[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.
Yu
Shao-jie
SJ
Department of Periodontology and Oral Medicine, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
Zhang
Jin-cai
JC
Zhang
Yun-hui
YH
Zhang
Jing-yi
JY
Liu
Hong-chun
HC
D003470:Culture Media / Q000737:chemistry*; D005947:Glucose; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy; D019533:Streptococcus oralis / Q000378:metabolism*
D003470:Culture Media; D019216:Metals, Heavy; D006861:Hydrogen Peroxide; D005947:Glucose