Fig. 3: FIB-SIMS imaging shows intracellular bioaccumulation of PFAS by E. coli ∆tolC.

A given area of the sample is imaged by scanning over it repeatedly with a gallium focused ion beam and analysing the chemical composition of the ablated material using FIB-SIMS. Shown is one of 120 cells imaged (additional images in Extended Data Fig. 6 and Supplementary Data). a, Secondary electron images (formed by secondary electrons resulting from the FIB scanning) of three different Z-frames of the sample, that is, at three different positions along the z-stack, provide spatial images of the imaged cells. The cells are fully embedded in ice in the first panel (frame 1), the second panel (frame 10) shows the interior of the cell and the last panel (frame 34) features the substrate with the cell almost completely removed. b–e, Top (b) and side (c) views of the three-dimensional stack of SIMS data for a mass-to-charge ratio of 19, corresponding to fluorine (F⁻), in which the colour scale represents the ion count per extraction. The top view (b) shows the lateral distribution (x–y) of fluorine within the imaged area that is inside the cells. The side view (c), corresponding to an x–z slice through the stack: for the first few frames, there is a fluorine signal from the whole field of view, stemming from the thin ice layer covering the sample (white arrow in c). The fluorine signal away from the cells drops to zero within the first frames. As the cells are initially covered in ice, in the first frames, no highly localized fluorine signal is observed from the cells, as shown by the top view generated from the initial frames (d). Once the ion beam mills into the cell, a fluorine signal from the cell can be seen both in the side view (c, marked by a white rectangle) and in the top view generated from the corresponding slices (e), confirming that the fluorine signal originates from inside the cell.