Anu (Irish goddess)

Anu or Ana (sometimes given as Anann or Anand) is the name of a goddess mentioned briefly in Irish mythology. The 9th century "Sanas Cormaic" (Cormac's Glossary) says in its entry for her: "Ana - mother of the gods of Ireland; well did she feed the gods". She may be a goddess in her own right, or another name for Danu. In the "Lebor Gabála Érenn", Anand is given as another name for The Morrígan. As her name is often conflated with a number of other goddesses, it is not always clear which figure is being referred to if the name is taken out of context. The name may be derived from the Proto-Celtic theonym *"Φanon-".
Anu has particular associations with Munster: the pair of breast shaped hills known as the Paps of Anu ("Dá Chích Anann" or "the breasts of Anu") in County Kerry are said to have been named after her.
While an Irish goddess, in parts of Britain a similar figure is referred to as “Gentle Annie”, in an effort to avoid offence, a tactic which is similar to referring to the fairies as “The Good People”.


Hypoxemia

Hypoxemia is an abnormally low level of oxygen in the blood. More specifically, it is oxygen deficiency in arterial blood. Hypoxemia has many causes, and often causes hypoxia as the blood is not supplying enough oxygen to the tissues of the body.
Definition.
"Hypoxemia" refers to the low level of oxygen in blood, and the more general term "hypoxia" is an abnormally low oxygen content in any tissue or organ, or the body as a whole. Hypoxemia can cause hypoxia (hypoxemic hypoxia), but hypoxia can also occur via other mechanisms, such as anemia.
Hypoxemia is usually defined in terms of reduced partial pressure of oxygen (mm Hg) in arterial blood, but also in terms of reduced content of oxygen (ml oxygen per dl blood) or percentage saturation of hemoglobin (the oxygen-binding protein within red blood cells) with oxygen, which is either found singly or in combination.
While there is general agreement that an arterial blood gas measurement which shows that the partial pressure of oxygen is lower than normal constitutes hypoxemia, there is less agreement concerning whether the oxygen content of blood is relevant in determining hypoxemia. This definition would include oxygen carried by hemoglobin. The oxygen content of blood is thus sometimes viewed as a measure of tissue delivery rather than hypoxemia.
Just as extreme hypoxia can be called anoxia, extreme hypoxemia can be called anoxemia.
Signs and symptoms.
In an acute context, hypoxemia can cause symptoms such as those in respiratory distress. These include breathlessness, an increased rate of breathing, use of the chest and abdominal muscles to breathe, and lip pursing.
Chronic hypoxemia may be compensated or uncompensated. The compensation may cause symptoms to be overlooked initially, however, further disease or a stress such as any increase in oxygen demand may finally unmask the existing hypoxemia. In a compensated state, blood vessels supplying less-ventilated areas of the lung may selectively contract, to redirect the blood to areas of the lungs which are better ventilated. However, in a chronic context, and if the lungs are not well ventilated generally, this mechanism can result in pulmonary hypertension, overloading the right ventricle of the heart and causing cor pulmonale and right sided heart failure. Polycythemia can also occur. In children, chronic hypoxemia may manifest as delayed growth, neurological development and motor development and decreased sleep quality with frequent sleep arousals.
Other symptoms of hypoxemia may include cyanosis, digital clubbing, and symptoms that may relate to the cause of the hypoxemia, including cough and hemoptysis.
Serious hypoxemia typically occurs when the partial pressure of oxygen in blood is less than , the beginning of the steep portion of the oxygen–hemoglobin dissociation curve, where a small decrease in the partial pressure of oxygen results in a large decrease in the oxygen content of the blood. Severe hypoxia can lead to respiratory failure
Causes.
Hypoxemia refers to insufficient oxygen in the blood. Thus any cause that influences the rate or volume of air entering the lungs (ventilation) or any cause that influences the transfer of air from the lungs to the blood may cause hypoxemia. As well as these respiratory causes, cardiovascular causes such as shunts may also result in hypoxemia.
Hypoxemia is caused by five categories of etiologies: hypoventilation, ventilation/perfusion mismatch, right-to-left shunt, diffusion impairment, and low PO2. Low PO2 and hypoventilation are associated with a normal alveolar–arterial gradient (A-a gradient) whereas the other categories are associated with an increased A-a gradient.
Ventilation.
If the alveolar ventilation is low, there will not be enough oxygen delivered to the alveoli for the body's use. This can cause hypoxemia even if the lungs are normal, as the cause is in the brainstem's control of ventilation or in the body's inability to breathe effectively.
Respiratory drive.
Respiration is controlled by centers in the medulla, which influence the rate of breathing and the depth of each breath. This is influenced by the blood level of carbon dioxide, as determined by central and peripheral chemoreceptors located in the central nervous system and carotid and aortic bodies, respectively. Hypoxia occurs when the breathing center doesn't function correctly or when the signal is not appropriate:
Physical states.
A variety of conditions that physically limit airflow can lead to hypoxemia.
Environmental oxygen.
In conditions where the proportion of oxygen in the air is low, or when the partial pressure of oxygen has decreased, less oxygen is present in the alveoli of the lungs. The alveolar oxygen is transferred to hemoglobin, a carrier protein inside red blood cells, with an efficiency that decreases with the partial pressure of oxygen in the air.
Perfusion.
Ventilation-perfusion mismatch.
This refers to a disruption in the ventilation/perfusion equilibrium. Oxygen entering the lungs typically diffuses across the alveolar-capillary membrane into blood. However this equilibration does not occur when the alveolus is insufficiently ventilated, and as a consequence the blood exiting that alveolus is relatively hypoxemic. When such blood is added to blood from well ventilated alveoli, the mix has a lower oxygen partial pressure than the alveolar air, and so the A-a difference develops. Examples of states that can cause a ventilation-perfusion mismatch include:
Shunting.
Shunting refers to blood that bypasses the pulmonary circulation, meaning that the blood does not receive oxygen from the alveoli. In general, a shunt may be within the heart or lungs, and cannot be corrected by administering oxygen alone. Shunting may occur in normal states:
Shunting may also occur in disease states:
Exercise.
Exercise-induced arterial hypoxemia occurs during exercise when a trained individual exhibits an arterial oxygen saturation below 93%. It occurs in fit, healthy individuals of varying ages and genders. Adaptations due to training include an increased cardiac output from cardiac hypertrophy, improved venous return, and metabolic vasodilation of muscles, and an increased VO2 Max. There must be a corresponding increase in VCO2 thus a necessity to clear the carbon dioxide to prevent a metabolic acidosis. Hypoxemia occurs in these individuals due to increased pulmonary blood flow causing:
Physiology.
Key to understanding whether the lung is involved in a particular case of hypoxemia is the difference between the alveolar and the arterial oxygen levels; this A-a difference is often called the A-a "gradient" and is normally small. The arterial oxygen partial pressure is obtained directly from an arterial blood gas determination. The oxygen contained in the alveolar air can be calculated because it will be directly proportional to its fractional composition in air. Since the airways humidify (and so dilute) the inhaled air, the barometric pressure of the atmosphere is reduced by the vapor pressure of water.
History.
The term hypoxemia was originally used to describe low blood oxygen occurring at high altitudes and was defined generally as defective oxygenation of the blood.


