Diseases caused by microbes 7.2
- Importance in ecology 8
- Hygiene 9
- See also 10
- References 11
- External links 12
Microorganisms are crucial to nutrient recycling in pathogenic and cause disease and even death in plants and animals. Microorganisms are often referred to as microbes, but this is usually used in reference to pathogens.
Microorganisms live in every part of the Antarctica. According to one researcher,"You can find microbes everywhere — they're extremely adaptable to conditions, and survive wherever they are."