Fake talk in bacteria: Quorum quenching in dental infections

Bacteria make up 78% of our planet’s living species and among them are present the main enemies of mouth health. Caries, plaque, and periodontitis are the most common diseases of the oral cavity and the main cause for them is the Gram-positive bacterium Streptococcus mutans (S. mutans). The growth and spread of drug-resistant strains have prompted research to evaluate and develop new strategies against pathogenic bacteria: among these new research frontiers, the study of the Quorum Sensing (QS) offers new and different pharmacological targets. Using QS, groups of bacteria can communicate with each other to coordinate their behavior and function as a multicellular organism would, thanks to the various kind of biochemical signals secreted that allows inter and intra-species communication. The behavior of QS-regulated bacteria depends on the population’s density and regulate different characteristic such as bioluminescence, virulence, biofilm formation, and sporulation. QS mechanism works through the production, release, and detection of particular signal molecules (called auto-inducers, AIs), when they reach a particular concentration threshold. Every AIs initiate a virulent cascade in bacteria belonging to the same species and, at the same time, inhibit the functions of other species. In particular, S. mutans secretes an AI formed of 21 ammino acids, called Competence Stimulating Peptide (21-CSP) that, after being processed by a membrane-bound protease (SepM), is transformed into its active form (18-CSP) which lead to the autoinduction of the QS circuitry. The purpose of this thesis is to create and study analogues of the 21-CSP and observing the interference in the QS system (namely Quorum Quenching, QQ) of these against the S. mutans through in vitro tests.