Fungal community composition on normal and moldy mural in Xu Xianxiu’s tomb of Northern Qi Dynasty, Taiyuan

Abstract:

[Objective] We explored the fungal community composition on mural surface, to analyze the major environmental factors that induce the explosion of fungal disease, and to provide the basis for the scientific conservation of murals. [Methods] Mural samples with and without whitish moldy necrosis were carefully and separately collected by sterile scalpel. The Scan Electronic Microscope (SEM) was used to analyze microcosmic features of fungus that caused mural biodeterioration. By the extraction of total genomic DNA, the following steps should be the amplification of fungal ITS region, clone library construction, sequencing, and phylogenetic analysis, thereafter the fungal community composition and structure characteristics were clarified. Combined with temperature and relative humidity (RH) monitoring, the environmental factors related to fungal growth can be figure out. [Results] A large amount of mycelia existed on mildewed murals, the volume of conidia ranged among 1.5?2.0 μm multiplied by 1.0?1.5 μm. Most of clone library sequences in mildewed murals were much similar to genera Engyodontium and Acremonium, of these fungi Engyodontium album was a dominant fungus (98.1%); however, sequences from mural samples without mildew were more similar to genera Penicillium, Aspergillus, Alternaria, Candida, Chaetomium and Engyodontium, in which Penicillium laeve was a dominant species (77.4%). All sequences belonged to Ascomycota in our study. The temperature below the tomb tunnel varied from ?0.3 °C to 17.6 °C, and RH varied mostly from 80% to 100%. [Conclusion] The fungal community composition in the moldy murals was distinct different from murals without apparently moldy necrosis. Engyodontium album was the dominant disease fungus which caused mildew of murals. Perennial higher RH below the tomb tunnel must be the primary environmental factor that induced mildew. As a result, it is necessary to carry out some salvage protection and certain environmental control measures for conservation of ancient murals in this archaeological site.