Studying the Competence Regulon Quorum Sensing Circuity in Streptococcus mitis
Quorum sensing (QS) is a bacterial mechanism for modulating gene expression in response to cell-population density via intercellular communication. QS bacteria generate and release chemical signal molecules known as autoinducers, which increase in concentration as cell density increases. To determine the cell density and initiate the group behaviors such as virulence factor production, biofilm formation, and competence development bacteria rely on the production and release of signaling molecules into their environment. QS could thus be utilized as a potential non-antibiotic therapeutic strategy to control infections without affecting the survival of the bacteria, thus minimizing the selective pressure for resistance development. Streptococcus mitis , a pathogenic bacterium, utilizes the comABCDE competence regulon QS circuity. However, the competence stimulating peptide (CSP), the signaling molecule, that is responsible for QS activation, is not identified yet. In this work, we set out to identify the CSP of S. mitis and study the molecular mechanisms underlying the interaction and binding of CSP and its analogs with the histidine kinase receptor, ComD. We isolated the CSP and confirmed its sequence by MS/MS analysis. Analyzing the structure-activity relationship of CSP's alanine screen analogs gave us insights of their binding and interaction with ComD receptor. Most of the analogs shows more activity than the native CSP.
Antibiotic Resistance, Biofilm Formation, Competence, Luciferase-gene Assay, Peptide, Quorum Sensing
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