“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 ...
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 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, cor ...
s and mycosporines represent passive physiological adaptations which enable black fungi to be highly resistant against environmental stresses. The term " polyextremotolerance" has been introduced to describe this phenotype, a good example of which is the species '' Aureobasidium pullulans''. 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 very different fungal groups. Many are found in the orders '' Capnodiales'', '' Dothideales'', and '' Pleosporales'' (class '' Dothideomycetes''). 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'' (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 ...
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 and sometimes with ants in specific ant-fungi associations.
In recent years, black fungi such as ''E. dermatitidis'' or '' Hortaea 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 investi ...
,
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, effect of ionizing radiations in contaminated area, biodeterioration of materials, and mechanisms of adaptation to high salt concentrations. A collaborative effort coordinated by the Broad Institute 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
Viral means "relating to viruses" (small infectious agents).
Viral may also refer to:
Viral behavior, or virality
Memetic behavior likened that of a virus, for example:
* Viral marketing, the use of existing social networks to spread a marke ...
.
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 ...