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Expression of a Cryptic Secondary Sigma Factor Gene Unveils Natural Competence for DNA Transformation in Staphylococcus aureus

Figure 5

Two distinct mechanisms are responsible for SigH activation.

The translation initiation codon of sigH is required for SigH activation in CS2 medium, but not for SJ-dependent SigH activation. A) Nucleotide sequence of the sigH translation initiation site region. The expected translation initiation codon, and the downstream in-frame TTG codon are underlined. Sequences for the wild type strain (N315ex; top), and the constructed mutant (N315ex-sigH*; bottom) are shown and the mutated residues are shown in lower case. B) Western blot analysis of SigH-dependent GFP production in WT (N315ex) and N315ex-sigH* carrying pMK3-com-gfp. Cells were grown in CS2 medium for the indicated times. No GFP signal was detected in the translation initiation codon mutant strain (N315ex-sigH*). C) Rare GFP expressing cells are still detectable in N315ex-sigH* carrying pMK3-com-gfp.

Figure 5