This shows corresponding FISH (left) and NanoSIMS (right) analysis of gut microorganisms. Bacteroides or Akkermansia cells were stained with the aid of specific FISH probes. The amount of stable isotope 15N was analyzed in the same cells by NanoSIMS. The higher the 15N content of a cell, the more intestinal mucosa was taken up. White arrows point to cells that have taken up mucus. The Bacteroides cell marked with a green arrow has not fed on mucus.