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. 2018 Sep 10;9:2103. doi: 10.3389/fmicb.2018.02103

FIGURE 2.

FIGURE 2

The promoter within crtS (PcrtS) is repressed by an unknown factor common to E. coli and V. cholerae. β-galactosidase activity in E. coli DH10-β (left) and monochromosome V. cholerae MCH1 (right), containing promoterless lacZ in a pBR-based plasmid (none, pMLB1109), or lacZ transcriptionally fused to either crtS (pBJH235), Δ3′crtS (pPC066), Δ5′crtS (pPC067) and Δ5′Δ3′crtS (pPC068). Additionally, the strains had a second plasmid, prctB (pRR24, black bars) supplying RctB or the corresponding empty vector (pPC020, white bars). The x-axis in the two graphs are scaled differently. Both in E. coli and MCH1, the promoter activity dramatically increases upon deletion of the 5′ crtS sequences. Since in both the strains the promoter repression is seen in the absence of RctB, the only factor known to bind crtS, an unknown factor common to two bacteria must be involved in repression of PcrtS. Supplying RctB recovers the repression partially, which indicates that the promoter is normally repressed by RctB as well as the unknown factor. Error bars denote standard deviation of mean from three biological replicates.