Higher abundance of ammonia-oxidizing bacteria than ammonia-oxidizing archaea in biofilms and the microbial community composition of Kaiping Diaolou of China

We here investigated microbial biofilm communities on the surfaces of Linlu Villa, a villa built on a cultural heritage site known as Kaiping Diaolou and Villages located in southern China, by using next-generation sequencing technology. Then, 16S rRNA gene sequences revealed that the dominant bacterial groups in these biofilms were Cyanobacteria, Proteobacteria, Actinobacteria, Chloroflexi, Acidobacteria, Bacteroidetes, and Deinococcus-Thermus. The site survey revealed that the unique climatic conditions (ambient temperature and humidity), activities in the surroundings (farming and domestic pollution), and the rough surface of Diaolou buildings were the main factors promoting microbial colonization and development, and subsequent biofilm formation. In addition, we conducted inorganic nitrogen detecting on the surrounding environment of the Diaolou buildings and found that the inorganic nitrogen content was very high, with inorganic nitrogen NO3−-N reaching 8947.27 mg/kg; the NH4+-N content can reach 895.88 mg/kg qPCR quantification of AOA-amoA and AOB-amoA genes was performed at four sites and found that the abundance of ammonia-oxidizing bacteria (AOB) was far higher than that of ammonia-oxidizing archaea (AOA), reaching a maximum of 4–5 orders of magnitude, which is different from the current results on other cultural heritage sites. This may be due to the specific geographical location of Kaiping Diaolou and villages in the southern China with severe nitrogen deposition, as well as the surrounding residential areas and agricultural cultivation areas where nitrogen fertilizer is used in nearby agricultural cultivation. This will be worth further investigation, and the results are valuable for the protection for the protection of Kaiping Diaolou and Villages.