Acid tolerance of oral bacteria is focus of new thesis
Gabriella Boisen's thesis explores the acid tolerance of oral bacteria, including by exposing them to decreasing pH values and probiotic bacteria.
Our mouths are full of bacteria that protect us from diseases. When we eat too much sugar or neglect to brush, the bacterial flora is disrupted – the environment becomes acidic. A new thesis sheds light on how oral bacteria adapt to acidic environments.
When bacteria in the mouth develop acid tolerance, it means that they can survive in, and contribute to, a low pH environment. And this in turn has negative consequences for oral health, as low pH contributes to the development of caries.
... the thesis shows that the acid tolerance of bacteria can be affected by a variety of signals in their environment.
Gabriella Boisen
Gabriella Boisen's thesis explores the acid tolerance of oral bacteria by exposing them to decreasing pH values and probiotic bacteria.
“If we gain a better understanding of how oral bacteria develop acid tolerance and other caries-related characteristics, we may also find new ways to detect and prevent oral diseases at an earlier stage,” she says.
The thesis consists of three sub-studies; in the first part, the researchers analysed how different oral bacteria reacted to growing in biofilms and being exposed to gradually decreasing pH values. The results showed that several different bacterial species can adapt to an acidic environment, and that acid tolerance can be enhanced when bacteria attach to a surface or come into contact with salivary proteins.
In the second part of the study, the researchers took plaque samples from children, half from those who were caries-free and half from children with multiple caries.
“The study showed that the bacteria from the children with caries had higher acid tolerance and a different acid production than the bacteria from the caries-free children,” says Boisen.
“This shows that plaque characteristics may differ depending on the oral health of the individual.”
The third sub-study explored whether oral bacteria could develop acid tolerance in the presence of probiotic bacteria. The results showed that a specific probiotic bacterium, lactobacillus reuteri, prevented the development of acid tolerance in the oral bacteria and altered their gene expression.
This means that such probiotic species could influence the properties of oral bacteria that contribute to caries development.
“Overall, the thesis shows that the acid tolerance of bacteria can be affected by a variety of signals in their environment. Further research in this area could therefore contribute to new insights into both biomarkers and preventive measures against caries,” she concludes.
