Gut Microbiota live as biofilms: a) Confocal laser micrograph of microbiota grown form a healthy human donor colonic biopsy ex vivo on the Calgary Biofilm Device ™, and illustrating their biofilm mode of growth (A3, merge image). The microbiota visibly contain a thick exopolysaccharide coating typical of bacterial biofilms (A2, wheat germ agglutinin stain) covering live bacteria (A1). Bars = 20 μm. B) Human microbiota biofilms grown on the Calgary Biofilm Device ™ and observed under scanning electron microscopy. The slimy exopolysaccharide coating of the biofilm hides underlying bacterial morphology in healthy conditions (B1), and this exopolysaccharide can be lost upon exposure to an enteropathogen like Giardia sp. (B2). C) Gut microbiota in the colon of a healthy rat, illustrating the biofilm sheet formed by the commensals (red), separated from the epithelial surface (blue) by the intestinal mucus barrier (not stained). Bar = 50 μm.