Virus classification

Virus classification is the process of naming viruses and placing them into a taxonomic system similar to the classification systems used for cellular organisms.
Viruses are classified by phenotypic characteristics, such as morphology, nucleic acid type, mode of replication, host organisms, and the type of disease they cause. The formal taxonomic classification of viruses is the responsibility of the International Committee on Taxonomy of Viruses (ICTV) system, although the Baltimore classification system can be used to place viruses into one of seven groups based on their manner of mRNA synthesis. Specific naming conventions and further classification guidelines are set out by the ICTV.
A catalogue of all the world's known viruses has been proposed and, in 2013, some preliminary efforts were underway.
Virus species definition.
Species form the basis for any biological classification system. Before 1982, it was thought that viruses could not be made to fit Ernst Mayr's reproductive concept of species, and so were not amenable to such treatment. In 1982, the ICTV started to define a species as "a cluster of strains" with unique identifying qualities. In 1991, the more specific principle that a virus species is a polythetic class of viruses that constitutes a replicating lineage and occupies a particular ecological niche was adopted.
In July 2013, the ICTV definition of species changed to state: "A species is a monophyletic group of viruses whose properties can be distinguished from those of other species by multiple criteria." Viruses are real physical entities produced by biological evolution and genetics, whereas virus species and higher taxa are abstract concepts produced by rational thought and logic. The virus/species relationship thus represents the front line of the interface between biology and logic.
The actual criteria used vary by the taxon, and can be inconsistent (arbitrary similarity thresholds) or unrelated to lineage (geography) at times. The matter is, for many, not yet settled.
ICTV classification.
The International Committee on Taxonomy of Viruses began to devise and implement rules for the naming and classification of viruses early in the 1970s, an effort that continues to the present. The ICTV is the only body charged by the International Union of Microbiological Societies with the task of developing, refining, and maintaining a universal virus taxonomy. The system shares many features with the classification system of cellular organisms, such as taxon structure. However, some differences exist, such as the universal use of italics for all taxonomic names, unlike in the International Code of Nomenclature for algae, fungi, and plants and International Code of Zoological Nomenclature.
Viral classification starts at the level of realm and continues as follows, with the taxonomic suffixes in parentheses:
Unlike the system of binomial nomenclature adopted in cellular species, there is currently no standardized form for virus species names. At present, the ICTV mandates that a species name must contain as few words as possible while remaining distinct, and must not only contain the word virus and the host name. Species names often take the form of "[Disease] virus", particularly for higher plants and animals. In 2019, the ICTV published a proposal to adopt a more formalized system of binomial nomenclature for virus species names, to be voted on in 2020. However, some virologists later objected to the potential naming system change, arguing that the debate came while many in the field were preoccupied due to the COVID-19 pandemic.
As of 2019, all levels of taxa except subrealm, subkingdom, and subclass are used. Four realms, one "incertae sedis" order, 24 "incertae sedis" families, and three "incertae sedis" genera are recognized:
Realms: "Duplodnaviria", "Monodnaviria", "Riboviria", and "Varidnaviria"
"Incertae sedis" order: "Ligamenvirales"
"Incertae sedis" families:
"Incertae sedis" genera: "Deltavirus", "Dinodnavirus", "Rhizidiovirus"
Structure-based virus classification.
It has been suggested that similarity in virion assembly and structure observed for certain viral groups infecting hosts from different domains of life (e.g., bacterial tectiviruses and eukaryotic adenoviruses or prokaryotic Caudovirales and eukaryotic herpesviruses) reflects an evolutionary relationship between these viruses. Therefore, structural relationship between viruses has been suggested to be used as a basis for defining higher-level taxa – structure-based viral lineages – that could complement the ICTV classification scheme of 2010.
The ICTV has gradually added many higher-level taxa using relationships in protein folds. All four realms defined in the 2019 release are defined by the presence of a protein of a certain structural family.
Baltimore classification.
Baltimore classification (first defined in 1971) is a classification system that places viruses into one of seven groups depending on a combination of their nucleic acid (DNA or RNA), strandedness (single-stranded or double-stranded), sense, and method of replication. Named after David Baltimore, a Nobel Prize-winning biologist, these groups are designated by Roman numerals. Other classifications are determined by the disease caused by the virus or its morphology, neither of which are satisfactory due to different viruses either causing the same disease or looking very similar. In addition, viral structures are often difficult to determine under the microscope. Classifying viruses according to their genome means that those in a given category will all behave in a similar fashion, offering some indication of how to proceed with further research. Viruses can be placed in one of the seven following groups:
DNA viruses.
Viruses with a DNA genome, except for the DNA reverse transcribing viruses, are members of three of the four recognized viral realms: "Duplodnaviria", "Monodnaviria", and "Varidnaviria". But the "incertae sedis" order "Ligamenvirales", and many other "incertae sedis" families and genera, are also used to classify DNA viruses. The domains "Duplodnaviria" and "Varidnaviria" consist of double-stranded DNA viruses; other double-stranded DNA viruses are "incertae sedis". The domain "Monodnaviria" consists of single-stranded DNA viruses that generally encode a HUH endonuclease; other single-stranded DNA viruses are "incertae sedis".
RNA viruses.
All viruses that have an RNA genome, and that encode an RNA-dependent RNA polymerase (RdRp), are members of the kingdom "Orthornavirae", within the realm "Riboviria".
Reverse transcribing viruses.
All viruses that encode a reverse transcriptase (also known as RT or RNA-dependent DNA polymerase) are members of the class "Revtraviricetes", within the phylum "Arterviricota", kingdom "Pararnavirae", and realm "Riboviria". The class "Blubervirales" contains the single family "Hepadnaviridae" of DNA RT (reverse transcribing) viruses; all other RT viruses are members of the class Ortervirales.
Historical systems.
Holmes classification.
Holmes (1948) used a Linnaean taxonomy with binomial nomenclature to classify viruses into 3 groups under one order, Virales. They are placed as follows:
The system was not accepted by others due to its neglect of morphological similarities.
Subviral agents.
The following infectious agents are smaller than viruses and have only some of their properties. Since 2015, the ICTV has allowed them to be classified in a similar way as viruses are.
Viroids and virus-dependent agents.
Satellites.
Satellites depend on co-infection of a host cell with a helper virus for productive multiplication. Their nucleic acids have substantially distinct nucleotide sequences from either their helper virus or host. When a satellite subviral agent encodes the coat protein in which it is encapsulated, it is then called a satellite virus.
Satellite-like nucleic acids resemble satellite nucleic acids, in that they replicate with the aid of helper viruses. However they differ in that they can encode functions that can contribute to the success of their helper viruses; while they are sometimes considered to be genomic elements of their helper viruses, they are not always found within their helper viruses.
Defective interfering particles.
Defective interfering particles are defective viruses that have lost their ability to replicate except in the presence of a helper virus, which is normally the parental virus. They can also interfere with the helper virus.


Tremella fuciformis

Tremella fuciformis is a species of fungus; it produces white, frond-like, gelatinous basidiocarps (fruiting bodies). It is widespread, especially in the tropics, where it can be found on the dead branches of broadleaf trees. This fungus is commercially cultivated and is one of the most popular fungi in the cuisine and medicine of China. "Tremella fuciformis" is commonly known as snow fungus, snow ear, silver ear fungus, and white jelly mushroom.
"Tremella fuciformis" is a parasitic yeast, and grows as a slimy, mucous-like film until it encounters its preferred hosts, various species of "Annulohypoxylon" (or possibly "Hypoxylon") fungi, whereupon it then invades, triggering the aggressive mycelial growth required to form the fruiting bodies.
Taxonomy and naming.
"Tremella fuciformis" was first described in 1856 by English mycologist Miles Joseph Berkeley, based on collections made in Brazil by the botanist and explorer Richard Spruce. In 1939, Japanese mycologist Yosio Kobayasi described "Nakaiomyces nipponicus", a similar-looking fungus that differed by having scattered, dark spines on its surface. Later research, however, showed that the fruit bodies were those of "Tremella fuciformis" parasitized by an ascomycete, "Ceratocystis epigloeum", that formed the dark spines. "Nakaiomyces nipponicus" is therefore a synonym of "T. fuciformis".
In Mandarin Chinese, it is called 银耳 (pinyin: "yín ěr"; literally "silver ear"), 雪耳 (pinyin: xuě ěr; literally "snow ear"); or 白木耳 (pinyin: "bái mù ěr", literally "white wood ear"), and in Japanese it is called "shiro kikurage" (シロキクラゲ, lit. "white tree jellyfish"). In Vietnam, it is called "nấm tuyết" or "ngân nhĩ".
In his book, "Growing Gourmet and Medicinal Mushrooms", Paul Stamets lists the following common names for "Tremella fuciformis" (which he calls "white jelly mushroom"): yin er, white jelly fungus, white jelly leaf ("shirokikurage"), silver ear mushroom, snow mushroom, chrysanthemum mushroom.
Description.
Fruit bodies are gelatinous, watery white, up to across (larger in cultivated specimens), and composed of thin but erect, seaweed-like, branching fronds, often crisped at the edges. Microscopically, the hyphae are clamped and occur in a dense gelatinous matrix. Haustorial cells arise on the hyphae, producing filaments that attach to and penetrate the hyphae of the host. The basidia are tremelloid (ellipsoid, with oblique to vertical septa), 10–13 μm × 6.5–10 μm, sometimes stalked. The basidiospores are ellipsoid, smooth, 5–8 μm × 4–6 μm, and germinate by hyphal tube or by yeast cells.
Habitat and distribution.
"Tremella fuciformis" is known to be a parasite of "Hypoxylon" species. Many of these species were reassigned to a new genus, "Annulohypoxylon", in 2005 including its preferred host, "Annulohypoxylon archeri", the species routinely used in commercial cultivation. Following its host, fruit bodies are typically found on dead, attached or recently fallen branches of broadleaf trees.
The species is mainly tropical and subtropical, but extends into temperate areas in Asia and North America. It is known throughout South and Central America, the Caribbean, parts of North America, sub-Saharan Africa, southern and eastern Asia, Australia, New Zealand, and the Pacific Islands.
Economic usage.
"Tremella fuciformis" has been cultivated in China since at least the nineteenth century. Initially, suitable wooden poles were prepared and then treated in various ways in the hope that they would be colonized by the fungus. This haphazard method of cultivation was improved when poles were inoculated with spores or mycelium. Modern production only began, however, with the realization that both the "Tremella" and its host species needed to be inoculated into the substrate to ensure success. The "dual culture" method, now used commercially, employs a sawdust mix inoculated with both fungal species and kept under optimal conditions. The most popular species to pair with "T. fuciformis" is its preferred host, "Annulohypoxylon archeri". Estimated production in China in 1997 was 130,000 tonnes. "Tremella fuciformis" is also cultivated in other East Asian countries, with some limited cultivation elsewhere.
In Chinese cuisine, "Tremella fuciformis" is traditionally used in sweet dishes. While tasteless, it is valued for its gelatinous texture as well as its supposed medicinal benefits. Most commonly, it is used to make a dessert soup called "luk mei" (六味) in Cantonese, often in combination with jujubes, dried longans, and other ingredients. It is also used as a component of a drink and as an ice cream. Since cultivation has made it less expensive, it is now additionally used in some savoury dishes.
In Vietnamese cuisine, it's often used in Chè (Vietnamese pronunciation: [cɛ̂]), a Vietnamese term that refers to any traditional Vietnamese sweet beverage, dessert soup or pudding.
Cosmetic use.
"Tremella fuciformis" extract is used in women's beauty products from China, Korea, and Japan.


