Bacterial gene expression control at population level
Group B Streptococcus agalactiae (GBS) is a human commensal bacterium of the gastrointestinal tract and vaginal mucosa of many healthy individuals. However, in new-borns this bacterium causes a life-threatening infection with increasing rates of antibiotic resistance. In earlier studies, a new cell-to-cell communication was discovered in GBS that comprises a transcriptional regulator of the Rgg family and a short hydrophobic peptide (SHP). The main goal of the EU-funded CELLCOM-GBS (Control of Streptococcus agalactiae virulence genes via peptide-based cell to cell communication) project was to elucidate the significance of this new QS signalling in the virulence of GBS. At the first project stage, researchers validated functional significance of this communication brought about by transcriptional regulator RovS of the Rgg family and the SHP. Project results for the first time indicated that this signalling is important for the virulence of GBS. DNAs of these peptides were highly conserved in all isolates of GBS meaning that this cell-cell communication system is important for the biology of this microbe. Application of different isogenic mutants led to identification of additional partners of this system. They included the Eep peptidase, the PptAB and the Opp1A-F oligopeptide transporters, essential for peptide maturation and transport. Researchers found a new target gene, gbs1556, of the RovS/SHP system. It encodes secreted protein with a protease/glutaminase domain but its function is unknown. They also re-evaluated a previously described target, gene fbsA. Expression of both genes was regulated by RovS/SHP system but fbsA was modulated through a non-identified indirect mechanism. In conclusion, CELLCOM-GBS has contributed significantly to better clarification of QS mechanisms and their role in GBS pathogenesis. These results might lead to establishing novel approaches to decrease GBS virulence.
