FIG. 4.

Contributions of Fur and MntR to repression of the S. flexneri sit and mntH promoters. (A and B) S. flexneri SM100 (wild type) and UR010 (fur::Tn5) were grown for 3 hours in EZ-RDM medium with or without 40 μM ferrous sulfate as indicated. (C) E. coli SIP879 (wild type) and SIP943 (mntR), both carrying pSIT, were grown for 5.5 h in EZ-RDM medium with or without 0.1 μM manganese sulfate as indicated. RNA was isolated from each sample and used to generate cDNAs, which were amplified using real-time PCR. The amount of sit and mntH gene expression was normalized to the housekeeping gene rrsA by dividing the relative amounts of sit or mntH cDNA by the relative amounts of rrsA cDNA in each sample. The data presented are the means of three experiments, and the standard errors of the means (error bars) are indicated.