Figure 5. Bacterial cells in close proximity to the hyphae receive carbon and nitrogen.

NanoSIMS images of P. ultimum hyphae (H), B. subtilis spores (S) and vegetative cells (V) identified in the secondary electron (SE) image (a) of ¹³C and ¹⁵N -enriched samples. The ratio images of ¹³C¹⁴N/¹²C¹⁴N (b) and ¹²C¹⁵N/¹²C¹⁴N (c) show the incorporation of label into the biomass of P. ultimum and B. subtilis. The colour scale indicates the relative enrichment in ¹³C and ¹⁵N (b,c) with warmer colours representing higher enrichment levels and cooler colours indicating lower values. The higher background signal for ¹³C on the left side of the hyphae (b) results from the topography-dependent re-deposition of sputtered sample material. Dashed lines indicate natural abundances of ¹³C and ¹⁵N. Vegetative cells and spores are framed in black and white, respectively. Images represent a field of analysis corresponding to a sample area of 40 × 40 μm. Scale bars, 4 μm.