Figure 4.

Persistence of Escherichia coli O157:H7 (A) and Salmonella enterica Typhimurium 14028s (B) after surface inoculation of leaves varies with lettuce genotypes. Lettuce plants (2.5- to 3-week-old) were dipped into 1 x 10⁸ CFU/mL bacterial inoculum. Leaves were surface sterilized prior to quantification of the bacterial population in the intercellular space. Results are shown as untransformed averages from three independent experiments (n = 9 ± standard error). Different letters on the top of adjacent bars (i.e., within the plant genotype) indicate significant statistical differences among the means (transformed with the root square function), as calculated with ANOVA followed by Tukey’s test (α = 0.05).