| 论文题目: | Function of the Pyruvate Oxidase-Lactate Oxidase Cascade in Interspecies Competition between Streptococcus oligofermentans and Streptococcus mutans |
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| 作者: | Liu, L; Tong, HC; Dong, XZ |
| 联系作者: | Tong, HC |
| 刊物名称: | APPLIED AND ENVIRONMENTAL MICROBIOLOGY |
| 期: | 7 |
| 卷: | 78 |
| 页: | 2120-2127 |
| 年份: | 2012 |
| 影响因子: | 3.829 |
| 论文下载: | 下载地址 |
| 摘要: | Complex interspecies interactions occur constantly between oral commensals and the opportunistic pathogen Streptococcus mutans in dental plaque. Previously, we showed that oral commensal Streptococcus oligofermentans possesses multiple enzymes for H2O2 production, especially lactate oxidase (Lox), allowing it to out-compete S. mutans. In this study, through extensive biochemical and genetic studies, we identified a pyruvate oxidase (pox) gene in S. oligofermentans. A pox deletion mutant completely lost Pox activity, while ectopically expressed pox restored activity. Pox was determined to produce most of the H2O2 in the earlier growth phase and log phase, while Lox mainly contributed to H2O2 production in stationary phase. Both pox and lox were expressed throughout the growth phase, while expression of the lox gene increased by about 2.5-fold when cells entered stationary phase. Since lactate accumulation occurred to a large degree in stationary phase, the differential Pox-and Lox-generated H2O2 can be attributed to differential gene expression and substrate availability. Interestingly, inactivation of pox causes a dramatic reduction in H2O2 production from lactate, suggesting a synergistic action of the two oxidases in converting lactate into H2O2. In an in vitro two-species biofilm experiment, the pox mutant of S. oligofermentans failed to inhibit S. mutans even though lox was active. In summary, S. oligofermentans develops a Pox-Lox synergy strategy to maximize its H2O2 formation so as to win the interspecies competition. |
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