Interspecies metabolite transfer fuels the methionine metabolism of Fusobacterium nucleatum to stimulate volatile methyl mercaptan production

Halitosis can have a significant impact on the social life of affected individuals. Among oral odor compounds, CH 3 SH has a low olfactory threshold and halitosis is a result of its production. Recently, there has been a growing interest in the collective properties of oral polymicrobial communities, regarded as important for the development of oral diseases, which are shaped by physical and metabolic interactions among community participants. However, it has yet to be investigated whether interspecies interactions have an impact on the production of volatile compounds, leading to the development of halitosis. The present findings provide mechanistic insights indicating that ornithine, a metabolite excreted by Streptococcus gordonii , promotes polyamine synthesis by Fusobacterium nucleatum , resulting in a compensatory increase in demand for methionine, which results in elevated methionine pathway activity and CH 3 SH production. Elucidation of the mechanisms related to CH 3 SH production is expected to lead to the development of new strategies for managing halitosis.