## 4 Discussion
fumosorosea_ (reported as _Isaria funososonea_), _M. suchlasporia_ (reported as _Pochonia suchlasporia_), _P. brevicompactum_, _P. chrysogenum_, _P. griseofulvum_, and _P. panourum_. Three years later, [PERSON] et al. [82] reported the presence of _C. viridescens_ in two caves in Canada: Grotte de la Baie de la Tour and Grotte du lac Maloin [82]. [PERSON] et al. [83] reported _C. viridescens_ in an underground iron ore mine in Soudan (Minnesota, USA). Additionally, we came across a record from the early 1960s of the presence of _A. multifatum_ (reported as _Chrysosporium_ sp.) in a cave in Romania [84]. The literature has also reported on other species of keratinophilic and keratinolytic fungi that were detected in underground ecosystems such as _Arthroderma curreyi_,Microsporum gypsum, Tricholyton mentagrophytes, T. rubrum, T. terrestre, and M. cookie, a clade with close affinities to _P. cookie_[31; 85; 86; 87; 88]. However, the methodology and results obtained by [PERSON] and [PERSON] [86] were imprecise (lack of adequate controls); the authors themselves admitted that they had no data on the animals being free from _T. mentagrophytes_ or if the proper controls were included. In conclusion, to the best of our knowledge, _A. eboreum_, _A. insingulare_, _Ch. europae_, _Ch. siglerae_, _K. wagneri_, and _P. charlesii_ have not yet been described in caves nor mines. Thus, we believe that we are the first to report their occurrence in underground sites. _Arthroderma eboreum_ and _A. insingulare_, together with the most abundant _Arthroderma_ in our research, _A. quadrifidum_, are representatives of the former _Trichophyton terrestre_ complex. _Arthroderma eboreum_ was first reported as _Trichophyton eboreum_ in 2005 [90], while its teleomorph _Arthroderma olidum_ was described the following year [91]. This species was isolated from the skin of an HIV-positive patient with _tinea pedis_. Despite being cured with the topical combination of cyclopiroxolamine and terbinafine [90], it was later described as fluconazole-resistant [92]. Similarly, _A. insingulare_ is reputed to be involved in skin inflammatory disorders (including hyperpigmentation) and was described to be resistant towards griseofulvin [93]. The closely related _A. quadrifidum_ is a known example of an opportunistic pathogen, the strains of which might demonstrate resistance towards itraconazole, nystatin, and griseofulvin [94]. Not much is known about _Ch. europae_, _Ch. siglerae_ (currently known as _Keratinophyton siglerae_[95] and _K. wagneri_. _Chrysosporium europae_ was reported as an isolate from soil and a children's sandpit in Slovakia [96]. This species displays a wide range of thermal tolerance as it was isolated from Antarctic permafrost sediments, but was also reported to survive heating up to 52 \({}^{\circ}\)C [97]. In addition, its nutrient requirements must be low as it is one of the most abundant species isolated from nutrient-poor coal ash heaps in Sosnowiec (Poland) [98]. _Chrysosporium siglerae_ and _K. wagneri_, based on ITS phylogeny, seem to be closely related as they occupy close (but separate) terminal clusters [95]. Already known distinctive traits include the presence of intercalary conidia in _Ch. siglerae_, the ability of _Ch. siglerae_ to grow at 37 \({}^{\circ}\)C, and much smaller conidium size in the case of _K. wagneri_[96]. Reporting their presence in underground sites may be of great importance in further understanding the biology of these poorly described fungal species. On the other hand, _P. charlesii_ is a species well-known for its wide metabolic abilities, and is constantly reported as useful in biotechnology. _P. charlesii_ was reported to produce tannases--enzymes that catalyze the hydrolysis of ester and depside bonds in hydrolysate tannins, releasing glucose and gallic acid [99]. Additionally, _P. charlesii_ is a known producer of alkaline proteases [100] and seven antinematodal and antiparasitic agents, including paraheruamide and its analogs [101].