Figure 7.
(A) β-Galactosidase activity of an invF::lac fusion in hilD 3′UTR+ and hilD Δ3′UTR hosts grown under different conditions: (i) standard conditions (black bars); (ii) exponentially growing cultures with high aeration (gray bars); and (iii) stationary phase cultures grown under low osmolarity (LB without salt). (B) Relative invasion ratios of epithelial HeLa cells by Salmonella enterica serovar Typhimurium carrying either the native hilD 3′UTR (wild-type strain ATCC 14018) or the hilD Δ3′UTR allele (hilD Δ3′UTR Kmr, strain SV6189). The invasion ratio was determined 2 h post-infection and is expressed as the ratio between viable intracellular bacteria and viable bacteria added to the HeLa cell culture. For simplicity, ratios were normalized to the infection ratio of ATCC 14028. Each experiment was run in triplicate, and the data represented are averages of five independent experiments, with standard deviations shown as error bars. The difference in invasion ratios was significant (P < 0.05) according to Student's t test.