FIG 1.

Outline of gut microbiota-mediated colonization resistance mechanisms. Fiber obtained from the diet is fermented by the gut microbiota into SCFAs. Bacteriocin producers produce bacteriocins capable of targeting a specific pathogen. Primary bile acids can be converted by a very select group of gut microbiota into secondary bile acids, which generally have properties antagonistic to pathogens. Nutrient competition of native microbiota can limit access to nutrients for a pathogen. Specific organisms can use SCFAs, bacteriocins, and primary bile acids to increase their virulence, as discussed in the text.