Abstract
From the 16th to the 18th centuries in Japan, saltpeter was produced using a biological niter-bed process and was formed under the floor of gassho-style houses in the historic villages of Shirakawa-go and Gokayama, which are classified as United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Sites. The relict niter-beds are now conserved in the underfloor space of gassho-style houses, where they are isolated from destabilizing environmental factors and retain the ability to produce nitrate. However, little is known about the nitrifying microbes in such relict niter-bed ecosystems. In this study, the microbial community structures within nine relict niter-bed soils were investigated using 454 pyrotag analysis targeting the 16S rRNA gene and the bacterial and archaeal ammonia monooxygenase gene (amoA). The 16S rRNA gene pyrotag analysis showed that members of the phyla Proteobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Gemmatimonadetes, and Planctomycetes were major microbial constituents, and principal coordinate analysis showed that the NO3 −, Cl−, K+, and Na+ contents were potential determinants of the structures of entire microbial communities in relict niter-bed soils. The bacterial and archaeal amoA libraries indicated that members of the Nitrosospira-type ammonia-oxidizing bacteria (AOB) and “Ca. Nitrososphaera”-type ammonia-oxidizing archaea (AOA), respectively, predominated in relict niter-bed soils. In addition, soil pH and organic carbon content were important factors for the ecological niche of AOB and AOA in relict niter-bed soil ecosystems.
Highlights
Until the early 20th century, saltpeter, which is known as the main source of gunpowder, was produced via an artificial bioprocess, the socalled ‘‘niter-bed’’ [1,2]
We investigated the microbial community structure of nine soil samples obtained from the underfloor areas of three gassho-style houses by using 454 pyrotag analysis targeting the 16S rRNA gene and the ammonium monooxygenase subunit A gene of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA)
The rarefaction curves showed that the accumulation of the 16S rRNA gene Operational taxonomic unit (OTU) was insufficient to achieve the goal of saturation (Fig. S1A), the coverage values were calculated to be 96.99–98.59%, suggesting that the OTUs retrieved here were sufficient for estimating the microbial diversity in the relict niter-bed ecosystems
Summary
Until the early 20th century, saltpeter (i.e., niter or potassium nitrate [KNO3]), which is known as the main source of gunpowder, was produced via an artificial bioprocess, the socalled ‘‘niter-bed’’ [1,2]. The basic concept of saltpeter production via niter-bed involves the nitrification of ammonia-containing wastes (e.g., plant residue, horse manure, and human urine) mixed with a certain amount of soil [1,2]. This nitrification reaction was thought to be performed by ammonia-oxidizing and nitriteoxidizing microbes [1,2]. The niter-bed process is a historically important industry in several nations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
