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. 2014 Jan 28;5(1):e01028-13. doi: 10.1128/mBio.01028-13

FIG 1 .

FIG 1 

An inner membrane transcriptional regulator in V. cholerae, TfoS, is critical for natural competence and acts upstream of TfoX. (A) Architecture of the tfoS gene product. ss, putative signal sequence; tmh, transmembrane helix; HTH, helix-turn-helix DNA-binding domain. (B) Natural transformation of WT and tfoS deletion strains on chitin flakes with 500 ng of a PCR product that confers resistance to kanamycin. (C) Natural transformation on chitin flakes of WT and TfoS mutant strains, each containing IPTG (isopropyl-β-d-thiogalactopyranoside)-regulated Ptac upstream of the endogenous copy of either tfoX or qstR on the genome in the presence of 1 mM IPTG with a PCR product that confers resistance to spectinomycin. White bars in panels B and C indicate that no transformants were obtained, and those data are presented at the limit of detection. Data in panels B and C are shown as means ± standard deviations (SD). (D) Transcript abundance of the indicated gene is shown for WT and TfoS deletion strains grown under competence-inducing [(GlcNAc)2] and noninducing (glucose) conditions. Data are normalized to the transcript abundance of RpoB and then again to the expression level of the WT under inducing conditions. Data are shown as median ± range. Statistical comparisons were made by nonparametric Mann-Whitney test. All data are from at least three independent biological replicates. *, P < 0.05; **, P < 0.01.