Molecular Analyses of the Competence Regulatory Network in Streptococcus mutans

Development of competence for genetic transformation is the means by which bacteria are able to take up DNA from their environments. In this way, bacteria rapidly acquire novel genes or traits that may allow them to survive in harsh environments, make them resistant to antibiotics or become more virulent (able to cause diseases). The incorporation of exogenous DNA through transformation enable the bacteria to gain genetic variations, which is a major force to drive bacterial evolution. In addition, introduction of a genetically constructed DNA into a bacterial strain by genetic transformation is a widely used method in molecular cloning and other genetic manipulations in bacteria. Many bacteria are known to develop competence for genetic transformation. However, when bacteria develop competence to take up DNA and how this process is regulated are not fully understood. In the group of bacteria known as Streptococci, which tend to live on humans and animals, competence is known to be regulated by one of two signaling systems, the ComCDE and ComRS. Interestingly, Streptococcus mutans, a resident member in dental plaque, possesses both ComCDE and ComRS systems that are shown to regulate genetic competence. Recent work from our lab and from others further suggests that competence development in S. mutans and other related species is regulated at multiple levels, involving a complex regulatory network and multiple cross-connections among signalling transduction pathways. However, the molecular details of such a complex regulatory network is not fully elucidated. The proposed research aims to unravel this complex regulatory network in S. mutans. The results of this research will significantly advance our understanding of how bacteria to regulate their genetic plasticity, resist antibiotics and adapt to changing environments.