Dietary Sugars and bacteria interactions affect cariogenic properties of cavity‐causing bacteria

Abstract

Cavity is becoming more prevalent in our society. One major contributor is the modern diet, specifically the large amounts of sugars in diet. Another key factor is bacteria in our mouth that eat these sugars. Streptococcus mutans is one of the leading bacteria that initiate and promote cavity. They metabolize sugars to build up plaque over time and simultaneously produce acid that erodes tooth surface and causes cavity. We were interested in studying how different sugars interact with S. mutans: how different sugars influence pH changes and affect S. mutans colonization, which would help us recognize what sugar is beneficial or harmful to your teeth.We used a fruit fly model because fruit flies like sugars and mixing S. mutans with sugars can facilitate S. mutans colonize fruit flies. To make sugary food I mixed 8 different sugar solutions with S. mutans (labeled with green fluorescent protein) and soaked them to small filters. Then we grew fruit flies and separated them into 8 different tubes that were prepared with the sugar‐bacteria soaked filters on top. We then waited for 6 days to let flies eat the food and grow at room temperature. After the incubation, we took 1–2 flies every 2 days and frozen them to image the green color under Fluorescent Microscope, which indicates S. mutans colonization. On the final day, we harvested all of the remaining flies, ground them up, made different solutions, and then streaked various dilutions onto agar plates and incubated them for 2 days to count bacterial colonies, which represents bacterial colonization of flies. Flies fed with five sugars including sucrose showed bacterial colonization by direct imaging and calculating bacterial colony forming units. Flies fed with sucrose exhibited the best colonization, while flies fed with xylitol did not show any colonization. Overall the data indicated that S. mutans utilizes some dietary sugars more efficiently and as a result, can colonize more by eating some sugar than others.To evaluate the effects of different sugars on the pH of S. mutans cultured in bacterial medium Todd Hewitt Broth, with pH adjusted to 7.5, we added various sugars to the medium and incubated for 30 minutes to monitor the pH changes using a pH meter. With all 8 sugars, the pH dropped significantly after five minutes. The pH did not drop below 4.5 with 6 sugars. But the pH dropped even below 4.5 with two sugars, glucose and sucrose. The pH dropped at an average of 2.91 during the 30 minutes testing period, suggesting sugars and bacteria fuel acid production. These studies reveal different sugars ate by S. mutans can produce different amounts of acid that drives the pH drop of S. mutant culture media, thus interactions between bacteria and sugars are important for the development of cavity.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.