FIG. 5.

ToxT-dependent transcription of ctxA and tcpA is relatively insensitive to temperature and bile in S. typhimurium. S. typhimurium strains containing chromosomal ctxAp-lacZ (KK201) and tcpAp-lacZ (KK207) transcriptional fusions and carrying either plasmid pKEK162, which expresses ToxT from the P_lac promoter (ToxT +), or the vector pUC118 (ToxT −) were grown as described in Materials and Methods (with streptomycin omitted from the medium) in LB containing 0.3 mM IPTG in the absence (black bars) or presence (hatched bars) of 0.4% bile at 30 or 37°C. Cultures were assayed for β-galactosidase as described in Materials and Methods. Results are the averages and standard deviations from three samples.