Researchers from Japan report that a particular combination of bacteria in our mouths may be responsible for producing some very unpleasant smells. In a study published last month in mSystems, researchers from Osaka University revealed that the interaction between two common types of oral bacteria leads to the production of a chemical compound that is a major cause of bad breath.

Bad breath is caused by volatile compounds that are produced when bacteria in the mouth digest substances like blood and food particles. One of the worst smelling of these compounds is methyl mercaptan (CH3SH), which is produced by microbes that live around the teeth and on the surface of the tongue. However, little is known about which specific bacterial species are involved in this process.

Lead author of the study Takeshi Hara, said: “Most previous studies investigating CH3SH-producing oral bacteria have used isolated enzymes or relatively small culture volumes. In this study, we aimed to create a more realistic environment in which to investigate CH3SH production by major oral bacteria”.

To do this, the researchers developed a large-volume anaerobic co-culture system that enabled them to test interactions between multiple different types of bacteria that live in the mouth.

Masae Kuboniwa, senior author said: “The results were very intriguing. We found that Fusobacterium nucleatum produces large quantities of CH3SH in response to Streptococcus gordonii, another oral bacterium”.

Hara said: “Taken together, these findings suggest that CH3SH production in the mouth is driven by the interaction between S. gordonii and F. nucleatum“.

Understanding how these two bacterial species work together to cause bad breath could be helpful in developing ways to treat or even prevent bad breath.


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