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σB and the σB-Dependent arlRS and yabJ-spoVG Loci Affect Capsule Formation in Staphylococcus aureus

Meier, Stefan, Goerke, Christiane, Wolz, Christiane, Seidl, Kati, Homerova, Dagmar, Schulthess, Bettina, Kormanec, Jan, Berger-Bächi, Brigitte, Bischoff, Markus
Infection and immunity 2007 v.75 no.9 pp. 4562-4571
Staphylococcus aureus, fluorescent antibody technique, loci, mutants, operon, signal transduction, transcription factors
The alternative transcription factor σB of Staphylococcus aureus affects the transcription of the cap gene cluster, required for the synthesis of capsular polysaccharide (CP), although this operon is lacking an apparent σB-dependent promoter. Regulation of cap expression and CP production in S. aureus strain Newman was shown here to be influenced by σB, the two-component signal transduction regulatory system ArlRS, and the yabJ-spoVG locus to different extents. Inactivation of arlR or deletion of the sigB operon strongly suppressed capA (CP synthesis enzyme A) transcription. Deletion of spoVG had a polar effect on yabJ-spoVG transcription and resulted in a two- to threefold decrease in capA transcription. Interestingly, immunofluorescence showed that CP production was strongly impaired in all three mutants, signaling that the yabJ-spoVG inactivation, despite its only partial effect on capA transcription, abolished capsule formation. trans-Complementation of the ΔspoVG mutant with yabJ-spoVG under the control of its native promoter restored CP-5 production and capA expression to levels seen in the wild type. Northern analyses revealed a strong impact of σB on arlRS and yabJ-spoVG transcription. We hypothesize that ArlR and products of the yabJ-spoVG locus may serve as effectors that modulate σB control over σB-dependent genes lacking an apparent σB promoter.