## 4 Discussion
### The Fungal Data Set
Finally, the plant pathogen species _Fusarium oxysporum_ has been shown to produce an extracellular pinkish pigment that disfigures and aesthetically damages colonized mural paintings and stone surfaces with permanent stains [78]. Phylum Basidiomycota was present with several occasional species, mostly represented by one or two records, and comprises litter, soil, and wood-saprotrophs, ectomy-cornhizal, epiphyte, and plant-pathogen species. Their occurrence must be regarded as sporadic, potentially aided by root penetration. The possible role of roots as a carrier for rhizosphere microorganisms, like a dripping line for water condensation, and as an organic carbon source by root exudates has been hypothesized [57; 120]. In any case, a Basidiomycte was also recorded at the entrance of Roman catacombs [121], possibly due to spores carried by water infiltrations and germinating using organic nutrients from the soil and/or the phototrophic biofilm. Mucoromycota was present with few species and records, and black meristematic fungi were rarely recorded as well. These latter may grow on a wide range of substrates and are resistant to a variety of environmental stresses, as well as being widely distributed epi- and endolithically on monuments [122; 123]. Although the biodiversity of black fungi on historical monuments is not fully elucidated, recent samplings indicate that they are also present on wall paintings and that their rare finding could be linked to the isolation protocols used, generally favoring fast-growing species [124]. Two new species of the genus _Neodevrisia_ have been found in the restricted sampling area of the Vallerano cave and another, still undescribed, from Maijishan grottoes [45; 99; 108]. _Sociocobsidium lascauxensis_ and _S. anomalous_ were isolated and described from black stains in Lascaux Cave, France [85; 115], while the chaetothyrialean black fungi _Cladophialophora_, _Exophilata_, and _Philaophora_ have been reported from different sites [23; 24; 42; 98]. Yeasts have been rarely reported, such as Saccharomyces (Ascomycota) that usually grow by individual yeast cells or _Rhodotorula_ spp. (Basidiomycota) often linked to pink/orange stains due to the release of carotenoids [19; 93]. Among those more commonly reported, some species such as those belonging to the genera _Alternaria_, _Fursium_, _Aspergillus_, _Penicillium_, and _Cladosporium_ may be responsible for annoying allergic and toxic reactions suffered by conservationists and visitors [81; 125; 126]. _Alternaria alternata_ is a very common fungal species, frequently recorded on frescoes. Its spores are recognized as common powerful aeroallergers, and indoor environments offer higher levels of exposure to this risk than open-air [59; 127]. Records of _Fursium_ species have also been reported, such as _F. solanti_ in the Lascaux caves [97] and _F. oxysporum_ in many sites. They are mainly plant pathogens, but they can also be the causal agents of human mycoses [97; 128; 129]. Some _Aspergillus_ species are pathogenic to humans and animals and are responsible for clinical manifestations ([[https://www.aspergillus.org.uk/species-archive/](https://www.aspergillus.org.uk/species-archive/)]([https://www.aspergillus.org.uk/species-archive/](https://www.aspergillus.org.uk/species-archive/)), 29 December 2021). Among these, _A. fumigatus_ is a human pathogenic fungus recorded on frescoes within different environments (3,11,22,29,42,49,70,71), causing infections in humans which can be fatal in immunocompromised patients (61). _Aspergillus flavus_ has been frequently recorded in monasteries, churches, temples, caves, and tombs, mostly due to their numerous aerosolized spores. It mainly grows in the soil, but it is also a facultative and opportunistic pathogen of both animals and plants, producing mycotoxins that are highly harmful to humans [130]. In light of the above, the identification of the species deteriorating wall painting is needed for the protection of restorers and visitors.