Fig. 6

Effect of the gut compounds on E. coli growth. a Examples of growth curves of E. coli MG1655 grown at 37 °C in TB containing dopamine, DHMA, melatonin or spermidine at indicated final concentrations (black line), and of control culture grown in TB (red line). Optical density of culture was measured at 600 nm as described in Methods. b The time-averaged OD, calculated as the area below the growth curves and divided by the duration of the experiment. For each experiment, the time-averaged OD was normalized to the time-averaged OD of the control culture in TB. Gray bars represent the catecholamine group; black bars the thyroid group; and white bars the polyamine group. A one-tailed student t-test was performed to assess the significance of the difference from the control (**P ≤ 0.01; *P ≤ 0.05). Each bar represents the mean of at least three independent experiments, with error bars indicating standard deviation