Myxotrichum chartarum

Myxotrichum chartarum was discovered by Gustav Kunze in 1823, along with another species in the new genus Myxotrichum, Myxotrichum murorum.[1]

There has been much confusion within the genus Myxotrichum due to numerous revisions in classification over the years and the scarcity of isolations.[1][3] Eventually, the genus, Myxotrichum became associated with ascomycota fungi which are dematiaceous hyphomycetes, commonly known as black yeasts or moulds.[3] At the microscopic level, these fungi have a mesh-like surrounding structures, peridium, with hooked appendages.[3]

It was mistakenly placed in the genus Oncidium by Nees, also in 1823, though that name which was already in use for a genus of orchid, giving Myxotrichum priority.[1][3][2] In 1838, August Carl Joseph Corda classified M. chartarum as a hyphomycete in the family Sporotrichacheae, as species belonging to this family had ornate appendages resembling deer antlers.[4] In 1854, Corda separated M. chartarum from Myxotrichum into the newly established genus, Actinospira because he believed it to produce conidia rather than ascospores.[1] In 1959, Kuehn, among other investigators, reviewed the status of the family Gymnoascaceae and placed M. chartarum into the ascomycetous genus, Myxotrichum rather than the newly established genus for conidial forms, Myxotrichella.[1]

In 1875, Fuckel declared M. chartarum to be the conidial form of Chaetomium kunzeanum.[4] Fries thought M. chartarum was a conidial form of Chaetomium chartarum.[5] His opinion was supported by Boulanger in 1897.[4] Their revelation was founded because of the high resemblance between Chaetomium and Myxotrichum fungal families due to the presence of ornamental hairs.[4][1] In 1889, Richon thought M. chartarum was the conidial form of Cephalotheca sulfurea, disputing the claim of Fuckel.[4] In 1891, Constantin showed that M. chartarum belonged to the newly established family, ascomycete of the family Gymnoascaceae, for ascomycetes that lacked true cleistothecia or perithecia.[1] In 1892, Rabenhorst classified M. chartarum into the order Gymnoascaceae.[4] This was later supported by Schroter in 1893.[4] Fischer later recognized the existence of ascospores in M. chartarum, but a distinct lack of conidial structures.[4] In 1893, Schroeter reviewed family Gymnoascaceae and placed species with uncinate appendages within the genus, Myxotrichum without regard for other characteristics.[1]

Different forms of M. chartarum were isolated by Robak and Udagawa that resembled a phenotypically similar species.[3] The isolate discovered by Robak (1932) of M. carminoparum resembled M. chartarum[3] in every way except in the characteristically flattened apical area. Another isolate was discovered by Udagawa (1963) to have flattened appendages, but the size of the ascomata was smaller, resembling those from M. carminoparum.[3] Later, the species, M. chartarum and M. carminoparum were merged due to the high resemblance between the two species.

M. chartarum is known for its inhabitation of paper and paper products. The specific epithet, chartarum, originated from the Latin word for paper and is in reference to its initial discovery from paper in books,[7] and its ability to decay these materials through the production of cellulose-degrading enzymes (cellulases).[10] It was deemed a “material pathogen”, since it is able to degrade specific materials for a source of nutrition.[10] It has also been recorded to inhabit other materials such as, drywall, straw, decaying leather, cloth, grouse dung, rabbit dung, bat guano, soil, leaves and fruit.[1][10][11][3][12] Reports of M. chartarum have come from around the world. Known distribution areas are as follows: Germany, Russia, Italy, France, Switzerland, England, Japan, Austria-Hungary, Czechoslovakia, Maine, Massachusetts, Ontario, New York.[1][3] The endemic region of this fungus is currently unknown. The presence of curved spines allow the fungus to adhere to the fur of animals, allowing the fungus to disperse to other areas.[4]

It has been observed by multiple researchers that M. chartarum exhibited slow growth between temperatures of 5-7 °C, so this fungus is classified as a psychrophilic organism.[1][7][3] However, no growth was observed at 37 °C and since it is unable to grow at the human body temperature, this fungus is not a disease agent or an opportunistic pathogen.[10] As found by Tribe and Weber (2002),[7] optimal growth in culture can be achieved on mineral salt agar with a sheet of Cellophane as the only carbon source.[7] In basements or cellars, M. chartarum has a preference for gypsum board ceilings and building paper on concrete surfaces on the cold side of foundation walls.[11] For optimal growth, it requires a relative humidity of greater than 98%.[11] Salinity and pH preferences are unknown, but it is thought to be halo-tolerant.[11]

• Photos of Myxotrichum chartarum on Global Biodiversity Information Facility