Pollution gradients shape structure and functions of stone heritage bacterial communities at global scale.

Previous studies mainly focused on the impact of climatic conditions on stone heritage microbial communities, while ignoring a global ecological perspective of pollution on heritage microorganisms. In particular, there is a lack of detailed analysis of the impact of pollution levels on microbial metabolic function. In this study, >6000 bacterial OTUs from 17 world cultural heritage sites were considered. The microbial diversity indexes and potential functions under different pollution levels were analyzed. The results show that particulate matter pollution, such as PM2.5, has an effect on the microbial community in heritage sites comparable to that of temperature and precipitation. High concentrations of particulate matter increased bacterial richness and facilitated the introduction of unique species. Among them, phototrophic bacteria (e.g., Cyanobacteria) and some heterotrophic bacteria (e.g., Actinobacteria and Proteobacteria) formed the core of the microbial community. However, high concentrations of particulate matter reduced the complexity and stability of microbial ecological networks, favoring pollution-tolerant species. Furthermore, elevated particulate concentrations partially suppressed the expression of certain metabolic pathways, particularly genes related to denitrification (e.g., nosZ and nirS). This study reveals the long-term impact of polluted environments on the diversity and potential functions of microbial communities, providing a theoretical basis for developing sustainable strategies for cultural heritage conservation.