FIG. 4.

Growth-dependent expression of the rpoS genes of P. putida R6C1 (○, •), and P. putida C1R1 (□, ▪). Exponentially growing cells in 10 mM citrate-supplemented AB minimal medium were diluted in the same medium, and growth (open symbols) and emission of light (solid symbols) were measured. Measurement of luminescence in liquid culture was carried out as described previously (34). LU values are not normalized per cell. Notice that the same range of log units, four, is plotted in both y axes, and therefore the curve slopes of light emission and optical density are comparable. Experiments were repeated with three cultures; results of a typical experiment from a single culture are presented. Duplicate measurements of LU in a single experiment yielded an average standard deviation of 10%.