''Microascus brevicaulis'' is a microfungus in the
Ascomycota
Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...
. It is the
teleomorph
In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota:
*Teleomorph: the sexual reproductive stage (morph), typically a fruiting body.
*Anamorph: an ase ...
form of ''Scopulariopsis brevicaulis.'' ''Microascus brevicaulis'' occurs world-wide as a saprotroph in soil, a common agent of biodeterioration, an irregular plant pathogen, and an occasional agent of human nail infection.
Name
Most of the discussion of this fungus in the scientific and medical literature has referred to the fungus using the name of its asexual form, or
anamorph
In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota:
*Teleomorph: the sexual reproductive stage (morph), typically a fruiting body.
*Anamorph: an ase ...
, ''Scopulariopsis brevicaulis''.
However, a sexual form (
teleomorph
In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota:
*Teleomorph: the sexual reproductive stage (morph), typically a fruiting body.
*Anamorph: an ase ...
) named ''Microascus brevicaulis'' was recently described.
Under the current revision of ''
'', as articulated in th
Shenzhen Code 2018 it remains unclear which name this fungus will ultimately take.
Until further clarification, ''Microascus brevicaulis'' is considered the most recent, accepted name.
Bartolomeo Gosio
Bartolomeo Gosio (17 March 1863 – 13 April 1944) was an Italian medical scientist. He discovered a toxic fume, eponymously named "Gosio gas", which is produced by microorganisms, that killed many people. He identified the chemical nature of the g ...
discovered in 1890 that under wet conditions ''M. brevicaulis'' produces significant amounts of
trimethylarsine
Trimethylarsine (abbreviated TMA or TMAs) is the chemical compound with the formula (CH3)3As, commonly abbreviated As Me3 or TMAs. This organic derivative of arsine has been used as a source of arsenic in microelectronics industry, a building block ...
via biomethylation of inorganic
pigment
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...
s especially
Paris green or
Scheele's Green
Scheele's Green, also called Schloss Green, is chemically a cupric hydrogen arsenite (also called copper arsenite or acidic copper arsenite), . It is chemically related to Paris Green. Scheele's Green was invented in 1775 by Carl Wilhelm Schee ...
used in indoor wallpapers which is then released into the air.
Morphology
''Microascus brevicaulis'' is a common
mold
A mold () or mould () is one of the structures certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal seco ...
. When cultured at a temperature of 25 °C on potato dextrose agar it forms white colonies which become powdery and/or granular as they mature. Under such conditions the fungus can grow rapidly, expanding as much as 4.5 - 5.5 cm within one week.
The hyphae of ''M. brevicaulis'' are hyaline (transparent) and septate (separated into segments by cross-walls). The anamorph has conidia that are flattened on the base and tapered at the apex, resembling a boat
keel
The keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. As the laying down of the keel is the initial step in the construction of a ship, in Br ...
in cross-section or a pontifical
mitre
The mitre (Commonwealth English) (; Greek: μίτρα, "headband" or "turban") or miter (American English; see spelling differences), is a type of headgear now known as the traditional, ceremonial headdress of bishops and certain abbots in ...
.
[ The conidia are produced in chains from cells known as annelides, ]phialide
The phialide ( ; el, phialis, 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 ...
-like cells that elongate with each successive conidium produced. These, in turn, range from solitary to arranged in complex broom-like clusters on fertile hyphae known as conidiophore
A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are al ...
s.[ The fungus is a typical ]perithecia
An ascocarp, or ascoma (), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascocarps are mo ...
l member of Phylum Ascomycota
Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...
, producing minute, enclosed fruiting bodies containing sexual spores (ascospore
An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or s ...
s) in sacs known as asci. The ascospores of ''M. brevicaulis'' are kidney-shaped and reddish-brown in colour.[
]
Ecology
This fungus usually occurs as a mold present in numerous different types of soil as well as various decaying types of organic matter.[ ''Microascus brevicaulis'' has a world-wide distribution, and occurs chiefly as a soil ]saprotroph
Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi (f ...
.[ The species is also encountered with some frequency as a non-]dermatophyte
Dermatophyte (from Greek '' derma'' "skin" (GEN ''dermatos'') and ''phyton'' "plant") is a common label for a group of fungus of ''Arthrodermataceae'' that commonly causes skin disease in animals and humans. Traditionally, these anamorphic (as ...
agent of nail infections (onychomycosis
Onychomycosis, also known as tinea unguium, is a fungal infection of the nail. Symptoms may include white or yellow nail discoloration, thickening of the nail, and separation of the nail from the nail bed. Toenails or fingernails may be affected ...
