Hydrogen sulfide production from cysteine and homocysteine by periodontal and oral bacteria

Background: Hydrogen sulfide is one of the predominant volatile sulfur compounds (VSCs) produced by oral bacteria. This study developed and evaluated a system for detecting hydrogen sulfide production by oral bacteria. Methods: L-methionine-α-deamino-γ-mercaptomethane-lyase (METase) and β carbon-sulfur (βC-S) lyase were used to degrade homocysteine and cysteine, respectively, to produce hydrogen sulfide. Enzymatic reactions resulting in hydrogen sulfide production were assayed by reaction with bismuth trichloride, which forms a black precipitate when mixed with hydrogen sulfide. The enzymatic activities of various oral bacteria that resultin hydrogen sulfide production and the capacity of bacteria from periodontal sites to form hydrogen sulfide in reaction mixtures containing L-cysteine or DL-homocysteine were assayed. Results: With L-cysteine as the substrate, Streptococcus anginosus FW73 producedthe mosthydrogen sulfide, whereas Porphyromonas gingivalis American Type Culture Collection (ATCC) 33277 and W83 and Fusobacterium nucleatum ATCC 10953 produced ̃ 35% of the amount produced by the P. gingivalis strains. Finally, the hydrogen sulfide found in sub-gingival plaque was analyzed. Using bismuth trichloride, the hydrogen sulfide producedby oral bacteria was visually detectable as a black precipitate. Conclusions: Hydrogen sulfide production by oral bacteria was easily analyzed using bismuth trichloride. However, further innovation is required for practical use.