Microbial Community Structure of Relict Niter-Beds Previously Used for Saltpeter Production

Relict niter-beds, preserved under the floors of gassho-style houses in Japan's UNESCO World Heritage Sites—Shirakawa-go and Gokayama—retain their nitrate-producing capacity. A study revealed that soil chemistry, particularly nitrate (NO₃⁻), chloride (Cl⁻), potassium (K⁺), and sodium (Na⁺) levels, shapes the microbial community structure in these ancient ecosystems. Proteobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Gemmatimonadetes, and Planctomycetes dominated the microbial composition, while Nitrosospira-type ammonia-oxidizing bacteria (AOB) and 'Ca. Nitrososphaera'-type ammonia-oxidizing archaea (AOA) were the primary nitrifying microbes. Soil pH and organic carbon content further influenced the ecological niches of AOB and AOA, providing insights into the microbial dynamics sustaining nitrate production in these historically significant sites.

Narihiro, T., Tamaki, H., Akiba, A., Takasaki, K., Nakano, K., Kamagata, Y., Hanada, S., & Maji, T. (2014). Microbial Community Structure of Relict Niter-Beds Previously Used for Saltpeter Production. PLoS ONE, 9(8), e104752. https://doi.org/10.1371/journal.pone.0104752