Benzoate-Evolved Strains of Escherichia coli K-12 Obtained by Experimental Evolution. Escherichia coli K-12

Benzoic acid is a common food preservative. At high concentration, benzoic acid conducts a proton across the membrane, depleting the proton motive force. In the absence of antibiotics, benzoate exposure selects against proton-driven multidrug efflux pumps and upregulates porins that admit fermentable substrates but also allow entry of antibiotics. Thus, evolution with benzoate requires a tradeoff for antibiotic sensitivity—a tradeoff that could help define a stable gut microbiome. Benzoate is a naturally occurring plant signal molecule that may modulate the microbiomes of plants and animal digestive tracts so as to favor fermenters and exclude drug-resistant pathogens.