Malassezia Dermatis
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''Malassezia'' is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
(specifically, a
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...
belonging to the division
Basidiomycota Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basi ...
). Some species of ''Malassezia'' are found on the skin of animals, including humans. Because malassezia requires
fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers specif ...
to grow, it is most common in areas with many
sebaceous gland A sebaceous gland or oil gland is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in ...
son the scalp, face, and upper part of the body.


Role in human diseases

''Malassezia'' infections of human skin can cause or aggravate a variety of conditions, including dandruff, seborrheic dermatitis, and acne.


Dermatitis and dandruff

When ''Malassezia'' grows too rapidly, the natural renewal of cells is disturbed, and dandruff can appear with itching (a similar process may also occur with other fungi or bacteria). Identification of ''Malassezia'' on skin has been aided by the application of molecular or DNA-based techniques. These investigations show that ''M. globosa'' is the species that causes most skin disease in humans, and that it is the most common cause of
dandruff Dandruff is a skin condition of the scalp. Symptoms include flaking and sometimes mild itchiness. It can result in social or self-esteem problems. A more severe form of the condition, which includes inflammation of the skin, is known as s ...
and
seborrhoeic dermatitis Seborrhoeic dermatitis (also spelled seborrheic dermatitis in American English) is a long-term skin disorder. Symptoms include flaky, scaly, greasy, and occasionally itchy and inflamed skin. Areas of the skin rich in oil-producing glands are ...
(though ''M. restricta'' is also involved). There can be as many as ten million ''M. globosa'' organisms on a human head. A project in 2007 sequenced the genome of dandruff-causing ''Malassezia globosa'' and found it to have 4,285 genes. ''M. globosa'' uses eight different types of
lipase In biochemistry, lipase ( ) refers to a class of enzymes that catalyzes the hydrolysis of fats. Some lipases display broad substrate scope including esters of cholesterol, phospholipids, and of lipid-soluble vitamins and sphingomyelinases; howe ...
, along with three phospholipases, to break down the oils on the scalp. Any of these 11 proteins would be a suitable target for dandruff medications. Prescription and over-the-counter shampoos containing
ketoconazole Ketoconazole, sold under the brand name Nizoral, among others, is an antiandrogen, antifungal drug, antifungal, and antiglucocorticoid medication used to treat a number of fungal infections. Applied to the skin it is used for fungal skin inf ...
are commonly used to treat dandruff caused by ''Malassezia''. ''M. globosa'' has been predicted to have the ability to reproduce sexually, but this has not been observed.


Skin pigmentation disorders

In occasional
opportunistic infection An opportunistic infection is an infection that occurs most commonly in individuals with an immunodeficiency disorder and acts more severe on those with a weakened immune system. These types of infections are considered serious and can be caused b ...
s of the trunk and other locations on humans, some species of ''Malassezia'' can cause
hypopigmentation Hypopigmentation is characterized specifically as an area of Human skin, skin becoming lighter than the baseline skin color, but not completely devoid of skin pigment, pigment. This is not to be confused with depigmentation, which is characterize ...
or
hyperpigmentation Hyperpigmentation, also known as the dark spots or circles on the skin, is the darkening of an area of Human skin, skin or nail (anatomy), nails caused by increased melanin. Causes Hyperpigmentation can be caused by sun damage, inflammation, or ...
.
Allergy test Skin allergy testing comprises a range of methods for medical diagnosis of allergies that attempts to provoke a small, controlled, allergic response. Methods A microscopic amount of an allergen is introduced to a patient's skin by various mean ...
s for these fungi are available. The skin rash of
tinea versicolor Tinea versicolor (also pityriasis versicolor) is a condition characterized by a skin eruption on the trunk and proximal extremities. The majority of tinea versicolor is caused by the fungus '' Malassezia globosa'', although '' Malassezia furfur' ...
(''pityriasis versicolor'') is also caused by an infection of this fungus.


Cancer

Translocation of ''Malassezia'' species from the intestines into pancreatic neoplasms has been associated with
pancreatic ductal adenocarcinoma The pancreas (plural pancreases, or pancreata) is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine ...
, and the fungi may promote tumor progression through activation of host
complement Complement may refer to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-class collections into complementary sets * Complementary color, in the visu ...
.