Pitthea famula

Pitthea famula is a species of moth in the family Geometridae. It was first described by Dru Drury in 1773 from Calabar, in what is now Nigeria. It is found in Angola, Benin, Cameroon, the Republic of the Congo, the Democratic Republic of the Congo, Equatorial Guinea (Bioko), Nigeria, Sierra Leone and Zambia.
Description.
Upperside: antennae long and pectinated (comb like). Thorax spiral. Neck orange. Thorax and abdomen dusky grey. Anterior wings about halfway from the tips black, but at the base are of a pellucid (transparent) white; being surrounded along the anterior edge and part of the posterior with black; an oblong white spot is placed near the tips on the black part. Posterior wings black and white; the white entirely surrounded by the black, which on the anterior and abdominal edges is very narrow.
Underside: palpi orange, black at the tips. Neck, breast, and sides orange. Feet black. Thighs white. Abdomen white, annulated with dusky grey. Anterior wings as on the upperside, the black parts being of a russet hue. Posterior wings differ a little, the white part running down to the middle of the external edges, with a white spot at the upper corners. Margins of the wings entire.
Wingspan 2 inches (50 mm).


L-A helper virus


Activation-induced cell death

AICD (activation-induced cell death) is programmed cell death caused by the interaction of Fas receptors (Fas, CD95) and Fas ligands (FasL, CD95 ligand). AICD is a negative regulator of activated T lymphocytes that results from repeated stimulation of their T-cell receptors (TCR) and helps to maintain peripheral immune tolerance. Alteration of the process may lead to autoimmune diseases.
The AICD effector cell is one that expresses FasL, and apoptosis is induced in the cell expressing the Fas receptor. Both activated T cells and B cells express Fas and undergo clonal deletion by the AICD mechanism. Activated T cells that express both Fas and FasL may be killed by themselves or by each other.
Signaling.
The binding of Fas ligand to Fas receptor triggers trimerization of Fas, whose cytoplasmic domain is then able to bind the death domain of the adaptor protein FADD (Fas-associated protein with death domain). Procaspase 8 binds to FADD's death effector domain (DED) and proteolytically self-activates as caspase 8. Fas, FADD, and procaspase 8 together form a death-inducing signaling complex (DISC). Activated caspase 8 is released into the cytosol, where it activates the caspase cascade that initiates apoptosis.
Regulation of Fas-FasL and AICD.
FasL is primarily regulated at the transcriptional level. (The other option is regulation of the signal emanating from the death receptor itself, controlling sensitivity to the induction of apoptosis.) NFAT activated by TCR stimulation activates FasL transcription, possibly indirectly by upregulating early growth response proteins. T cell activation-induced transcription of FasL is further regulated by c-Myc–MAX heterodimers, and can be blocked by c-Myc downregulation. Interferon regulatory factors IRF1 and IRF2 also upregulate FasL transcription by directly binding to the FasL promoter.
Not much is known about the regulation of Fas and other death receptors. However, overexpression of the protein CFLAR (caspase and FADD-like apoptosis regulator) inhibits Fas-mediated apoptosis.


Saccharomyces cerevisiae virus LA


Sporosarcina aquimarina

Sporosarcina aquimarina is a rod-shaped bacterium of the genus "Sporosarcina".
Characteristics.
Cells of "Sporosarcina aquimarina" are 0.9–1.2 μm x 2.0–3.5 μm. It is motile by means of a single polar flagellum. The bacterium forms endospores (like all species of the genus).
Metabolism.
"Sporosarcina aquimarina" is heterotrophic, as it does not perform photosynthesis. It is facultative anaerobe. If oxygen is present the metabolism is due to cellular respiration, but it can also grow anaerobic if oxygen is absent. The species is halophilic. 13% NaCl are still tolerated. "Sporosarcina aquimarina" is one of the bacteria that can make use of urea with the enzyme urease. Others bacteria of the same genus which possess the enzyme urease are for example "S. ureaea" und "S. pasteurii".
Etymology.
The genus name derives from the Greek word "spora" ("spore") and the Latin word "sarcina" ("package", "bundle") and refers to the fact that it forms endospores and the typical arrangement of the cells. The species name "S. aquimarina" derives from the fact that it was found in sea water.
Systematics.
The species "Sporosarcina aquimarina" belongs to the family Planococcaceae of the Firmicutes.


Aureusvirus

Aureusvirus is a genus of viruses, in the family "Tombusviridae". Plants serve as natural hosts. There are six species in this genus.
Taxonomy.
The genus contains the following species:
Structure.
Viruses in "Aureusvirus" are non-enveloped, with icosahedral and Spherical geometries, and T=3 symmetry. The diameter is around 30 nm. Genomes are linear, around 4.4kb in length.
Life cycle.
Viral replication is cytoplasmic, and is lysogenic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the positive stranded RNA virus replication model. Positive stranded RNA virus transcription, using the premature termination model of subgenomic RNA transcription is the method of transcription. Translation takes place by leaky scanning, and suppression of termination. The virus exits the host cell by tubule-guided viral movement. Plants serve as the natural host. Transmission routes are mechanical, seed borne, and contact.


Chrysomeridaceae


Aerobiology

Aerobiology (from Greek ἀήρ, "aēr", "air"; βίος, "bios", "life"; and -λογία, "-logia") is a branch of biology that studies organic particles, such as bacteria, fungal spores, very small insects, pollen grains and viruses, which are passively transported by the air. Aerobiologists have traditionally been involved in the measurement and reporting of airborne pollen and fungal spores as a service to allergy sufferers.
The first finding of airborne algae took place in Germany in 1910.
The minimum requirements published after a big consensus are an international standard to ensure the quality in Aerobiological method.


Synchytrium endobioticum

Synchytrium endobioticum is a chytrid fungus that causes the potato wart disease, or black scab. It also infects some other plants of the genus "Solanum", though potato is the only cultivated host.
Systematics.
Traditionally, "Synchytrium endobioticum" has been placed to the subgenus "Mesochytrium", but it has been suggested that on the basis of the mode of germination it should be transferred to the subgenus "Microsynchytrium". It was first identified and studied by Vera Charles.
The New Zealand scientist Kathleen Maisey Curtis also studied "Synchytrium endobioticum" for her doctoral thesis that, in 1919, resulted in her being recognised as producing groundbreaking research on the organism's pathology.
At least 18 pathotypes of the fungus exist, most of them with quite limited ranges in Central Europe. The most widely distributed is the pathotype 1.
Morphology.
Like some other Chytridiales, "Synchytrium endobioticum" develops no mycelium. The fungus produces a thick walled structure known as a winter sporangium. It is 25-75 µm in diameter and contains 200-300 spores. Sporangia are clustered into thin-walled soruses.
The motile life stage, zoospore is about 0,5 µm in diameter and has one posterior flagellum.
Life cycle.
In spring, at higher temperature and moisture, overwintering sporangia germinate to release motile zoospores which infect suitable host epidermal cells. In infected cells, the summer sporangia develop, which quickly release new populations of zoospores. The infection cycle may be repeated as long as infection conditions are suitable. The infected plant cells swell, divide and surround the dividing zoospores resulting in the wart.
Under certain stress conditions some zoospore pairs fuse, resulting in a zygote. The zygote bearing host cells divide, forming eventually the walls of a new winter sporangium. In autumn, the warts rot and disintegrate, releasing new thick-walled resting spores of the fungus into the soil. The diploid resting spores (pro-soruses) undergo a dormancy period and before germination (probably) a meiotic division and several mitotic divisions, becoming a sorus.
Ecology.
"Synchytrium endobioticum" is an obligate parasite that infects several plants of the genus "Solanum". The most favourable conditions for its development are warm temperatures (but not over 20 °C) with enough humidity. Winter sporangia can remain viable for up to 20–30 years. It can survive at depths of 50 cm in the soil. Three different fungi have been observed to parasitize the resting sporangia.
"S. endobioticum" originates from the Andean region of South-America, with now almost worldwide distribution in areas where potatoes are cultivated (absent in most of tropical Africa, Middle East, most of Canada, Japan and Australia).
Environment.
Cool and wet soils are conducive to potato wart disease development. While there are discrepancies in the reported temperatures for maximal potato wart infection, summers with an average temperature of 18 °C or less, winters below 5 °C, and annual precipitation of 700 mm or more are considered to be favorable for the disease. Soil pH does not appear to be associated with disease occurrence; "S. endobioticum" infections have been reported in soils with pH ranging from 3.9-8.5.
Overwintering sporangia of "S. endobioticum" are extremely resilient. Dry sporangia can survive at 100 °C for 11–12 h, composting for 12 days at 60– 65 °C, pasteurization for 90 min at 70 °C, the digestive system of animals feeding on infected tubers, as well as treatment in 1% formaldehyde and 0.1% mercuric chloride for one hour and three hours, respectively. A soil temperature of at least 8 °C and water is required for sporangia germination and the dispersal of zoospores. The microelements B, Cu, Zn, and Mo, have been reported to induce the germination of sporangia following overwintering.
Management.
The resilient nature of the resting spores, the overwintering sporangia, is the principal challenge in managing the disease. Several means of control have been explored, including chemical and biological, but have been largely ineffective, impractical, or neglected. Cultivation of resistant varieties is the best management approach. However, the development of resistant varieties is challenged by the discovery of novel pathotypes and the polygenic nature of resistance to potato wart. Despite these challenges, legislative action has been taken that leverages the use of resistant varieties and has effectively curtailed the spread of potato wart. This action enforces the demarcation of contaminated plots and safety zones and the disposal of infected potato material. Safety zones are areas where only resistant varieties can be grown, and potatoes cannot be grown in sites until the absence of sporangia can be demonstrated. These legislative efforts also include measures that forbid the trade of infected potatoes and the presence of the disease in potato seed production.
Pathogenesis.
Very little is known about the pathogenesis of "S. endobioticum" at a molecular level. Indeed, this is true of chytrids more generally, excepting a few well-studied species. However, recent genome sequencing and annotation of "S. endobioticum" has shed light on the potential molecular mechanisms of pathogenesis. For example, this analysis demonstrated the coding capacity of "S. endobioticum" to process complex sugars, which may include cellulose and starch. However, genes for cell wall degrading hemicellulases are reduced in "S. endobioticum" relative to the closely related, saprophytic chytrid, "S. microbalum." The lack of hemicellulases may allow the pathogen to evade defense responses triggered by damage-associated molecular patterns from cell wall degradation. Several regions within the genome have been identified as possible effector coding regions, but further work will need to be done to verify this. "S. endobioticum" did not contain genes coding for enzymes that are crucial to the biosynthesis of purine and pyrimidine. It is probable "S. endobioticum" exacts purine and pyrimidine from its host.
Legal.
Added to the USA's federal bioterrorism list for agricultural plant pathogens in 2002 in accordance with the Public Health Security and Bioterrorism Preparedness Response Act.


Acidophile

Acidophiles or acidophilic organisms are those that thrive under highly acidic conditions (usually at pH 2.0 or below). These organisms can be found in different branches of the tree of life, including Archaea, Bacteria, and Eukarya.
List of acidophilic organisms.
A list of these organisms includes:
Mechanisms of adaptation to acidic environments.
Most acidophile organisms have evolved extremely efficient mechanisms to pump protons out of the intracellular space in order to keep the cytoplasm at or near neutral pH. Therefore, intracellular proteins do not need to develop acid stability through evolution. However, other acidophiles, such as "Acetobacter aceti", have an acidified cytoplasm which forces nearly all proteins in the genome to evolve acid stability. For this reason, "Acetobacter aceti" has become a valuable resource for understanding the mechanisms by which proteins can attain acid stability.
Studies of proteins adapted to low pH have revealed a few general mechanisms by which proteins can achieve acid stability. In most acid stable proteins (such as pepsin and the soxF protein from "Sulfolobus acidocaldarius"), there is an overabundance of acidic residues which minimizes low pH destabilization induced by a buildup of positive charge. Other mechanisms include minimization of solvent accessibility of acidic residues or binding of metal cofactors. In a specialized case of acid stability, the NAPase protein from "Nocardiopsis alba" was shown to have relocated acid-sensitive salt bridges away from regions that play an important role in the unfolding process. In this case of kinetic acid stability, protein longevity is accomplished across a wide range of pH, both acidic and basic.


Microbial synergy

Microbial synergy is a phenomenon in which aerobic and anaerobic microbes support each other's growth and proliferation. In this process aerobes invade and destroy host tissues, reduce tissue oxygen concentration and redox potential, thus creating favorable conditions for anaerobic growth and proliferation. Anaerobes grow and produce short chain fatty acids such as butyric acid, propionic acid. These short chain fatty acids inhibit phagocytosis of aerobes. Thus aerobes grow, proliferate and destroy more tissues. Microbial synergy complicates and delays the healing of surgical and other chronic wounds or ulcers such as diabetic foot ulcers, venous ulcers, pressure ulcers etc. Microbial synergy also helps with eliminating oxygen redox. This allows the growth of organisms without the effects of oxygen reacting negatively. As a result, Microbial growth increases because other organisms can grow in the absence of Oxygen redox.
References.
Rotstein, O. D., T. L. Pruett, and R. L. Simmons. "Mechanisms of Microbial Synergy in Polymicrobial Surgical Infections." Reviews of Infectious Diseases. U.S. National Library of Medicine, n.d. Web. 19 Apr. 2017.


Azygospore

Azygospore is an asexually formed zygospore in fungi.
Also known as parthenogenically formed from a gamete without gametic fusion.


Cucullanus epinepheli

Cucullanus epinepheli is a species of parasitic nematodes. It is an endoparasite of the brown spotted reef cod "Epinephelus chlorostigma". The species has been described in 2018 by František Moravec & Jean-Lou Justine from material collected off New Caledonia in the South Pacific Ocean.
"Cucullanus epinepheli" was characterized from other members of the genus "Cucullanus" mainly in possessing a unique structure of the anterior, elevated cloacal lip with a large posterior outgrowth covering the cloacal aperture and in the presence of cervical alae and two small preanal papillae on the median dome-shaped precloacal elevation.


