Nitrogen (N) is frequently a limiting nutrient in soil; its availability can govern ecosystem functions such as primary production and decomposition. Assimilation of N by microorganisms impacts the availability of N in soil. Despite its established ecological significance, the contributions of microbial taxa to N assimilation are unknown. Here we measure N uptake and use by microbial phylotypes and taxonomic groups within a diverse assemblage of soil microbes through quantitative stable isotope probing (qSIP) with 15N. Following incubation with 15 NH4+, distinct patterns of 15N assimilation among taxonomic groups were observed. For instance, glucose addition stimulated 15N assimilation in most members of Actinobacteria and Proteobacteria but generally decreased 15N use by Firmicutes and Bacteriodetes. While NH4+ is considered a preferred and universal source of N to prokaryotes, the majority (> 80%) of N assimilation in our soils could be attributed to a handful of active orders. Characterizing N assimilation of taxonomic groups with 15N qSIP may provide a basis for understanding how microbial community composition influences N availability in the environment.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics