Description:
<jats:title>Summary</jats:title><jats:p>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 <jats:sup>15</jats:sup>N. Following incubation with <jats:sup>15</jats:sup>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/emi14051-math-0004.png" xlink:title="urn:x-wiley:14622912:media:emi14051:emi14051-math-0004" />, distinct patterns of <jats:sup>15</jats:sup>N assimilation among taxonomic groups were observed. For instance, glucose addition stimulated <jats:sup>15</jats:sup>N assimilation in most members of Actinobacteria and Proteobacteria but generally decreased <jats:sup>15</jats:sup>N use by Firmicutes and Bacteriodetes. While
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/emi14051-math-0005.png" xlink:title="urn:x-wiley:14622912:media:emi14051:emi14051-math-0005" /> 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 <jats:sup>15</jats:sup>N qSIP may provide a basis for understanding how microbial community composition influences N availability in the environment.</jats:p>