Crohn's and inflammatory bowel disease

''M. restricta'', which is normally found in the skin, is linked to disorders like
Crohn's disease Crohn's disease is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract. Symptoms often include abdominal pain, diarrhea, fever, abdominal distension, and weight loss. Complications outside of the ...
and
inflammatory bowel disease Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the colon and small intestine, with Crohn's disease and ulcerative colitis (UC) being the principal types. Crohn's disease affects the small intestine and large intestine ...
when found in the gut. This is especially true for organism with the N12
CARD9 Caspase recruitment domain-containing protein 9 is an adaptor protein of the CARD-CC protein family, which in humans is encoded by the ''CARD9'' gene. It mediates signals from pattern recognition receptors to activate pro-inflammatory and anti-i ...
allele, which provokes a stronger inflammatory response.


Malassezia folliculitis

''
Malassezia folliculitis Malassezia folliculitis or pityrosporum folliculitis, is a skin condition caused by infection by ''Malassezia'' (formerly ''Pityrosporum'') yeast. The skin of the upper trunk area including the back, chest, arms and sometimes the neck is often a ...
'' (also called ''pityrosporum folliculitis'') is caused by infection with ''Malassezia''.


Systematics

''Malassezia'' is the sole genus in
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Malasseziaceae, which is the only family in
order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...
Malasseziales, itself the single member of
class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...
Malasseziomycetes. Due to progressive changes in their nomenclature, some confusion exists about the naming and classification of ''Malassezia''
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...
species. Work on these yeasts has been complicated because they require specific
growth media A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss ''Physcomitrella patens''. Differe ...
and sometimes grow very slowly in laboratory culture. ''Malassezia'' was originally identified by the French scientist
Louis-Charles Malassez Louis-Charles Malassez (21 September 1842 – 22 December 1909) was a French anatomist and histologist born in Nevers, department of Nièvre. He studied medicine in Paris, where he worked as an ''interne'' from 1867. He served with the 5th Ambu ...
in the late nineteenth century; he associated it with the condition
seborrhoeic dermatitis Seborrhoeic dermatitis (also spelled seborrheic dermatitis in American English) is a long-term skin disorder. Symptoms include flaky, scaly, greasy, and occasionally itchy and inflamed skin. Areas of the skin rich in oil-producing glands are ...
.
Raymond Sabouraud Raymond Jacques Adrien Sabouraud (; 24 November 1864 – 4 February 1938) was a French physician born in Nantes. He specialized in dermatology and mycology, and was also an accomplished painter and sculptor. He studied medicine in Nantes and ...
identified a
dandruff Dandruff is a skin condition of the scalp. Symptoms include flaking and sometimes mild itchiness. It can result in social or self-esteem problems. A more severe form of the condition, which includes inflammation of the skin, is known as s ...
-causing organism in 1904 and called it ''Pityrosporum Malassezii'', honoring Malassez, but at the species level as opposed to the genus level. When it was determined that the organisms were the same, the term "Malassezia" was judged to possess priority. In the mid-twentieth century, it was reclassified into two species: * ''Pityrosporum (Malassezia) ovale'', which is
lipid Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing ...
-dependent and found only on humans. ''P. ovale'' was later divided into two species, ''P. ovale'' and ''P. orbiculare'', but current sources consider these terms to refer to a single species of fungus, with ''M. furfur'' the preferred name. * ''Pityrosporum (Malassezia) pachydermatis'', which is lipophilic but not lipid-dependent. It is found on the skin of most animals. ''Malassezia'' is the sole genus in the family Malasseziaceae, which was validated by Cvetomir Denchev and
Royall T. Moore Royall Tyler Moore (October 11, 1930 – August 17, 2014) was an American-born mycologist and mycology professor. Education and work He received his doctorate from the Harvard University in 1959, writing his dissertation on the fungal genus '' ...
in 2009. The order Malasseziales had been previously proposed by Moore in 1980, and later emended by Begerow and colleagues in 2000. At this time the order was classified as a member of
unknown Unknown or The Unknown may refer to: Film and television Film * The Unknown (1915 comedy film), ''The Unknown'' (1915 comedy film), Australian silent film * The Unknown (1915 drama film), ''The Unknown'' (1915 drama film), American silent drama ...
class placement in the subdivision
Ustilaginomycotina The Ustilaginomycotina is a subdivision within the division Basidiomycota of the kingdom Fungi. It consists of the classes Ustilaginomycetes and Exobasidiomycetes, and in 2014 the subdivision was reclassified and the two additional classes Mal ...
. In 2014, Cvetomir and Teodor Denchev
circumscribed In geometry, a circumscribed circle for a set of points is a circle passing through each of them. Such a circle is said to ''circumscribe'' the points or a polygon formed from them; such a polygon is said to be ''inscribed'' in the circle. * Circum ...
the class Malasseziomycetes to contain the group.


