FIG. 3.

IPTG induction of LLO is dose dependent. (A) The hemolytic-activity values listed in Table 1 for the iLLO strain (DP-L3885) were plotted versus the IPTG concentration. A best-fit line for linear induction of hemolytic activity is shown. (B) An overnight culture of iLLO strain DP-L3885 was diluted 1:10 in BHI broth into replicate flasks and grown for 5 h at 37°C in the presence of various concentrations of IPTG. The OD₆₀₀ values of all of the cultures were identical. Culture supernatants were precipitated for 1 h on ice in the presence of 10% (vol/vol) trichloroacetic acid. Samples were centrifuged and resuspended in protein sample buffer. An equivalent amount of each sample was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by Western blot assay with a rabbit polyclonal anti-LLO antibody. The position of the LLO bands (58 kDa) relative to that of a molecular size standard (61.3 kDa) is shown.