Circuitry Rewiring Directly Couples Competence to Predation in the Gut Dweller Streptococcus salivarius (Mignolet et al, Cell Reports, 13 February 2018)

Bacteriocins are known to play a role in bacterial communication and ecology. For example, the gut and oral cavity are parts of the human body that accommodate thousands of different bacterial species. These bacteria, often beneficial for human health, are continuously in a stressful environment and compete for food and space. When he was researcher in Prof. Pascal Hols lab (UCL/LIBST), Dr. Johann Mignolet (now R&D Project Manager of Syngulon) demonstrated that Streptococcus salivarius, a commensal human gut bacterium, uses a communication pheromone to concomitantly trigger two responses: the ability to modify its genome via the acquisition of “foreign” DNA and the production of potent bacteriocins. These toxins or non-transformable variants of S. Salivarius could be used for medical purposes to kill harmful multi-resistant superbugs such as Staphylococcus aureus and several streptococci.

This figure adapted from Mignolet et al, 2018, shows the different transcriptional cascades that trigger competence entry and expression of bacteriocin–encoding genes in four different streptococci models: S. salivarius, S. thermophilus, S. mutans and pneumoniae. Specifically interesting is that the BlpRH/BlpC bacteriocin regulatory system is missing or incomplete in S. Salivarius. The boxes show systems shared between species. Large continuous arrows depict transcriptional control, and dashed arrows display protein translation. Small continuous arrows indicate protein/peptide/phosphate motion.

The bacterium-killing assay below demonstrates addition of a pheromone inducing bacteriocin production, which leads to an inhibitory effect on surrounding bacteria.