Fungal diversity of brick murals with salt efflorescence and their surroundings in different ancient tombs

Abstract:

[Background] Salt Efflorescence is one of the major diseases caused by combined action of humidity and salt which threated the preservation of ancient wall paintings, but the fields like composition of fungi, its origin and salt tolerance have seldom been reported. [Objective] This study aimed at exploring the community difference of culturable fungi that isolated from brick murals with salt efflorescence disease and their surroundings in tombs, including Dunhuang Han dynasty tomb, Dunhuang Jin dynasty tomb, and Jiayuguan No. 5 tomb, meanwhile, it has purpose to explore the halotolerant ability of the isolated fungal strains in order to provide theoretical basis for better conservation of the brick-tomb wall paintings. [Methods] The surface morphology and crystal phase of samples were analyzed by scanning electron microscope combined with energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD). The culture-dependent method was employed to isolate fungal strains, and to combine with molecular techniques for identification, the community composition and structure characteristics of fungi were identified thereafter. Halotolerancy of all the isolated strains were determined by salt-gradient culture medium method. [Results] The dominant genera of the cultivated fungal genus were Penicillium, Aspergillus, Cladosporium, and the other groups including Fusarium and Chaetomium were rarely isolated. All of the salt efflorescence samples have some common species, such as A. versicolor, P. Aurantiogriseum and A. fumigatus. The community compositions of fungi isolated from the efflorescence samples were similar with their surrounding airborne samples. Most of the isolated strains could grow on culture medium containing 15% sodium chloride, a strain of P. chrysogenum do have their growth even in the 30% salt concentration. [Conclusion] Pencillium and Aspergillus were dominated in different ancient tombs, most of the fungal strains most of the strains have relatively strong capacity of salt tolerance.