Organism

In biology, an organism (from Greek: ὀργανισμός, "organismos") is an entity capable of carrying on life functions. All organisms are composed of cells. Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fungi; or unicellular microorganisms such as protists, bacteria, and archaea. All types of organisms are capable of reproduction, growth and development, maintenance, and some degree of response to stimuli. Humans, squids, mushrooms, and vascular plants are examples of multicellular organisms that differentiate specialized tissues and organs during development.
An organism may be either a prokaryote or a eukaryote. Prokaryotes are represented by two separate domains – bacteria and archaea. Eukaryotic organisms are characterized by the presence of a membrane-bound cell nucleus and contain additional membrane-bound compartments called organelles (such as mitochondria in animals and plants and plastids in plants and algae, all generally considered to be derived from endosymbiotic bacteria). Fungi, animals and plants are examples of kingdoms of organisms within the eukaryotes.
Estimates on the number of Earth's current species range from 2 million to 1 trillion, of which over 1.7 million have been documented. More than 99% of all species, amounting to over five billion species, that ever lived are estimated to be extinct.
In 2016, a set of 355 genes from the last universal common ancestor (LUCA) of all organisms was identified.
Etymology.
The term "organism" (from Greek ὀργανισμός, "organismos", from ὄργανον, "organon", i.e. "instrument, implement, tool, organ of sense or apprehension") first appeared in the English language in 1703 and took on its current definition by 1834 (Oxford English Dictionary). It is directly related to the term "organization". There is a long tradition of defining organisms as self-organizing beings, going back at least to Immanuel Kant's 1790 "Critique of Judgment".
Definitions.
An organism may be defined as an assembly of molecules functioning as a more or less stable whole that exhibits the properties of life. Dictionary definitions can be broad, using phrases such as "any living structure, such as a plant, animal, fungus or bacterium, capable of growth and reproduction". Many definitions exclude viruses and possible man-made non-organic life forms, as viruses are dependent on the biochemical machinery of a host cell for reproduction. A superorganism is an organism consisting of many individuals working together as a single functional or social unit.
There has been controversy about the best way to define the organism and indeed about whether or not such a definition is necessary. Several contributions are responses to the suggestion that the category of "organism" may well not be adequate in biology.
Viruses.
Viruses are not typically considered to be organisms because they are incapable of autonomous reproduction, growth or metabolism. Although some organisms are also incapable of independent survival and live as obligatory intracellular parasites, they are capable of independent metabolism and procreation. Although viruses have a few enzymes and molecules characteristic of living organisms, they have no metabolism of their own; they cannot synthesize and organize the organic compounds from which they are formed. Naturally, this rules out autonomous reproduction: they can only be passively replicated by the machinery of the host cell. In this sense, they are similar to inanimate matter.
While viruses sustain no independent metabolism and thus are usually not classified as organisms, they do have their own genes, and they do evolve by mechanisms similar to the evolutionary mechanisms of organisms. Thus, an argument that viruses should be classed as living organisms is their ability to undergo evolution and replicate through self-assembly. However, some scientists argue that viruses neither evolve nor self-reproduce. Instead, viruses are evolved by their host cells, meaning that there was co-evolution of viruses and host cells. If host cells did not exist, viral evolution would be impossible. This is not true for cells. If viruses did not exist, the direction of cellular evolution could be different, but cells would nevertheless be able to evolve. As for the reproduction, viruses totally rely on hosts' machinery to replicate. The discovery of viruses with genes coding for energy metabolism and protein synthesis fuelled the debate about whether viruses are living organisms. The presence of these genes suggested that viruses were once able to metabolize. However, it was found later that the genes coding for energy and protein metabolism have a cellular origin. Most likely, these genes were acquired through horizontal gene transfer from viral hosts.
Chemistry.
Organisms are complex chemical systems, organized in ways that promote reproduction and some measure of sustainability or survival. The same laws that govern non-living chemistry govern the chemical processes of life. It is generally the phenomena of entire organisms that determine their fitness to an environment and therefore the survival of their DNA-based genes.
Organisms clearly owe their origin, metabolism, and many other internal functions to chemical phenomena, especially the chemistry of large organic molecules. Organisms are complex systems of chemical compounds that, through interaction and environment, play a wide variety of roles.
Organisms are semi-closed chemical systems. Although they are individual units of life (as the definition requires), they are not closed to the environment around them. To operate they constantly take in and release energy. Autotrophs produce usable energy (in the form of organic compounds) using light from the sun or inorganic compounds while heterotrophs take in organic compounds from the environment.
The primary chemical element in these compounds is carbon. The chemical properties of this element such as its great affinity for bonding with other small atoms, including other carbon atoms, and its small size making it capable of forming multiple bonds, make it ideal as the basis of organic life. It is able to form small three-atom compounds (such as carbon dioxide), as well as large chains of many thousands of atoms that can store data (nucleic acids), hold cells together, and transmit information (protein).
Macromolecules.
Compounds that make up organisms may be divided into macromolecules and other, smaller molecules. The four groups of macromolecule are nucleic acids, proteins, carbohydrates and lipids. Nucleic acids (specifically deoxyribonucleic acid, or DNA) store genetic data as a sequence of nucleotides. The particular sequence of the four different types of nucleotides (adenine, cytosine, guanine, and thymine) dictate many characteristics that constitute the organism. The sequence is divided up into codons, each of which is a particular sequence of three nucleotides and corresponds to a particular amino acid. Thus a sequence of DNA codes for a particular protein that, due to the chemical properties of the amino acids it is made from, folds in a particular manner and so performs a particular function.
These protein functions have been recognized:
A bilayer of phospholipids makes up the membrane of cells that constitutes a barrier, containing everything within a cell and preventing compounds from freely passing into, and out of, the cell. Due to the selective permeability of the phospholipid membrane, only specific compounds can pass through it.
Structure.
All organisms consist of structural units called cells; some contain a single cell (unicellular) and others contain many units (multicellular). Multicellular organisms are able to specialize cells to perform specific functions. A group of such cells is a tissue, and in animals these occur as four basic types, namely epithelium, nervous tissue, muscle tissue, and connective tissue. Several types of tissue work together in the form of an organ to produce a particular function (such as the pumping of the blood by the heart, or as a barrier to the environment as the skin). This pattern continues to a higher level with several organs functioning as an organ system such as the reproductive system, and digestive system. Many multicellular organisms consist of several organ systems, which coordinate to allow for life.
Cell.
The cell theory, first developed in 1839 by Schleiden and Schwann, states that all organisms are composed of one or more cells; all cells come from preexisting cells; and cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.
There are two types of cells, eukaryotic and prokaryotic. Prokaryotic cells are usually singletons, while eukaryotic cells are usually found in multicellular organisms. Prokaryotic cells lack a nuclear membrane so DNA is unbound within the cell; eukaryotic cells have nuclear membranes.
All cells, whether prokaryotic or eukaryotic, have a membrane, which envelops the cell, separates its interior from its environment, regulates what moves in and out, and maintains the electric potential of the cell. Inside the membrane, a salty cytoplasm takes up most of the cell volume. All cells possess DNA, the hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. There are also other kinds of biomolecules in cells.
All cells share several similar characteristics of:
Evolution.
Last universal common ancestor.
The last universal common ancestor (LUCA) is the most recent organism from which all organisms now living on Earth descend. Thus it is the most recent common ancestor of all current life on Earth. The LUCA is estimated to have lived some 3.5 to 3.8 billion years ago (sometime in the Paleoarchean era). The earliest evidence for life on Earth is graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. Although more than 99 percent of all species that ever lived on the planet are estimated to be extinct, it is likely that more than a billion species of life exist on Earth currently, with the highest estimates and projections reaching one trillion species.
Information about the early development of life includes input from many different fields, including geology and planetary science. These sciences provide information about the history of the Earth and the changes produced by life. However, a great deal of information about the early Earth has been destroyed by geological processes over the course of time.
All organisms are descended from a common ancestor or ancestral gene pool. Evidence for common descent may be found in traits shared between all living organisms. In Darwin's day, the evidence of shared traits was based solely on visible observation of morphologic similarities, such as the fact that all birds have wings, even those that do not fly.
There is strong evidence from genetics that all organisms have a common ancestor. For example, every living cell makes use of nucleic acids as its genetic material, and uses the same twenty amino acids as the building blocks for proteins. All organisms use the same genetic code (with some extremely rare and minor deviations) to translate nucleic acid sequences into proteins. The universality of these traits strongly suggests common ancestry, because the selection of many of these traits seems arbitrary. Horizontal gene transfer makes it more difficult to study the last universal ancestor. However, the universal use of the same genetic code, same nucleotides, and same amino acids makes the existence of such an ancestor overwhelmingly likely.
Location of the root.
The most commonly accepted location of the root of the tree of life is between a monophyletic domain Bacteria and a clade formed by Archaea and Eukaryota of what is referred to as the "traditional tree of life" based on several molecular studies. A very small minority of studies have concluded differently, namely that the root is in the domain Bacteria, either in the phylum Firmicutes or that the phylum Chloroflexi is basal to a clade with Archaea and Eukaryotes and the rest of Bacteria as proposed by Thomas Cavalier-Smith.
Research published in 2016, by William F. Martin, by genetically analyzing 6.1 million protein-coding genes from sequenced prokaryotic genomes of various phylogenetic trees, identified 355 protein clusters from amongst 286,514 protein clusters that were probably common to the LUCA. The results "depict LUCA as anaerobic, CO2-fixing, H2-dependent with a Wood–Ljungdahl pathway (the reductive acetyl-coenzyme A pathway), N2-fixing and thermophilic. LUCA's biochemistry was replete with FeS clusters and radical reaction mechanisms. Its cofactors reveal dependence upon transition metals, flavins, S-adenosyl methionine, coenzyme A, ferredoxin, molybdopterin, corrins and selenium. Its genetic code required nucleoside modifications and S-adenosylmethionine-dependent methylations." The results depict methanogenic clostria as a basal clade in the 355 lineages examined, and suggest that the LUCA inhabited an anaerobic hydrothermal vent setting in a geochemically active environment rich in H2, CO2, and iron. However, the identification of these genes as being present in LUCA was criticized, suggesting that many of the proteins assumed to be present in LUCA represent later horizontal gene transfers between archaea and bacteria.
Reproduction.
Sexual reproduction is widespread among current eukaryotes, and was likely present in the last common ancestor. This is suggested by the finding of a core set of genes for meiosis in the descendants of lineages that diverged early from the eukaryotic evolutionary tree. and Malik et al. It is further supported by evidence that eukaryotes previously regarded as "ancient asexuals", such as "Amoeba", were likely sexual in the past, and that most present day asexual amoeboid lineages likely arose recently and independently.
In prokaryotes, natural bacterial transformation involves the transfer of DNA from one bacterium to another and integration of the donor DNA into the recipient chromosome by recombination. Natural bacterial transformation is considered to be a primitive sexual process and occurs in both bacteria and archaea, although it has been studied mainly in bacteria. Transformation is clearly a bacterial adaptation and not an accidental occurrence, because it depends on numerous gene products that specifically interact with each other to enter a state of natural competence to perform this complex process. Transformation is a common mode of DNA transfer among prokaryotes.
Horizontal gene transfer.
The ancestry of living organisms has traditionally been reconstructed from morphology, but is increasingly supplemented with phylogenetics – the reconstruction of phylogenies by the comparison of genetic (DNA) sequence.
Sequence comparisons suggest recent horizontal transfer of many genes among diverse species including across the boundaries of phylogenetic "domains". Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes.
Biologist Peter Gogarten suggests "the original metaphor of a tree no longer fits the data from recent genome research", therefore "biologists (should) use the metaphor of a mosaic to describe the different histories combined in individual genomes and use (the) metaphor of a net to visualize the rich exchange and cooperative effects of HGT among microbes."
Future of life (cloning and synthetic organisms).
Modern biotechnology is challenging traditional concepts of organism and species. Cloning is the process of creating a new multicellular organism, genetically identical to another, with the potential of creating entirely new species of organisms. Cloning is the subject of much ethical debate.
In 2008, the J. Craig Venter Institute assembled a synthetic bacterial genome, "Mycoplasma genitalium", by using recombination in yeast of 25 overlapping DNA fragments in a single step. The use of yeast recombination greatly simplifies the assembly of large DNA molecules from both synthetic and natural fragments. Other companies, such as Synthetic Genomics, have already been formed to take advantage of the many commercial uses of custom designed genomes.


Maria Prokhorova

Maria Illarionovna Prokhorova (, ) was a Russian scientist, biologist, the Head of Molotov University, the Dean of Faculty of Biology and Soil Studies at Leningrad State University; also she was the Head of A.A. Ukhtomsky Physiology Institute, a member of International Society for Neurochemistry, Doctor of Biology, and professor. Maria Prokhorova took part in the Great Patriotic War (WWII's Eastern Front) as a researcher on gas gangrene and its methods of treatment.


Heterosigma


Mosaic (genetics)

