The diversity of cultivable fungi on corridor murals and controlling of microbial deterioration in Xu Xianxiu's tomb of Northern Qi dynasty, Taiyuan

Abstract:

[Background] The tomb murals preserved at the original sites are generally threatened by the microbial disease, and the long-term controlling of these microorganisms is a long-standing problem in the field of cultural heritage conservation. [Objective] we aimed to explore the cultivable fungal diversity on moldy murals of the tomb corridor surfaces, to isolate the dominant fungal strains and screen the long-acting biocides, and provide a scientific support for the control of the mural's fungal disease of this tomb. [Methods] Mural samples with whitish moldy necrosis were carefully collected by sterile swabs. The surface morphology of samples was analyzed by scanning electron microscope (SEM). The culture-dependent method was employed to isolate fungal strains, and combine with molecular techniques for identification, the community composition of fungi was analyzed thereafter. Combined with the laboratory inhibition zone test and the in-situ biocides test, the size of the inhibition zone of different biocides, the in-situ cultivable microbial concentration after biocides application, and the ATP fluorescence values differences were analyzed in order to find a lasting efficacy of the biocides. [Results] There were a large amount of mycelia with conidia, the culturable fungi in the white mycelium samples affilliated to the six genera of Ascomycota phylum, the dominant cultivated fungus was Parengyodontium album (98.13%). After screening and evaluation in laboratory and in-situ tests, it is clear that the most effective biocide was dichlorophene compounds (0.5% dichlorophene with 75% ethanol), and no repeated outbreaks of microorganisms occurred during the 7-year consecutive monitoring period. [Conclusion] P. album was the dominant cultivable fungi that caused mural moldy at tomb corridor. Dichlorophene compound biocide used in the controlling test of Xu Xianxiu's tomb mural of Northern Qi dynasty has achieved the longest timeliness of maintenance; and it is recommended to combine the emergency protection, environmental regulation and follow-up monitoring in the future, as a result, to achieve long-term prevention and control of the microbial hazards to the tomb murals.