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首页> 外文期刊>Applied Microbiology >Function of the Pyruvate Oxidase-Lactate Oxidase Cascade in Interspecies Competition between Streptococcus oligofermentans and Streptococcus mutans
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Function of the Pyruvate Oxidase-Lactate Oxidase Cascade in Interspecies Competition between Streptococcus oligofermentans and Streptococcus mutans

机译：丙酮酸氧化酶-乳酸氧化酶级联在低聚链球菌和变形链球菌种间竞争中的功能。

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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 H_(2)O_(2) 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 H_(2)O_(2) in the earlier growth phase and log phase, while Lox mainly contributed to H_(2)O_(2) 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 H_(2)O_(2) can be attributed to differential gene expression and substrate availability. Interestingly, inactivation of pox causes a dramatic reduction in H_(2)O_(2) production from lactate, suggesting a synergistic action of the two oxidases in converting lactate into H_(2)O_(2). 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 , S. oligofermentans develops a Pox-Lox synergy strategy to maximize its H_(2)O_(2) formation so as to win the interspecies competition.
机译：口腔礼膜和牙菌斑中的变形链球菌的机会性病原体之间不断发生复杂的种间相互作用。以前，我们表明口服共生寡链球菌拥有多种酶来生产H_（2）O_（2），尤其是乳酸氧化酶（Lox），使其能够胜过变形链球菌。在这项研究中，通过广泛的生化和遗传研究，我们在低聚链球菌中​​鉴定了丙酮酸氧化酶（pox）基因。一个痘缺失突变体完全失去了痘活性，而异位表达的痘恢复了活性。确定Pox可以在较早的生长期和对数生长期产生大部分H_（2）O_（2），而Lox主要在固定相中贡献了H_（2）O_（2）的产生。 pox和lox都在整个生长期表达，而当细胞进入静止期时，lox基因的表达增加了约2.5倍。由于乳酸的积累在固定相中大量发生，差异的Pox和Lox生成的H_（2）O_（2）可以归因于差异的基因表达和底物可用性。有趣的是，pox的失活导致乳酸中H_（2）O_（2）的产生显着降低，表明这两种氧化酶在将乳酸转化为H_（2）O_（2）中具有协同作用。在体外两物种生物膜实验中，即使lox活跃，S。oligofermentans的pox突变体也不能抑制S. mutans。在，S. oligofermentans开发了Pox-Lox协同策略，以最大化其H_（2）O_（2）的形成，从而赢得种间竞争。

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