Expression of a Cryptic Secondary Sigma Factor Gene Unveils Natural Competence for DNA Transformation in Staphylococcus aureus
A) Western blot analyses directed against GFP showing that SigH is not active in standard culture conditions. Strains N315aspGFP (asp23 promoter), N315comGFP (comG promoter) and N315-GFP (promoter-less) were grown aerobically in BHI or RPMI 1640 medium. B) Western blot against GFP showing that SigH activity is induced in CS2 medium. Incubation times (hours) are indicated above the panel. Positive control cells of N315aspGFP were grown in TSB for 10.5 h. C) Northern blot analysis confirming SigH-dependent expression of SA1365, one of the comG operon genes. Strains N315, NKSH (sigH inactivation mutant), and NKSHh (complemented strain) were grown in anaerobic and static conditions in -GS medium.