Regulation of the expression of genes in the YdcI regulon has evolved differently in different bacteria [2]. YdcI appears to regulate genes with different cellular functions in E. coli than the genes it regulates in S. Typhimurium [1]. Compared to known global TFs, YdcI exhibits some interesting regulatory features. First, it has more intragenic binding peaks and fewer peaks located within putative regulatory regions. Second, it has fewer binding peaks than global TFs, such as CRP, Lrp, Fnr, and ArcA. Third, it binds to more genes with putative functions. Finally, its expression level is lower relative to that of the majority of global TFs [3]. The transcriptional factor binding sites (TFBS) of YdcI enclose AT-rich inverted repeats separated by 7 nt. This finding is consistent with structural predictions that this TF likely forms homodimers or tetramers which facilitate tight binding to DNA molecules in the cell [3]. YdcI affects, direct or indirectly, about 60 genes in E. coli [1]. The Escherichia coli YdcI protein is expressed at lower levels than the S. enterica serovar Typhimurium protein, suggesting that E. coli has evolved a lower endogenous YdcI expression level and does not tolerate increases above this level [2]. It is interesting that both bacterial proteins display high homology (83% identity, e value =10^-150). YdcI expression in bacteria nontolerant more susceptible to antibiotics and oxidative stress [2]. The ydcI gene is responsible for the reduced phenotypic inheritance (RPI) phenotype, causing an increase in the frequency of persisters [4].