Description

''Malassezia'' grows rapidly, typically maturing within 5 days when incubated at temperatures ranging from . Growth is slower at , and certain species struggle at . These organisms can proliferate on media infused with
cycloheximide Cycloheximide is a naturally occurring fungicide produced by the bacterium '' Streptomyces griseus''. Cycloheximide exerts its effects by interfering with the translocation step in protein synthesis (movement of two tRNA molecules and mRNA in re ...
. An essential factor for the growth of ''Malassezia'' is the presence of
long-chain fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...
s, with ''M. pachydermatis'' being an exception. The most conventional cultivation method involves overlaying solid media with a layer of
olive oil Olive oil is a vegetable oil obtained by pressing whole olives (the fruit of ''Olea europaea'', a traditional Tree fruit, tree crop of the Mediterranean Basin) and extracting the oil. It is commonly used in cooking for frying foods, as a cond ...
. However, for nurturing some clinically relevant species, such as the challenging-to-cultivate ''M. restricta'', more intricate culture media may be required. For the most efficient recovery of ''Malassezia'', it has been recommended to collect blood through a lipid infusion
catheter In medicine, a catheter ( ) is a thin tubing (material), tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. ...
and subsequently use lysis-centrifugation—a recommendation backed by multiple comparative studies. The yeast-like cells of ''Malassezia'', measuring between 1.5–4.5 
μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...
by 3–7 μm, are characterised as
phialide The phialide ( ; , diminutive of phiale, a broad, flat vessel) is a flask-shaped projection from the vesicle (dilated part of the top of conidiophore) of certain fungi. It projects from the mycelium without increasing in length unless a subsequ ...
s featuring tiny collarettes (a small, collar-like flange or lip at the mouth of a phialide from which spores or conidia are produced and released). These collarettes are challenging to identify using standard
light microscope The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible spectrum, visible light and a system of lens (optics), lenses to generate magnified images of small objects. Optical microscopes ...
s. A defining characteristic of cells from this genus is their
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...
: one end is round, while the other has a distinctly blunt termination. This latter end is where singular, broad-based bud-like structures emerge, although in certain species, these structures might be narrower. To effectively visualise the organism's shape, a
staining Staining is a technique used to enhance contrast in samples, generally at the Microscope, microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissue (biology), tissues), in cytology (microscopic ...
technique involving
safranin Safranin (Safranin O or basic red 2) is a biological stain used in histology and cytology. Safranin is used as a counterstain in some staining protocols, colouring cell nuclei red. This is the classic counterstain in both Gram stains and endo ...
is recommended, followed by observation under
oil immersion In optical microscope, light microscopy, oil immersion is a technique used to increase the Angular resolution#Definition of terms, resolving power of a microscope. This is achieved by immersing both the Objective (optics), objective lens and the ...
. Furthermore,
Calcofluor-white Calcofluor-white or CFW is a fluorescent blue dye used in biology and textiles. It binds to 1–3 beta and 1–4 beta polysaccharides of chitin and cellulose that are present in cell walls on fungi, plants, and algae. In plant cell biology re ...
staining provides an enhanced clarity of the cell wall and its unique contour. While ''Malassezia'' typically lacks
hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...
l elements, rudimentary forms can sporadically be present.


