Control of competence for DNA transformation in Streptococcus suis

Streptococcus suis (S. suis) is one of the major bacterial pathogens of pigs worldwide and is considered an important zoonotic pathogen due to the high mortality observed in recent human outbreaks in China.

Infections by S. suis can lead to meningitis, endocarditis and septicaemia due to the ability of S. suis to disseminate rapidly to the organs after entering the bloodstream. Recently, several highly virulent and drug resistant strains have been isolated from pigs and humans, making cross-protective vaccines all the more urgent. At the moment little is known about the factors contributing to S. suis virulence. This is also due to the few molecular tools that have so far been available to study this pathogen.

Natural competence is a state in which bacteria can temporarily take up DNA present in the extracellular environment. This mechanism has a primary evolutionary function and if the genes regulating competence are known, it could be attempted to develop this mechanism to be used as a fundamental genetic tool to manipulate S. suis in the lab. Even if this species does not fall within any of the phylogenetic clusters of streptococci previously shown to regulate competence via peptide pheromones, we observed that S. suis genome sequences show the presence of all the genes involved in competence including the alternative sigma factor comX, core gene for competence induction and conserved in all naturally competent streptococci. This project is centred on the discovery, characterization and optimization of the competence system in S. suis. The first characterisation of the natural competence system of S. suis can be found here.