Mosaicism or genetic mosaicism is a condition in multi-cellular organism in which a single organism possesses more than one genetic line as the result of genetic mutation. This means that various genetic lines resulted from a single fertilized egg. Genetic mosaics may often be confused with chimerism, in which two or more genotypes arise in one individual similarly to mosaicism. In chimerism, though, the two genotypes arise from the fusion of more than one fertilized zygote in the early stages of embryonic development, rather than from a mutation or chromosome loss.
Genetic mosaicism can result from many different mechanisms including chromosome nondisjunction, anaphase lag, and endoreplication. Anaphase lagging is the most common way by which mosaicism arises in the preimplantation embryo. Mosaicism can also result from a mutation in one cell during development in which the mutation is passed on to only its daughter cells. Therefore, the mutation is only going to be present in a fraction of the adult cells. Somatic mosaicism is not generally inheritable as it does does not generally affect germ cells.
History.
In 1929, Alfred Sturtevant studied mosaicism in "Drosophila". Muller in 1930 demonstrated that mosaicism in "Drosophila" is always associated with chromosomal rearrangements and Schultz in 1936 showed that in all cases studied these rearrangements were associated with heterochromatic inert regions, several hypotheses on the nature of such mosaicism were proposed. One hypothesis assumed that mosaicism appears as the result of a break and loss of chromosome segments. Curt Stern in 1935 assumed that the structural changes in the chromosomes took place as a result of "somatic crossing", as a result of which mutations or small chromosomal rearrangements in somatic cells. Thus the inert region causes an increase in mutation frequency or small chromosomal rearrangements in active segments adjacent to inert regions.
In the 1930s, Stern demonstrated that genetic recombination, normal in meiosis, can also take place in mitosis. When it does, it results in somatic (body) mosaics. These organisms contain two or more genetically distinct types of tissue. The term "somatic mosaicism" was used by CW Cotterman in 1956 in his seminal paper on antigenic variation.
In 1944, Belgovskii proposed that mosaicism could not account for certain mosaic expressions caused by chromosomal rearrangements involving heterochromatic inert regions. The associated weakening of biochemical activity led to what he called a "genetic chimera".
Types.
Germline mosaicism.
Germline or gonadal mosaicism is a particular form of mosaicism wherein some gametes—i.e., sperm or oocytes—carry a mutation, but the rest are normal. The cause is usually a mutation that occurred in an early stem cell that gave rise to all or part of the gametes.
Somatic mosaicism.
Somatic mosaicism occurs when the somatic cells of the body are of more than one genotype. In the more common mosaics, different genotypes arise from a single fertilized egg cell, due to mitotic errors at first or later cleavages.
Somatic mutation leading to mosaicism is prevalent in the beginning and end stages of human life. Somatic mosaics are common in embryogenesis due to retrotransposition of long interspersed nuclear element-1 (LINE-1 or L1) and Alu transposable elements. In early development, DNA from undifferentiated cell types may be more susceptible to mobile element invasion due to long, unmethylated regions in the genome. Further, the accumulation of DNA copy errors and damage over a lifetime lead to greater occurrences of mosaic tissues in aging humans. As longevity has increased dramatically over the last century, human genome may not have had time to adapt to cumulative effects of mutagenesis. Thus, cancer research has shown that somatic mutations are increasingly present throughout a lifetime and are responsible for most leukemia, lymphomas, and solid tumors.
Trisomies, Monosomies and Related Conditions.
The most common form of mosaicism found through prenatal diagnosis involves trisomies. Although most forms of trisomy are due to problems in meiosis and affect all cells of the organism, some cases occur where the trisomy occurs in only a selection of the cells. This may be caused by a nondisjunction event in an early mitosis, resulting in a loss of a chromosome from some trisomic cells. Generally, this leads to a milder phenotype than in nonmosaic patients with the same disorder.
In rare cases, intersex conditions can be caused by mosaicism where some cells in the body have XX and others XY chromosomes (46, XX/XY). In the fruit fly "Drosophila melanogaster", where a fly possessing two X chromosomes is a female and a fly possessing a single X chromosome is a sterile male, a loss of an X chromosome early in embryonic development can result in sexual mosaics, or gynandromorphs. Likewise, a loss of the Y chromosome can result in XY/X mosaic males.
An example of this is one of the milder forms of Klinefelter syndrome, called 46,XY/47,XXY mosaic wherein some of the patient's cells contain XY chromosomes, and some contain XXY chromosomes. The 46/47 annotation indicates that the XY cells have the normal number of 46 total chromosomes, and the XXY cells have a total of 47 chromosomes.
Also monosomies can present with some form of mosaicism. The only non-lethal full monosomy occurring in humans is the one causing Turner's syndrome. Around 30% of Turner's syndrome cases demonstrate mosaicism, while complete monosomy (45, X) occurs in about 50–60% of cases.
Mosaicism need not necessarily be deleterious, though. Revertant somatic mosaicism is a rare recombination event with a spontaneous correction of a mutant, pathogenic allele. In revertant mosaicism, the healthy tissue formed by mitotic recombination can outcompete the original, surrounding mutant cells in tissues such as blood and epithelia that regenerate often. In the skin disorder ichthyosis with confetti, normal skin spots appear early in life and increase in number and size over time.
Other endogenous factors can also lead to mosaicism, including mobile elements, DNA polymerase slippage, and unbalanced chromosomal segregation. Exogenous factors include nicotine and UV radiation. Somatic mosaics have been created in "Drosophila" using X‑ray treatment and the use of irradiation to induce somatic mutation has been a useful technique in the study of genetics.
True mosaicism should not be mistaken for the phenomenon of X‑inactivation, where all cells in an organism have the same genotype, but a different copy of the X chromosome is expressed in different cells. The latter is the case in normal (XX) female mammals, although it is not always visible from the phenotype (as in calico cats). However, all multicellular organisms are likely to be somatic mosaics to some extent.
Gonosomal mosaicism.
Gonosomal mosaicism is a type of somatic mosaicism that occurs very early in the organisms development and thus is present within both germline and somatic cells. Somatic mosaicism is not generally inheritable as it does not usually affect germ cells.  In the instance of gonosomal mosaicism, organisms have the potential to pass the genetic alteration, including to potential offspring because the altered allele is present in both somatic and germline cells.
Brain cell mosaicism.
A frequent type of neuronal genomic mosaicism is copy number variation. Possible sources of such variation were suggested to be incorrect repair of DNA damages and somatic recombination.
Mitotic recombination.
One basic mechanism that can produce mosaic tissue is mitotic recombination or somatic crossover. It was first discovered by Curt Stern in "Drosophila" in 1936. The amount of tissue that is mosaic depends on where in the tree of cell division the exchange takes place. A phenotypic character called "twin spot" seen in "Drosophila" is a result of mitotic recombination. However, it also depends on the allelic status of the genes undergoing recombination. Twin spot occurs only if the heterozygous genes are linked in repulsion, i.e. the trans phase. The recombination needs to occur between the centromeres of the adjacent gene. This gives an appearance of yellow patches on the wild-type background in "Drosophila". another example of mitotic recombination is the Bloom's syndrome, which happens due to the mutation in the "blm" gene. The resulting BLM protein is defective. The defect in RecQ, a helicase, facilitates the defective unwinding of DNA during replication, thus is associated with the occurrence of this disease.
Use in experimental biology.
Genetic mosaics are a particularly powerful tool when used in the commonly studied fruit fly, where specially selected strains frequently lose an X or a Y chromosome in one of the first embryonic cell divisions. These mosaics can then be used to analyze such things as courtship behavior, and female sexual attraction.
More recently, the use of a transgene incorporated into the "Drosophila" genome has made the system far more flexible. The flip recombinase (or "FLP") is a gene from the commonly studied yeast "Saccharomyces cerevisiae" that recognizes "flip recombinase target" (FRT) sites, which are short sequences of DNA, and induces recombination between them. FRT sites have been inserted transgenically near the centromere of each chromosome arm of "D. melanogaster". The "FLP" gene can then be induced selectively, commonly using either the heat shock promoter or the GAL4/UAS system. The resulting clones can be identified either negatively or positively.
In negatively marked clones, the fly is transheterozygous for a gene encoding a visible marker (commonly the green fluorescent protein) and an allele of a gene to be studied (both on chromosomes bearing FRT sites). After induction of "FLP" expression, cells that undergo recombination will have progeny homozygous for either the marker or the allele being studied. Therefore, the cells that do not carry the marker (which are dark) can be identified as carrying a mutation.
Using negatively marked clones is sometimes inconvenient, especially when generating very small patches of cells, where seeing a dark spot on a bright background is more difficult than a bright spot on a dark background. Creating positively marked clones is possible using the so-called MARCM ("mosaic analysis with a repressible cell marker" system, developed by Liqun Luo, a professor at Stanford University, and his postdoctoral student Tzumin Lee, who now leads a group at Janelia Farm Research Campus. This system builds on the GAL4/UAS system, which is used to express GFP in specific cells. However, a globally expressed "GAL80" gene is used to repress the action of GAL4, preventing the expression of GFP. Instead of using GFP to mark the wild-type chromosome as above, GAL80 serves this purpose, so that when it is removed by mitotic recombination, GAL4 is allowed to function, and GFP turns on. This results in the cells of interest being marked brightly in a dark background.


Massilia cf. timonae

Massilia" cf. "timonae is a "Massilia timonae"-like, Gram-negative, aerobic bacterium from the genus "Massilia" and family of Oxalobacteraceae which was isolated from human patients.


Pixie cup

Pixie cup may refer to:


