Lactate enhances the production of hydrogen sulfide by oral Veillonella

Objective: Oral Veillonella is one of the dominant hydrogen sulfide (H₂S)-producing bacteria in the tongue coating (Washio et al. ,2005). This study aimed to examine effects of oral environmental factors such as pH, acid anion (lactate and acetate) and metabolic substrate on the H₂S production by Veillonella.

Methods: V. atypica ATCC17744, V. dispar ATCC17748 and V. parvula ATCC10740 were grown, and the bacterial cell suspensions were incubated with 1mM cysteine, 1mM glutathione or 0.5% tryptone at pH5 or 7 (adjusted by phosphate buffer) in the presence or absence of lactate, acetate or glucose. After 3-hr incubation, the amounts of H₂S produced were measured by methylene blue method. Likewise, cell-extracts prepared by sonic oscillation were used to measure the H₂S production.

Results: The H₂S were produced at pH7 and pH5 from cysteine (22-52 and 16-17mM), glutathione (1.7-15 and 1.5-12mM) and tryptone (2.3-31 and 1.2-19mM). The H₂S production was higher at pH7 than pH5. Lactate increased the H₂S production at pH7 and pH5 from cysteine (4.5-6.9 and 4.6-15 times) and glutathione (11-80 and 11-38 times) (p<0.05 except for V. dispar at pH5), but had no effect on the production from tryptone. Acetate and glucose had no effects. The cell-extracts produced H₂S from cysteine, glutathione and tryptone, and the production was higher at pH7 than pH5, but not affected by lactate.

Conclusion: These results indicate that Veillonella produces H2S from various cysteine-containing substrates, and that the H₂S production tends to be higher at neutral pH than acidic pH. Lactate increased the H₂S production by the cell suspension while there was no effect on the cell-extracts, suggesting that lactate activates not intracellular enzymes responsible for H₂S production but the uptake-system of cysteine and glutathione. Oral Veillonella may produce an odorous compound, H₂S efficiently in the presence of lactate at neutral pH. Supported by JSPS (18890031 and 19390539).