Schematic maps of plasmid pF1, pHF, and pY and growth rates of <i>Salmonella</i> strains harboring these plasmids.

<p>(<b>A</b>) In pF1, the <i>caf</i> operon is regulated by its native promoter P<i>caf1M</i>. (<b>B</b>) In pHF, the <i>caf</i> operon is regulated by a fusion promoter pM. (<b>C</b>) Plasmid pY is an empty vector. (<b>D, E</b>) Comparison of growth rates of P1-pF1, pHF, and pY. The bacterial growth rates were determined by measuring the OD₆₀₀ every half hour (<b>D</b>) or determining bacterial CFU every hour (<b>E</b>), and the statistical differences were analyzed using the Tukey Kramer multiple comparisons test with * <i>P</i><0.05, ** <i>P</i><0.01, and *** <i>P</i><0.001 for P1-pF1 vs -pY; ^†<i>P</i><0.05, ^††<i>P</i><0.01, and ^†††<i>P</i><0.001 for -pHF vs -pY; and ^¶<i>P</i><0.05, ^¶¶<i>P</i><0.01, and ^¶¶¶<i>P</i><0.001 for -pHF vs -pF1. Depicted are mean ± SEM of three independent experiments.