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首页> 外文期刊>Infection and immunity >Characterization of Recombinant, Ureolytic Streptococcus mutans Demonstrates an Inverse Relationship between Dental Plaque Ureolytic Capacity and Cariogenicity
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Characterization of Recombinant, Ureolytic Streptococcus mutans Demonstrates an Inverse Relationship between Dental Plaque Ureolytic Capacity and Cariogenicity

机译：重组变形溶尿链球菌的表征证明了牙菌斑的溶尿能力与致龋性之间存在反比关系

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Dental caries results from prolonged plaque acidification that leads to the establishment of a cariogenic microflora and demineralization of the tooth. Urease enzymes of oral bacteria hydrolyze urea to ammonia, which can neutralize plaque acids. To begin to examine the relationship between plaque ureolytic activity and the incidence of dental caries, recombinant, ureolytic strains ofStreptococcus mutans were constructed. Specifically, theureABCEFGD operon from Streptococcus salivarius57.I was integrated into the S. mutans chromosome in such a way that the operon was transcribed from a weak, cognate promoter inS. mutans ACUS4 or a stronger promoter in S. mutans ACUS6. Both strains expressed NiCl2-dependent urease activity, but the maximal urease levels in ACUS6 were threefold higher than those in ACUS4. In vitro pH drop experiments demonstrated that the ability of the recombinant S. mutans strains to moderate a decrease in pH during the simultaneous metabolism of glucose and urea increased proportionately with the level of urease activity expressed. Specific-pathogen-free rats that were infected with ACUS6 and fed a cariogenic diet with drinking water containing 25 mM urea and 50 μM NiCl2 had relatively high levels of oral urease activity, as well as dramatic decreases in the prevalence of smooth-surface caries and the severity of sulcal caries, relative to controls. Urease activity appears to influence plaque biochemistry and metabolism in a manner that reduces cariogenicity, suggesting that recombinant, ureolytic bacteria may be useful to promote dental health.
机译：龋齿是由长期的牙菌斑酸化导致的，该酸化导致建立龋齿微生物区系和牙齿脱矿质。口腔细菌的脲酶将尿素水解成氨，可以中和噬菌斑酸。为了开始研究斑块的尿素分解活性与龋齿发生率之间的关系，构建了变形链球菌的重组，尿素分解菌株。具体而言，将唾液链球菌57.I的theureABCEFGD操纵子整合到变形链球菌染色体中，从而使操纵子从弱的同源同源启动子中转录出来。变形链球菌ACUS4或变形链球菌ACUS6中更强的启动子。两种菌株均表达NiCl2依赖性脲酶活性，但是ACUS6中的最大脲酶水平比ACUS4中的高三倍。体外pH下降实验表明，重组葡聚糖变形链球菌在葡萄糖和尿素同时代谢期间缓和pH下降的能力与表达的脲酶活性成正比。感染ACUS6并用含25 mM尿素和50μMNiCl2的饮用水喂养成龋饮食的无特定病原体的大鼠，其口服脲酶活性相对较高，并且光滑表面龋齿的患病率显着降低。相对于对照，龋齿的严重程度。脲酶活性似乎以降低致龋性的方式影响噬菌斑的生物化学和代谢，表明重组的溶尿细菌可能有助于促进牙齿健康。

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