GFP expression in the yopE::gfp strain. Stationary-phase yopE::gfp were diluted into media optimized for inductive Yop expression (see Materials and methods) either at 26°C or 37°C. At the indicated times samples of bacteria were removed from each culture and analyzed by flow cytometry. Shown is the FL1 signal (green channel) of 104 size-gated bacteria (not shown; see Fig. 4a) from the 26°C (thin line) and the 37°C (thick line) cultures. The mean fluorescence intensity of the size-gated bacteria from each culture is shown.