Team:Northwestern

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Poor oral health (tooth decay and infection) can lead to many painful symptoms and complicated treatments. As mouth bacteria are a primary culprit in tooth decay, as lactic acid secreted by natural bacteria in the human mouth decreases pH, leading to cavity formation. The enamel demineralization threshold is known to be around pH 5.5. The overall vision is to prevent mouth pH from falling below 5.5 by engineering bacteria to sense pH and respond by increasing alkalinity. Our summer project aimed at creating genetic pH sensing elements that would work in the mouth. Previous research has found that the genes asr and gadA are highly expressed when pH drops below 5.5. Our project laid the foundation for a dual-state promoter consisting of two promoters in series with a constitutive promoter on at a (tunable) basal level and a downstream pH inducible promoter. In the process, we have characterized a new pH responsive promoter, asr, as well as the individual gadA and constitutive promoters. Ongoing work will evaluate how promoters in series affect each other and characterize the dual state phenomenon. This project lays the groundwork for sensing pH drops and could induce enzymes that catalyze reactions to increase the pH.