Microbial Diversity Analysis on Rammed Earth Wall Surfaces in the Lingnan Region: A Case Study of Paishan Village, China

Rammed earth walls in traditional villages in the humid and hot climate of Lingnan are susceptible to microbial damage and disease. Paishan Village in Zhuhai, which is the largest extant rammed earth building complex in the Pearl River Delta with rammed earth walls dating from the Ming (1368–1644) and Qing (1644–1912) Dynasties to the Republic of China (1912–1949) period, faces weathering and hollowing issues, yet targeted microbial research is lacking. This study, with a focus on the village’s rammed earth walls, aimed to reveal microbial diversity and its relationship to the environment, providing a basis for heritage conservation. We used SEM (scanning electron microscopy) to analyze the microstructure of walls facing different orientations. High-throughput sequencing (based on the 16S rRNA gene V3–V4 region) was combined with microbial community analysis. Species annotation and differential analysis were performed using QIIME2 and R. The results indicated that the west wall had the highest microbial diversity (45 at the phylum level and 2969 at the genus level), while the south wall exhibited the lowest. Different orientations shaped distinct community structures, with the north wall harboring a higher concentration of hygrophilous microorganisms, while the south wall was dominated by thermotolerant bacteria. All four walls shared only 0.29% of the core microorganisms. This study elucidates the distribution patterns of microorganisms in rammed earth walls in humid and hot areas, offering scientific support for their ecological restoration.