Fig. 6: Model for the regulation of the development of competence in S. aureus under strong O2 limitation.
a The development of competence for natural transformation is usually presented as a sequential process. First, a signal (stress) is sensed by the cells, which in turn activate signal transduction pathways. These pathways ultimately activate the central competence regulators responsible for the activation of the late competence genes, among which are found all the genes encoding for the proteins involved in natural transformation. b Under microaerobic conditions, we have shown that oxygen rarefaction is sensed by the SrrAB two-component system which in turn activate the alternative sigma factor SigH. Together with ComK1, SigH is required to activate the expression of the natural transformation genes13. c Under strong oxygen limitation, SigH and ComK1 still activate the expression of the natural transformation genes but much less efficiently than under microaerobic conditions. This inhibition is performed by the third competence regulator, ComK2, probably through a direct protein-protein interaction with SA2107, a small protein of so far unknown structure and function. Furthermore, we showed that the two-component system NreBC senses the strong O2 limitation and is involved in the ComK2/SA2107 inhibitory pathway, potentially through the activation of SA2107.
