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.