FIG 1 .
Interplay between chromosome segregation and regulation of competence in S. pneumoniae. ParB (orange rectangle) binds to parS sites (blue stars), which are located close to the origin of replication (oriC). Basal levels of comCDE transcription are required to build up the extracellular levels of competence-stimulating peptide (CSP), encoded by comC. Once a threshold level of CSP is reached and sensed by ComD, an autocatalytic loop is activated in which phosphorylated ComE (purple triangles) stimulates further expression of comCDE and comAB (encoding the CSP exporter), leading to expression of the alternative sigma factor σX and downstream competence genes. By spreading from parS and/or forming DNA loops, ParB binds the comCDE locus, effectively reducing CSP accumulation and thereby controlling competence development.