环境因素对口腔链球菌产生过氧化氢速率的影响

目的 观察口腔环境多种因素对口腔链球菌（Streptococcus oralis．S.oralis）H2O2产生速率的影响。方法采用微量板法测定S、oralis在不同浓度的葡萄糖、蔗糖、Ca^2＋、F^-、HFPO3^-及不同pH值条件下产生H2O2的速率。结果S．oralis在无外源性糖的条件下H2O2产生速率为每分钟7．48μmol／L；加入0．01～10mmol／L葡萄糖和蔗糖后，H2O2产生速率显著增高（P〈0．05）；不同浓度的葡萄糖、蔗糖间，S．oralis H2O2产生速率差异无统计学意义（P〉0.05）；pH〈6．0时S．oralis的H2O2产生速率显著降低（P〈0．05）；Ca^2＋、F^-和FHPO3^-对S．oralis H2O2产生速率的50％抑制浓度分别为1820．71、1．90和12．65mmol／L。结论环境因素对S．oralis H2O2产生速率有一定影响。

Influence of environmental factors on synthesis rate of hydrogen peroxide by Streptococcus oralis

OBJECTIVE: To investigate the influence of a broad range of environmental conditions on initial rates of hydrogen peroxide produced by Streptococcus oralis (S. oralis). METHODS: For each rate measurement, 1 ml aliquots of 10(12) cells/L mid-logarithmic phase S. oralis in TSBY were centrifuged and respectively washed by phosphate buffer containing 0.01-10 mmol/L glucose or sucrose, phosphate buffer with 5.0-7.5 pH or Bis-Tris buffer containing 0.01-100 mmol/L Ca(2+), 0.01-100 mmol/L F(-) or 0.01-100 mmol/L HFPO(3)(-). After S. oralis was cultured in respective buffer for 10, 20 and 30 min at 37 degrees C, the concentration of hydrogen peroxide in supernatant was assayed spectrophotometrically in 96-well micro-plate by ABTS-HRP at A(405). RESULTS: Synthesis rate of hydrogen peroxide by S. oralis was 7.48 micromol/L per minute without carbohydrate, the synthesis rate of hydrogen peroxide by S. oralis increased with 0.01-10 mmol/L glucose and 0.01-10 mmol/L sucrose, but there was no statistically significant difference in synthesis rate among the carbohydrate groups. The rates of H2O2 synthesis were inhibited in the buffer at pH 5.0-6.0, compared with pH 7.0 (P < 0.05). Ca(2+) had little influence on the rate of H2O2 synthesis. IC(50) of H2O2 synthesis rates by S. oralis responded to FHPO(3)(-) and F(-) were 12.65 mmol/L and 1.90 mmol/L respectively. CONCLUSIONS: Environmental conditions may influence the synthesis rate of H2O2 by S. oralis.