“Black yeasts”, sometimes also black fungi, dematiaceous fungi, microcolonial fungi or meristematic fungi is a diverse group of slow-growing

microfungi Microfungi or micromycetes are fungi—eukaryotic organisms such as molds, mildews and rusts—which have microscopic spore-producing structures. They exhibit tube tip-growth and have cell walls composed of chitin, a polymer of ''N''-acetylgluco ...

which reproduce mostly asexually ( fungi imperfecti). Only few genera reproduce by budding cells, while in others

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 or ...

l or meristematic (isodiametric) reproduction is preponderant. Black yeasts share some distinctive characteristics, in particular a dark colouration ( melanisation) of their

cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mec ...

. Morphological plasticity, incrustation of the cell wall with melanins and presence of other protective substances like

carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, ...

s and mycosporines represent passive physiological adaptations which enable black fungi to be highly resistant against

environmental stresses Stress, either physiological, biological or psychological, is an organism's response to a stressor such as an environmental condition. Stress is the body's method of reacting to a condition such as a threat, challenge or physical and psycholog ...

. The term " polyextremotolerance" has been introduced to describe this phenotype, a good example of which is the species ''

Aureobasidium pullulans ''Aureobasidium pullulans'' is a ubiquitous and generalistic black, yeast-like fungus that can be found in different environments (e.g. soil, water, air and limestone). It is well known as a naturally occurring epiphyte or endophyte of a wide ra ...

''. Presence of 1,8-dihydroxynaphthalene melanin in the cell wall confers to the microfungi their characteristic olivaceous to dark brown/black colour. The consortium comprises two

phylogenetically In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...

very different fungal groups. Many are found in the orders ''

Capnodiales Capnodiales is a diverse order of Dothideomycetes, initially based on the family Capnodiaceae, also known as sooty mold fungi. Sooty molds grow as epiphytes, forming masses of black cells on plant leaves and are often associated with the honeyd ...

'', ''

Dothideales Dothideales are an order of bitunicate fungi consisting mainly of saprobic or plant parasitic species. Description Taxa in this order are characterized by the absence of a hamathecium (defined as hyphae or other tissues between asci) in a loc ...

'', and ''

Pleosporales The Pleosporales is the largest order in the fungal class Dothideomycetes. By a 2008 estimate it contains 23 families, 332 genera and more than 4700 species. The majority of species are saprobes on decaying plant material in fresh water, marin ...

'' (class ''

Dothideomycetes Dothideomycetes is the largest and most diverse class of ascomycete fungi. It comprises 11 orders 90 families, 1300 genera and over 19,000 known species. Traditionally, most of its members were included in the loculoascomycetes, which is not pa ...

''). These black fungi mostly have an extremotolerant life style. Many representatives of this group can colonize bare rocks e.g. in the Mediterranean basin or in hot and cold dry deserts and are therefore referred to as rock-inhabiting fungi, or occur in salterns. These black yeasts are believed to be the most resistant eukaryotic organisms known to-date. They were firstly described in the early 80s by three almost concomitant seminal research articles. Members of ''

Chaetothyriales The Chaetothyriales are an order of ascomycetous fungi in the class Eurotiomycetes and within the subclass Chaetothyriomycetidae. The order was circumscribed in 1987 by mycologist Margaret Elizabeth Barr-Bigelow. Families and genera , Species ...

'' (class ''

Eurotiomycetes Eurotiomycetes is a large class of ascomycetes with cleistothecial ascocarps within the subphylum Pezizomycotina, currently containing around 3810 species according to the Catalogue of Life. It is the third largest lichenized class, with more tha ...

'') are found in hydrocarbon-rich environments or in nutrient poor, moist indoor environments, and may occur as

opportunistic pathogens An opportunistic infection is an infection caused by pathogens ( bacteria, fungi, parasites or viruses) that take advantage of an opportunity not normally available. These opportunities can stem from a variety of sources, such as a weakened immun ...

of vertebrate hosts, such as ''Exophiala'' (''Wangiella'') ''dermatitidis''. Several species are associated with

lichens A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.phototrophs Phototrophs () are organisms that carry out photon capture to produce complex organic compounds (e.g. carbohydrates) and acquire energy. They use the energy from light to carry out various cellular metabolic processes. It is a common misconcep ...

and sometimes with ants in specific ant-fungi associations. In recent years, black fungi such as ''E. dermatitidis'' or ''

Hortaea werneckii ''Hortaea werneckii'' is a species of yeast in the family Teratosphaeriaceae. It is a black yeast that is investigated for its remarkable halotolerance. While the addition of salt to the medium is not required for its cultivation, ''H. werneckii' ...

'' have attracted increasingly attention as model microorganisms in studies on

astrobiology Astrobiology, and the related field of exobiology, is an interdisciplinary scientific field that studies the origins, early evolution, distribution, and future of life in the universe. Astrobiology is the multidisciplinary field that invest ...

bioremediation Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi, and plants), living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluent ...

of polluted ecosystems by

biofiltration Biofiltration is a pollution control technique using a bioreactor containing living material to capture and biologically degrade pollutants. Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, a ...

, effect of

ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...

s in contaminated area, biodeterioration of materials, and mechanisms of adaptation to high salt concentrations. A collaborative effort coordinated by the

Broad Institute The Eli and Edythe L. Broad Institute of MIT and Harvard (IPA: , pronunciation respelling: ), often referred to as the Broad Institute, is a biomedical and genomic research center located in Cambridge, Massachusetts, United States. The insti ...

is currently ongoing to sequence the genomes of several black fungi to shed light into their ecology, phylogeny and pathogenicity. In 2011, a research paper about occurrence of potentially pathogenic black fungi in household dishwashers was partially misreported by the media and went viral. Black yeasts are not related to the edible

cloud ear fungus ''Auricularia cornea'' (毛木耳, maomuer or cloud ear) is a species of fungus in the order Auriculariales. It is commercially cultivated for food in China. The species was previously referred to ''Auricularia polytricha'', but the latter speci ...

''Auricularia polytricha''.

References

External links

* Website of th
Working Group Black Yeast
{{Webarchive, url=https://web.archive.org/web/20120115151310/http://www.blackyeast.org/ , date=2012-01-15

from the

Ascomycota Fungus common names