Potato mop-top virus

Potato mop-top virus (PMTV) is a plant pathogenic virus transmitted through the vector "Spongospora subterranea" that affects potatoes. PMTV belongs to family of "Virgaviridae", and the genus "Pomovirus" (Potato mop-top virus). The virus was first identified in 1966 by Calvert and Harrison in Britain, and is now reported in many other potato cultivating regions of the world including U.S.A., Canada, China, Pakistan, Japan, South American countries and many parts of Europe. Many disease management systems have been found to be ineffective against the virus, although a combination of sanitation and vector controls seems to work well.
Hosts and symptoms.
As the name implies, the main host is potato; however, this virus also affects some common vegetable plants and weeds. Some of them include tomato, black nightshade, lambsquarters and ground cherry. The potato mop top virus' primary hosts are plants in the Solanaceae and Chenopodiaceae. Potatoes that are infected by PMTV generally show hollow necrotic spots on the inside. This virus shows different symptoms in Europe; for example, the infected plants usually show dark brown necrotic arcs that discolor the tuber's flesh (these symptoms are very similar to those caused by alfalfa mosaic virus). Plants showing no symptoms of PMTV tend to produce larger quantities of infected tubers if they are derived from plants that have shown foliar symptoms in the previous year.
Disease cycle.
The spores that PMTV is vectored in can live in the soil for up to 18 years giving the virus a long period of survival. The critical period for infection of "S. subterranea" and consequently PMTV is earlier in the potato growth cycle, during stolon formation and tuber set, which lasts 3–4 weeks. The disease cycle of PMTV begins with the virus entering the host plant's cell and disassembling its capsid to release the viral RNA into the cell. As a pomovirus, PMTV uses the host plant's machinery for replication and translation which both follow positive-stranded RNA models. After replicates of the viral RNA and of the capsid proteins are made in the cytosol, the virus reassembles itself and exits the cell to infect other cells. Because it is vectored by a protist, it generally appears in cooler and more moist times of the year.
The naturally occurring virus has been found to have systemic effects on "Nicotiana benthamiana." However, when the gene for TRIPLE GENE BLOCK1 (TGB1), which is a movement factor protein, was silenced, the systemic movement of the virus was hindered. The virus moves through the xylem to infect plants systemically, but can also spread locally through cell-to-cell movement. In host plants, the infected tissues include both leaves and the cytoplasm. It has been shown that PMTV infected seeds are planted, they only partially infect the following generations of plants, showing that its vector, "S. subterranea" is very important for transmission.
Environment.
The vector for PMTV, "S. subterranea", is a slime mold known to cause powdery scab disease that favors wet and humid conditions, specifically poorly drained soil. In fact, this disease doesn’t occur often in areas with less than 30 inches of rain per year. The chance of disease onset increases in areas that get more than 45 inches of rain per year. Such moist environments helps facilitate the vector's zoospore movement to the infection sites (roots and tubers). It is thought that powdery scab disease development increases when high soil moisture gradually dries out, as this increases zoospore germination. "S. subterranea" tends to prefer more acidic soil, ranging from pHs of 4.7 to 7.6. "S. subterranea" thrives in temperate conditions, between 52 and 75 degrees Fahrenheit, with the optimal temperature for infection by the vector being 60 degrees.
Disease development can also be encouraged by certain agricultural practices. For example, increased use of nitrate or ammonium nitrogen containing fertilizers increases the incidence and severity of powdery scab disease, caused by the PMTV vector "S. subterranea" . This can be due to the fact that fertilization enhances root growth, which provides a larger amount of tissue that can be infected.
Management.
Chemical treatments for field application against viruses are currently not available. This holds especially true for potatoes, because once infected by a virus, they will stay infected for the remainder of their lives. Thus, preventative methods are more viable options. This includes methods such as resistance-breeding, vector management, and crop sanitation.
Resistance-breeding, or generating plants that are genetically resistant to pathogen infections, is another option being explored. Generating vector-resistant plants have been proven to be largely unsuccessful for PMTV. This is because plants need to have immunity towards "S. subterranea" in its tubers, roots, and stolons in order to completely resist infection by the vector and virus. To this date, however, potatoes have been produced with resistant tubers but susceptible roots. Although resistance breeding has not yet provided benefits for commercially available PMTV varieties, there have been some promising results in ongoing research. There are some partially resistant varieties of commercial crop that are available now. An example is NY99, a breeding line that has shown a low incidence of PMTV-infected tubers. Resistance-breeding, if successful, would prevent the virus from starting its pathogenesis.
Vector management concentrates its efforts to reduce the level of "S. subterranea" in the soil as a way to combat the virus. Soil treatments, such as fungicides containing fluazinam, have been shown to be partially effective at reducing numbers of viable "S. subterranea" spores available to germinate into zoospores. Another form of vector management is crop rotations with brassicas and datura (a weed). Rotating with these plants has shown to produce low levels of "S. subterranea" in the soil.
Proper crop sanitation is achieved by planting certified seed potatoes. It is crucial that these seed potatoes come from production areas that have had no previous contact with either the vector or the virus itself. Further risk reduction can be achieved by properly sanitizing all machinery that has come in contact with soil and plant debris.
Importance.
PMTV is a relatively new discovery, having first been reported in Britain in 1966, and then in the U.S. in 2002. The vector "S. subterranea," however, has been around for over 150 years, being first discovered in Germany in 1841. It was first discovered in the U.S. in 1913.
PMTV can lead to a very significant loss in the yield of potatoes. For example, a study conducted on Scottish seed potatoes showed a yield reduction as great as 67%. The virus also causes spraing and necrosis in the flesh of tubers. These symptoms are mainly morphological defects that yield unaesthetic potatoes which face commercial rejection from processors and packers. If potatoes exported to other countries are found to be infected, it can negatively affect agricultural trading. For example, Maine was quarantined due to its fairly recent outbreaks. In addition to economic losses, the presence of PMTV can also negatively impact the reputation of a country (or region, state, or farm) for other exports.
Genome.
PMTV is a (+)ssRNA virus with a tripartite genome. The longest segment of PMTV, RNA-rep encodes RNA dependent RNA polymerase and replicase subunits. The second segment, RNA-CP codes for virus coat protein (CP), and CP-RT or minor CP, which is produced by translational read-through of the CP stop codon. The third segment, RNA-TGB encodes triple gene block of movement proteins, TGB1, TGB2, TGB3, and 8K protein which is a viral suppressor of RNA silencing.
Pathogenesis.
The vector for PMTV is a protist, "S. subterranea". As "S. subterranea" infects the roots of potatoes, the virus is given access to the root cells and starts its habitation of the plant. By taking control of the cell's cellular machinery, the virus can replicate. The virus then moves onto more potato cells and spreads systemically through the plant. The systemic movement of PMTV is facilitated in large by a protein named TRIPLE GENE BLOCK1 (TGB1) which has an internal domain spurring transportation of the virus to neighboring cells, and an N-terminal domain used for long-distance (systemic) travel. This N-terminal domain of TGB1 has shown some promise as a target to limit systemic infection of the pathogen in "N. benthamiana", since systemic infection requires an interaction between a molecule called importin-a within the host plant and the N-terminal domain. Of the three positive-sense RNA molecules used by PMTV, there is one thought to code for a virulence factor protein. The other two molecules code for a polymerase and a coat protein both of which are necessary for the survival of the virus. RNA-TGB is a gene with 4 open reading frames (ORFs); the first three overlapping ORFs form an area called the triple gene block. This 3 frame block codes for essential movement factor proteins that facilitate cell-to-cell movement. The fourth ORF codes for another cysteine-rich protein that increases virulence and has some RNA silencing suppressive activity.


Polyploviricotina

Polyploviricotina is a subphylum of viruses in the phylum "Negarnaviricota". It is one of only two virus subphyla, the other being "Haploviricotina", which is also in "Negarnaviricota". The name comes from , the Ancient Greek for 'complex', along with the suffix for a virus subphylum; 'viricotina'.


Avalofractus

Avalofractus abaculus is a frond-like rangeomorph fossil described from the Ediacaran of the Trepassey Formation, Spaniard's Bay, Newfoundland.
Morphology.
"Avalofractus" displays a strongly fractal body shape, with four levels of nearly perfectly self-similar, pinnate, alternate branches. It was about 5 cm long on average, with a 1 cm-diameter holdfast at the base of the frond. The stem length is from 1/3 to 1/2 that of the whole frond. It is quite similar to "Rangea", even if with distinct morphological differences that justify the creation of a new genus (e.g. absence of subsidiary quilts, frond elements free to rotate independently instead of being attached to each other by a membrane).
Distribution.
In contrast with other rangeomorphs, which have wide distributions, "Avalofractus" seems to have been an endemic species, being known only from the Spaniard's Bay deposits.
Reproduction.
It has been suggested that "Avalofractus" could have been capable of vegetative reproduction: loose fronds could have detached and grow, rather like a plant cutting. This could explain the mysterious lack of independent rangeomorph fronds smaller than 10 mm in the fossil record.
A previous suggestion that "Avalofractus" younger individuals were encased in a sheath-like structure has been later dismissed.


Acaulospora mellea

Acaulospora mellea is a species of fungi in the family Acaulosporaceae. It forms arbuscular mycorrhiza and vesicles in roots.


Dictydiaethalium

Dictydiaethalium is a genus of slime molds composed of "D. plumbeum" and "D. dictyosporum".


Spironema (flagellate)


