Figure 2: Antimicrobial activity of six basil essential oils. The average values (with standard deviations as error bars) of the diameter of inhibition zone (upper segment-Figure 2a) and minimum inhibitory concentration (MIC, lower segment-Figure 2b) observed after the application of the six basil essential oils under study [Red (R), Small-leaved (S), Large-leaved (L), Lettuce-leaved (Le), Lettuce-leaved Flower (F), Cinnamon (C)] on 17 Gram-negative (black columns) and 16 Gram-positive bacteria (white columns) are displayed. On the top of each column, the code name of the essential oil examined is accompanied in parenthesis by the code names of the other essential oils with which it shows similar antimicrobial activity. The asterisks denote the essential oils which display a statistically significant larger antimicrobial activity in Gram-positive relative to Gram-negative bacteria.