Characterization of surface microbial community structure and identification of dominant species on the Dazu Thousand-handed and Thousand-eyed Avalokitesvara

The Dazu Thousand-handed and Thousand-eyed Avalokitesvara is regarded as the largest and most completely preserved cliff carving of its kind in China. It is a remarkable integration of rock carving, polychromy, and gold foil application, and is regarded as the largest and most completely preserved Thousand-handed Avalokitesvara cliff carving extant in China. Recent continuous monitoring has revealed evident deterioration of the gold foil surface, primarily manifested as discolouration, cracking, and loss of the foil. A plethora of studies have examined the influence of environmental physicochemical factors and material characteristics on the corrosion of gold foil, however, the influence of microorganisms has received limited attention. The present study was conducted for the purpose of systematic characterisation of the microbial communities colonizing the gold foil surface using sterile swab sampling followed by high-throughput sequencing technology of the 16S rRNA gene and the Internal Transcribed Spacer (ITS). The results showed that bacterial communities were dominated by Firmicutes, Actinobacteriota and Proteobacteria at the phylum level, with Salinisphaera and Pseudonocardia identified as the core dominant genera. Fungal communities were primarily composed of Ascomycota and Mucoromycota, exhibiting dominance of Aspergillus, Filobasidium, and Mucor. Two dominant fungal strains (Aspergillus versicolor and Mucor fragilis) were successfully identified through selective media isolation, combined with colonial morphology observation and ITS sequence analysis. Based on the existing literature on microbial metabolism, these strains are hypothesized to facilitate gold foil corrosion via synergistic physical, chemical, and bioelectrochemical mechanisms.