## 4 Discussion  
According to [PERSON]'s classification, the environment in the churches where the fungi were isolated for the present research was a confined non-hypogean environment (C-NHE). Monasteries are partially isolated from the external environment and have relatively more stable humidity and temperature than outdoor conditions, but they are influenced by external day-night cycles, seasonal variations in temperature and relative humidity values. They are more prone to biodeterioration since they include sites that are often visited. The main genera found on the mural paintings as biodeteriogens were: _Aspergillus_, _Penicillium_, _Chaetomium_, _Cladosporium_, _Acremonium_ and _Fusarium_[57; 58; 59; 60; 61]. Our research into their role as biodeteriogens of consolidants is in progress. _Aspergillus niger_ and _Ullodalium charatum_ are common contaminants of mural paintings [15; 62]. A space experiment performed with _U. charatum_ isolated from Humor Monastery proved its adaptability to growth in microgravity conditions [46]. The present results revealed the resistance of _Ullodalium_ sp. H1 to biocides. The fungal strains isolated from the murals could have possibly originated from contaminated plant debris used in the production of the murals, outdoor airspora, percolation of water from the upper soil or outside soil brought in by visitors and small animals. Similar results were obtained in the case of _Fusarium solani_ found in the Lascaux caves, France [63]. [PERSON] et al. [64] isolated entomogenous fungi from caves in northern Spain and showed that species of fungi can grow both on arthropod bodies and on wet mural paintings. In Romania, _Acremonium roseum_, _Trichthecium roseum_ and _Titriachium album_ were found in 1973 in the parochial church of Sucevita that had been spread by an arthropod [65]. Later, the same species were also found on mural paintings and historical buildings [60; 66; 67], most probably spread by spiders and mites. Our results highlight the role of the larva identified among the deposited frescoes in the spreading of microorganisms. [PERSON] et al. [12] demonstrated that microcolonial black fungi are among the most dangerous fungi for cultural heritage and can influence the resistance of mortar and marble to shear and torsion stress, contributing to the separation of different layers of material in  
Figure 12: Resistance of TDC to _Bipolaris_ sp. M7 colonization after biocide treatment. (**a**) Culture developed on frescoes without biocide; (**b**) masses of spores on BR\({}_{\text{s}}\); (**c**) masses of spores on BT\({}_{\text{s}}\); (**d**) masses of spores on P\({}_{\text{s}}\); (**e**) masses of spores on P\({}_{\text{m}}\). mural paintings. Our results revealed that, except for the species _A. niger_, all the other fungi produced melanin pigments that were fixed in the cell wall or diffused over the surface of the consolidants. Consolidants used in restoration, such as Paraloid(r) B72 and TDC, can be used as nutrients by microorganisms. Other nutrients may also arrive from the external environment as airborne particles [4; 68; 69; 70]. The polymer B72 was found to protect and fix the surface of the pictorial layer, but it reduced the permeability to vapours and thus altered the physicochemical activity in the interface between the mural and the environment. Humidity and microbial activity accelerate oxidation and cause blackening of damaged areas fixed with Paraloid(r) B72 [71]. Our results also revealed fungal growth after 48 of incubation and morphological damage after 30 days of incubation in the painted laboratory models. The secretion of organic acids plays a significant role in the chemical degradation of consolidants by causing acidification of the substrate, which then becomes favourable for acidophilic microorganisms [14; 17; 72].