Diversity and Composition of Culturable Microorganisms and Their Biodeterioration Potentials in the Sandstone of Beishiku Temple, China.

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.

Community assembly, potential functions and interactions between fungi and microalgae associated with biodeterioration of sandstone at the Beishiku Temple in Northwest China.

Fungi, cyanobacteria and algae are specific microbial groups associated with the deterioration and safety of stone monuments. In this study, high-throughput sequencing analysis was used to investigate the diversity, distributions, ecological functions, and interaction patterns of both the fungal and microalgal (including cyanobacteria and algae) communities on sandstone in the Beishiku Temple, located on the ancient Silk Road. The results showed that the core phyla of fungi were affiliated with unclassified Lecanoromycetes, Engyodontium, Knufia, Epicoccum, Endocarpon, and Cladosporium of Ascomycota whereas the phyla of microalgae were dominated by prokaryotic Cyanobacteria and eukaryotic Chlorophyta. The environmental factors of temperature, relative humidity, and light intensity were monitored simultaneously. The structure of the microbial communities was much more strongly shaped by soluble Cl-, Na+, NO3- ions than by the light intensity, moisture content or temperature, especially for the weathered sandstone located outside the caves. The co-occurrence network analysis suggested that a more stable community structure was evident outside the caves than inside. The stronger positive connections and coexistence patterns that were detected indicate a strong adaptability of fungi and microalgae to the distinct oligotrophic microhabitats on sandstone. The metacommunity co-occurrence network exhibited the ecological predominance of fungi, and most of the functional fungi in the biofilms outside the caves belonged to the Lichenized group, based on the FUNGuild prediction. These findings highlight the ecology and functions of stone-inhabiting microorganisms to further advance the current understanding and knowledge of sandstone biodeterioration for protection and management.