Species

The ''
Index Fungorum ''Index Fungorum'' is an international project to index all formal names (scientific names) in the fungus kingdom. As of 2015, the project is based at the Royal Botanic Gardens, Kew, one of three partners along with Landcare Research and th ...
'' lists 22 species of ''Malassezia''. The following list gives the name, the
taxonomic authority In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are given ...
(those who first described the fungus, or who transferred it into ''Malassezia'' from another genus; standardized author abbreviations are used), and the name of the organism from which the fungus was isolated, if not human. In the mid-1990s, scientists at the
Pasteur Institute The Pasteur Institute (, ) is a French non-profit private foundation dedicated to the study of biology, micro-organisms, diseases, and vaccines. It is named after Louis Pasteur, who invented pasteurization and vaccines for anthrax and rabies. Th ...
in Paris, France, discovered additional species. *'' Malassezia arunalokei'' *'' Malassezia brasiliensis'' – from lesions on the beak of
turquoise-fronted amazon The blue-fronted amazon (''Amazona aestiva''), also called the blue-fronted parrot, the turquoise-fronted amazon and the turquoise-fronted parrot, is a South American species of amazon parrot and one of the most common amazon parrots kept in cap ...
parrot *'' Malassezia caprae'' – from skin of goat *'' Malassezia cuniculi'' – from healthy skin of external ear canal of rabbit *'' Malassezia dermatis'' *'' Malassezia equi'' – from skin of horse *'' Malassezia equina'' – from skin of horse *''
Malassezia furfur ''Malassezia furfur'' (formerly known as ''Pityrosporum ovale'') is a species of yeast (a type of fungus) that is naturally found on the skin surfaces of humans and some other mammals. It is associated with a variety of dermatological conditions ...
'' *'' Malassezia globosa'' *'' Malassezia japonica'' *'' Malassezia muris'' – skin of mouse *'' Malassezia nana'' – from discharge from ear of
cat The cat (''Felis catus''), also referred to as the domestic cat or house cat, is a small domesticated carnivorous mammal. It is the only domesticated species of the family Felidae. Advances in archaeology and genetics have shown that the ...
*'' Malassezia obtusa'' *'' Malassezia ochoterenai'' *'' Malassezia pachydermatis'' – from skin of
Indian rhinoceros The Indian rhinoceros (''Rhinoceros unicornis''), also known as the greater one-horned rhinoceros, great Indian rhinoceros or Indian rhino, is a species of rhinoceros found in the Indian subcontinent. It is the second largest living rhinocer ...
*'' Malassezia psittaci'' – from lesions on the beak of
blue-headed parrot The blue-headed parrot, also known as the blue-headed pionus (''Pionus menstruus'') is a medium-sized parrot of about in length. The body is mostly green, with a blue head and neck, and red undertail coverts. It is a resident in tropical and sub ...
*'' Malassezia restricta'' *'' Malassezia slooffiae'' – from skin of pig *'' Malassezia sympodialis'' *'' Malassezia tropica'' *''
Malassezia vespertilionis ''Malassezia vespertilionis'' is a species of yeast-like fungus that grows on the skin of bats. It was described as a new species in 2018. The holotype was obtained from a swab of wing skin of a hibernating northern long-eared bat (''Myotis sep ...
'' – from
vesper bats Vespertilionidae is a family of microbats, of the order Chiroptera, flying, insect-eating mammals variously described as the common, vesper, or simple nosed bats. The vespertilionid family is the most diverse and widely distributed of bat familie ...
in subfamily
Myotinae Myotinae is a subfamily of vesper bats. It contains three genera: '' Eudiscopus'', ''Myotis'', and ''Submyotodon''. Before the description of ''Submyotodon'' and analysis of its phylogenetics, as well as a phylogenetic analysis of '' Eudiscopus'', ...
*'' Malassezia yamatoensis''


References


Further reading

* {{Taxonbar, from=Q14488912 Basidiomycota Parasitic fungi Yeasts Taxa described in 1889 Taxa named by Henri Ernest Baillon Basidiomycota genera