Tissue stress

Tissue stress (tissue adaptive syndrome) is an unspecific adaptive reaction universal for all tissues of adult organism which forms in tissue as a response to various external influences. The latter are tissue cells’ damage, overload of their specialized functions or regulatory influences.
Tissue stress mechanism.
According to tissue adaptive syndrome (TAS) concept, this adaptive mechanism (see adaptation) comes into effect in damaged tissue (see Tissue (biology)) as a result of concurrence of two events. The first one is accumulation of TAS effectors in tissue (comutons, chalones, and contactins), which possess a unique feature of tissue specificity in their action on homologous tissue cells without species specificity. The second one is increase in sensitivity of damaged cells to these regulators, as it was demonstrated on the example of comuton. These effectors cause tissuespecific self-damage of homologous cells via disturbance of their ion homeostasis and energy-production processes. As a result, unspecific reaction to damage (CURD) is activated in the cells. This universal physiological reaction plays a role of TAS executive mechanism. Thus, the adaptive function of tissue stress is brought into action using such CURD properties as increase of cell unspecific resistance, as well as influence on the rate of cell metabolic processes. It is obvious that in the case of TAS these changes have to be tissuespecific, since they are initiated by way of cell self-damage under tissuespecific influence of TAS effectors.
As is well known the CURD consists of two phases. In the process of a slight damage of the cell the phase of metabolism stimulation is forming in it. When the cell is slightly damaged, it begins to form the phase of metabolism stimulation. Strong damaging influences initiate the CURD phase of metabolism inhibition in the cell.
According to the TAS concept, the protective effect of the tissue stress is realized in the case of forming of CURD metabolism stimulation phase by TAS effectors as a result of acceleration of reparative processes in the damaged cell. In the process of forming of CURD phase of metabolism inhibition by the above effectors the protective influence of tissue stress develops a result of cell reactivity decrease in response to the external damaging influences.
The place of the tissue stress in line of the unspecific adaptive reactions.
The main feature of the tissue stress is its formation with participation of the tissuespecific effectors of intratissue intercellular interactions – comutons, chalones and contactins, which are produced by the cells of a tissue under a stressor's influence. This distinguishes the tissue stress from the general adaptive syndrome, which is realized via hormones – effectors of interorgan interactions (see Stress (biological)). Regional (local) stress forms with participation of not one but several tissues making up an organ or a body part. This is why it can be believed that regional stress-reaction is realized with the participation of effectors of intraorgan intertissue interactions. Finally, the cell stress is realized via intracellular mechanisms, without any participation of intercellular interactions. In the latter case the CURD formation and synthesis of heat shock proteins act as “self-defense” mechanism of the cell.
Another distinctive feature of tissue stress is the principle of formation of its executive mechanism, the CURD, via tissuespecific self-damage of homologous tissue cells. Despite the fact that TAS, just as the cell stress, is realized via CURD, the TAS has a variety of features which distinguish it from the cell stress, the key one being the tissue-selectivity of CURD initiation under TAS effectors influence. In addition, under cell stress the cell protection is realized with CURD participation only via “passive” mechanism. It consists in the formation of the protective phase of this physiological reaction. Meanwhile, under tissue stress, its protective function may be carried out both the “passive” and “active” CURD-induced mechanisms. Thus, the cell stress mechanism is just one of the two instruments with which TAS protects the cells of homologous tissue. The third difference between tissue and cell stresses lies in ability of the former not only to increase but also to decrease the unspecific resistance of the cells. Meanwhile, the cell stress concept considers only the first possibility.
At the present moment, two physiological functions of tissue stress, which are realized in the process of participation of its adaptive mechanism, can be considered. One of them is expressed in an increase of cell specialized functions stability in the conditions of prolonged functional load. Another tissue stress function is to regulate homologous tissue cell mass in various physiological conditions.
Tissue stress function on homologous tissue cells specialized functions stability improvement.
It is well known that only some part of tissue functional units participate in its cells specialized functions realization (Barcroft, 1937). Because of universality of this phenomenon it was named “the law of intermittent activity of functioning structures” (Kryshanovskii, 1973; Kryshanovskii, 1974). According to this law, functional units of actively functioning tissue (or cells) form two populations where one is in “intensive functioning” state and the other one – is in “resting” state.
Thereat the “rest” is not a passive state since there active reparation of cellular structures occurs damaged in the course of specialized functions performing by cells. “Intermittent” pattern of tissue cells specialized functions realization is that the cells pass from one population to another when the tissue is in intensive functioning mode. In such a way the cells damaged in consequence of intensive functioning gain an offing to recover in “resting” population. Meanwhile, recovered cells pass from the “resting” population into “intensively functioning” one. It is safe to say that such organization of tissue functioning favors stability of its cells functions performance. Yet, the mechanisms which regulate cells passage from one population to another on intratissue level are unknown.
Considering the law of “intermittent activity of functioning structures” one can talk about two results of the TAS mechanism action on the cells of actively functioning tissue. In conditions where the TAS effector (effectors) forms CURD phase of metabolism stimulation one should expect an acceleration of reparative processes in the cells of “resting” population. Obviously that will promote accelerated recovery of such cells and their pass to intensively functioning cell population. In case if TAS mechanism forms the CURD phase of metabolism inhibition in intensively functioning cells population this will lead to cell signaling inhibition and promote cells “autonomy” from other external influences. Such autonomy may provoke an inhibition of cell's specialized functions in mentioned population in case if they are stimulated by external regulatory influences. An inhibition of cells specialized functions by the TAS mechanism may promote defense of intensively functioning cells from self-damage and also their pass into the “resting” state. Thus, the properties of tissue stress executive mechanism – CURD – allow it to raise tissue functions stability in conditions of continuous intensive activity in many ways.
Tissue stress function on regulation of homologous tissue cell mass.
According to the TAS concept, tissue stress possess the ability to regulate the cell mass of homologous tissue via executive mechanism described above – the CURD. As in the case of cells specialized functions regulation there are two ways of tissue-specific control of homologous tissue cell mass. These are cells unspecific resistance modulation and influencing the speed of physiological processes occurring in the cell.
Tissue stress mechanism able to control tissue cell mass influencing both its mitotic and apoptotic (see Apoptosis) activities tissue-specifically. In case if TAS effectors form CURD phase of metabolism stimulation one should expect acceleration of proliferative (see Proliferation) pool cells passage through mitotic cycle (MC). Herewith there will be also an acceleration of cells maturation and ageing. This will provoke an increase of both mitotic and apoptotic activity in tissue. On the contrary, formation of CURD phase of metabolism protective inhibition should result in opposite results – an inhibition of all mentioned processes and, as a result, to inhibition of both mitotic and apoptotic activities. One cannot exclude the possibility that tissue stress mechanism considered able to regulate apoptosis through inhibition of its energy-dependent stage. As concerns the modulation of cells unspecific resistance by tissue stress mechanism, this property of CURD allows to regulate cells entrance into MC as well as their entrance into apoptosis.
Regulation of tissue cell mass by the TAS mechanism can be carried out in two physiological regimes – ether by formation of “conservative” or “dynamic” phase of this adaptive reaction. TAS conservative phase is forming under the influence of “weak” unspecific external damaging or “load” influences on cells specialized functions. Here tissue stress provides intratissue adaptation by preservation of the existing cell population in the tissue. It is achieved by raise of cells unspecific resistance under the influence of tissue-specific self-damage of cells by TAS effectors. This prevents entrance of postmitotic cells both into MC and apoptosis. The TAS dynamic phase forms under “strong” external unspecific damaging or “loading” influences on cells specialized functions. According to TAS concept in dynamic phase of tissue stress a summation of damaging influence of stressor (stressors) with cells self-damage by TAS effectors occurs. This leads to stimulation of proliferation (see Proliferation) and to an increase of apoptotic activity (see Apoptosis) simultaneously. Thus, in above case adaptive function of tissue stress realizes by replacement of damaged, dying cells by descendants of cells more resistant to stressor(s) influence.
As is clear from the foregoing, according to the TAS concept tissue stress mechanism effect on homologous tissue cells is multifarious. It may protect them against the unspecific damaging influences as well as to increase stability of tissue specialized functions in the conditions of prolonged intensive functional activity. Simultaneously, the same mechanism performs intratissue control of cell mass of homologous tissue.


Mycobacterium holsaticum

Mycobacterium holsaticum is a species of the phylum Actinobacteria (Gram-positive bacteria with high guanine and cytosine content, one of the dominant phyla of all bacteria), belonging to the genus "Mycobacterium".
Type strain.
Strain 1406 = CCUG 46266 = DSM 44478 = JCM 12374


Mucorales

The Mucorales is the largest and best studied order of zygomycete fungi. Members of this order are sometimes called pin molds. The term mucormycosis is now preferred for infections caused by molds belonging to the order Mucorales.
Systematics.
The order includes: 11 families, 56 genera, and approximately 300 species. Mucoralean classification has traditionally been based on morphological, developmental, and ecological characteristics. Recently, molecular data has revealed, that some aspects of traditional classification are quite artificial. For example, the Mucoraceae is believed to be polyphyletic, as are the Thamnidiaceae, Chaetocladiaceae and Radiomycetaceae. Some of the genera, (including "Mucor", "Absidia" and "Backusella") appear to be polyphyletic. Today, the traditional system is still largely in use, as further studies are needed to reconcile morphological and molecular concepts of families and genera.
Families.
The order consists of the following families:
Description.
Mucoralean fungi are typically fast-growing, and their wide hyphae ("long, filamentous structures") lack septa (multi-perforate septa are present only in sporangiophores and gametangia). The hyphae grow mostly within the substrate. "Sporangiophores" are upright (simple or ramified) hyphae, that support sac-like sporangia filled with asexual sporangiospores. Other structures include merospores, oidia, and sporangiola.
Many are known by the damage they do to stored food such as bread. Others can cause mucormycosis, generally in immunosuppressed patients, or patients already infected with other diseases.
Life cycle.
The sporangiospores are asexual "mitospores" (formed via mitosis), produced inside sporangia ("thousands of spores") or sporangioles ("single or few spores"). They are released when mature by the disintegration of the sporangium wall, or as a whole sporangiole that separates from the sporangiophore.
The sporangiospores germinate to form the haploid hyphae of a new mycelium. Asexual reproduction often occurs continuously.
In heterothallic species, sexual reproduction occurs when opposite mating types (designated + and -) come into close proximity, inducing the formation of specialized hyphae called "gametangia". The gametangia grow toward each other, then fuse, forming a diploid zygote at the point of fusion. The zygote develops a resistant cell wall, forming a single-celled "zygospore", the characteristic that gives its name to this group of fungi. Meiosis occurs within the "zygospore" (see article Phycomyces). Upon germination, a new haploid mycelium or sporangium is formed. Some species are homothallic.
The original report of sex in fungi, occurred two centuries ago, based on observations of the fungus "Syzygites megalocarpus" ("Mucoromycotina") (reviewed by Idnurm). This species, was subsequently used in 1904, to represent self-fertile species when the concept of two major mating strategies were developed for the fungi. These strategies are homothallism for self-fertile fungi and heterothallism for self-incompatible, outcrossing fungi.
Ecology.
Most Mucoralean species are saprotrophic, and grow on organic substrates (such as fruit, soil, and dung). Some species are parasites or pathogens of animals, plants and fungi. A few species cause human and animal disease zygomycosis, as well as allergic reactions.


Eustigmatales