Studies from a variety of scientific fields point at the importance of biofilms in the gut. For example, Jeffrey Gordon and colleagues,¹ evaluating data from immunologists, environmental engineers and glycobiologists, proposed that “symbionts inhabiting the polysaccharide-rich mucus gel layer overlying the gut epithelium constitute a biofilm-like community and that retention in such a matrix benefits the host by promoting functions served by the microbiota, including digestion of luminal contents and fortification of host defenses.” Evaluating our own immunological data, data from microbiologists and the medical literature, we independently came to the same conclusions.²

Direct observations of biofilms in the normal gut were lacking as recently as five years ago, probably because preservation of the epithelial glycocalyx, like the preservation of other glycocalyx structures, is technically challenging, as has long been known.^3–5 In fact, we have found that manipulations as seemingly …