Diversity and biocide susceptibility of fungal assemblages dwelling in the Art Gallery of Magura Cave, Bulgaria

Abstract

Abstract:Magura Cave, north-western Bulgaria, possesses valuable rock-art paintings made with bat guano and dated from the period between the Eneolithic and Bronze Ages. Since 2008, the Art Gallery is closed to the general public in order to protect the paintings from vandalism, microclimatic changes caused by visitors and artificial illumination, and the consequent growth of fungi and phototrophs. Nevertheless, some tourist visits are allowed under the supervision of cave managers. This study provides the first scientific report on cultivable fungal assemblages dwelling different substrata in the Art Gallery. A total of 78 strains, belonging to 37 OTUs (Ascomycota 81%, Zygomycota 14%, Basidiomycota 5%), were isolated in the study. This fungal diversity was clearly dominated by Penicillium (50% of strains) and Aspergillus (13%). The most relevant visible fungal colonies were detected in sediments rich in bat guano, where, besides Penicillium, other guanophilic fungi such as Mucor, Mortierella, Trichosporon and Trichoderma were dominant. Conversely, scarce fungi were detected on rock surface of painted walls. Based on the biocide susceptibility assay, octylisothiazolinone (OIT) and benzalkonium chloride (BAC) were effective inhibiting the in vitro growth of dominant fungal species in Magura Cave, when applied at concentrations ranged from 100 to 1,000 mg/L. These data provide a valuable knowledge about Magura fungi, and exemplify a type of preliminary test that may be conducted before planning any biocide treatment. However, considering the irreversible effects of biocides on the ecological balance in caves, and the low fungal contamination in painted walls of Magura Cave, there is no reason to use conventional biocides in this cave. Further studies, monitoring microbial communities and microclimatic parameters, should be conducted to improve the knowledge on microbial ecology in Magura Cave and possible human impacts, as well as to allow the early detection of potential microbial outbreaks.fungi, cultivable microorganisms, rock-art caves, bat guano, biocides Received 14 September 2016; Revised 3 February 2017; Accepted 3 February 2017 Mitova M.M., Iliev M., Nováková A., Gorbushina A.A., Groudeva V.I. and Martin-Sanchez P.M., 2017. Diversity and biocide susceptibility of fungal assemblages dwelling in the Art Gallery of

Evaluation of Plant Origin Essential Oils as Herbal Biocides for the Protection of Caves Belonging to Natural and Cultural Heritage Sites

“…All the isolated fungi of the study belonged to the phylum Ascomycota and more specifically in the classes Sordariomycetes (11 isolates), Eurotiomycetes (7 isolates) and Dothideomycetes (1 isolate) (Table 3, Supplementary Table S2). Ascomycota is usually the dominating phylum along the cave mycobiota, with Zygomycota and Basidiomycota being less present [4,[13][14][15]18,[66][67][68][69]. Penicillium (9 isolates) was the most apparent genus followed by Clonostachys (5), Fusarium (4), Doratomyces (4), Cephalotrichum (3), Talaromyces In this study, the retrieval of cyanobacteria or yeasts was not feasible from the specific spots of the cave walls covered by dark stains (either by swab sampling or by small weathered pieces of rocks).…”

Comparative Study Between Ammonium Phosphate and Ethyl Silicate Towards Conservation of Prehistoric Paintings in the Magura Cave (Bulgaria)

“…The preservation of the cave paintings requires challenging interventions to face the growth of bio-organisms and the deterioration of the stone. As for biological growth, the use of biocides is dangerous because they may completely alter the balance of microbial communities in the cave with negative consequences [7]. For this reason, biodeactivation by non-thermal plasma sterilization has been attempted, and some encouraging results have been obtained [8].…”

“…In the case of other prehistoric paintings, the pigments, usually red (Fe 2 O 3 ), black (charcoal, soot, bone charcoal, or Mn oxides), and more rarely yellow (FeOOH) and brown (ochres), were mixed with an extender and/or a binder [10,11]. The case of the Magura cave, with paintings laid on the cave walls by bat guano having a plastic consistency similar to clay [5], is substantially different from the situations discussed above, with only a few similar cases, such as the Baylovo Cave in Bulgaria and the "Grotta dei Cervi" (Deer cave) in Italy [7]. To our knowledge, no case of consolidation of cave paintings made of bat guano has been reported in the scientific literature.…”

Characterisation of Environmental Biofilms Colonising Wall Paintings of the Fornelle Cave in the Archaeological Site of Cales

“…and Fusarium verticilloides), while the others were present on different substrata (Table 3). These taxa are well-known inhabitants of bare cave environments [60][61][62] as well as cave wall paintings [63,64] or cultural heritages in general [65]. Fungi were mostly found on tuff rock, followed by frescoes in dark and light conditions (Table 3).…”