Fig. 4.

NanoSIMS/FISH analysis of small bowel microbiota from enterally fed and TPN-dependent mice receiving intravenous [¹³C]leucine. A and B: small bowel effluents were hybridized with FISH probes targeting all Bacteria (EUB338 I–III, green) and Enterobacteriaceae (Ebac1790, red). NanoSIMS atom % (at%) ¹³C distribution maps of the same fields of view for fed (C) and TPN-dependent (D) samples show Enterobacteriaceae significantly enriched in ¹³C (white arrows) compared with non-Enterobacteriaceae cells from fed mice (scale bar = 5 μm). E: summary of cellular carbon isotope composition from single cells. The dashed line indicates the threshold value for considering a cell ¹³C enriched over cells from ¹²C+Fed control effluent (mean + 5 SD). The at% threshold for calling a cell enriched in ¹³C was +5 standard deviations of the mean ¹³C isotopic composition of cells from control ¹²C+Fed mice (1.122 at% ¹³C; 104 cells analyzed). Asterisks indicate significant differences between treatments and/or target populations (Tukey post hoc test, P < 0.001).