Microbial colonization on stone monuments leads to subsequent biodeterioration; determining the microbe diversity, compositions, and metabolic capacities is essential for understanding biodeterioration mechanisms and undertaking heritage management. Here, samples of epilithic biofilm and naturally weathered and exfoliated sandstone particles from different locations at the Beishiku Temple were collected to investigate bacterial and fungal community diversity and structure using a culture-based method. The biodeterioration potential of isolated fungal strains was analyzed in terms of pigmentation, calcite dissolution, organic acids, biomineralization ability, and biocide susceptibility. The results showed that the diversities and communities of bacteria and fungi differed for the different sample types from different locations. The population of culturable microorganisms in biofilm samples was more abundant than that present in the samples exposed to natural weathering. The environmental temperature, relative humidity, and pH were closely related to the variation in and distribution of microbial communities. Fungal biodeterioration tests showed that isolated strains four and five were pigment producers and capable of dissolving carbonates, respectively. Their biomineralization through the precipitation of calcium oxalate and calcite carbonate could be potentially applied as a biotechnology for stone heritage consolidation and the mitigation of weathering for monuments. This study adds to our understanding of culturable microbial communities and the bioprotection potential of fungal biomineralization.

White and black biofilms threatened the wall paintings in UNESCO-listed Maijishan Grottoes. This study investigates these biofilms for viability, composition, functional groups, and degradation potential. The results revealed Scopulariopsis and unclassified_Eurotiomycetes as the core fungal taxa in black and white biofilms, respectively. Fluorescence microscopy and RNA-based high-throughput sequencing proved that white biofilms exhibited higher viability. In addition, we isolated Arachnomyces sp. (unclassified_Eurotiomycetes) as the dominant strain in white biofilms. Laboratory assays demonstrated that Arachnomyces sp. has strong capacities to degrade cellulose, gelatin, casein, and keratin, indicating its biodeterioration of wall paintings. Furthermore, black biofilms were dominated by dung saprotrophic fungi, likely introduced through animal activities within the grottoes. Our findings underscore that the divergences in fungal composition between black and white biofilms are driven by microenvironmental factors, substrate properties, animal activities and ecological selections. The interplay of microbial dispersal and environmental selection shapes biofilms, and microenvironmental control is the essential targeted strategy.

Microbial deterioration as one of the widespread problems in archaeological site museums significantly affects their safety and exhibits. This paper systemically investigated the environments and conditions of microbial outbreaks in the Dadiwan No. F901 site museum, which is a representative archaeological site of prehistoric Yangshao culture. The morphology and harmful characteristics of the outbreak microorganisms were analyzed by microscopic techniques. The ultraviolet resistance of harmful microorganisms was also studied. Combining these findings with the original facilities of the site museum, a scientific and reasonable project was proposed to control and prevent the activity of harmful microorganisms. In addition, a 1% OIT/DCOIT biocide concentration was applied to inhibit microorganism-caused deterioration, in combination with mechanical removal based on laboratory tests and screening in situ. The effectiveness of microbial control was assessed using a portable microscope, ATP bioluminescence assay, and color difference detection. As a long-lasting preventive measure for microbial deterioration, an ultraviolet sterilization system can efficaciously prevent the re-outbreak of microbial deterioration to form a relatively stable dynamic balance for the surroundings of the site. This study is a resultful exploration in terms of microbial control and plays an important role in the sustainable protection of archaeological site museums.

The Maijishan and Mogao Grottoes, both UNESCO World Heritage Sites along the Silk Road, are increasingly threatened by microbial biodeterioration. To characterize bacterial communities of different microbial damages on wall paintings and identify environmental drivers, we combined high-throughput DNA/RNA sequencing with microenvironmental monitoring and conducted a cross-site comparison. At Maijishan, bacterial communities associated with black and white mycelia showed no significant compositional differences within the same cave but varied markedly between caves, indicating site-specific community assembly. Actinobacteria (>50%), particularly Pseudonocardia and Actinomycetospora, predominated, while RNA-based analysis revealed active populations of Escherichia and Stenotrophomonas, likely introduced via exogenous contamination from animal activities. In contrast, black spots from the Mogao Grottoes were dominated by Actinobacteria, Firmicutes, and Proteobacteria, with Rhodococcus as a core genus. No core bacterial OTUs were shared between the sites, suggesting strong microenvironmental filtering. Multivariate analysis identified substrate properties (total organic carbon, total nitrogen, pH) and microclimatic fluctuations (diurnal temperature/humidity ranges) as critical drivers. Maijishan’s persistently humid conditions (RH > 70% for over 180 days/ year) favored Actinobacteria proliferation, whereas Mogao’s arid climate (RH < 70% for over 240 days/year) selected for xerotolerant Firmicutes. These results reveal distinct site-specific microbial colonization patterns and provide a scientific basis for targeted conservation strategies to mitigate microbial damage and preserve these invaluable wall paintings.