Couradeau, E. et al. Nat. Commun. 10, 2770 (2019).

Recent studies suggest that in soil samples, microbial taxa could possibly be recovered from extracellular DNA or dead cells. Thus, the link between soil processes and microbial composition can be misleading because of the presence of inactive cells. Methods such as BrdU labeling of DNA have been used to measure active microorganisms; however, these usually require extensively labeled DNA for sequencing. Couradeau et al. extended bioorthogonal noncanonical amino acid tagging (BONCAT) to probe translationally active cells. Specifically, soil samples are incubated with homopropargylglycine, which is incorporated into newly synthesized proteins and subsequently conjugated with fluorescent dyes via click chemistry. They then used fluorescence-activated cell sorting to recover BONCAT-positive cells and carried out 16S rRNA-seq analysis for the active community. They compared the active fraction extracted from two soil depths from Oak Ridge, TN, USA, and observed that the phylogenetic composition varied from the active fraction to the total population of extractable cells.