Niches and adaptation of polyextremotolerant black fungi.

Environmental changes such as increased levels of carbon dioxide and UV radiation are usually perceived as a threat to living organisms and associated with shrinking populations and extinction. We frequently forget that some species cope really well with a range of extreme and rapidly changing conditions and may actually benefit from such changes. Black meristematic fungi, for example, are well adapted to high doses of radiation and survive long periods of desiccation. They seem not only robust under moderate stress conditions but seem to adapt and diversify, in agreement with the so-called concept of antifragility. We hypothesise that this behaviour is mediated by the polymer melanin in the cell walls; yet, other protective molecules and phenotypic plasticity play an important role as well. Evolution of these fungi is thought to have originated in the harsh oligotrophic habitats on the surface and subsurface of rocks, but their potentials are much wider than that. Their polyextremotolerance helps them to colonise numerous habitats in which competition with other fungi is low due to stressful conditions. This includes a range of anthropogenic environments and in some cases also animal bodies. Some of these fungi also undergo lichen-like associations with photoautotrophs or benefit from growing on lichens.