), particularly in toenails. Besides the typical soil life of a decomposer, this fungus is also known to live within the American dog tick, ''Dermacentor variabilis''. This relationship seems to be highly adapted but not as a classic host-parasite interaction. Studies have shown ''M. brevicaulis'' inhabits its host as an endosymbiont, and may provides protection against the insect-pathogenic fungus, ''Metarhizium anisopliae''.
Pathogenicity in humans
''Microascus brevicaulis'' has typically been associated with infections located on the skin surface of patients. Though this fungus is responsible for causing several skin related diseases, it is not considered a habitual pathogen. It is however categorized as a dermatomycotic mold which is known to cause onychomycosis.[ This is the most prevalent disease affecting human nails but ''M. brevicaulis'' has been isolated from healthy nails as well as diseased ones, indicating that it could be a harmless contaminant in some situations but behave as an opportunistic pathogen in others. ''Microascus brevicaulis'' is also known to cause granulomatous skin infections in humans.][Granulomatous skin infection caused by Scopulariopsis brevicaulis Ineke Bruynzeel, MD, PhD, a and Theo M. Starink, MD, PhDb Amsterdam, The Netherlands] Yet another dermatological disease which may be caused by ''M.. brevicaulis'' is skin infection on the sole of the foot.[Plantar Infection by Scopulariopsis brevicaulis Ginarte M. Pereiro Jr. M. Fernández-Redondo V. Toribio J] These infections appear as red bumps or (less commonly ridges) around the patients hands and feet. Usually, these infections cause no pain and do not last very long thus resolve without treatment. In some cases however, these types of infection may be persistent and cause great discomfort.[ Yet another dermatological disease which may be caused by ''M. brevicaulis'' is plantar infection.] This consists of a (potentially thick) scaly plaque that accumulates on the feet. Despite the discomfort and pain which dermatological infections of this sort inflict upon patients, ''M. brevicaulis'' is considerably more dangerous (even fatal) in situations where it manages to bypass the skin and reach deep tissues. The danger arises because ''M. brevicaulis'' is a multi-drug resistant, opportunistic pathogen.[Scopulariopsis brevicaulis, a Fungal Pathogen Resistant to Broad-Spectrum Antifungal Agents Manuel Cuenca-Estrella, Alicia Gomez-Lopez, Emilia Mellado, Maria J. Buitrago, Araceli Monzón, and Juan L. Rodriguez-Tudela] In the past, these kinds of infections mostly occurred if an individual punctured their skin with a stick or experienced some similar form of trauma that could implant ''M. brevicaulis'' below the skin. However, in recent years there has been an increase in the previously rare number of cases of deep tissue infections resulting from ''M. brevicaulis''. In contemporary cases where deep tissue invasion has occurred, the patients are almost always immunocompromised. It is believed that the increasing incidence of diseases like AIDS
Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual m ...
and diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
coupled with medical practices like chemo-therapy and broad-spectrum antibiotic treatments are primarily responsible for creating a large number of individuals who are predisposed to potentially fatal infections of ''M. brevicaulis''. Another more recent entry route for this fungus has been an increase in the number of elective surgeries which raise its exposure to internal environments. The occurrence of such infections is on the rise and includes several life-threatening conditions such as: the formation of fungus balls in preformed pulmonary cavities, keratitis, posttraumatic endophthalmitis, disseminated skin lesions in AIDS patients, granulomatous subcutaneous infections, invasive hyalohyphomycosis, pneumonia in leukemic patients, endocarditis related to valvuloplasty or prosthetic valves, and fatal disseminated infection after bone marrow transplantation. In other cases, ''M. brevicaulis'' has caused death in immunocompromised patients with hematological diseases.[Disseminated Scopulariopsis brevicaulis infection in an allogeneic stem cell recipient M Vignon, D Michonneau, M-T Baixench, C Al-Nawakil, D Bouscary, A Buzyn, D Salmon and A Paugam]
References
External links
Index Fungorum
USDA ARS Fungal Database
{{Taxonbar, from=Q704790
Microascales
Fungal plant pathogens and diseases
Fungi described in 1886