Fig. 5

A schematic model for regulation of competence through extracellular signalling peptide-mediated QS in B. licheniformis. The ComX precursor is processed and secreted by ComQ into at least two separate peptides, one of which is the ComX pheromone. The transmembrane histidine kinase sensor protein (ComP) interacts with the ComX pheromone leading to phosphorylation of the ComA response regulator/transcription factor, which in turn drives transcription of the srf operon. The second peptide (marked ‘?’) has been identified in this study as a 10-amino-acid long component of the ComX precursor. The role of this new peptide is presently unknown