“Black yeasts”, sometimes also
black fungi,
dematiaceous fungi,
microcolonial fungi or
meristematic fungi is a diverse group of slow-growing
microfungi which reproduce mostly
asexually (
fungi imperfecti). Only few genera reproduce by
budding cells, while in others
hyphal or meristematic (isodiametric) reproduction is preponderant. Black yeasts share some distinctive characteristics, in particular
melanisation of their cell wall.
Morphological plasticity, incrustation of the cell wall with melanins and presence of other protective substances like
carotenoids 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-dihydroxynaphtalene melanin in the cell wall confers to the microfungi their characteristic olivaceous to dark brown/black colour.